我正在寻找一种最佳的方法来调整包装文本在一个TextView，使它将适合它的getHeight和getWidth界限。我不是简单地寻找一种方法来包装文本-我想确保它既包装，又足够小，完全适合在屏幕上。
我在StackOverflow上看到了一些需要自动调整大小的情况，但它们要么是非常特殊的情况下的hack解决方案，没有解决方案，或涉及重新绘制TextView递归直到它足够小(这是内存紧张，迫使用户观看文本收缩一步一步与每次递归)。
但我相信有人已经找到了一个很好的解决方案，它不涉及我正在做的事情:编写几个繁重的例程来解析和测量文本，调整文本的大小，然后重复，直到找到一个合适的小尺寸。
TextView使用什么例程来包装文本?难道这些不能用来预测文本是否足够小吗?
是否有一个最佳实践的方法来自动调整TextView的大小，以适应，包装，在它的getHeight和getWidth边界?
当前回答
更新:下面的代码也满足了一个理想的AutoScaleTextView的要求，如这里所述:自动适合Android的TextView，并被标记为赢家。
更新2:增加了对maxlines的支持，现在在API级别16之前工作正常。
更新3:支持android: drawablleft, android:drawableRight, android:drawableTop和android:drawableBottom标签添加，感谢MartinH在这里的简单修复。
我的要求有点不同。我需要一种有效的方法来调整大小，因为我是动画一个整数从，可能是0 ~4000在TextView在2秒内，我想相应地调整大小。我的解决方法有点不同。这是最终的结果:
以及产生它的代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp" >
<com.vj.widgets.AutoResizeTextView
android:layout_width="match_parent"
android:layout_height="100dp"
android:ellipsize="none"
android:maxLines="2"
android:text="Auto Resized Text, max 2 lines"
android:textSize="100sp" /> <!-- maximum size -->
<com.vj.widgets.AutoResizeTextView
android:layout_width="match_parent"
android:layout_height="100dp"
android:ellipsize="none"
android:gravity="center"
android:maxLines="1"
android:text="Auto Resized Text, max 1 line"
android:textSize="100sp" /> <!-- maximum size -->
<com.vj.widgets.AutoResizeTextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Auto Resized Text"
android:textSize="500sp" /> <!-- maximum size -->
</LinearLayout>
最后是java代码:
import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.RectF;
import android.os.Build;
import android.text.Layout.Alignment;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.SparseIntArray;
import android.util.TypedValue;
import android.widget.TextView;
public class AutoResizeTextView extends TextView {
private interface SizeTester {
/**
*
* @param suggestedSize
* Size of text to be tested
* @param availableSpace
* available space in which text must fit
* @return an integer < 0 if after applying {@code suggestedSize} to
* text, it takes less space than {@code availableSpace}, > 0
* otherwise
*/
public int onTestSize(int suggestedSize, RectF availableSpace);
}
private RectF mTextRect = new RectF();
private RectF mAvailableSpaceRect;
private SparseIntArray mTextCachedSizes;
private TextPaint mPaint;
private float mMaxTextSize;
private float mSpacingMult = 1.0f;
private float mSpacingAdd = 0.0f;
private float mMinTextSize = 20;
private int mWidthLimit;
private static final int NO_LINE_LIMIT = -1;
private int mMaxLines;
private boolean mEnableSizeCache = true;
private boolean mInitiallized;
public AutoResizeTextView(Context context) {
super(context);
initialize();
}
public AutoResizeTextView(Context context, AttributeSet attrs) {
super(context, attrs);
initialize();
}
public AutoResizeTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initialize();
}
private void initialize() {
mPaint = new TextPaint(getPaint());
mMaxTextSize = getTextSize();
mAvailableSpaceRect = new RectF();
mTextCachedSizes = new SparseIntArray();
if (mMaxLines == 0) {
// no value was assigned during construction
mMaxLines = NO_LINE_LIMIT;
}
mInitiallized = true;
}
@Override
public void setText(final CharSequence text, BufferType type) {
super.setText(text, type);
adjustTextSize(text.toString());
}
@Override
public void setTextSize(float size) {
mMaxTextSize = size;
mTextCachedSizes.clear();
adjustTextSize(getText().toString());
}
@Override
public void setMaxLines(int maxlines) {
super.setMaxLines(maxlines);
mMaxLines = maxlines;
reAdjust();
}
public int getMaxLines() {
return mMaxLines;
}
@Override
public void setSingleLine() {
super.setSingleLine();
mMaxLines = 1;
reAdjust();
}
@Override
public void setSingleLine(boolean singleLine) {
super.setSingleLine(singleLine);
if (singleLine) {
mMaxLines = 1;
} else {
mMaxLines = NO_LINE_LIMIT;
}
reAdjust();
}
@Override
public void setLines(int lines) {
super.setLines(lines);
mMaxLines = lines;
reAdjust();
}
@Override
public void setTextSize(int unit, float size) {
Context c = getContext();
Resources r;
if (c == null)
r = Resources.getSystem();
else
r = c.getResources();
mMaxTextSize = TypedValue.applyDimension(unit, size,
r.getDisplayMetrics());
mTextCachedSizes.clear();
adjustTextSize(getText().toString());
}
@Override
public void setLineSpacing(float add, float mult) {
super.setLineSpacing(add, mult);
mSpacingMult = mult;
mSpacingAdd = add;
}
/**
* Set the lower text size limit and invalidate the view
*
* @param minTextSize
*/
public void setMinTextSize(float minTextSize) {
mMinTextSize = minTextSize;
reAdjust();
}
private void reAdjust() {
adjustTextSize(getText().toString());
}
private void adjustTextSize(String string) {
if (!mInitiallized) {
return;
}
int startSize = (int) mMinTextSize;
int heightLimit = getMeasuredHeight() - getCompoundPaddingBottom()
- getCompoundPaddingTop();
mWidthLimit = getMeasuredWidth() - getCompoundPaddingLeft()
- getCompoundPaddingRight();
mAvailableSpaceRect.right = mWidthLimit;
mAvailableSpaceRect.bottom = heightLimit;
super.setTextSize(
TypedValue.COMPLEX_UNIT_PX,
efficientTextSizeSearch(startSize, (int) mMaxTextSize,
mSizeTester, mAvailableSpaceRect));
}
private final SizeTester mSizeTester = new SizeTester() {
@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
public int onTestSize(int suggestedSize, RectF availableSPace) {
mPaint.setTextSize(suggestedSize);
String text = getText().toString();
boolean singleline = getMaxLines() == 1;
if (singleline) {
mTextRect.bottom = mPaint.getFontSpacing();
mTextRect.right = mPaint.measureText(text);
} else {
StaticLayout layout = new StaticLayout(text, mPaint,
mWidthLimit, Alignment.ALIGN_NORMAL, mSpacingMult,
mSpacingAdd, true);
// return early if we have more lines
if (getMaxLines() != NO_LINE_LIMIT
&& layout.getLineCount() > getMaxLines()) {
return 1;
}
mTextRect.bottom = layout.getHeight();
int maxWidth = -1;
for (int i = 0; i < layout.getLineCount(); i++) {
if (maxWidth < layout.getLineWidth(i)) {
maxWidth = (int) layout.getLineWidth(i);
}
}
mTextRect.right = maxWidth;
}
mTextRect.offsetTo(0, 0);
if (availableSPace.contains(mTextRect)) {
// may be too small, don't worry we will find the best match
return -1;
} else {
// too big
return 1;
}
}
};
/**
* Enables or disables size caching, enabling it will improve performance
* where you are animating a value inside TextView. This stores the font
* size against getText().length() Be careful though while enabling it as 0
* takes more space than 1 on some fonts and so on.
*
* @param enable
* enable font size caching
*/
public void enableSizeCache(boolean enable) {
mEnableSizeCache = enable;
mTextCachedSizes.clear();
adjustTextSize(getText().toString());
}
private int efficientTextSizeSearch(int start, int end,
SizeTester sizeTester, RectF availableSpace) {
if (!mEnableSizeCache) {
return binarySearch(start, end, sizeTester, availableSpace);
}
String text = getText().toString();
int key = text == null ? 0 : text.length();
int size = mTextCachedSizes.get(key);
if (size != 0) {
return size;
}
size = binarySearch(start, end, sizeTester, availableSpace);
mTextCachedSizes.put(key, size);
return size;
}
private static int binarySearch(int start, int end, SizeTester sizeTester,
RectF availableSpace) {
int lastBest = start;
int lo = start;
int hi = end - 1;
int mid = 0;
while (lo <= hi) {
mid = (lo + hi) >>> 1;
int midValCmp = sizeTester.onTestSize(mid, availableSpace);
if (midValCmp < 0) {
lastBest = lo;
lo = mid + 1;
} else if (midValCmp > 0) {
hi = mid - 1;
lastBest = hi;
} else {
return mid;
}
}
// make sure to return last best
// this is what should always be returned
return lastBest;
}
@Override
protected void onTextChanged(final CharSequence text, final int start,
final int before, final int after) {
super.onTextChanged(text, start, before, after);
reAdjust();
}
@Override
protected void onSizeChanged(int width, int height, int oldwidth,
int oldheight) {
mTextCachedSizes.clear();
super.onSizeChanged(width, height, oldwidth, oldheight);
if (width != oldwidth || height != oldheight) {
reAdjust();
}
}
}
其他回答
更新:下面的代码也满足了一个理想的AutoScaleTextView的要求，如这里所述:自动适合Android的TextView，并被标记为赢家。
更新2:增加了对maxlines的支持，现在在API级别16之前工作正常。
更新3:支持android: drawablleft, android:drawableRight, android:drawableTop和android:drawableBottom标签添加，感谢MartinH在这里的简单修复。
我的要求有点不同。我需要一种有效的方法来调整大小，因为我是动画一个整数从，可能是0 ~4000在TextView在2秒内，我想相应地调整大小。我的解决方法有点不同。这是最终的结果:
以及产生它的代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp" >
<com.vj.widgets.AutoResizeTextView
android:layout_width="match_parent"
android:layout_height="100dp"
android:ellipsize="none"
android:maxLines="2"
android:text="Auto Resized Text, max 2 lines"
android:textSize="100sp" /> <!-- maximum size -->
<com.vj.widgets.AutoResizeTextView
android:layout_width="match_parent"
android:layout_height="100dp"
android:ellipsize="none"
android:gravity="center"
android:maxLines="1"
android:text="Auto Resized Text, max 1 line"
android:textSize="100sp" /> <!-- maximum size -->
<com.vj.widgets.AutoResizeTextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Auto Resized Text"
android:textSize="500sp" /> <!-- maximum size -->
</LinearLayout>
最后是java代码:
import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.RectF;
import android.os.Build;
import android.text.Layout.Alignment;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.SparseIntArray;
import android.util.TypedValue;
import android.widget.TextView;
public class AutoResizeTextView extends TextView {
private interface SizeTester {
/**
*
* @param suggestedSize
* Size of text to be tested
* @param availableSpace
* available space in which text must fit
* @return an integer < 0 if after applying {@code suggestedSize} to
* text, it takes less space than {@code availableSpace}, > 0
* otherwise
*/
public int onTestSize(int suggestedSize, RectF availableSpace);
}
private RectF mTextRect = new RectF();
private RectF mAvailableSpaceRect;
private SparseIntArray mTextCachedSizes;
private TextPaint mPaint;
private float mMaxTextSize;
private float mSpacingMult = 1.0f;
private float mSpacingAdd = 0.0f;
private float mMinTextSize = 20;
private int mWidthLimit;
private static final int NO_LINE_LIMIT = -1;
private int mMaxLines;
private boolean mEnableSizeCache = true;
private boolean mInitiallized;
public AutoResizeTextView(Context context) {
super(context);
initialize();
}
public AutoResizeTextView(Context context, AttributeSet attrs) {
super(context, attrs);
initialize();
}
public AutoResizeTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initialize();
}
private void initialize() {
mPaint = new TextPaint(getPaint());
mMaxTextSize = getTextSize();
mAvailableSpaceRect = new RectF();
mTextCachedSizes = new SparseIntArray();
if (mMaxLines == 0) {
// no value was assigned during construction
mMaxLines = NO_LINE_LIMIT;
}
mInitiallized = true;
}
@Override
public void setText(final CharSequence text, BufferType type) {
super.setText(text, type);
adjustTextSize(text.toString());
}
@Override
public void setTextSize(float size) {
mMaxTextSize = size;
mTextCachedSizes.clear();
adjustTextSize(getText().toString());
}
@Override
public void setMaxLines(int maxlines) {
super.setMaxLines(maxlines);
mMaxLines = maxlines;
reAdjust();
}
public int getMaxLines() {
return mMaxLines;
}
@Override
public void setSingleLine() {
super.setSingleLine();
mMaxLines = 1;
reAdjust();
}
@Override
public void setSingleLine(boolean singleLine) {
super.setSingleLine(singleLine);
if (singleLine) {
mMaxLines = 1;
} else {
mMaxLines = NO_LINE_LIMIT;
}
reAdjust();
}
@Override
public void setLines(int lines) {
super.setLines(lines);
mMaxLines = lines;
reAdjust();
}
@Override
public void setTextSize(int unit, float size) {
Context c = getContext();
Resources r;
if (c == null)
r = Resources.getSystem();
else
r = c.getResources();
mMaxTextSize = TypedValue.applyDimension(unit, size,
r.getDisplayMetrics());
mTextCachedSizes.clear();
adjustTextSize(getText().toString());
}
@Override
public void setLineSpacing(float add, float mult) {
super.setLineSpacing(add, mult);
mSpacingMult = mult;
mSpacingAdd = add;
}
/**
* Set the lower text size limit and invalidate the view
*
* @param minTextSize
*/
public void setMinTextSize(float minTextSize) {
mMinTextSize = minTextSize;
reAdjust();
}
private void reAdjust() {
adjustTextSize(getText().toString());
}
private void adjustTextSize(String string) {
if (!mInitiallized) {
return;
}
int startSize = (int) mMinTextSize;
int heightLimit = getMeasuredHeight() - getCompoundPaddingBottom()
- getCompoundPaddingTop();
mWidthLimit = getMeasuredWidth() - getCompoundPaddingLeft()
- getCompoundPaddingRight();
mAvailableSpaceRect.right = mWidthLimit;
mAvailableSpaceRect.bottom = heightLimit;
super.setTextSize(
TypedValue.COMPLEX_UNIT_PX,
efficientTextSizeSearch(startSize, (int) mMaxTextSize,
mSizeTester, mAvailableSpaceRect));
}
private final SizeTester mSizeTester = new SizeTester() {
@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
public int onTestSize(int suggestedSize, RectF availableSPace) {
mPaint.setTextSize(suggestedSize);
String text = getText().toString();
boolean singleline = getMaxLines() == 1;
if (singleline) {
mTextRect.bottom = mPaint.getFontSpacing();
mTextRect.right = mPaint.measureText(text);
} else {
StaticLayout layout = new StaticLayout(text, mPaint,
mWidthLimit, Alignment.ALIGN_NORMAL, mSpacingMult,
mSpacingAdd, true);
// return early if we have more lines
if (getMaxLines() != NO_LINE_LIMIT
&& layout.getLineCount() > getMaxLines()) {
return 1;
}
mTextRect.bottom = layout.getHeight();
int maxWidth = -1;
for (int i = 0; i < layout.getLineCount(); i++) {
if (maxWidth < layout.getLineWidth(i)) {
maxWidth = (int) layout.getLineWidth(i);
}
}
mTextRect.right = maxWidth;
}
mTextRect.offsetTo(0, 0);
if (availableSPace.contains(mTextRect)) {
// may be too small, don't worry we will find the best match
return -1;
} else {
// too big
return 1;
}
}
};
/**
* Enables or disables size caching, enabling it will improve performance
* where you are animating a value inside TextView. This stores the font
* size against getText().length() Be careful though while enabling it as 0
* takes more space than 1 on some fonts and so on.
*
* @param enable
* enable font size caching
*/
public void enableSizeCache(boolean enable) {
mEnableSizeCache = enable;
mTextCachedSizes.clear();
adjustTextSize(getText().toString());
}
private int efficientTextSizeSearch(int start, int end,
SizeTester sizeTester, RectF availableSpace) {
if (!mEnableSizeCache) {
return binarySearch(start, end, sizeTester, availableSpace);
}
String text = getText().toString();
int key = text == null ? 0 : text.length();
int size = mTextCachedSizes.get(key);
if (size != 0) {
return size;
}
size = binarySearch(start, end, sizeTester, availableSpace);
mTextCachedSizes.put(key, size);
return size;
}
private static int binarySearch(int start, int end, SizeTester sizeTester,
RectF availableSpace) {
int lastBest = start;
int lo = start;
int hi = end - 1;
int mid = 0;
while (lo <= hi) {
mid = (lo + hi) >>> 1;
int midValCmp = sizeTester.onTestSize(mid, availableSpace);
if (midValCmp < 0) {
lastBest = lo;
lo = mid + 1;
} else if (midValCmp > 0) {
hi = mid - 1;
lastBest = hi;
} else {
return mid;
}
}
// make sure to return last best
// this is what should always be returned
return lastBest;
}
@Override
protected void onTextChanged(final CharSequence text, final int start,
final int before, final int after) {
super.onTextChanged(text, start, before, after);
reAdjust();
}
@Override
protected void onSizeChanged(int width, int height, int oldwidth,
int oldheight) {
mTextCachedSizes.clear();
super.onSizeChanged(width, height, oldwidth, oldheight);
if (width != oldwidth || height != oldheight) {
reAdjust();
}
}
}
我从Chase的AutoResizeTextView类开始，并做了一个微小的更改，以便它可以垂直和水平地适应。
我还发现了一个bug，在一些相当模糊的条件下，在布局编辑器(在Eclipse中)中导致空指针异常。
更改1:垂直和水平对齐文本
Chase的原始版本减小了文本大小，直到垂直对齐，但允许文本比目标更宽。在我的例子中，我需要文本符合指定的宽度。
这一更改使它调整大小，直到文本垂直和水平都适合。
在resizeText(int,int)中更改为:
// Get the required text height
int textHeight = getTextHeight(text, textPaint, width, targetTextSize);
// Until we either fit within our text view or we had reached our min text size, incrementally try smaller sizes
while(textHeight > height && targetTextSize > mMinTextSize) {
targetTextSize = Math.max(targetTextSize - 2, mMinTextSize);
textHeight = getTextHeight(text, textPaint, width, targetTextSize);
}
to:
// Get the required text height
int textHeight = getTextHeight(text, textPaint, width, targetTextSize);
int textWidth = getTextWidth(text, textPaint, width, targetTextSize);
// Until we either fit within our text view or we had reached our min text size, incrementally try smaller sizes
while(((textHeight >= height) || (textWidth >= width) ) && targetTextSize > mMinTextSize) {
targetTextSize = Math.max(targetTextSize - 2, mMinTextSize);
textHeight = getTextHeight(text, textPaint, width, targetTextSize);
textWidth = getTextWidth(text, textPaint, width, targetTextSize);
}
然后，在文件的末尾追加getTextWidth()例程;它只是稍微修改了一下getTextHeight()。将它们组合成一个返回高度和宽度的例程可能会更有效。
// Set the text size of the text paint object and use a static layout to render text off screen before measuring
private int getTextWidth(CharSequence source, TextPaint paint, int width, float textSize) {
// Update the text paint object
paint.setTextSize(textSize);
// Draw using a static layout
StaticLayout layout = new StaticLayout(source, paint, width, Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, true);
layout.draw(sTextResizeCanvas);
return layout.getWidth();
}
变更2:修复Eclipse Android布局编辑器中的EmptyStackException
在相当模糊和非常精确的条件下，布局编辑器将无法显示布局的图形显示;它会在com.android.ide.eclipse.adt中抛出一个"EmptyStackException: null"异常。
所需的条件是: -创建一个AutoResizeTextView小部件 -为那个小部件创建一个样式 -指定样式中的文本项;不在小部件定义中
如:
res / layout / main。xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<com.ajw.DemoCrashInADT.AutoResizeTextView
android:id="@+id/resizingText"
style="@style/myTextStyle" />
</LinearLayout>
res /价值/ myStyles.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="myTextStyle" parent="@android:style/Widget.TextView">
<item name="android:layout_height">wrap_content</item>
<item name="android:layout_width">fill_parent</item>
<item name="android:text">some message</item>
</style>
</resources>
使用这些文件，在编辑main.xml时选择图形布局选项卡将显示:
错误! EmptyStackException:零 “> Show View > Error Log”记录异常详细信息
而不是布局的图形视图。
为了让已经太长的故事变得更短，我追踪到以下几行(同样是在resizeText中):
// If there is a max text size set, use the lesser of that and the default text size
float targetTextSize = mMaxTextSize > 0 ? Math.min(mTextSize, mMaxTextSize) : mTextSize;
问题是，在特定的条件下，mTextSize从未初始化;它的值是0。
通过上述操作，targetTextSize被设置为零(这是Math.min的结果)。
这个零被传递给getTextHeight()(和getTextWidth())作为textSize参数。当它到达 layout.draw (sTextResizeCanvas); 我们得到了异常。
在resizeText()的开始测试if (mTextSize == 0)比在getTextHeight()和getTextWidth()测试更有效;更早地测试可以节省所有的中间工作。
通过这些更新，文件(就像在我的崩溃演示测试应用程序中一样)现在是:
//
// from: http://stackoverflow.com/questions/5033012/auto-scale-textview-text-to-fit-within-bounds
//
//
package com.ajw.DemoCrashInADT;
import android.content.Context;
import android.graphics.Canvas;
import android.text.Layout.Alignment;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.widget.TextView;
/**
* Text view that auto adjusts text size to fit within the view. If the text
* size equals the minimum text size and still does not fit, append with an
* ellipsis.
*
* 2011-10-29 changes by Alan Jay Weiner
* * change to fit both vertically and horizontally
* * test mTextSize for 0 in resizeText() to fix exception in Layout Editor
*
* @author Chase Colburn
* @since Apr 4, 2011
*/
public class AutoResizeTextView extends TextView {
// Minimum text size for this text view
public static final float MIN_TEXT_SIZE = 20;
// Interface for resize notifications
public interface OnTextResizeListener {
public void onTextResize(TextView textView, float oldSize, float newSize);
}
// Off screen canvas for text size rendering
private static final Canvas sTextResizeCanvas = new Canvas();
// Our ellipse string
private static final String mEllipsis = "...";
// Registered resize listener
private OnTextResizeListener mTextResizeListener;
// Flag for text and/or size changes to force a resize
private boolean mNeedsResize = false;
// Text size that is set from code. This acts as a starting point for
// resizing
private float mTextSize;
// Temporary upper bounds on the starting text size
private float mMaxTextSize = 0;
// Lower bounds for text size
private float mMinTextSize = MIN_TEXT_SIZE;
// Text view line spacing multiplier
private float mSpacingMult = 1.0f;
// Text view additional line spacing
private float mSpacingAdd = 0.0f;
// Add ellipsis to text that overflows at the smallest text size
private boolean mAddEllipsis = true;
// Default constructor override
public AutoResizeTextView(Context context) {
this(context, null);
}
// Default constructor when inflating from XML file
public AutoResizeTextView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
// Default constructor override
public AutoResizeTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mTextSize = getTextSize();
}
/**
* When text changes, set the force resize flag to true and reset the text
* size.
*/
@Override
protected void onTextChanged(final CharSequence text, final int start,
final int before, final int after) {
mNeedsResize = true;
// Since this view may be reused, it is good to reset the text size
resetTextSize();
}
/**
* If the text view size changed, set the force resize flag to true
*/
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
if (w != oldw || h != oldh) {
mNeedsResize = true;
}
}
/**
* Register listener to receive resize notifications
*
* @param listener
*/
public void setOnResizeListener(OnTextResizeListener listener) {
mTextResizeListener = listener;
}
/**
* Override the set text size to update our internal reference values
*/
@Override
public void setTextSize(float size) {
super.setTextSize(size);
mTextSize = getTextSize();
}
/**
* Override the set text size to update our internal reference values
*/
@Override
public void setTextSize(int unit, float size) {
super.setTextSize(unit, size);
mTextSize = getTextSize();
}
/**
* Override the set line spacing to update our internal reference values
*/
@Override
public void setLineSpacing(float add, float mult) {
super.setLineSpacing(add, mult);
mSpacingMult = mult;
mSpacingAdd = add;
}
/**
* Set the upper text size limit and invalidate the view
*
* @param maxTextSize
*/
public void setMaxTextSize(float maxTextSize) {
mMaxTextSize = maxTextSize;
requestLayout();
invalidate();
}
/**
* Return upper text size limit
*
* @return
*/
public float getMaxTextSize() {
return mMaxTextSize;
}
/**
* Set the lower text size limit and invalidate the view
*
* @param minTextSize
*/
public void setMinTextSize(float minTextSize) {
mMinTextSize = minTextSize;
requestLayout();
invalidate();
}
/**
* Return lower text size limit
*
* @return
*/
public float getMinTextSize() {
return mMinTextSize;
}
/**
* Set flag to add ellipsis to text that overflows at the smallest text size
*
* @param addEllipsis
*/
public void setAddEllipsis(boolean addEllipsis) {
mAddEllipsis = addEllipsis;
}
/**
* Return flag to add ellipsis to text that overflows at the smallest text
* size
*
* @return
*/
public boolean getAddEllipsis() {
return mAddEllipsis;
}
/**
* Reset the text to the original size
*/
public void resetTextSize() {
super.setTextSize(TypedValue.COMPLEX_UNIT_PX, mTextSize);
mMaxTextSize = mTextSize;
}
/**
* Resize text after measuring
*/
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
if (changed || mNeedsResize) {
int widthLimit = (right - left) - getCompoundPaddingLeft()
- getCompoundPaddingRight();
int heightLimit = (bottom - top) - getCompoundPaddingBottom()
- getCompoundPaddingTop();
resizeText(widthLimit, heightLimit);
}
super.onLayout(changed, left, top, right, bottom);
}
/**
* Resize the text size with default width and height
*/
public void resizeText() {
int heightLimit = getHeight() - getPaddingBottom() - getPaddingTop();
int widthLimit = getWidth() - getPaddingLeft() - getPaddingRight();
resizeText(widthLimit, heightLimit);
}
/**
* Resize the text size with specified width and height
*
* @param width
* @param height
*/
public void resizeText(int width, int height) {
CharSequence text = getText();
// Do not resize if the view does not have dimensions or there is no
// text
// or if mTextSize has not been initialized
if (text == null || text.length() == 0 || height <= 0 || width <= 0
|| mTextSize == 0) {
return;
}
// Get the text view's paint object
TextPaint textPaint = getPaint();
// Store the current text size
float oldTextSize = textPaint.getTextSize();
// If there is a max text size set, use the lesser of that and the
// default text size
float targetTextSize = mMaxTextSize > 0 ? Math.min(mTextSize, mMaxTextSize)
: mTextSize;
// Get the required text height
int textHeight = getTextHeight(text, textPaint, width, targetTextSize);
int textWidth = getTextWidth(text, textPaint, width, targetTextSize);
// Until we either fit within our text view or we had reached our min
// text size, incrementally try smaller sizes
while (((textHeight > height) || (textWidth > width))
&& targetTextSize > mMinTextSize) {
targetTextSize = Math.max(targetTextSize - 2, mMinTextSize);
textHeight = getTextHeight(text, textPaint, width, targetTextSize);
textWidth = getTextWidth(text, textPaint, width, targetTextSize);
}
// If we had reached our minimum text size and still don't fit, append
// an ellipsis
if (mAddEllipsis && targetTextSize == mMinTextSize && textHeight > height) {
// Draw using a static layout
StaticLayout layout = new StaticLayout(text, textPaint, width,
Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, false);
layout.draw(sTextResizeCanvas);
int lastLine = layout.getLineForVertical(height) - 1;
int start = layout.getLineStart(lastLine);
int end = layout.getLineEnd(lastLine);
float lineWidth = layout.getLineWidth(lastLine);
float ellipseWidth = textPaint.measureText(mEllipsis);
// Trim characters off until we have enough room to draw the
// ellipsis
while (width < lineWidth + ellipseWidth) {
lineWidth = textPaint.measureText(text.subSequence(start, --end + 1)
.toString());
}
setText(text.subSequence(0, end) + mEllipsis);
}
// Some devices try to auto adjust line spacing, so force default line
// spacing
// and invalidate the layout as a side effect
textPaint.setTextSize(targetTextSize);
setLineSpacing(mSpacingAdd, mSpacingMult);
// Notify the listener if registered
if (mTextResizeListener != null) {
mTextResizeListener.onTextResize(this, oldTextSize, targetTextSize);
}
// Reset force resize flag
mNeedsResize = false;
}
// Set the text size of the text paint object and use a static layout to
// render text off screen before measuring
private int getTextHeight(CharSequence source, TextPaint paint, int width,
float textSize) {
// Update the text paint object
paint.setTextSize(textSize);
// Draw using a static layout
StaticLayout layout = new StaticLayout(source, paint, width,
Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, true);
layout.draw(sTextResizeCanvas);
return layout.getHeight();
}
// Set the text size of the text paint object and use a static layout to
// render text off screen before measuring
private int getTextWidth(CharSequence source, TextPaint paint, int width,
float textSize) {
// Update the text paint object
paint.setTextSize(textSize);
// Draw using a static layout
StaticLayout layout = new StaticLayout(source, paint, width,
Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, true);
layout.draw(sTextResizeCanvas);
return layout.getWidth();
}
}
非常感谢Chase发布了初始代码。我很喜欢通读它，看看它是如何工作的，我很高兴能够添加它。
我结合了上面的一些建议，用二分法制作了一个上下伸缩的图。它还在宽度范围内缩放。
/**
* DO WHAT YOU WANT TO PUBLIC LICENSE
* Version 2, December 2004
*
* Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>
*
* Everyone is permitted to copy and distribute verbatim or modified
* copies of this license document, and changing it is allowed as long
* as the name is changed.
*
* DO WHAT YOU WANT TO PUBLIC LICENSE
* TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
*
* 0. You just DO WHAT YOU WANT TO.
*/
import android.content.Context;
import android.text.Layout.Alignment;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.widget.TextView;
/**
* Text view that auto adjusts text size to fit within the view. If the text
* size equals the minimum text size and still does not fit, append with an
* ellipsis.
*
* @author Chase Colburn
* @since Apr 4, 2011
*/
public class AutoResizeTextView extends TextView {
// Minimum text size for this text view
public static final float MIN_TEXT_SIZE = 10;
// Minimum text size for this text view
public static final float MAX_TEXT_SIZE = 128;
private static final int BISECTION_LOOP_WATCH_DOG = 30;
// Interface for resize notifications
public interface OnTextResizeListener {
public void onTextResize(TextView textView, float oldSize, float newSize);
}
// Our ellipse string
private static final String mEllipsis = "...";
// Registered resize listener
private OnTextResizeListener mTextResizeListener;
// Flag for text and/or size changes to force a resize
private boolean mNeedsResize = false;
// Text size that is set from code. This acts as a starting point for
// resizing
private float mTextSize;
// Temporary upper bounds on the starting text size
private float mMaxTextSize = MAX_TEXT_SIZE;
// Lower bounds for text size
private float mMinTextSize = MIN_TEXT_SIZE;
// Text view line spacing multiplier
private float mSpacingMult = 1.0f;
// Text view additional line spacing
private float mSpacingAdd = 0.0f;
// Add ellipsis to text that overflows at the smallest text size
private boolean mAddEllipsis = true;
// Default constructor override
public AutoResizeTextView(Context context) {
this(context, null);
}
// Default constructor when inflating from XML file
public AutoResizeTextView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
// Default constructor override
public AutoResizeTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mTextSize = getTextSize();
}
/**
* When text changes, set the force resize flag to true and reset the text
* size.
*/
@Override
protected void onTextChanged(final CharSequence text, final int start,
final int before, final int after) {
mNeedsResize = true;
// Since this view may be reused, it is good to reset the text size
resetTextSize();
}
/**
* If the text view size changed, set the force resize flag to true
*/
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
if (w != oldw || h != oldh) {
mNeedsResize = true;
}
}
/**
* Register listener to receive resize notifications
*
* @param listener
*/
public void setOnResizeListener(OnTextResizeListener listener) {
mTextResizeListener = listener;
}
/**
* Override the set text size to update our internal reference values
*/
@Override
public void setTextSize(float size) {
super.setTextSize(size);
mTextSize = getTextSize();
}
/**
* Override the set text size to update our internal reference values
*/
@Override
public void setTextSize(int unit, float size) {
super.setTextSize(unit, size);
mTextSize = getTextSize();
}
/**
* Override the set line spacing to update our internal reference values
*/
@Override
public void setLineSpacing(float add, float mult) {
super.setLineSpacing(add, mult);
mSpacingMult = mult;
mSpacingAdd = add;
}
/**
* Set the upper text size limit and invalidate the view
*
* @param maxTextSize
*/
public void setMaxTextSize(float maxTextSize) {
mMaxTextSize = maxTextSize;
requestLayout();
invalidate();
}
/**
* Return upper text size limit
*
* @return
*/
public float getMaxTextSize() {
return mMaxTextSize;
}
/**
* Set the lower text size limit and invalidate the view
*
* @param minTextSize
*/
public void setMinTextSize(float minTextSize) {
mMinTextSize = minTextSize;
requestLayout();
invalidate();
}
/**
* Return lower text size limit
*
* @return
*/
public float getMinTextSize() {
return mMinTextSize;
}
/**
* Set flag to add ellipsis to text that overflows at the smallest text size
*
* @param addEllipsis
*/
public void setAddEllipsis(boolean addEllipsis) {
mAddEllipsis = addEllipsis;
}
/**
* Return flag to add ellipsis to text that overflows at the smallest text
* size
*
* @return
*/
public boolean getAddEllipsis() {
return mAddEllipsis;
}
/**
* Reset the text to the original size
*/
public void resetTextSize() {
if (mTextSize > 0) {
super.setTextSize(TypedValue.COMPLEX_UNIT_PX, mTextSize);
// mMaxTextSize = mTextSize;
}
}
/**
* Resize text after measuring
*/
@Override
protected void onLayout(boolean changed, int left, int top, int right,
int bottom) {
if (changed || mNeedsResize) {
int widthLimit = (right - left) - getCompoundPaddingLeft()
- getCompoundPaddingRight();
int heightLimit = (bottom - top) - getCompoundPaddingBottom()
- getCompoundPaddingTop();
resizeText(widthLimit, heightLimit);
}
super.onLayout(changed, left, top, right, bottom);
}
/**
* Resize the text size with default width and height
*/
public void resizeText() {
// Height and width with a padding as a percentage of height
int heightLimit = getHeight() - getPaddingBottom() - getPaddingTop();
int widthLimit = getWidth() - getPaddingLeft() - getPaddingRight();
resizeText(widthLimit, heightLimit);
}
/**
* Resize the text size with specified width and height
*
* @param width
* @param height
*/
public void resizeText(int width, int height) {
CharSequence text = getText();
// Do not resize if the view does not have dimensions or there is no
// text
if (text == null || text.length() == 0 || height <= 0 || width <= 0
|| mTextSize == 0) {
return;
}
// Get the text view's paint object
TextPaint textPaint = getPaint();
// Store the current text size
float oldTextSize = textPaint.getTextSize();
// Bisection method: fast & precise
float lower = mMinTextSize;
float upper = mMaxTextSize;
int loop_counter = 1;
float targetTextSize = (lower + upper) / 2;
int textHeight = getTextHeight(text, textPaint, width, targetTextSize);
int textWidth = getTextWidth(text, textPaint, width, targetTextSize);
while (loop_counter < BISECTION_LOOP_WATCH_DOG && upper - lower > 1) {
targetTextSize = (lower + upper) / 2;
textHeight = getTextHeight(text, textPaint, width, targetTextSize);
textWidth = getTextWidth(text, textPaint, width, targetTextSize);
if (textHeight > (height) || textWidth > (width))
upper = targetTextSize;
else
lower = targetTextSize;
loop_counter++;
}
targetTextSize = lower;
textHeight = getTextHeight(text, textPaint, width, targetTextSize);
// If we had reached our minimum text size and still don't fit, append
// an ellipsis
if (mAddEllipsis && targetTextSize == mMinTextSize
&& textHeight > height) {
// Draw using a static layout
// modified: use a copy of TextPaint for measuring
TextPaint paintCopy = new TextPaint(textPaint);
paintCopy.setTextSize(targetTextSize);
StaticLayout layout = new StaticLayout(text, paintCopy, width,
Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, false);
// Check that we have a least one line of rendered text
if (layout.getLineCount() > 0) {
// Since the line at the specific vertical position would be cut
// off,
// we must trim up to the previous line
int lastLine = layout.getLineForVertical(height) - 1;
// If the text would not even fit on a single line, clear it
if (lastLine < 0) {
setText("");
}
// Otherwise, trim to the previous line and add an ellipsis
else {
int start = layout.getLineStart(lastLine);
int end = layout.getLineEnd(lastLine);
float lineWidth = layout.getLineWidth(lastLine);
float ellipseWidth = paintCopy.measureText(mEllipsis);
// Trim characters off until we have enough room to draw the
// ellipsis
while (width < lineWidth + ellipseWidth) {
lineWidth = paintCopy.measureText(text.subSequence(
start, --end + 1).toString());
}
setText(text.subSequence(0, end) + mEllipsis);
}
}
}
// Some devices try to auto adjust line spacing, so force default line
// spacing
// and invalidate the layout as a side effect
setTextSize(TypedValue.COMPLEX_UNIT_PX, targetTextSize);
setLineSpacing(mSpacingAdd, mSpacingMult);
// Notify the listener if registered
if (mTextResizeListener != null) {
mTextResizeListener.onTextResize(this, oldTextSize, targetTextSize);
}
// Reset force resize flag
mNeedsResize = false;
}
// Set the text size of the text paint object and use a static layout to
// render text off screen before measuring
private int getTextHeight(CharSequence source, TextPaint originalPaint,
int width, float textSize) {
// modified: make a copy of the original TextPaint object for measuring
// (apparently the object gets modified while measuring, see also the
// docs for TextView.getPaint() (which states to access it read-only)
TextPaint paint = new TextPaint(originalPaint);
// Update the text paint object
paint.setTextSize(textSize);
// Measure using a static layout
StaticLayout layout = new StaticLayout(source, paint, width,
Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, true);
return layout.getHeight();
}
// Set the text size of the text paint object and use a static layout to
// render text off screen before measuring
private int getTextWidth(CharSequence source, TextPaint originalPaint,
int width, float textSize) {
// Update the text paint object
TextPaint paint = new TextPaint(originalPaint);
// Draw using a static layout
paint.setTextSize(textSize);
StaticLayout layout = new StaticLayout(source, paint, width,
Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, true);
return (int) layout.getLineWidth(0);
}
}
为那些在Xamarin.Android上编码的人提供了这个用c#重写的顶级答案版本。对我来说很管用。
/**
* DO WHAT YOU WANT TO PUBLIC LICENSE
* Version 2, December 2004
*
* Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>
*
* Everyone is permitted to copy and distribute verbatim or modified
* copies of this license document, and changing it is allowed as long
* as the name is changed.
*
* DO WHAT YOU WANT TO PUBLIC LICENSE
* TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
*
* 0. You just DO WHAT YOU WANT TO.
*/
using System;
using Android.Content;
using Android.Runtime;
using Android.Text;
using Android.Util;
using Android.Widget;
using Java.Lang;
namespace App.GuestGuide.Droid.Controls
{
public class OnTextResizeEventArgs : EventArgs
{
public TextView TextView { get; set; }
public float OldSize { get; set; }
public float NewSize { get; set; }
}
/// <inheritdoc />
/// <summary>
/// Text view that auto adjusts text size to fit within the view.
/// If the text size equals the minimum text size and still does not
/// fit, append with an ellipsis.
/// </summary>
public class AutoResizeTextView : TextView
{
/// <summary>
/// Minimum text size for this text view
/// </summary>
public static float MIN_TEXT_SIZE = 10;
/// <summary>
/// Our ellipse string
/// </summary>
private const string Ellipsis = "...";
private float _mMaxTextSize;
private float _mMinTextSize = MIN_TEXT_SIZE;
/// <summary>
/// Register subscriber to receive resize notifications
/// </summary>
public event EventHandler<OnTextResizeEventArgs> OnTextResize;
/// <summary>
/// Flag for text and/or size changes to force a resize
/// </summary>
private bool _needsResize;
/// <summary>
/// Text size that is set from code. This acts as a starting point for resizing
/// </summary>
private float _textSize;
/// <summary>
/// Text view line spacing multiplier
/// </summary>
private float _spacingMult = 1.0f;
/// <summary>
/// Text view additional line spacing
/// </summary>
private float _spacingAdd;
/// <summary>
/// Add ellipsis to text that overflows at the smallest text size
/// </summary>
public bool ShouldAddEllipsis { get; set; }
/// <inheritdoc />
/// <summary>
/// Override the set text size to update our internal reference values
/// </summary>
public override float TextSize
{
get => base.TextSize;
set
{
base.TextSize = value;
_textSize = TextSize;
}
}
/// <summary>
/// Temporary upper bounds on the starting text size
/// </summary>
public float MaxTextSize
{
get => _mMaxTextSize;
// Set the upper text size limit and invalidate the view
set
{
_mMaxTextSize = value;
RequestLayout();
Invalidate();
}
}
/// <summary>
/// Lower bounds for text size
/// </summary>
public float MinTextSize
{
get => _mMinTextSize;
//Set the lower text size limit and invalidate the view
set
{
_mMinTextSize = value;
RequestLayout();
Invalidate();
}
}
public AutoResizeTextView(Context context) : this(context, null)
{
}
public AutoResizeTextView(Context context, IAttributeSet attrs) : this(context, attrs, 0)
{
}
public AutoResizeTextView(Context context, IAttributeSet attrs, int defStyleAttr) : base(context, attrs, defStyleAttr)
{
_textSize = TextSize;
}
public AutoResizeTextView(Context context, IAttributeSet attrs, int defStyleAttr, int defStyleRes) : base(context, attrs, defStyleAttr, defStyleRes)
{
_textSize = TextSize;
}
protected AutoResizeTextView(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
{
_textSize = TextSize;
}
/// <inheritdoc />
/// <summary>
/// When text changes, set the force resize flag to true and reset the text size.
/// </summary>
/// <param name="text"></param>
/// <param name="start"></param>
/// <param name="lengthBefore"></param>
/// <param name="lengthAfter"></param>
protected override void OnTextChanged(ICharSequence text, int start, int lengthBefore, int lengthAfter)
{
_needsResize = true;
// Since this view may be reused, it is good to reset the text size
ResetTextSize();
}
/// <inheritdoc />
/// <summary>
/// If the text view size changed, set the force resize flag to true
/// </summary>
/// <param name="w"></param>
/// <param name="h"></param>
/// <param name="oldw"></param>
/// <param name="oldh"></param>
protected override void OnSizeChanged(int w, int h, int oldw, int oldh)
{
if (w != oldw || h != oldh)
{
_needsResize = true;
}
}
public override void SetTextSize([GeneratedEnum] ComplexUnitType unit, float size)
{
base.SetTextSize(unit, size);
_textSize = TextSize;
}
/// <inheritdoc />
/// <summary>
/// Override the set line spacing to update our internal reference values
/// </summary>
/// <param name="add"></param>
/// <param name="mult"></param>
public override void SetLineSpacing(float add, float mult)
{
base.SetLineSpacing(add, mult);
_spacingMult = mult;
_spacingAdd = add;
}
/// <summary>
/// Reset the text to the original size
/// </summary>
public void ResetTextSize()
{
if (_textSize > 0)
{
base.SetTextSize(ComplexUnitType.Px, _textSize);
_mMaxTextSize = _textSize;
}
}
/// <inheritdoc />
/// <summary>
/// Resize text after measuring
/// </summary>
/// <param name="changed"></param>
/// <param name="left"></param>
/// <param name="top"></param>
/// <param name="right"></param>
/// <param name="bottom"></param>
protected override void OnLayout(bool changed, int left, int top, int right, int bottom)
{
if (changed || _needsResize)
{
var widthLimit = (right - left) - CompoundPaddingLeft - CompoundPaddingRight;
var heightLimit = (bottom - top) - CompoundPaddingBottom - CompoundPaddingTop;
ResizeText(widthLimit, heightLimit);
}
base.OnLayout(changed, left, top, right, bottom);
}
/// <summary>
/// Resize the text size with default width and height
/// </summary>
public void ResizeText()
{
var heightLimit = Height - PaddingBottom - PaddingTop;
var widthLimit = Width - PaddingLeft - PaddingRight;
ResizeText(widthLimit, heightLimit);
}
/// <summary>
/// Resize the text size with specified width and height
/// </summary>
/// <param name="width"></param>
/// <param name="height"></param>
public void ResizeText(int width, int height)
{
ICharSequence text = null;
if (!string.IsNullOrEmpty(Text))
{
text = new Java.Lang.String(Text);
}
// Do not resize if the view does not have dimensions or there is no text
if (text == null || text.Length() == 0 || height <= 0 || width <= 0 || _textSize == 0)
{
return;
}
if (TransformationMethod != null)
{
text = TransformationMethod.GetTransformationFormatted(text, this);
}
// Get the text view's paint object
var textPaint = Paint;
// Store the current text size
var oldTextSize = textPaint.TextSize;
// If there is a max text size set, use the lesser of that and the default text size
var targetTextSize = _mMaxTextSize > 0 ? System.Math.Min(_textSize, _mMaxTextSize) : _textSize;
// Get the required text height
var textHeight = GetTextHeight(text, textPaint, width, targetTextSize);
// Until we either fit within our text view or we had reached our min text size, incrementally try smaller sizes
while (textHeight > height && targetTextSize > _mMinTextSize)
{
targetTextSize = System.Math.Max(targetTextSize - 2, _mMinTextSize);
textHeight = GetTextHeight(text, textPaint, width, targetTextSize);
}
// If we had reached our minimum text size and still don't fit, append an ellipsis
if (ShouldAddEllipsis && targetTextSize == _mMinTextSize && textHeight > height)
{
// Draw using a static layout
// modified: use a copy of TextPaint for measuring
var paint = new TextPaint(textPaint);
// Draw using a static layout
var layout = new StaticLayout(text, paint, width, Layout.Alignment.AlignNormal, _spacingMult, _spacingAdd, false);
// Check that we have a least one line of rendered text
if (layout.LineCount > 0)
{
// Since the line at the specific vertical position would be cut off,
// we must trim up to the previous line
var lastLine = layout.GetLineForVertical(height) - 1;
// If the text would not even fit on a single line, clear it
if (lastLine < 0)
{
Text = string.Empty;
}
// Otherwise, trim to the previous line and add an ellipsis
else
{
var start = layout.GetLineStart(lastLine);
var end = layout.GetLineEnd(lastLine);
var lineWidth = layout.GetLineWidth(lastLine);
var ellipseWidth = textPaint.MeasureText(Ellipsis);
// Trim characters off until we have enough room to draw the ellipsis
while (width < lineWidth + ellipseWidth)
{
lineWidth = textPaint.MeasureText(text.SubSequence(start, --end + 1));
}
Text = text.SubSequence(0, end) + Ellipsis;
}
}
}
// Some devices try to auto adjust line spacing, so force default line spacing
// and invalidate the layout as a side effect
SetTextSize(ComplexUnitType.Px, targetTextSize);
SetLineSpacing(_spacingAdd, _spacingMult);
var notifyArgs = new OnTextResizeEventArgs
{
TextView = this,
NewSize = targetTextSize,
OldSize = oldTextSize
};
// Notify the listener if registered
OnTextResize?.Invoke(this, notifyArgs);
// Reset force resize flag
_needsResize = false;
}
/// <summary>
/// Set the text size of the text paint object and use a static layout to render text off screen before measuring
/// </summary>
/// <param name="source"></param>
/// <param name="paint"></param>
/// <param name="width"></param>
/// <param name="textSize"></param>
/// <returns></returns>
private int GetTextHeight(ICharSequence source, TextPaint paint, int width, float textSize)
{
// modified: make a copy of the original TextPaint object for measuring
// (apparently the object gets modified while measuring, see also the
// docs for TextView.getPaint() (which states to access it read-only)
// Update the text paint object
var paintCopy = new TextPaint(paint)
{
TextSize = textSize
};
// Measure using a static layout
var layout = new StaticLayout(source, paintCopy, width, Layout.Alignment.AlignNormal, _spacingMult, _spacingAdd, true);
return layout.Height;
}
}
}
AppcompatTextView现在支持从支持库26.0开始自动调整大小。TextView在Android O也以同样的方式工作。更多信息可以在这里找到。一个简单的演示程序可以在这里找到。
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:autoSizeTextType="uniform"
app:autoSizeMinTextSize="12sp"
app:autoSizeMaxTextSize="100sp"
app:autoSizeStepGranularity="2sp"
/>
</LinearLayout>
