我需要调整文本的大小，以完美地适应视图边界。Chase的解决方案只是减小文本大小，如果有足够的空间，这个方案也会扩大文本。

为了使所有的快速和精确，我使用了平分方法而不是迭代while，正如你可以在resizeText()方法中看到的那样。这就是为什么你也有一个MAX_TEXT_SIZE选项。我还附上了onoelle的建议。

Android 4.4测试

/**
 *               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 = 26;

    // Maximum 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() {
        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);
        while(loop_counter < BISECTION_LOOP_WATCH_DOG && upper - lower > 1) {
            targetTextSize = (lower+upper)/2;
            textHeight = getTextHeight(text, textPaint, width, targetTextSize);
            if(textHeight > height)
                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();
    }

}

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>

从2018年6月起，Android正式开始支持Android 4.0 (API级别14)及更高版本的此功能。 查看它在:Autosizing TextViews

Android 8.0 (API级别26)及更高版本:

<?xml version="1.0" encoding="utf-8"?>
<TextView
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:autoSizeTextType="uniform"
    android:autoSizeMinTextSize="12sp"
    android:autoSizeMaxTextSize="100sp"
    android:autoSizeStepGranularity="2sp" />

编程:

setAutoSizeTextTypeUniformWithConfiguration(int autoSizeMinTextSize, int autoSizeMaxTextSize, 
        int autoSizeStepGranularity, int unit)

textView.setAutoSizeTextTypeUniformWithConfiguration(
                1, 17, 1, TypedValue.COMPLEX_UNIT_DIP);

Android 8.0之前的Android版本(API级别26):

<?xml version="1.0" encoding="utf-8"?>
<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="match_parent">

  <TextView
      android:layout_width="match_parent"
      android:layout_height="200dp"
      app:autoSizeTextType="uniform"
      app:autoSizeMinTextSize="12sp"
      app:autoSizeMaxTextSize="100sp"
      app:autoSizeStepGranularity="2sp" />

</LinearLayout>

编程:

TextViewCompat.setAutoSizeTextTypeUniformWithConfiguration(
TextView textView, int autoSizeMinTextSize, int autoSizeMaxTextSize, int autoSizeStepGranularity, int unit) 

TextViewCompat.setAutoSizeTextTypeUniformWithConfiguration(textView, 1, 17, 1,
TypedValue.COMPLEX_UNIT_DIP);

注意:TextView必须有layout_width="match_parent"或绝对大小!

你可以使用android.text.StaticLayout类。这就是TextView内部使用的。

我从Chase的解决方案开始，但在我的设备(Galaxy Nexus, Android 4.1)上正常工作之前，我必须调整两件事:

using a copy of TextPaint for measuring layout The documentation for TextView.getPaint() states that it should be used read-only, so I made a copy in both places where we use the paint object for measuring: // 1. in resizeText() if (mAddEllipsis && targetTextSize == mMinTextSize && textHeight > height) { // Draw using a static layout // modified: use a copy of TextPaint for measuring TextPaint paint = new TextPaint(textPaint); // 2. in getTextHeight() 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); ... adding a unit to setting the text size // modified: setting text size via this.setTextSize (instead of textPaint.setTextSize(targetTextSize)) setTextSize(TypedValue.COMPLEX_UNIT_PX, targetTextSize); setLineSpacing(mSpacingAdd, mSpacingMult);

With these two modifications the solution is working perfectly for me, thanks Chase! I don't know whether it is due to Android 4.x that the original solution was not working. In case you want to see it in action or test whether it really works on your device, you can have a look at my flashcard app Flashcards ToGo where I use this solution to scale the text of a flashcard. The text can have arbitrary length, and the flashcards are displayed in different activities, sometimes smaller sometimes bigger, plus in landscape + portrait mode, and I haven't found any corner case where the solution would not work properly...

警告，Android蜂巢和冰淇淋三明治有bug

android版本:3.1 - 4.04有一个错误，setTextSize()内部的TextView只工作第一次(第一次调用)。

Bug描述如下:http://code.google.com/p/android/issues/detail?id=22493 http://code.google.com/p/android/issues/detail?id=17343#c9

解决方法是添加新的行字符文本分配给TextView之前改变大小:

final String DOUBLE_BYTE_SPACE = "\u3000";
textView.append(DOUBLE_BYTE_SPACE);

我在我的代码中使用它如下:

final String DOUBLE_BYTE_SPACE = "\u3000";
AutoResizeTextView textView = (AutoResizeTextView) view.findViewById(R.id.aTextView);
String fixString = "";
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.HONEYCOMB_MR1
   && android.os.Build.VERSION.SDK_INT <= android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1) {  
    fixString = DOUBLE_BYTE_SPACE;
}
textView.setText(fixString + "The text" + fixString);

我将这个“\u3000”字符添加到文本的左侧和右侧，以保持文本居中。如果你把它对齐到左边，那么只追加到右边。当然，它也可以嵌入到AutoResizeTextView小部件中，但我希望将修复代码保留在外部。