我已经设置了一个简单的ViewPager，它在每个页面上都有一个高度为200dp的ImageView。
这是我的寻呼机:
pager = new ViewPager(this);
pager.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
pager.setBackgroundColor(Color.WHITE);
pager.setOnPageChangeListener(listener);
layout.addView(pager);
尽管高度设置为wrap_content，但即使imageview只有200dp，分页器也总是充满屏幕。我尝试用“200”替换寻呼机的高度，但在不同分辨率下会得到不同的结果。我无法将“dp”添加到该值。如何将200dp添加到寻呼机的布局?
当前回答
我也遇到了这个问题，但在我的情况下，我有一个FragmentPagerAdapter，它为ViewPager提供它的页面。我遇到的问题是，ViewPager的onMeasure()在任何片段被创建之前被调用(因此不能正确地大小自己)。
经过一些尝试和错误之后，我发现FragmentPagerAdapter的finishUpdate()方法在片段已经初始化(从FragmentPagerAdapter中的instantiateItem())之后被调用，并且在页面滚动之后/期间。我做了一个小界面:
public interface AdapterFinishUpdateCallbacks
{
void onFinishUpdate();
}
我传递到我的FragmentPagerAdapter并调用:
@Override
public void finishUpdate(ViewGroup container)
{
super.finishUpdate(container);
if (this.listener != null)
{
this.listener.onFinishUpdate();
}
}
这反过来允许我调用setVariableHeight()在我的CustomViewPager实现:
public void setVariableHeight()
{
// super.measure() calls finishUpdate() in adapter, so need this to stop infinite loop
if (!this.isSettingHeight)
{
this.isSettingHeight = true;
int maxChildHeight = 0;
int widthMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredWidth(), MeasureSpec.EXACTLY);
for (int i = 0; i < getChildCount(); i++)
{
View child = getChildAt(i);
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.UNSPECIFIED));
maxChildHeight = child.getMeasuredHeight() > maxChildHeight ? child.getMeasuredHeight() : maxChildHeight;
}
int height = maxChildHeight + getPaddingTop() + getPaddingBottom();
int heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
super.measure(widthMeasureSpec, heightMeasureSpec);
requestLayout();
this.isSettingHeight = false;
}
}
我不确定这是最好的方法，如果你认为它是好的/坏的/邪恶的，我会喜欢评论，但它似乎在我的实现中工作得很好:)
希望这能帮助到一些人!
编辑:我忘记在调用super.measure()后添加requestLayout()(否则它不会重绘视图)。
我还忘记在最终高度中添加父元素的填充。
我还放弃了保留原来的宽度/高度度量，以便根据需要创建一个新的度量。已更新相应的代码。
我遇到的另一个问题是，它不会在ScrollView中正确地调整自己的大小，并发现罪魁祸首是用MeasureSpec测量孩子。EXACTLY而不是measurespect . unspecified。更新以反映这一点。
这些更改都已添加到代码中。如果需要，您可以检查历史记录以查看旧的(不正确的)版本。
其他回答
下面的代码是唯一对我有用的东西
1. 使用这个类来声明一个hightwrappingviewpager:
public class HeightWrappingViewPager extends ViewPager {
public HeightWrappingViewPager(Context context) {
super(context);
}
public HeightWrappingViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int mode = MeasureSpec.getMode(heightMeasureSpec);
// Unspecified means that the ViewPager is in a ScrollView WRAP_CONTENT.
// At Most means that the ViewPager is not in a ScrollView WRAP_CONTENT.
if (mode == MeasureSpec.UNSPECIFIED || mode == MeasureSpec.AT_MOST) {
// super has to be called in the beginning so the child views can be initialized.
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int height = 0;
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
int h = child.getMeasuredHeight();
if (h > height) height = h;
}
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
}
// super has to be called again so the new specs are treated as exact measurements
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
2. 在xml文件中插入高度包装视图分页器:
<com.project.test.HeightWrappingViewPager
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent">
</com.project.test.HeightWrappingViewPager>
3.声明您的视图分页:
HeightWrappingViewPager mViewPager;
mViewPager = (HeightWrappingViewPager) itemView.findViewById(R.id.pager);
CustomAdapter adapter = new CustomAdapter(context);
mViewPager.setAdapter(adapter);
mViewPager.measure(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
我的情况下添加android:fillViewport="true"解决了这个问题
在我的例子中，当应用大小时，我需要一个带有wrap_content的viewpager来显示当前选择的元素和动画。下面您可以看到我的实现。有人能派上用场吗?
package one.xcorp.widget
import android.animation.ValueAnimator
import android.content.Context
import android.util.AttributeSet
import android.view.View
import android.view.ViewGroup.LayoutParams.MATCH_PARENT
import android.view.ViewGroup.LayoutParams.WRAP_CONTENT
import one.xcorp.widget.R
import kotlin.properties.Delegates.observable
class ViewPager : android.support.v4.view.ViewPager {
var enableAnimation by observable(false) { _, _, enable ->
if (enable) {
addOnPageChangeListener(onPageChangeListener)
} else {
removeOnPageChangeListener(onPageChangeListener)
}
}
private var animationDuration = 0L
private var animator: ValueAnimator? = null
constructor (context: Context) : super(context) {
init(context, null)
}
constructor (context: Context, attrs: AttributeSet?) : super(context, attrs) {
init(context, attrs)
}
private fun init(context: Context, attrs: AttributeSet?) {
context.theme.obtainStyledAttributes(
attrs,
R.styleable.ViewPager,
0,
0
).apply {
try {
enableAnimation = getBoolean(
R.styleable.ViewPager_enableAnimation,
enableAnimation
)
animationDuration = getInteger(
R.styleable.ViewPager_animationDuration,
resources.getInteger(android.R.integer.config_shortAnimTime)
).toLong()
} finally {
recycle()
}
}
}
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
val heightMode = MeasureSpec.getMode(heightMeasureSpec)
val measuredHeight = if (heightMode == MeasureSpec.EXACTLY) {
MeasureSpec.getSize(heightMeasureSpec)
} else {
val currentViewHeight = findViewByPosition(currentItem)?.also {
measureView(it)
}?.measuredHeight ?: 0
if (heightMode != MeasureSpec.AT_MOST) {
currentViewHeight
} else {
Math.min(
currentViewHeight,
MeasureSpec.getSize(heightMeasureSpec)
)
}
}
super.onMeasure(
widthMeasureSpec,
MeasureSpec.makeMeasureSpec(measuredHeight, MeasureSpec.EXACTLY)
)
}
private fun measureView(view: View) = with(view) {
val horizontalMode: Int
val horizontalSize: Int
when (layoutParams.width) {
MATCH_PARENT -> {
horizontalMode = MeasureSpec.EXACTLY
horizontalSize = this@ViewPager.measuredWidth
}
WRAP_CONTENT -> {
horizontalMode = MeasureSpec.UNSPECIFIED
horizontalSize = 0
}
else -> {
horizontalMode = MeasureSpec.EXACTLY
horizontalSize = layoutParams.width
}
}
val verticalMode: Int
val verticalSize: Int
when (layoutParams.height) {
MATCH_PARENT -> {
verticalMode = MeasureSpec.EXACTLY
verticalSize = this@ViewPager.measuredHeight
}
WRAP_CONTENT -> {
verticalMode = MeasureSpec.UNSPECIFIED
verticalSize = 0
}
else -> {
verticalMode = MeasureSpec.EXACTLY
verticalSize = layoutParams.height
}
}
val horizontalMeasureSpec = MeasureSpec.makeMeasureSpec(horizontalSize, horizontalMode)
val verticalMeasureSpec = MeasureSpec.makeMeasureSpec(verticalSize, verticalMode)
measure(horizontalMeasureSpec, verticalMeasureSpec)
}
private fun findViewByPosition(position: Int): View? {
for (i in 0 until childCount) {
val childView = getChildAt(i)
val childLayoutParams = childView.layoutParams as LayoutParams
val childPosition by lazy {
val field = childLayoutParams.javaClass.getDeclaredField("position")
field.isAccessible = true
field.get(childLayoutParams) as Int
}
if (!childLayoutParams.isDecor && position == childPosition) {
return childView
}
}
return null
}
private fun animateContentHeight(childView: View, fromHeight: Int, toHeight: Int) {
animator?.cancel()
if (fromHeight == toHeight) {
return
}
animator = ValueAnimator.ofInt(fromHeight, toHeight).apply {
addUpdateListener {
measureView(childView)
if (childView.measuredHeight != toHeight) {
animateContentHeight(childView, height, childView.measuredHeight)
} else {
layoutParams.height = animatedValue as Int
requestLayout()
}
}
duration = animationDuration
start()
}
}
private val onPageChangeListener = object : OnPageChangeListener {
override fun onPageScrollStateChanged(state: Int) {
/* do nothing */
}
override fun onPageScrolled(
position: Int,
positionOffset: Float,
positionOffsetPixels: Int
) {
/* do nothing */
}
override fun onPageSelected(position: Int) {
if (!isAttachedToWindow) {
return
}
findViewByPosition(position)?.let { childView ->
measureView(childView)
animateContentHeight(childView, height, childView.measuredHeight)
}
}
}
}
在项目中添加attrs.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="ViewPager">
<attr name="enableAnimation" format="boolean" />
<attr name="animationDuration" format="integer" />
</declare-styleable>
</resources>
和使用:
<one.xcorp.widget.ViewPager
android:id="@+id/wt_content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:enableAnimation="true" />
如果你正在使用的ViewPager是一个ScrollView的子视图，并且有一个PagerTitleStrip子视图，你将需要对已经提供的答案进行轻微修改。作为参考，我的XML看起来像这样:
<ScrollView
android:id="@+id/match_scroll_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@color/white">
<LinearLayout
android:id="@+id/match_and_graphs_wrapper"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<view
android:id="@+id/pager"
class="com.printandpixel.lolhistory.util.WrapContentHeightViewPager"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v4.view.PagerTitleStrip
android:id="@+id/pager_title_strip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
android:background="#33b5e5"
android:paddingBottom="4dp"
android:paddingTop="4dp"
android:textColor="#fff" />
</view>
</LinearLayout>
</ScrollView>
在你的onMeasure中，你必须添加PagerTitleStrip的measuredHeight，如果找到一个。否则，即使它占用了额外的空间，它的高度也不会被认为是所有子结点的最大高度。
希望这能帮助到其他人。很抱歉，这有点黑…
public class WrapContentHeightViewPager extends ViewPager {
public WrapContentHeightViewPager(Context context) {
super(context);
}
public WrapContentHeightViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int pagerTitleStripHeight = 0;
int height = 0;
for(int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
int h = child.getMeasuredHeight();
if (h > height) {
// get the measuredHeight of the tallest fragment
height = h;
}
if (child.getClass() == PagerTitleStrip.class) {
// store the measured height of the pagerTitleStrip if one is found. This will only
// happen if you have a android.support.v4.view.PagerTitleStrip as a direct child
// of this class in your XML.
pagerTitleStripHeight = h;
}
}
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height+pagerTitleStripHeight, MeasureSpec.EXACTLY);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
给ViewPager的父布局NestedScrollView
<androidx.core.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:fillViewport="true">
<androidx.viewpager.widget.ViewPager
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</androidx.viewpager.widget.ViewPager>
</androidx.core.widget.NestedScrollView>
别忘了设置android:fillViewport="true"
这将拉伸滚动视图及其子内容以填充视口。
https://developer.android.com/reference/android/widget/ScrollView.html#attr_android:fillViewport
