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
从爆米花时间安卓应用程序的源代码，我发现这个解决方案，动态调整大小的viewpager与漂亮的动画取决于当前的孩子的大小。
https://git.popcorntime.io/popcorntime/android/blob/5934f8d0c8fed39af213af4512272d12d2efb6a6/mobile/src/main/java/pct/droid/widget/WrappingViewPager.java
public class WrappingViewPager extends ViewPager {
private Boolean mAnimStarted = false;
public WrappingViewPager(Context context) {
super(context);
}
public WrappingViewPager(Context context, AttributeSet attrs){
super(context, attrs);
}
@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if(!mAnimStarted && null != getAdapter()) {
int height = 0;
View child = ((FragmentPagerAdapter) getAdapter()).getItem(getCurrentItem()).getView();
if (child != null) {
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
height = child.getMeasuredHeight();
if (VersionUtils.isJellyBean() && height < getMinimumHeight()) {
height = getMinimumHeight();
}
}
// Not the best place to put this animation, but it works pretty good.
int newHeight = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
if (getLayoutParams().height != 0 && heightMeasureSpec != newHeight) {
final int targetHeight = height;
final int currentHeight = getLayoutParams().height;
final int heightChange = targetHeight - currentHeight;
Animation a = new Animation() {
@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
if (interpolatedTime >= 1) {
getLayoutParams().height = targetHeight;
} else {
int stepHeight = (int) (heightChange * interpolatedTime);
getLayoutParams().height = currentHeight + stepHeight;
}
requestLayout();
}
@Override
public boolean willChangeBounds() {
return true;
}
};
a.setAnimationListener(new Animation.AnimationListener() {
@Override
public void onAnimationStart(Animation animation) {
mAnimStarted = true;
}
@Override
public void onAnimationEnd(Animation animation) {
mAnimStarted = false;
}
@Override
public void onAnimationRepeat(Animation animation) {
}
});
a.setDuration(1000);
startAnimation(a);
mAnimStarted = true;
} else {
heightMeasureSpec = newHeight;
}
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
其他回答
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
我编辑cybergen答案使viewpager改变高度取决于选定的项目 类是cybergen的相同，但我添加了一个整数向量，这是所有viewpager的子视图高度，我们可以在页面更改为更新高度时访问它
这是这个类:
import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.viewpager.widget.ViewPager;
import java.util.Vector;
public class WrapContentHeightViewPager extends ViewPager {
private Vector<Integer> heights = new Vector<>();
public WrapContentHeightViewPager(@NonNull Context context) {
super(context);
}
public WrapContentHeightViewPager(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
for(int i=0;i<getChildCount();i++) {
View view = getChildAt(i);
if (view != null) {
view.measure(widthMeasureSpec, heightMeasureSpec);
heights.add(measureHeight(heightMeasureSpec, view));
}
}
setMeasuredDimension(getMeasuredWidth(), measureHeight(heightMeasureSpec, getChildAt(0)));
}
public int getHeightAt(int position){
return heights.get(position);
}
private int measureHeight(int measureSpec, View view) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
if (specMode == MeasureSpec.EXACTLY) {
result = specSize;
} else {
if (view != null) {
result = view.getMeasuredHeight();
}
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
}
然后在你的活动中添加一个OnPageChangeListener
WrapContentHeightViewPager viewPager = findViewById(R.id.my_viewpager);
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}
@Override
public void onPageSelected(int position) {
LinearLayout.LayoutParams params = (LinearLayout.LayoutParams) viewPager.getLayoutParams();
params.height = viewPager.getHeightAt(position);
viewPager.setLayoutParams(params);
}
@Override
public void onPageScrollStateChanged(int state) {}
});
这里是xml:
<com.example.example.WrapContentHeightViewPager
android:id="@+id/my_viewpager"
android:fillViewport="true"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
如有必要请纠正我的英语
这个ViewPager只调整到当前可见的子节点(不是它实际的最大子节点)
这个想法来自https://stackoverflow.com/a/56325869/4718406
public class DynamicHeightViewPager extends ViewPager {
public DynamicHeightViewPager (Context context) {
super(context);
initPageChangeListener();
}
public DynamicHeightViewPager (Context context, AttributeSet attrs) {
super(context, attrs);
initPageChangeListener();
}
private void initPageChangeListener() {
addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
requestLayout();
}
});
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//View child = getChildAt(getCurrentItem());
View child = getCurrentView(this);
if (child != null) {
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0,
MeasureSpec.UNSPECIFIED));
int h = child.getMeasuredHeight();
heightMeasureSpec = MeasureSpec.makeMeasureSpec(h, MeasureSpec.EXACTLY);
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
View getCurrentView(ViewPager viewPager) {
try {
final int currentItem = viewPager.getCurrentItem();
for (int i = 0; i < viewPager.getChildCount(); i++) {
final View child = viewPager.getChildAt(i);
final ViewPager.LayoutParams layoutParams = (ViewPager.LayoutParams)
child.getLayoutParams();
Field f = layoutParams.getClass().getDeclaredField("position");
//NoSuchFieldException
f.setAccessible(true);
int position = (Integer) f.get(layoutParams); //IllegalAccessException
if (!layoutParams.isDecor && currentItem == position) {
return child;
}
}
} catch (NoSuchFieldException e) {
e.fillInStackTrace();
} catch (IllegalArgumentException e) {
e.fillInStackTrace();
} catch (IllegalAccessException e) {
e.fillInStackTrace();
}
return null;
}
}
我在这里看到的大多数解决方案似乎都在做双重测量:首先测量子视图，然后调用super.onMeasure()
我提出了一个自定义的WrapContentViewPager是更有效的，与RecyclerView和片段工作得很好
你可以在这里查看演示:
github/ssynhtn/WrapContentViewPager
这个类的代码是: WrapContentViewPager.java
我只是在回答一个非常类似的问题，在寻找一个链接来支持我的说法时，碰巧发现了这个，你很幸运:)
我的另一个回答是: ViewPager不支持wrap_content，因为它(通常)不会同时加载所有的子页面，因此无法获得适当的大小(可以选择在每次切换页面时改变大小)。
然而，你可以设置一个精确的尺寸(例如150dp)和match_parent也可以。 您还可以通过更改其LayoutParams中的height-属性，从代码中动态修改维度。
根据你的需要，你可以在它自己的xml文件中创建ViewPager, layout_height设置为200dp，然后在你的代码中，而不是从头创建一个新的ViewPager，你可以扩展这个xml文件:
LayoutInflater inflater = context.getLayoutInflater();
inflater.inflate(R.layout.viewpagerxml, layout, true);
