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
当在viewpager中使用静态内容时，你不希望有花哨的动画，你可以使用下面的viewpager
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) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
View firstChild = getChildAt(0);
firstChild.measure(widthMeasureSpec, heightMeasureSpec);
super.onMeasure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(firstChild.getMeasuredHeight(), MeasureSpec.EXACTLY));
}
}
其他回答
测量ViewPager的高度:
public class WrapViewPager extends ViewPager {
View primaryView;
public WrapViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (primaryView != null) {
int height = 0;
for (int i = 0; i < getChildCount(); i++) {
if (primaryView == getChildAt(i)) {
int childHeightSpec = MeasureSpec.makeMeasureSpec(0x1 << 30 - 1, MeasureSpec.AT_MOST);
getChildAt(i).measure(widthMeasureSpec, childHeightSpec);
height = getChildAt(i).getMeasuredHeight();
}
}
setMeasuredDimension(widthMeasureSpec, MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY));
}
}
public void setPrimaryView(View view) {
primaryView = view;
}
}
调用setPrimaryView(视图):
public class ZGAdapter extends PagerAdapter {
@Override
public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
super.setPrimaryItem(container, position, object);
((WrapViewPager)container).setPrimaryView((View)object);
}
}
另一个更通用的解决方案是让wrap_content正常工作。
我已经扩展了ViewPager来覆盖onMeasure()。高度被包裹在第一个子视图周围。如果子视图的高度不完全相同，这可能会导致意想不到的结果。因此，类可以很容易地扩展，让我们说动画到当前视图/页面的大小。但我不需要。
你可以在yout XML布局中使用这个ViewPager，就像原来的ViewPager一样:
<view
android:layout_width="match_parent"
android:layout_height="wrap_content"
class="de.cybergen.ui.layout.WrapContentHeightViewPager"
android:id="@+id/wrapContentHeightViewPager"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"/>
优点:这种方法允许在任何布局(包括RelativeLayout)中使用ViewPager来覆盖其他ui元素。
还有一个缺点:如果你想使用页边距，你必须创建两个嵌套的布局，并给内部的一个指定所需的页边距。
代码如下:
public class WrapContentHeightViewPager extends ViewPager {
/**
* Constructor
*
* @param context the context
*/
public WrapContentHeightViewPager(Context context) {
super(context);
}
/**
* Constructor
*
* @param context the context
* @param attrs the attribute set
*/
public WrapContentHeightViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// find the first child view
View view = getChildAt(0);
if (view != null) {
// measure the first child view with the specified measure spec
view.measure(widthMeasureSpec, heightMeasureSpec);
}
setMeasuredDimension(getMeasuredWidth(), measureHeight(heightMeasureSpec, view));
}
/**
* Determines the height of this view
*
* @param measureSpec A measureSpec packed into an int
* @param view the base view with already measured height
*
* @return The height of the view, honoring constraints from measureSpec
*/
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 {
// set the height from the base view if available
if (view != null) {
result = view.getMeasuredHeight();
}
if (specMode == MeasureSpec.AT_MOST) {
result = Math.min(result, specSize);
}
}
return result;
}
}
我有一个版本的WrapContentHeightViewPager是在API 23之前正确工作的，它将根据当前选定的子视图调整父视图的高度。
在升级到API 23后，它停止工作。原来旧的解决方案是使用getChildAt(getCurrentItem())来获取当前的子视图，以测量哪个不工作。参见解决方案:https://stackoverflow.com/a/16512217/1265583
下面是API 23的工作原理:
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int height = 0;
ViewPagerAdapter adapter = (ViewPagerAdapter)getAdapter();
View child = adapter.getItem(getCurrentItem()).getView();
if(child != null) {
child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
height = child.getMeasuredHeight();
}
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
我也遇到了同样的问题。我有一个ViewPager，我想在它的按钮上显示一个广告。我发现的解决方案是让寻呼机进入一个RelativeView，并设置它的layout_above的视图id，我想看到它下面。这对我很管用。
这是我的布局XML:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:id="@+id/AdLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:orientation="vertical" >
</LinearLayout>
<android.support.v4.view.ViewPager
android:id="@+id/mainpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@+id/AdLayout" >
</android.support.v4.view.ViewPager>
</RelativeLayout>
我的答案基于Daniel López Lacalle和这篇文章http://www.henning.ms/2013/09/09/viewpager-that-simply-dont-measure-up/。丹尼尔回答的问题是，在某些情况下，我的孩子的身高为零。不幸的是，解决办法是测量两次。
@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);
}
这也允许你在ViewPager上设置一个高度，如果你想要的话，或者只是wrap_content。
