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?
使用Daniel López Localle answer,我在Kotlin中创建了这个类。希望能节省你更多的时间
class DynamicHeightViewPager @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null) : ViewPager(context, attrs) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
var heightMeasureSpec = heightMeasureSpec
var height = 0
for (i in 0 until childCount) {
val child = getChildAt(i)
child.measure(widthMeasureSpec, View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED))
val h = child.measuredHeight
if (h > height) height = h
}
if (height != 0) {
heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.EXACTLY)
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
}}
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;
}
}
另一种解决方案是根据PagerAdapter中的当前页面高度更新ViewPager高度。假设你用这种方式创建ViewPager页面:
@Override
public Object instantiateItem(ViewGroup container, int position) {
PageInfo item = mPages.get(position);
item.mImageView = new CustomImageView(container.getContext());
item.mImageView.setImageDrawable(item.mDrawable);
container.addView(item.mImageView, 0);
return item;
}
其中,mPages是动态添加到PagerAdapter的PageInfo结构的内部列表,CustomImageView只是常规的ImageView,覆盖onMeasure()方法,根据指定的宽度设置其高度并保持图像纵横比。
你可以在setPrimaryItem()方法中强制ViewPager的高度:
@Override
public void setPrimaryItem(ViewGroup container, int position, Object object) {
super.setPrimaryItem(container, position, object);
PageInfo item = (PageInfo) object;
ViewPager pager = (ViewPager) container;
int width = item.mImageView.getMeasuredWidth();
int height = item.mImageView.getMeasuredHeight();
pager.setLayoutParams(new FrameLayout.LayoutParams(width, Math.max(height, 1)));
}
注意数学。这修复了ViewPager不更新显示的页面(显示为空白),当前一页的高度为零时(即CustomImageView中可绘制的空),在两页之间每次奇怪的来回滑动。
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。
重写你的ViewPager的onMeasure如下将使它获得它目前拥有的最大子节点的高度。
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int height = 0;
int childWidthSpec = MeasureSpec.makeMeasureSpec(
Math.max(0, MeasureSpec.getSize(widthMeasureSpec) -
getPaddingLeft() - getPaddingRight()),
MeasureSpec.getMode(widthMeasureSpec)
);
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
child.measure(childWidthSpec, MeasureSpec.UNSPECIFIED);
int h = child.getMeasuredHeight();
if (h > height) height = h;
}
if (height != 0) {
heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}