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
我发现了一个解决方案，它有点像这里提到的一些解决方案的合并。
其思想是测量ViewPager的当前视图。
以下是完整的代码:
MainActivity.kt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewPager.adapter = WrapHeightViewPager.CustomPagerAdapter(this)
}
}
activity_main.xml
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.android.myapplication.WrapHeightViewPager
android:layout_width="match_parent" android:id="@+id/viewPager"
android:background="#33ff0000"
android:layout_height="wrap_content"/>
</FrameLayout>
view_pager_page.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:gravity="center"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView android:layout_width="wrap_content" android:layout_height="wrap_content"
android:src="@android:drawable/sym_def_app_icon"/>
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/textView"/>
</LinearLayout>
WrapHeightViewPager.kt
class WrapHeightViewPager : ViewPager {
constructor(context: Context) : super(context) {}
constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {}
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
val adapter = adapter as CustomPagerAdapter?
val currentView = adapter?.currentView
if (currentView != null) {
currentView.measure(widthMeasureSpec, heightMeasureSpec)
super.onMeasure(
widthMeasureSpec,
View.MeasureSpec.makeMeasureSpec(currentView.measuredHeight, View.MeasureSpec.EXACTLY)
)
return
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
}
class CustomPagerAdapter(private val context: Context) : PagerAdapter() {
var currentView: View? = null
override fun instantiateItem(parent: ViewGroup, position: Int): Any {
val inflater = LayoutInflater.from(context)
val view = inflater.inflate(R.layout.view_pager_page, parent, false)
view.textView.text = "item$position"
parent.addView(view)
return view
}
override fun setPrimaryItem(container: ViewGroup, position: Int, obj: Any) {
super.setPrimaryItem(container, position, obj)
currentView = obj as View
}
override fun destroyItem(collection: ViewGroup, position: Int, view: Any) = collection.removeView(view as View)
override fun getCount(): Int = 3
override fun isViewFromObject(view: View, obj: Any) = view === obj
override fun getPageTitle(position: Int): CharSequence? = "item $position"
}
}
如果你使用RecyclerPagerAdapter库，获取"currentView"的方法是从你设置的pager-view-holder中获取:
val item = obj as PagerViewHolder
currentView = item.itemView
其他回答
以上建议对我都没用。我的用例是在ScrollView中有4个自定义ViewPagers。它们的顶部是基于纵横比测量的，其余的只是layout_height=wrap_content。我试过cybergen, Daniel López Lacalle解决方案。没有一个是完全适合我的。
我猜为什么cybergen不能在页面> 1上工作是因为它基于第1页计算寻呼机的高度，如果你进一步滚动，这是隐藏的。
cybergen和Daniel López Lacalle建议在我的情况下都有奇怪的行为:3个中的2个加载ok, 1个随机高度为0。似乎onMeasure是在儿童被填充之前被调用的。所以我想出了这两个答案加上我自己的修正:
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (getLayoutParams().height == ViewGroup.LayoutParams.WRAP_CONTENT) {
// 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);
int h = view.getMeasuredHeight();
setMeasuredDimension(getMeasuredWidth(), h);
//do not recalculate height anymore
getLayoutParams().height = h;
}
}
}
想法是让ViewPager计算子尺寸，并在ViewPager的布局参数中保存计算出的第一页高度。不要忘记将fragment的布局高度设置为wrap_content，否则你可以得到height=0。我用过这个:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="wrap_content">
<!-- Childs are populated in fragment -->
</LinearLayout>
请注意，如果所有页面都具有相同的高度，则此解决方案非常有效。否则，你需要基于当前的子活动重新计算ViewPager的高度。我不需要它，但如果你提出解决方案，我很乐意更新答案。
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Kotlin代码
class DynamicViewPager @JvmOverloads constructor(
context: Context,
attrs: AttributeSet? = null
) : ViewPager(context, attrs) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
var height = 0
(0 until childCount).forEach {
val child = getChildAt(it)
child.measure(
widthMeasureSpec,
MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)
)
height = max(height, child.measuredHeight)
}
if (height > 0) {
super.onMeasure(
widthMeasureSpec,
MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY)
)
} else {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
}
}
}
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);
对于那些想要ViewPager2的解决方案，将ViewPager2具有与所有页面的最大高度相同的高度，遗憾的是，我只找到了这个解决方案:
viewPager.doOnPreDraw {
//workaround to set the viewPagerheight the same as its children
var height = 0
for (i in 0 until featuresViewPager.adapter!!.itemCount) {
val viewHolder = viewPager.adapter!!.createViewHolder(viewPager, 0)
viewPager.adapter!!.bindViewHolder(viewHolder, i)
val child: View = viewHolder.itemView
child.layoutParams.height = ViewGroup.LayoutParams.WRAP_CONTENT
val widthMeasureSpec = View.MeasureSpec.makeMeasureSpec(viewPager.width, View.MeasureSpec.EXACTLY)
val heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED)
child.measure(widthMeasureSpec, heightMeasureSpec)
val childHeight = child.measuredHeight
child.layoutParams.height = ViewGroup.LayoutParams.MATCH_PARENT
if (childHeight > height)
height = childHeight
}
viewPager.layoutParams.height = height
}
我说“可悲”是因为它遍历了所有的页面，创建了它们的视图，度量了它们，并在此过程中调用了用于其他目的的函数。
应该在大多数情况下工作良好。
如果你知道更好的解决办法，请告诉我。
