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
改进丹尼尔López Lacalle回答，重写在Kotlin:
class MyViewPager(context: Context, attrs: AttributeSet): ViewPager(context, attrs) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
val zeroHeight = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)
val maxHeight = children
.map { it.measure(widthMeasureSpec, zeroHeight); it.measuredHeight }
.max() ?: 0
if (maxHeight > 0) {
val maxHeightSpec = MeasureSpec.makeMeasureSpec(maxHeight, MeasureSpec.EXACTLY)
super.onMeasure(widthMeasureSpec, maxHeightSpec)
return
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
}
}
其他回答
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
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" />
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)
}
}
}
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);
}
}
