并非所有答案都完美无缺。所以我创建了一个。下面的类将请求布局时，一个新的页面被选择，使viewPager的高度是当前子视图的高度。

class WrapContentViewPager : ViewPager {
    constructor(context: Context) : super(context)
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)

    private var curPos = 0

    init {
        addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
            override fun onPageScrollStateChanged(state: Int) {}

            override fun onPageScrolled(
                position: Int,
                positionOffset: Float,
                positionOffsetPixels: Int
            ) {}

            override fun onPageSelected(position: Int) {
                curPos = position
                requestLayout()
            }
        })
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        if (childCount == 0) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec)
            return
        }
        measureChildren(widthMeasureSpec, heightMeasureSpec)
        setMeasuredDimension(measuredWidth, getChildAt(curPos).measuredHeight)
    }
}

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));
  }
}

并非所有答案都完美无缺。所以我创建了一个。下面的类将请求布局时，一个新的页面被选择，使viewPager的高度是当前子视图的高度。

class WrapContentViewPager : ViewPager {
    constructor(context: Context) : super(context)
    constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)

    private var curPos = 0

    init {
        addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
            override fun onPageScrollStateChanged(state: Int) {}

            override fun onPageScrolled(
                position: Int,
                positionOffset: Float,
                positionOffsetPixels: Int
            ) {}

            override fun onPageSelected(position: Int) {
                curPos = position
                requestLayout()
            }
        })
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        if (childCount == 0) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec)
            return
        }
        measureChildren(widthMeasureSpec, heightMeasureSpec)
        setMeasuredDimension(measuredWidth, getChildAt(curPos).measuredHeight)
    }
}

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

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" />

我也遇到了这个问题，但在我的情况下，我有一个FragmentPagerAdapter，它为ViewPager提供它的页面。我遇到的问题是，ViewPager的onMeasure()在任何片段被创建之前被调用(因此不能正确地大小自己)。

经过一些尝试和错误之后，我发现FragmentPagerAdapter的finishUpdate()方法在片段已经初始化(从FragmentPagerAdapter中的instantiateItem())之后被调用，并且在页面滚动之后/期间。我做了一个小界面:

public interface AdapterFinishUpdateCallbacks
{
    void onFinishUpdate();
}

我传递到我的FragmentPagerAdapter并调用:

@Override
public void finishUpdate(ViewGroup container)
{
    super.finishUpdate(container);

    if (this.listener != null)
    {
        this.listener.onFinishUpdate();
    }
}

这反过来允许我调用setVariableHeight()在我的CustomViewPager实现:

public void setVariableHeight()
{
    // super.measure() calls finishUpdate() in adapter, so need this to stop infinite loop
    if (!this.isSettingHeight)
    {
        this.isSettingHeight = true;

        int maxChildHeight = 0;
        int widthMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredWidth(), MeasureSpec.EXACTLY);
        for (int i = 0; i < getChildCount(); i++)
        {
            View child = getChildAt(i);
            child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.UNSPECIFIED));
            maxChildHeight = child.getMeasuredHeight() > maxChildHeight ? child.getMeasuredHeight() : maxChildHeight;
        }

        int height = maxChildHeight + getPaddingTop() + getPaddingBottom();
        int heightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

        super.measure(widthMeasureSpec, heightMeasureSpec);
        requestLayout();

        this.isSettingHeight = false;
    }
}

我不确定这是最好的方法，如果你认为它是好的/坏的/邪恶的，我会喜欢评论，但它似乎在我的实现中工作得很好:)

希望这能帮助到一些人!

编辑:我忘记在调用super.measure()后添加requestLayout()(否则它不会重绘视图)。

我还忘记在最终高度中添加父元素的填充。

我还放弃了保留原来的宽度/高度度量，以便根据需要创建一个新的度量。已更新相应的代码。

我遇到的另一个问题是，它不会在ScrollView中正确地调整自己的大小，并发现罪魁祸首是用MeasureSpec测量孩子。EXACTLY而不是measurespect . unspecified。更新以反映这一点。

这些更改都已添加到代码中。如果需要，您可以检查历史记录以查看旧的(不正确的)版本。