我有一个包含两个 View 的聊天屏幕:一个用于显示以前聊天的回收器 View 和一个封装编辑文本的自定义 View 、一个发送按钮和另一个回收器 View ，让用户选择要发送的其他内容，如照片等. 这个自定义 View 叫做“Panel”。

因此，我的聊天 Activity 具有以下布局:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <chat.example.app.widget.Panel
        style="@style/PanelStyle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|center"
        android:id="@+id/panel" />

    <android.support.v7.widget.RecyclerView
        android:background="@android:color/holo_red_dark"
        android:layout_margin="@dimen/activity_horizontal_margin"
        android:scrollbars="vertical"
        android:id="@+id/previous_chat"
        android:layout_above="@id/panel"
        android:layout_alignParentTop="true"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</RelativeLayout>

我的“面板” View 具有以下布局:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:color/white">
    <RelativeLayout
        android:id="@+id/staging_area_root"
        android:layout_gravity="center"
        android:gravity="center"
        android:paddingLeft="5dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <!-- Chat box and send -->
    </RelativeLayout>
    <!-- THIS GUY IS PROBLEMATIC -->
    <android.support.v7.widget.RecyclerView
        android:id="@+id/card_set"
        android:layout_margin="15dp"
        android:layout_below="@id/staging_area_root"
        android:background="@android:color/holo_blue_bright"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</RelativeLayout>  

问题是 Panel 中的回收器 View 占用了整个屏幕空间。所以我所看到的只是来自 Panel 类的 Mr. problemed recycler View 。

这两个回收器 View 都分配了 LinearLayoutManager。 还没有适配器。

我的 build.gradle 中有最新的支持库:

compile 'com.android.support:recyclerview-v7:23.2.0'  

并查看最新的 android 开发人员博客文章:

This release brings an exciting new feature to the LayoutManager API: auto-measurement! This allows a RecyclerView to size itself based on the size of its contents. This means that previously unavailable scenarios, such as using WRAP_CONTENT for a dimension of the RecyclerView, are now possible. You’ll find all built in LayoutManagers now support auto-measurement.

我错过了什么吗？

更新 1:

我向 Mr. problemed recycler view 添加了一个适配器，其中包含 0 个项目。仍然没有解决办法。

更新2:
截图:

最佳答案

取自 23.2 RecyclerView onMeasure() 调用的代码 fragment :

if (mLayout.mAutoMeasure) {
        final int widthMode = MeasureSpec.getMode(widthSpec);
        final int heightMode = MeasureSpec.getMode(heightSpec);
        final boolean skipMeasure = widthMode == MeasureSpec.EXACTLY
                && heightMode == MeasureSpec.EXACTLY;
        mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec);
        if (skipMeasure || mAdapter == null) {
            return;
        }
        if (mState.mLayoutStep == State.STEP_START) {
            dispatchLayoutStep1();
        }
        // set dimensions in 2nd step. Pre-layout should happen with old dimensions for
        // consistency
        mLayout.setMeasureSpecs(widthSpec, heightSpec);
        mState.mIsMeasuring = true;
        dispatchLayoutStep2();

        // now we can get the width and height from the children.
        mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);

        // if RecyclerView has non-exact width and height and if there is at least one child
        // which also has non-exact width & height, we have to re-measure.
        if (mLayout.shouldMeasureTwice()) {
            mLayout.setMeasureSpecs(
                    MeasureSpec.makeMeasureSpec(getMeasuredWidth(), MeasureSpec.EXACTLY),
                    MeasureSpec.makeMeasureSpec(getMeasuredHeight(), MeasureSpec.EXACTLY));
            mState.mIsMeasuring = true;
            dispatchLayoutStep2();
            // now we can get the width and height from the children.
            mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
        }
    }

mLayout.setMeasuredDimensionFromChildren() 调用将根据 RecyclerView 的子项的大小进行自动测量。这意味着，需要一个具有 1 个或多个子级的有效 RecyclerView.Adapter 才能触发自动测量。

关于android - RecyclerView 不尊重 height=wrap_content？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35726839/