Android 6.0 RecyclerView嵌套在ScrollView中显示不全

ScrollView

嵌套

RecyclerView

在

Android6.0

以下能正常显示，但是在

6.0

以上就会出现

RecyclerView

显示不全的

bug

。尝试多种方法之后终于找到解决办法，特在此记录下。

无效方法之一

ScrollView

嵌套

RecyclerView

时出现的各种冲突一般是靠重写

RecyclerView

的

LayoutManager

来解决的。如下，重写

GridLayoutManager

。

public class FullyGridLayoutManager extends GridLayoutManager {
public FullyGridLayoutManager(Context context, int spanCount) {
super(context, spanCount);
}

public FullyGridLayoutManager(Context context, int spanCount, int orientation, boolean reverseLayout) {
super(context, spanCount, orientation, reverseLayout);
}

private int[] mMeasuredDimension = new int[2];

@Override
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {
final int widthMode = View.MeasureSpec.getMode(widthSpec);
final int heightMode = View.MeasureSpec.getMode(heightSpec);
final int widthSize = View.MeasureSpec.getSize(widthSpec);
final int heightSize = View.MeasureSpec.getSize(heightSpec);

int width = 0;
int height = 0;
int count = getItemCount();
int span = getSpanCount();
for (int i = 0; i < count; i++) {
measureScrapChild(recycler, i,
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
mMeasuredDimension);

if (getOrientation() == HORIZONTAL) {
if (i % span == 0) {
width = width + mMeasuredDimension[0];
}
if (i == 0) {
height = mMeasuredDimension[1];
}
} else {
if (i % span == 0) {
height = height + mMeasuredDimension[1];
}
if (i == 0) {
width = mMeasuredDimension[0];
}
}
}

switch (widthMode) {
case View.MeasureSpec.EXACTLY:
width = widthSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}

switch (heightMode) {
case View.MeasureSpec.EXACTLY:
height = heightSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}

setMeasuredDimension(width, height);
}

private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
int heightSpec, int[] measuredDimension) {
if (position < getItemCount()) {
try {
View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException
if (view != null) {
RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
getPaddingLeft() + getPaddingRight(), p.width);
int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
getPaddingTop() + getPaddingBottom(), p.height);
view.measure(childWidthSpec, childHeightSpec);
measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
recycler.recycleView(view);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}

无效方法之二

于是又想到当初

ListView

在

ScrollView

中显示不全时，重写

ListView

的

onMeasure()

方法可以完美解决。试试

@Override
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, expandSpec);
}

终极解决方案

终极解决办法是在

RecyclerView

的外部套上一层

RelativeLayout

<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:descendantFocusability="blocksDescendants">

<android.support.v7.widget.RecyclerView
android:id="@+id/menuRv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="@dimen/margin_16"
android:layout_marginRight="@dimen/margin_16"/>

</RelativeLayout>

发现

RecyclerView

完全显示出来了，完美解决！

隐隐感觉只是

android:descendantFocusability="blocksDescendants"

一句在起作用。于是尝试在根布局上加这句，再把这个

RelativeLayout

删除。。问题又重现了。。可是后来发现不加

android:descendantFocusability="blocksDescendants"

同样能完美解决，好奇怪的解决方案！！先不求甚解地用上吧。。

android:descendantFocusability

属性的值有三种：

beforeDescendants：viewgroup

会优先其子类控件而获取到焦点

blocksDescendants：viewgroup

会覆盖子类控件而直接获得焦点

afterDescendants：viewgroup

只有当其子类控件不需要获取焦点时才获取焦点