摘要:开发中经常遇到ScrollView嵌套ListView,GridView,或者RecyclerView嵌套RecyclerView的情况,常常会出现显示不全的现象,下面提供几种不同的解决方法
1.在不是很复杂的布局的情况下,尽量不嵌套,使用添加头布局尾布局的方式进行实现;RecyclerView的添加方式可以参考张鸿洋的博客
2.网上比较流行的是自定义ListView和RecyclerView的LayoutManager
(1)自定义ListView,GridView,重写onMeasure方法
ListView:
public class MyListView extends ListView {
public MyListView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int mExpandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec, mExpandSpec);
}
}
这种方法是将ListView的允许高度设置为极大值,比较简单,但是有一个后果是会造成adapter的getView方法调用多次,也就是多次重绘计算高度.导致的结果就是加载卡顿,如果item中有EditText的话可能会造成数据显示混乱
GridView也类似:
public class MyGridView extends GridView {
public MyGridView(Context context) {
super(context);
}
public MyGridView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public MyGridView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE>>2,MeasureSpec.AT_MOST);
super.onMeasure(widthMeasureSpec,expandSpec);
}
}
(2)自定义RecyclerView的LayoutManager
LinearLayoutManager:
public class MyLinearLayoutManager extends LinearLayoutManager {
private static final String TAG = MyLinearLayoutManager.class.getSimpleName();
public MyLinearLayoutManager(Context context) {
super(context);
}
public MyLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, 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;
for (int i = 0; i < getItemCount(); i++) {
measureScrapChild(recycler, i,
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
mMeasuredDimension);
if (getOrientation() == HORIZONTAL) {
width = width + mMeasuredDimension[0];
if (i == 0) {
height = mMeasuredDimension[1];
}
} else {
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) {
try {
View view = recycler.getViewForPosition(0);
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();
} finally {
}
}
}
GridLayoutManager:**[java]** [view plain](http://blog.csdn.net/kinly1993/article/details/54616348#) [copy](http://blog.csdn.net/kinly1993/article/details/54616348#)
public class MyGridLayoutManager extends GridLayoutManager {
private Context context;
public MyGridLayoutManager(Context context, int spanCount) {
super(context, spanCount);
this.context = context;
}
public MyGridLayoutManager(Context context, int spanCount,
int orientation, boolean reverseLayout) {
super(context, spanCount, orientation, reverseLayout);
this.context = context;
}
private int[] mMeasuredDimension = new int[2];
@SuppressLint("NewApi")
@Override
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {
final int heightMode = View.MeasureSpec.getMode(heightSpec);
final int widthSize = View.MeasureSpec.getSize(widthSpec);
final int heightSize = View.MeasureSpec.getSize(heightSpec);
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 == 0) {
height = mMeasuredDimension[1];
}
} else {
if (i % span == 0) {
height = (int) (height + mMeasuredDimension[1]);
}
}
}
switch (heightMode) {
case View.MeasureSpec.EXACTLY:
height = heightSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
setMeasuredDimension(widthSize, height);
}
private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec, int heightSpec, int[] measuredDimension) {
if (position < getItemCount()) {
try {
View view = recycler.getViewForPosition(position);// 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();
}
}
}
}
通过LayoutManager去测量条目的宽高然后设置出高度.但是这种方法我在4.1的手机上运行正常,但是在7.0手机上依然显示不全(具体不知道哪个版本以上就不能完全显示);解决方法就是在RecyclerView外面包裹一层RealativeLayout;下面是代码修改前后的对比.
修改之前,4.1能显示完整,而7.0不能显示完整:
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="match_parent"
android:layout_height="100dp"
android:text="文本"/>
<android.support.v7.widget.RecyclerView
android:id="@+id/rv"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="1">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
</ScrollView>
修改之后完整显示:
**[java]** [view plain](http://blog.csdn.net/kinly1993/article/details/54616348#) [copy](http://blog.csdn.net/kinly1993/article/details/54616348#)
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="match_parent"
android:layout_height="100dp"
android:text="我是文本"/>
<android.support.v7.widget.RecyclerView
android:id="@+id/rv"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="1">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
</RelativeLayout>
</ScrollView>
3.手动设置LayoutParams,适用于题目上的任何一种情况
ListView和RecyclerView都能去获取item,然后测量出高度进行累加得到总高度再设置给自己,如果每条的高度已知并且高度都一致,那可以直接计算(注意加上分割线高度);如果是GridView或者多列RecyclerView.需要除以每行的条目数
listview:
LinearLayout.LayoutParams params = (LayoutParams) listview.getLayoutParams();
int totalHeight = 0;
for (int i = 0; i < list.size(); i++) {//list为数据集合,也可以通过adapter.getCount()得到
View listItem = buyAdapter.getView(i, null, listview);
listItem.measure(0, 0);
int perHeight = listItem.getMeasuredHeight();
totalHeight += perHeight;
}
float dividerHeight = listview.getDividerHeight();
params.height = (int) ((list.size()-1)*dividerHeight+totalHeight);
listview.setLayoutParams(params);
RecyclerView:
**[java]** [view plain](http://blog.csdn.net/kinly1993/article/details/54616348#) [copy](http://blog.csdn.net/kinly1993/article/details/54616348#)
int h = 0;
for (int i = 0; i < list.size(); i++) {
View view = recyclerView.getLayoutManager().getChildAt(0);
view.measure(0, 0);
h += view.getMeasuredHeight();
}
ViewGroup.LayoutParams layoutParams = recyclerView.getLayoutParams();
layoutParams.height = h;
recyclerView.setLayoutParams(layoutParams);
注意:当视图未初始化完成时直接设置会报空指针,比如在onCreate方法中去设置,因为itemView还没有完全初始化,这时候可以通过设置view渲染完成的监听实现,以RecyclerView为例:
rootview.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {//rootView为根ViewGroup
@Override
public void onGlobalLayout() {
rootview.getViewTreeObserver().removeGlobalOnLayoutListener(this);
int h = 0;
for (int i = 0; i < list.size(); i++) {
View view = rv.getLayoutManager().getChildAt(0);
view.measure(0, 0);
h += view.getMeasuredHeight();
}
ViewGroup.LayoutParams layoutParams = rv.getLayoutParams();
layoutParams.height = h;
rv.setLayoutParams(layoutParams);
}
});
