EqualSizeLinearLayout extends LinearLayout
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int childSize = (getOrientation() == HORIZONTAL) ? getMeasuredHeight()-getPaddingTop()-getPaddingBottom()
: getMeasuredWidth()-getPaddingLeft()-getPaddingRight();
final int childCount = getChildCount();
for(int i=0; i<childCount; ++i)
{
final View child = getChildAt(i);
if(getOrientation() == HORIZONTAL)
{
if(child.getMeasuredHeight() < childSize)
{
// adjust this child height to be childSize
child.measure(MeasureSpec.makeMeasureSpec(child.getMeasuredWidth(), MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(childSize, MeasureSpec.EXACTLY));
}
}
else
{
if(child.getMeasuredWidth() < childSize)
{
// adjust this child width to be childSize
child.measure(MeasureSpec.makeMeasureSpec(childSize, MeasureSpec.EXACTLY),
MeasureSpec.makeMeasureSpec(child.getMeasuredHeight(), MeasureSpec.EXACTLY));
}
}
}
}
getHeight()和 getMeasuredHeight()区别：
前者是最终的大小，后者是测量的大小，举个列子，当布局还没完成的时候，getHeight就是0的，
或者是在onmeasure方法里，这个方法会进来两次，第一次进来的时候getheight是0的，第二次进来才有真正的高度【也不一定额，比如进行child.measure以后这个getheight也不准了。具体看日志下边的解释】
如下的布局：
<widget.SquarLinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<Button
android:id="@+id/btn_system"
android:layout_width="wrap_content"
android:layout_height="100dp"
android:text="系统" />
<ToggleButton
android:id="@+id/toggleButton1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textOn="on"
android:textOff="off"
android:text="ToggleButton" />
</widget.SquarLinearLayout>
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// System.err.println("widthMeasureSpec==========="+widthMeasureSpec+"============heightMeasureSpec="+heightMeasureSpec);
// System.err.println("getMode==============w="+MeasureSpec.getMode(widthMeasureSpec)+"===h="+MeasureSpec.getMode(heightMeasureSpec));
// System.err.println("getSize========"+MeasureSpec.getSize(widthMeasureSpec)+" ========="+MeasureSpec.getSize(heightMeasureSpec));
//
System.err.println(getChildCount()+"===11111======"+MeasureSpec.UNSPECIFIED+"======"+MeasureSpec.EXACTLY+"======="+MeasureSpec.AT_MOST);
for(int i=0;i<getChildCount();i++) {
View child=getChildAt(i);
if(child!=null) {
if(getOrientation()==LinearLayout.HORIZONTAL) {
System.err.println("i=="+i+" =="+child.getHeight()+"==="+child.getMeasuredHeight());
if(child.getMeasuredHeight()<getHeight()) {
child.measure(child.getMeasuredWidth(), MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.EXACTLY));
}System.err.println("i=="+i+" =="+child.getHeight()+"==="+child.getMeasuredHeight());
}else {
if(child.getMeasuredWidth()<getWidth()) {
child.measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.EXACTLY),child.getMeasuredHeight());
}
}
}
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
System.err.println("onLayout============="+changed+"========="+(b-t)+"============"+getChildAt(1).getHeight()+"=="+getChildAt(1).getMeasuredHeight());
super.onLayout(changed, l, t, r, b);
}
日志如下：
02-11 02:01:59.767: W/System.err(28512): i==0 ==0===100
02-11 02:01:59.767: W/System.err(28512): i==0 ==0===100
02-11 02:01:59.767: W/System.err(28512): i==1 ==0===48
02-11 02:01:59.767: W/System.err(28512): i==1 ==0===48
02-11 02:01:59.787: W/System.err(28512): onLayout=============true=========100============0==48
02-11 02:01:59.797: W/System.err(28512): i==0 ==100===100
02-11 02:01:59.797: W/System.err(28512): i==0 ==100===100
02-11 02:01:59.797: W/System.err(28512): i==1 ==48===48
02-11 02:01:59.797: W/System.err(28512): i==1 ==48===100
02-11 02:01:59.797: W/System.err(28512): onLayout=============false=========100============48==100
//完事点击toggleButton，布局会重置的，可以看到，经过如下方法super.onMeasure(widthMeasureSpec, heightMeasureSpec);
child的measureHeight又还原回去了。
02-11 02:04:37.637: W/System.err(28512): i==0 ==100===100
02-11 02:04:37.637: W/System.err(28512): i==0 ==100===100
02-11 02:04:37.637: W/System.err(28512): i==1 ==100===48
02-11 02:04:37.637: W/System.err(28512): i==1 ==100===100
02-11 02:04:37.637: W/System.err(28512): onLayout=============false=========100============100==100
对日志的解释，首次加载线性布局的onmeasure会进行2次的，第一次没高度，不考虑。
第二次的高度48，进行child.measure之后高度看到还是48，这是真的吗，其实不是真的，这时候getheight应该已经是100，不过就和我们在oncreate里getheight一样，这个时候获取到的高度并不准确，你可以延迟1秒才调用child.getHeigth就可以看到返回的是100，和我们实际显示的大小一致。
第二次的日志，点击togglebutton以后整个线性布局会进行重绘，因为调用了super.onMeasure(widthMeasureSpec, heightMeasureSpec); 其实这时候child的大小又恢复原始大小48了，可其实我们看到打印的日志getheight还是100，这个是不准确的。延迟获取才能看到真实的大小。
或者给这个线性布局设置个背景，让它可以走onDraw方法，在onDraw方法里获取高度也是真实的
看下源码draw方法里如下的注释
/*
* Draw traversal performs several drawing steps which must be executed
* in the appropriate order:
*
* 1. Draw the background
* 2. If necessary, save the canvas' layers to prepare for fading
* 3. Draw view's content
* 4. Draw children
* 5. If necessary, draw the fading edges and restore layers
* 6. Draw decorations (scrollbars for instance)
*/
/**
* Flag indicating whether a view failed the quickReject() check in draw(). This condition
* is used to check whether later changes to the view's transform should invalidate the
* view to force the quickReject test to run again.
*/
static final int PFLAG2_VIEW_QUICK_REJECTED = 0x10000000;
//16080行
if (!drawingWithDrawingCache) {
if (drawingWithRenderNode) {
mPrivateFlags &= ~PFLAG_DIRTY_MASK;
((DisplayListCanvas) canvas).drawRenderNode(renderNode);
} else {
// Fast path for layouts with no backgrounds
if ((mPrivateFlags & PFLAG_SKIP_DRAW) == PFLAG_SKIP_DRAW) {
mPrivateFlags &= ~PFLAG_DIRTY_MASK;
dispatchDraw(canvas);
} else {
draw(canvas);
}
}
}
线性布局，相对布局，帧布局，只有设置了背景才会执行 draw和onDraw方法。 最后执行的是dispathDraw
另外，线性布局如果设置divider也是可以的，不需要背景。
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