解析:继承ViewGroup后的子类如何重写onMeasure方法
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int measureWidth = MeasureSpec.getSize(widthMeasureSpec);
int measureHeigth = MeasureSpec.getSize(heightMeasureSpec);
setMeasuredDimension(measureWidth, measureHeigth);
// TODO Auto-generated method stub
for(int i= 0;i<getChildCount();i++){
View v = getChildAt(i);
Log.v(TAG, "measureWidth is " +v.getMeasuredWidth() + "measureHeight is "+v.getMeasuredHeight());
int widthSpec = 0;
int heightSpec = 0;
LayoutParams params = v.getLayoutParams();
if(params.width > 0){
widthSpec = MeasureSpec.makeMeasureSpec(params.width, MeasureSpec.EXACTLY);
}else if (params.width == -1) {
widthSpec = MeasureSpec.makeMeasureSpec(measureWidth, MeasureSpec.EXACTLY);
} else if (params.width == -2) {
widthSpec = MeasureSpec.makeMeasureSpec(measureWidth, MeasureSpec.AT_MOST);
}
if(params.height > 0){
heightSpec = MeasureSpec.makeMeasureSpec(params.height, MeasureSpec.EXACTLY);
}else if (params.height == -1) {
heightSpec = MeasureSpec.makeMeasureSpec(measureHeigth, MeasureSpec.EXACTLY);
} else if (params.height == -2) {
heightSpec = MeasureSpec.makeMeasureSpec(measureWidth, MeasureSpec.AT_MOST);
}
v.measure(widthSpec, heightSpec);
}
}
解释一下:
首先判断params.width的值是多少,有三种情况。
如果是大于零的话,及传递的就是一个具体的值,那么,构造MeasupreSpec的时候可以直接用EXACTLY。
如果为-1的话,就是MatchParent的情况,那么,获得父View的宽度,再用EXACTLY来构造MeasureSpec。
如果为-2的话,就是wrapContent的情况,那么,构造MeasureSpec的话直接用一个负数就可以了。