viewgroup onMeasure例子

叁歲伎倆 2022-08-03 12:55 142阅读 0赞

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);
    
            }
        }

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。