自定义view(一)

 /**
     * 测量就是确定自己自定义控件的大小
     *
     * @param widthMeasureSpec
     * @param heightMeasureSpec
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        //漏了这一句，界面一直不显示，child的测量全是0
        //实际就是测量一下子View
        
        measureChildren(widthMeasureSpec, heightMeasureSpec);

        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);

        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

				//宽度默认是自己的宽度，实际上可以在AT_MOST模式下，进行一些计算
				//如把所有的子控件的宽和padding+margin这些都加起来，这样换算成自己的宽度
        int width = widthSize;
        int height;


        if (heightMode == MeasureSpec.EXACTLY) {
            height = heightSize;
        } else {
        	//根据策略来进行子空间的摆放
            int row = 1;
//            int widthSpace = width; //宽度剩余空间
            int tempWidth = 0;

            for (int i = 0; i < getChildCount(); i++) {
                View view = getChildAt(i);
                int childW = view.getMeasuredWidth();
                if (childW + tempWidth <= width) {
                    tempWidth += width;
                } else {
                    row++;
                    //换行了
                    tempWidth = 0;
                }

//                if (widthSpace >= childW) {
//                    widthSpace -= childW;
//                } else {
//                    row++;
//                    widthSpace = width - childW;
//                }

            }

            int childH = getChildAt(0).getMeasuredHeight();
            height = childH * row;
        }

        setMeasuredDimension(width, height);
    }

/**
 * @param changed
 * @param l
 * @param t
 * @param r
 * @param b
 */
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {

    int offsetWidth = 0; //测量偏移的宽度
    int offsetHeight = 0; //测量偏移的高度

    int right = 0;

    for (int i = 0; i < getChildCount(); i++) {
        View childView = getChildAt(i);
        int measuredWidth = childView.getMeasuredWidth();
        int measuredHeight = childView.getMeasuredHeight();
        //这一行还可以放下
        if (offsetWidth + measuredWidth <= r) {
            childView.layout(offsetWidth, offsetHeight, measuredWidth + offsetWidth, measuredHeight + offsetHeight);

            //加上已经填充好的宽度
            offsetWidth += measuredWidth;
        } else { //换一行
            offsetHeight += measuredHeight;
            offsetWidth = 0; //我换一行了，所以重新开始计算偏移的宽度

            childView.layout(offsetWidth, offsetHeight, measuredWidth + offsetWidth, measuredHeight + offsetHeight);

            //这里也要加偏移量
            offsetWidth += measuredWidth;
        }
    }

    Log.e(TAG, "onLayout: changed: " + changed + ", l: " + l + ", t: " + t
            + ", r: " + r + ", b: " + b);
}