View 默认的onMeasure
lp 其实就是上个博客提到的Window Attribute 只不过是ViewRoot的。

    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),                getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));    }    /**     * Utility to return a default size. Uses the supplied size if the     * MeasureSpec imposed no contraints. Will get larger if allowed     * by the MeasureSpec.     *     * @param size Default size for this view     * @param measureSpec Constraints imposed by the parent     * @return The size this view should be.     */    public static int getDefaultSize(int size, int measureSpec) {        int result = size;        int specMode = MeasureSpec.getMode(measureSpec);        int specSize =  MeasureSpec.getSize(measureSpec);        switch (specMode) {        case MeasureSpec.UNSPECIFIED:            result = size;            break;        case MeasureSpec.AT_MOST:        case MeasureSpec.EXACTLY:            result = specSize;            break;        }        return result;    }