layout_margintop 百分比_layout marginleft_layout marginend用法(7)

到这里onMeasure中通过百分比值设置宽高以及margin的部分就看完了，那我们接着看一下关于百分比值过小时对wrap_content的处理:

if (mHelper.handleMeasuredStateTooSmall()) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}

看一下PercentLayoutHelper.handleMeasuredStateTooSmall()方法的实现:

/**
     * Iterates over children and checks if any of them would like to get more space than it
     * received through the percentage dimension.
     *
     * If you are building a layout that supports percentage dimensions you are encouraged to take
     * advantage of this method. The developer should be able to specify that a child should be
     * remeasured by adding normal dimension attribute with {@code wrap_content} value. For example
     * he might specify child's attributes as {@code app:layout_widthPercent="60%p"} and
     * {@code android:layout_width="wrap_content"}. In this case if the child receives too little
     * space, it will be remeasured with width set to {@code WRAP_CONTENT}.
     *
     * @return True if the measure phase needs to be rerun because one of the children would like
     * to receive more space.
     */
    public boolean handleMeasuredStateTooSmall() {
        boolean needsSecondMeasure = false;
        for (int i = 0, N = mHost.getChildCount(); i < N; i++) {
            View view = mHost.getChildAt(i);
            ViewGroup.LayoutParams params = view.getLayoutParams();
            if (Log.isLoggable(TAG, Log.DEBUG)) {
                Log.d(TAG, "should handle measured state too small " + view + " " + params);
            }
            if (params instanceof PercentLayoutParams) {
                PercentLayoutInfo info =
                        ((PercentLayoutParams) params).getPercentLayoutInfo();
                if (info != null) {
                    // shouldHandleMeasuredWidthTooSmall方法来进行判断
                    if (shouldHandleMeasuredWidthTooSmall(view, info)) {
                        needsSecondMeasure = true;
                        params.width = ViewGroup.LayoutParams.WRAP_CONTENT;
                    }
                    if (shouldHandleMeasuredHeightTooSmall(view, info)) {
                        needsSecondMeasure = true;
                        params.height = ViewGroup.LayoutParams.WRAP_CONTENT;
                    }
                }
            }
        }
        if (Log.isLoggable(TAG, Log.DEBUG)) {
            Log.d(TAG, "should trigger second measure pass: " + needsSecondMeasure);
        }
        return needsSecondMeasure;
    }

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