自定义View解决wrap_content无效的问题

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

    int desiredWidth = 100;
    int desiredHeight = 100;

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

    int width;
    int height;

    //Measure Width
    if (widthMode == MeasureSpec.EXACTLY) {
        //Must be this size
        width = widthSize;
    } else if (widthMode == MeasureSpec.AT_MOST) {
        //Can't be bigger than...
        width = Math.min(desiredWidth, widthSize);
    } else {
        //Be whatever you want
        width = desiredWidth;
    }

    //Measure Height
    if (heightMode == MeasureSpec.EXACTLY) {
        //Must be this size
        height = heightSize;
    } else if (heightMode == MeasureSpec.AT_MOST) {
        //Can't be bigger than...
        height = Math.min(desiredHeight, heightSize);
    } else {
        //Be whatever you want
        height = desiredHeight;
    }

    //MUST CALL THIS
    setMeasuredDimension(width, height);
}

解决的方法总结：

• 1。指定一个默认的内部宽高，例如本方法中的desiredWidth = 100。
• 2。判断当MeasureSpec的模式为AT_MOST(对应于wrap_content)时，设置结果为设置的值（最大为我们设置的值，如果小于设置值就设置为specSize）。
• 3。判断当MeasureSpec的模式为非AT_MOST时，直接设置为系统的测量值即可。
• 4。设置值没有特定的标准，以实际情况为准。