Android customView如何计算onMeasure来填充父级

Question

我正在尝试绘制一个自定义视图,一切都很好,除了最右边的部分被切断.我希望视图填充父级,只使用所需的高度(即我正在绘制的位图的高度.当我从活动的xml布局中删除填充时,自定义视图渲染得很好.所以我不是计算onMeasure并考虑父母填充.

请有人看看这段代码,并描述我为什么以及如何出错？谢谢

编辑包括@ nicko的答案和更多细节:

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

    int parentWidth = MeasureSpec.getSize(widthMeasureSpec);
    int parentHeight = MeasureSpec.getSize(heightMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);

    ViewParent parent = getParent();
    int leftPadding = 0;
    int rightPadding = 0;

    if (parent instanceof ViewGroup) {
        leftPadding = ((ViewGroup) parent).getPaddingLeft();
        rightPadding = ((ViewGroup) parent).getPaddingRight();
    }
    float wanabeHeight = calendar.getHeight();
    float wanabeWidth = parentWidth - leftPadding - rightPadding;

    int height = 0;
    //Determine Height
    switch(heightMode){
        case MeasureSpec.EXACTLY: height = parentHeight;
            break;
        case MeasureSpec.AT_MOST:
            height = Math.min((int)wanabeHeight, parentHeight);
            break;
        case MeasureSpec.UNSPECIFIED:
        default:
            height = (int)wanabeHeight;
            break;
    }
    setMeasuredDimension((int)wanabeWidth, height);
}


@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    super.onLayout(changed, left, top, right, bottom);
    calendarX = left;
    personX = (int)((right - left) * 0.5);
    checkX = right - check.getWidth() - getPaddingRight();
    lineY = (int)((bottom - top) * 0.5);
    bitmapY = (int)(((bottom - top) * 0.5) - (calendar.getHeight() * 0.5));
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawBitmap(calendar, calendarX, bitmapY, paint);
    canvas.drawBitmap(person, personX, bitmapY, paint);
    canvas.drawBitmap(check, checkX, bitmapY, paint);

    canvas.drawLine((calendarX + calendar.getWidth() + PADDING), lineY, personX - PADDING, lineY, linePaint);
    canvas.drawLine((personX + person.getWidth() + PADDING), lineY, checkX - PADDING, lineY, linePaint);
}

Answer 1

在 中onDraw，所有内容都相对于画布 - 但似乎您是根据相对于onLayout屏幕的视图位置来绘制所有内容。

因此，对于右手图像，您实际上需要像这样计算 X 位置：

checkX = right - left - check.getWidth();

您还可能会发现，如果父级有任何填充，左侧图像会缩进一点，因此请尝试将其定位在 0：

calendarX = 0;