ViewGroup代码示例

程序语言 Java
1

有关Android的ViewGroup的使用例子比较少，早期的Android Home中使用到了这个ViewGroup相对于GridView来说ViewGroup更为灵活，下面是Android中一段经典的示例代码

public class FitCenterFrameLayout extends ViewGroup {
public FitCenterFrameLayout(Context context) {
super(context);
}

public FitCenterFrameLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  //修改尺寸
    final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
    final int height = resolveSize(getSuggestedMinimumHeight(), heightMeasureSpec);
    setMeasuredDimension(width, height);

    int childWidthSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.UNSPECIFIED);
    int childHeightSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.UNSPECIFIED);

    int childCount = getChildCount();
    for (int i = 0; i < childCount; i++) {
        getChildAt(i).measure(childWidthSpec, childHeightSpec);
    }
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
    final int childCount = getChildCount();

    final int parentLeft = getPaddingLeft();
    final int parentTop = getPaddingTop();
    final int parentRight = r - l - getPaddingRight();
    final int parentBottom = b - t - getPaddingBottom();

    final int parentWidth = parentRight - parentLeft;
    final int parentHeight = parentBottom - parentTop;

    int unpaddedWidth, unpaddedHeight, parentUnpaddedWidth, parentUnpaddedHeight;
    int childPaddingLeft, childPaddingTop, childPaddingRight, childPaddingBottom;

    for (int i = 0; i < childCount; i++) {
        final View child = getChildAt(i);
        if (child.getVisibility() == GONE) {
            continue;
        }

        childPaddingLeft = child.getPaddingLeft();
        childPaddingTop = child.getPaddingTop();
        childPaddingRight = child.getPaddingRight();
        childPaddingBottom = child.getPaddingBottom();

        unpaddedWidth = child.getMeasuredWidth() - childPaddingLeft - childPaddingRight;
        unpaddedHeight = child.getMeasuredHeight() - childPaddingTop - childPaddingBottom;

        parentUnpaddedWidth = parentWidth - childPaddingLeft - childPaddingRight;
        parentUnpaddedHeight = parentHeight - childPaddingTop - childPaddingBottom;

        if (parentUnpaddedWidth * unpaddedHeight > parentUnpaddedHeight * unpaddedWidth) {
             final int scaledChildWidth = unpaddedWidth * parentUnpaddedHeight
                    / unpaddedHeight + childPaddingLeft + childPaddingRight;
            child.layout(
                    parentLeft + (parentWidth - scaledChildWidth) / 2,
                    parentTop,
                    parentRight - (parentWidth - scaledChildWidth) / 2,
                    parentBottom);
        } else {
             final int scaledChildHeight = unpaddedHeight * parentUnpaddedWidth
                    / unpaddedWidth + childPaddingTop + childPaddingBottom;
            child.layout(
                    parentLeft,
                    parentTop + (parentHeight - scaledChildHeight) / 2,
                    parentRight,
                    parentTop + (parentHeight + scaledChildHeight) / 2);
        }
    }
}

}