Question

我有一个自定义类，我从ScrollView扩展而来。我想要做的是用这个类实现缩放缩放，我想用它缩放到ScrollView的子节点并根据需要滚动缩放的内容。基本上，我想要iOS UIScrollView类具有的相同行为（它是 SHAME ，Android不提供任何内置的缩放功能，如iOS我们必须从头开始写一切。我的班级内有ScaleGestureListener，当我收到ScrollView个事件时，我会更新onScale内部子视图的布局维度：我将布局宽度和高度乘以我从ScaleGestureListener收到的比例因子。困扰我的是ScrollView不会根据其子项的新维度更新其滚动条。例如，如果孩子的宽度变得大于ScrollView，则不会显示水平滚动条。我在滚动视图及其子项上调用了invalidate和requestLayout，但它们都失败了。

在下面我给出了我的代码：

public class PinchZoomScrollView extends ScrollView{

private ScaleGestureDetector mScaleDetector;// = new ScaleGestureDetector(context, new ScaleListener());
private float mScaleFactor = 1.0f;
private float referenceTextSize;
private static final float MIN_ZOOM_AMOUNT = 1.0f;
private static final float MAX_ZOOM_AMOUNT = 2.0f;

private float refChildWidth;
private float refChildHeight;

private boolean shownForTheFirstTime = true;
//private View content;


private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {

    private WeakReference<PinchZoomScrollView> containerRef;

    public ScaleListener(PinchZoomScrollView container)
    {
        super();

        containerRef = new WeakReference<PinchZoomScrollView>(container);
    }

    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor *= detector.getScaleFactor();

        // Don't let the object get too small or too large.
        mScaleFactor = Math.max(MIN_ZOOM_AMOUNT, Math.min(mScaleFactor, MAX_ZOOM_AMOUNT));

        //Get Child object
        View content = containerRef.get().getChildAt(0);

        if(shownForTheFirstTime)
        {
            shownForTheFirstTime = false;

            refChildWidth  = content.getWidth();
            refChildHeight = content.getHeight();
        }

        LayoutParams params = new LayoutParams(Math.round(mScaleFactor*refChildWidth), Math.round(mScaleFactor*refChildHeight));
        content.setLayoutParams(params);


        System.out.println("this.width="+containerRef.get().getWidth());
        System.out.println("content.width="+Math.round(mScaleFactor*refChildWidth));


        content.invalidate();
        content.requestLayout();

        containerRef.get().updateViewLayout(content, params);

        containerRef.get().invalidate();
        containerRef.get().requestLayout();

        return true;
    }
}


public PinchZoomScrollView(Context context)
{
    super(context);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener(this));
}

public PinchZoomScrollView(Context context, AttributeSet attrs)
{
    super(context,attrs);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener(this));
}

public PinchZoomScrollView(Context context, AttributeSet attrs, int defStyle)
{
    super(context,attrs,defStyle);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener(this));
}

@Override
public boolean onTouchEvent(MotionEvent ev) {

    super.onTouchEvent(ev);

    mScaleDetector.onTouchEvent(ev);

    return true;
}

}

简而言之，我需要ScrollView根据孩子的更新大小更新其滚动条，每次用户进行缩放放大。

提前致谢

Answer 1

这是一个解决方案：

我没有扩展ScrollView，而是编写了一个扩展FrameLayout的TwoDimensionScrollView，它是ScrollView和HorizontalScrollView的组合，因此它可以显示水平/垂直滚动条，即使缩放了子项也是如此。我也没有使用手势检测器。相反，我实现了自己的缩放。

要更新滚动条，请重写以下函数：

@Override
protected int computeVerticalScrollRange() {
    final int count = getChildCount();
    final int contentHeight = getHeight() - getPaddingBottom()
        - getPaddingTop();
    if (count == 0) {
        return contentHeight;
    }


@Override
protected int computeVerticalScrollOffset() {
    int result = Math.max(0, super.computeVerticalScrollOffset());
    return result - getScrollVerticalMin();
}
@Override
protected int computeHorizontalScrollRange() {
    final int count = getChildCount();
    final int contentWidth = getWidth() - getPaddingLeft()
        - getPaddingRight();
    if (count == 0) {
        return contentWidth;
    }

    int scrollRange = getChildAt(0).getRight();
    final int scrollX = getScrollX();
    final int overscrollRight = Math.max(0, scrollRange - contentWidth);
    if (scrollX < 0) {
        scrollRange -= scrollX;
    } else if (scrollX > overscrollRight) {
        scrollRange += scrollX - overscrollRight;
    }
    return (int) (scrollRange * mScaleFactor + getScrollHorizontalMin());
}

@Override
protected int computeHorizontalScrollOffset() {
    int result = Math.max(0, super.computeHorizontalScrollOffset());
    return result - getScrollHorizontalMin();
}
@Override
protected int computeVerticalScrollExtent() {
    return getHeight() + getScrollVerticalMin();
}

@Override
protected int computeHorizontalScrollExtent() {
    return getWidth() + getScrollHorizontalMin();
}
private int getScrollHorizontalMin() {
    if (this.getChildCount() < 1)
        return 0;
    View child = this.getChildAt(0);
    return (int) ((1 - mScaleFactor) * child.getPivotX());
}

private int getScrollVerticalMin() {
    if (this.getChildCount() < 1)
        return 0;
    View child = this.getChildAt(0);
    return (int) ((1 - mScaleFactor) * child.getPivotY());
}
private int getScrollVerticalRange() {
    int scrollRange = 0;
    if (getChildCount() > 0) {
        View child = getChildAt(0);
        scrollRange = (int) Math.max(0, child.getHeight() * mScaleFactor
                - (getHeight() - getPaddingBottom() - getPaddingTop())
                + getScrollVerticalMin());
    }
return scrollRange;
}

private int getScrollHorizontalRange() {
    int scrollRange = 0;
    if (getChildCount() > 0) {
        View child = getChildAt(0);
        scrollRange = (int) Math.max(0, child.getWidth() * mScaleFactor
                - (getWidth() - getPaddingRight() - getPaddingLeft())
                + getScrollHorizontalMin());
    }
    return scrollRange;
}

您还需要找到所有调用SpringBack（）和fling（）的代码，然后使用上面的函数getScrollHorizontalMin（）和getScrollVerticalMin（）而不是0来设置x和y的最小值

使用ScrollView进行缩放缩放：当子大小更改时更新它的滚动行为

1 个答案: