我有一个自定义类，它是从 ScrollView 扩展而来的。我想做的是用这个类实现捏缩放，我想用它缩放到 ScrollView 的子级并根据需要滚动缩放的内容。基本上，我想要 iOS 的 UIScrollView 类具有的相同行为(这是一个 SHAME Android 不提供任何内置缩放像 iOS 这样的功能，我们必须从头开始编写所有内容)。我的类中有一个 ScaleGestureListener，当我收到 onScale 事件时，我更新了 ScrollView 中 subview 的布局维度:我将布局宽度和高度乘以从 ScaleGestureListener 收到的比例因子。令我困扰的是 ScrollView 不会根据其子项的新尺寸更新其滚动条。例如，如果子项的宽度变得大于 ScrollView 的宽度，它就不会显示水平滚动条。我在 ScrollView 及其 subview 上调用了 invalidate 和 requestLayout，但它们都失败了。

下面我给出我的代码:

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;
}

}

长话短说，我需要 ScrollView 根据其子项的更新大小更新其滚动条，每次用户进行缩放操作时。

提前致谢

最佳答案

解决方法:

1. 我没有扩展 ScrollView，而是编写了一个扩展 FrameLayout 的 TwoDimensionScrollView，它是 ScrollView 和 Horizo​​ntalScrollView 的组合，因此它可以同时显示水平/垂直滚动条，即使缩放子项也是如此。我也没有使用手势检测器。相反，我实现了自己的双指缩放。

2. 要更新滚动条，重写下面的函数:

   @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;
   }
   

3. 您还需要找到所有调用 SpringBack() 和 fling() 的代码，然后使用上述函数 getScrollHorizo​​ntalMin() 和 getScrollVerticalMin() 设置 x 和 y 的最小值而不是 0

关于android - 使用 ScrollView 捏合缩放 : Updating its scrolling behaivor when child size changes，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15880913/