使用ScrollView缩放缩放：在子尺寸更改时更新其滚动行为

我有一个自定义类，我从ScrollView扩展。我想要做的是实现与这个班的缩放缩放，我想要缩放到ScrollView的孩子，并根据需要滚动放大的内容。基本上，我希望iOS的UIScrollView类别具有相同的行为（它是一个SHAME，Android不提供像iOS这样的任何内置缩放功能，我们必须从头开始编写所有内容）。我在课堂中有ScaleGestureListener，我在ScrollView内更新子视图的布局维度，当我收到onScale事件时：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根据其孩子的新维度不更新其滚动条。例如，如果孩子的宽度大于ScrollView's，它将不会显示水平滚动条。我在滚动视图及其子视图上调用了invalidate和requestLayout，但它们都失败了。使用ScrollView缩放缩放：在子尺寸更改时更新其滚动行为

下面我给我的代码：

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; 
} 

}

采取长话短说，我需要的滚动型根据其孩子的更新大小，以更新其滚动条，每次用户进行捏放大和缩小。

预先感谢

来源

2013-04-08 Ufuk Can Bicici

这里是一个解决方案：

而不是延伸滚动型，我写延伸的FrameLayout其是滚动型和HorizontalScrollView的组合的TwoDimensionScrollView，以便它可以显示两个水平/垂直滚动条，即使孩子被缩放。另外我没有使用手势检测器。相反，我实现了我自己的捏缩放。

要更新滚动条，改写以下功能：

@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; 
}

您还需要找到所有代码调用回弹（）和一扔（），然后使用设定的最小值为x和y上述函数getScrollHorizontalMin（）和getScrollVerticalMin（）而不是0

来源

2013-05-22 19:25:00 user2407188

使用ScrollView缩放缩放：在子尺寸更改时更新其滚动行为

回答

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