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:
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。
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; }
您还需要找到所有调用 SpringBack() 和 fling() 的代码,然后使用上述函数 getScrollHorizontalMin() 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/