我有一个自定义类,我从ScrollView扩展.我想要做的是用这个类实现缩放缩放,我想用它来缩放到ScrollView的子节点并根据需要滚动缩放的内容.基本上,我想要iOS的UIScrollView类所具有的相同行为(它是一个SHAME,Android不提供任何内置的缩放功能,如iOS,我们必须从头开始编写所有内容).我在我的类中有一个ScaleGestureListener,当我收到onScale事件时,我更新了ScrollView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,如果子项的宽度大于ScrollView的宽度,则不会显示水平滚动条.我在滚动视图及其子节点上调用invalidate和requestLayout,但它们都失败了.

在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 containerRef;

public ScaleListener(PinchZoomScrollView container)

{

super();

containerRef = new WeakReference(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

解决方法:

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Horizo​​ntalScrollView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getScrollHorizo​​ntalMin()和getScrollVerticalMin()而不是0来设置x和y的最小值.

标签：android,android-layout,scrollview,pinchzoom

来源： https://codeday.me/bug/20190625/1284978.html