Crash治理：图片缩放pointerIndex out of range.

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背景: API28,PhotoView+Viewpager

场景: 对图片进行双指缩放操作.

异常:

E AndroidRuntime: java.lang.IllegalArgumentException: pointerIndex out of range
E AndroidRuntime: at android.view.MotionEvent.nativeGetAxisValue(Native Method)
E AndroidRuntime: at android.view.MotionEvent.getX(MotionEvent.java:2205)
E AndroidRuntime: at androidx.viewpager.widget.ViewPager.onInterceptTouchEvent(ViewPager.java:2072)
E AndroidRuntime: at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2573)
E AndroidRuntime: at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3030)

原因: 根据上面异常信息可以发现出错位置在ViewPager.java2072行ev.getX(pointerIndex)（如下），而这次的异常也就是其中的参数（pointerIndex）超出了范围导致，pointerIndex每次通过MotionEvent.findPointerIndex(activePointerId)来获取，在双指对图片进行双指缩放时，一个手指抬起，activePointerId却没有进行重新赋值，获取到值错误，就直接影响了pointerIndex，也就在这个时候出现了异常。

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@Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
    
    ...
    
    switch (action) {
            case MotionEvent.ACTION_MOVE: {
                ...
                final int activePointerId = mActivePointerId;
                if (activePointerId == INVALID_POINTER) {
                    // If we don't have a valid id, the touch down wasn't on content.
                    break;
                }

                final int pointerIndex = ev.findPointerIndex(activePointerId);
                final float x = ev.getX(pointerIndex);
                
                ...
    }

解决方案：
查阅了资料，比较简单明了的处理方法就是自定义Viewpager对ViewPager的onInterceptTouchEvent（）进行try{}catch()操作。值得注意的是，在try{}catch()中直接return super.onInterceptTouchEvent(ev)，图片会出现滑动异常，所以进行了如下的特殊处理。

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public class CustomViewPager extends ViewPager {
	public CustomViewPager(@NonNull Context context) {
        super(context);
    }
    
    public CustomViewPager(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }
    
    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        boolean isIntercept = false;
        try {
            isIntercept = super.onInterceptTouchEvent(ev);
        } catch (IllegalArgumentException exception) {
            exception.printStackTrace();

        }
        return isIntercept;
    }
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        try {
            super.onTouchEvent(ev);
        } catch (IllegalArgumentException exception) {
            exception.printStackTrace();

        }
        return false;
    }
}