自定义手势缩放View,能显示Bitmap,能设置缩放中心点
时间: 2024-01-04 10:03:08 浏览: 26
要自定义一个支持手势缩放的View,可以继承Android的View类,并通过覆盖onDraw方法来绘制Bitmap。同时,可以使用GestureDetector类来检测手势,实现缩放逻辑,并且可以通过设置缩放中心点来使缩放更加灵活。
以下是一个简单的示例代码:
```java
public class ZoomImageView extends View {
private Bitmap mBitmap;
private float mScaleFactor = 1f;
private float mFocusX = 0f;
private float mFocusY = 0f;
private GestureDetector mGestureDetector;
public ZoomImageView(Context context) {
super(context);
init();
}
public ZoomImageView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public ZoomImageView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
mGestureDetector = new GestureDetector(getContext(), new GestureDetector.SimpleOnGestureListener() {
@Override
public boolean onScale(ScaleGestureDetector detector) {
mScaleFactor *= detector.getScaleFactor();
mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));
mFocusX = detector.getFocusX();
mFocusY = detector.getFocusY();
invalidate();
return true;
}
});
}
public void setImageBitmap(Bitmap bitmap) {
mBitmap = bitmap;
invalidate();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
mGestureDetector.onTouchEvent(event);
return true;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mBitmap != null) {
canvas.save();
canvas.scale(mScaleFactor, mScaleFactor, mFocusX, mFocusY);
canvas.drawBitmap(mBitmap, 0, 0, null);
canvas.restore();
}
}
}
```
通过继承View类并覆盖onTouchEvent方法,我们可以检测用户的手势,并通过GestureDetector类来处理缩放逻辑。在onDraw方法中,我们将画布进行缩放并绘制Bitmap。通过设置缩放中心点,可以让缩放更加灵活。