Android開發中多點觸控的實現方法
阿新 • • 發佈：2019-02-03
// import略
public class ImageViewerActivity extends Activity implements OnTouchListener {
private ImageView mImageView;
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;
// 第一個按下的手指的點
private PointF startPoint = new PointF();
// 兩個按下的手指的觸控點的中點
private PointF midPoint = new PointF();
// 初始的兩個手指按下的觸控點的距離
private float oriDis = 1f;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.imageviewer);
mImageView = (ImageView) this.findViewById(R.id.imageView);
mImageView.setOnTouchListener(this);
}
@Override
public boolean onTouch(View v, MotionEvent event) {
ImageView view = (ImageView) v;
// 進行與操作是為了判斷多點觸控
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
// 第一個手指按下事件
matrix.set(view.getImageMatrix());
savedMatrix.set(matrix);
startPoint.set(event.getX(), event.getY());
mode = DRAG;
break;
case MotionEvent.ACTION_POINTER_DOWN:
// 第二個手指按下事件
oriDis = distance(event);
if (oriDis > 10f) {
savedMatrix.set(matrix);
midPoint = middle(event);
mode = ZOOM;
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
// 手指放開事件
mode = NONE;
break;
case MotionEvent.ACTION_MOVE:
// 手指滑動事件
if (mode == DRAG) {
// 是一個手指拖動
matrix.set(savedMatrix);
matrix.postTranslate(event.getX() - startPoint.x, event.getY()
- startPoint.y);
} else if (mode == ZOOM) {
// 兩個手指滑動
float newDist = distance(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oriDis;
matrix.postScale(scale, scale, midPoint.x, midPoint.y);
}
}
break;
}
// 設定ImageView的Matrix
view.setImageMatrix(matrix);
return true;
}
// 計算兩個觸控點之間的距離
private float distance(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath.sqrt(x * x + y * y);
}
// 計算兩個觸控點的中點
private PointF middle(MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
return new PointF(x / 2, y / 2);
}
}