Question

我一直在学习Android上的多点触控，但我无法理解我发现的一些行。我搜索谷歌但找不到那些可以理解的资源。我发布了代码。

除了“onTouch方法的前两行”，if (event.getAction() != MotionEvent.ACTION_MOVE && i != pointerIndex)和case MotionEvent.ACTION_MOVE:

之外，我理解了大部分内容

请解释一下。谢谢你的帮助~~

package --- ;

--imports--

@TargetApi(5)
public class MultiTouchTest extends Activity implements OnTouchListener {
StringBuilder builder = new StringBuilder();
TextView textView;
float[] x = new float[10];
float[] y = new float[10];
boolean[] touched = new boolean[10];
int[] id = new int[10];

private void updateTextView() {
    builder.setLength(0);
    for (int i = 0; i < 10; i++) { 
        builder.append(touched[i]);
        builder.append(", ");
        builder.append(id[i]);
        builder.append(", ");
        builder.append(x[i]);
        builder.append(", ");
        builder.append(y[i]);
        builder.append("\n");
    }
    textView.setText(builder.toString());
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    textView = new TextView(this);
    textView.setText("Touch and drag(multiple fingers supported!");
    textView.setOnTouchListener(this);
    setContentView(textView);
    for (int i = 0; i < 10; i++) {
        id[i] = -1; 
    }
    updateTextView();
}

@Override
public boolean onTouch(View v, MotionEvent event) {
    int action = event.getAction() & MotionEvent.ACTION_MASK; 
    int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >> MotionEvent.ACTION_POINTER_ID_SHIFT; 
    int pointerCount = event.getPointerCount(); 
    for (int i = 0; i < 10; i++) { 
        if (i >= pointerCount) {
            touched[i] = false;
            id[i] = -1;
            continue;
        }

        if (event.getAction() != MotionEvent.ACTION_MOVE
                && i != pointerIndex) { 

            continue;
        }
        int pointerId = event.getPointerId(i);
        switch (action) {
        case MotionEvent.ACTION_DOWN:
        case MotionEvent.ACTION_POINTER_DOWN:
            touched[i] = true;
            id[i] = pointerId;
            x[i] = (int) event.getX(i);
            y[i] = (int) event.getY(i);
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_POINTER_UP:
        case MotionEvent.ACTION_OUTSIDE:
        case MotionEvent.ACTION_CANCEL:
            touched[i] = false;
            id[i] = -1;
            x[i] = (int) event.getX(i);
            y[i] = (int) event.getY(i);
            break;
        case MotionEvent.ACTION_MOVE:
            touched[i] = true;
            id[i] = pointerId;
            x[i] = (int) event.getX(i);
            y[i] = (int) event.getY(i);
            break;
        }

    }
    updateTextView();

    return true;
}
}

Answer 1

    /*Extract the index of the pointer that touch the sensor
    Return the masked action being performed, without pointer index 
     information.
    May be any of the actions: ACTION_DOWN, ACTION_MOVE, ACTION_UP,
     ACTION_CANCEL, ACTION_POINTER_DOWN, or ACTION_POINTER_UP.
    And return the index associated with pointer actions.*/

 **int action = event.getAction() & MotionEvent.ACTION_MASK;** 

     /* Extract the index of the pointer that left the touch sensor
     For ACTION_POINTER_DOWN or ACTION_POINTER_UP as returned by getActionMasked(),
     this returns the associated pointer index. The index may be used with 
getPointerId(int), getX(int), getY(int), getPressure(int), and getSize(int)
to get information about the pointer that has gone down or up.*/

**int pointerIndex = (event.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >> MotionEvent.ACTION_POINTER_ID_SHIFT;**

有关详细信息，请参阅： Link 1 Link 2

了解Android中的多点触控

1 个答案: