Android Studio GridLayout onTouch 事件

Question

我想创建一个可以更改 GridLayout 手势颜色的应用程序。 My_GridLayout它适用于以下代码:

@Override
public void onDraw(Canvas canvas) {
    if (touchOn) {
        canvas.drawColor(Color.RED);
    } else {
        canvas.drawColor(Color.GRAY);
    }
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    super.onTouchEvent(event);
    touchOn = true;
    invalidate();
    return true;
}

使用xml代码:

<GridLayout
    android:id="@+id/mygrid"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:columnCount="8"
    android:rowCount="8"
    android:layout_gravity="center"
    android:background="@android:color/background_light"
    android:layout_below="@+id/linearLayout3">
</GridLayout>

但我只能通过触摸网格来改变一个手势的颜色。是否有 MotionEvent 或其他检测到我触摸了一个手势并移动(没有松开手指)到下一个手势的东西？这样我就可以用手指在网格上移动，颜色会一个接一个地变化。

谢谢!!!

Answer 1

您可以通过在 MainActivity 中实现 GestureDetector.OnGestureListener 和 GestureDetector.OnDoubleTapListener 方法来检测手势，并更改每个手势的颜色:

public class MainActivity extends Activity implements 
        GestureDetector.OnGestureListener,
        GestureDetector.OnDoubleTapListener{

    private static final String DEBUG_TAG = "Gestures";
    private GestureDetectorCompat mDetector; 

    // Called when the activity is first created. 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Instantiate the gesture detector with the
        // application context and an implementation of
        // GestureDetector.OnGestureListener
        mDetector = new GestureDetectorCompat(this,this);
        // Set the gesture detector as the double tap
        // listener.
        mDetector.setOnDoubleTapListener(this);
    }

    @Override 
    public boolean onTouchEvent(MotionEvent event){ 
        this.mDetector.onTouchEvent(event);
        // Be sure to call the superclass implementation
        return super.onTouchEvent(event);
    }

    @Override
    public boolean onDown(MotionEvent event) { 
        Log.d(DEBUG_TAG,"onDown: " + event.toString()); 
        return true;
    }

    @Override
    public boolean onFling(MotionEvent event1, MotionEvent event2, 
            float velocityX, float velocityY) {
        Log.d(DEBUG_TAG, "onFling: " + event1.toString()+event2.toString());
        return true;
    }

    @Override
    public void onLongPress(MotionEvent event) {
        Log.d(DEBUG_TAG, "onLongPress: " + event.toString()); 
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,
            float distanceY) {
        Log.d(DEBUG_TAG, "onScroll: " + e1.toString()+e2.toString());
        return true;
    }

    @Override
    public void onShowPress(MotionEvent event) {
        Log.d(DEBUG_TAG, "onShowPress: " + event.toString());
    }

    @Override
    public boolean onSingleTapUp(MotionEvent event) {
        Log.d(DEBUG_TAG, "onSingleTapUp: " + event.toString());
        return true;
    }

    @Override
    public boolean onDoubleTap(MotionEvent event) {
        Log.d(DEBUG_TAG, "onDoubleTap: " + event.toString());
        return true;
    }

    @Override
    public boolean onDoubleTapEvent(MotionEvent event) {
        Log.d(DEBUG_TAG, "onDoubleTapEvent: " + event.toString());
        return true;
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent event) {
        Log.d(DEBUG_TAG, "onSingleTapConfirmed: " + event.toString());
        return true;
    }
}

您还可以跟踪触摸事件中的移动。

You could have a movement-based gesture that is simply based on the distance and/or direction the pointer traveled. But velocity often is a determining factor in tracking a gesture's characteristics or even deciding whether the gesture occurred. To make velocity calculation easier, Android provides the VelocityTracker class and the VelocityTrackerCompat class in the Support Library. VelocityTracker helps you track the velocity of touch events. This is useful for gestures in which velocity is part of the criteria for the gesture, such as a fling.

这是一个例子。

public class MainActivity extends Activity {
    private static final String DEBUG_TAG = "Velocity";
        ...
    private VelocityTracker mVelocityTracker = null;
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int index = event.getActionIndex();
        int action = event.getActionMasked();
        int pointerId = event.getPointerId(index);

        switch(action) {
            case MotionEvent.ACTION_DOWN:
                if(mVelocityTracker == null) {
                    // Retrieve a new VelocityTracker object to watch the velocity of a motion.
                    mVelocityTracker = VelocityTracker.obtain();
                }
                else {
                    // Reset the velocity tracker back to its initial state.
                    mVelocityTracker.clear();
                }
                // Add a user's movement to the tracker.
                mVelocityTracker.addMovement(event);
                break;
            case MotionEvent.ACTION_MOVE:
                mVelocityTracker.addMovement(event);
                // When you want to determine the velocity, call 
                // computeCurrentVelocity(). Then call getXVelocity() 
                // and getYVelocity() to retrieve the velocity for each pointer ID. 
                mVelocityTracker.computeCurrentVelocity(1000);
                // Log velocity of pixels per second
                // Best practice to use VelocityTrackerCompat where possible.
                Log.d("", "X velocity: " + 
                        VelocityTrackerCompat.getXVelocity(mVelocityTracker, 
                        pointerId));
                Log.d("", "Y velocity: " + 
                        VelocityTrackerCompat.getYVelocity(mVelocityTracker,
                        pointerId));
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                // Return a VelocityTracker object back to be re-used by others.
                mVelocityTracker.recycle();
                break;
        }
        return true;
    }
}

见 https://developer.android.com/training/gestures/detector.html :

A "touch gesture" occurs when a user places one or more fingers on the touch screen, and your application interprets that pattern of touches as a particular gesture. There are correspondingly two phases to gesture detection:

• Gathering data about touch events.
• Interpreting the data to see if it meets the criteria for any of the gestures your app supports.

和https://developer.android.com/training/gestures/movement.html#velocity :

A new onTouchEvent() is triggered with an ACTION_MOVE event whenever the current touch contact position, pressure, or size changes. As described in Detecting Common Gestures, all of these events are recorded in the MotionEvent parameter of onTouchEvent().