java - onSingleTapConfirmed 未给出准确的 y 坐标

Question

MainActivity类使用GestureDetector获取坐标的代码:

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

    DrawView drawView;
    private GestureDetectorCompat g1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        drawView = new DrawView(this);
        drawView.setBackgroundColor(Color.TRANSPARENT);
        setContentView(drawView);
        g1 = new GestureDetectorCompat(this,this);
        g1.setOnDoubleTapListener(this);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        g1.onTouchEvent(event);
        return super.onTouchEvent(event);
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
        drawView.setXandY(e.getX(), e.getY());
        Log.v("id2","message2");
        return false;
    }

使用此坐标的代码:

public class DrawView extends View {
    Paint paint = new Paint();
    static float x_touch = -1;
    static float y_touch = -1;
    static int [][] arr = new int[][]{{-1,-1,-1},{-1,-1,-1},{-1,-1,-1}};
    static int maxX = -1, maxY = -1;
    public DrawView(Context context) {
        super(context);
        super.setWillNotDraw(false);
        paint.setColor(Color.BLACK);
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Display mdisp = ((WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
        Point mdispSize = new Point();
        mdisp.getSize(mdispSize);
        maxX = mdispSize.x;
        maxY = mdispSize.y;
        canvas.drawLine(maxX/3, 0, maxX/3, maxY, paint);
        canvas.drawLine(maxX*2/3, 0, maxX*2/3, maxY, paint);
        canvas.drawLine(0, maxY / 3, maxX, maxY / 3, paint);//This is first Horizontal line

        canvas.drawLine(0, maxY * 2 / 3, maxX, maxY * 2 / 3, paint); //This is second horizontal line

        Log.v("id1", "message1");
        paint.setTextSize(150f);
        if (x_touch>0 && y_touch>0) {
            if (x_touch < maxX/3 && y_touch < maxY/3)
                canvas.drawText("X", maxX/6, maxY/6, paint);
            else if (x_touch>maxX/3 && x_touch<2*maxX/3 && y_touch<maxY/3)
                canvas.drawText("X", maxX/2, maxY/6, paint);
            else if (x_touch>maxX*2/3 && y_touch<maxY/3)
                canvas.drawText("X", 5*maxX/6, maxY/6, paint);
            else if (x_touch<maxX/3 && y_touch>maxY/3 && y_touch<2*maxY/3)
                canvas.drawText("X", maxX/6, maxY/2, paint);
            else if (x_touch>maxX/3 && x_touch<2*maxX/3 && y_touch>maxY/3 && y_touch<2*maxY/3)
                canvas.drawText("X", maxX/2, maxY/2, paint);
            else if (x_touch>2*maxX/3 && y_touch>maxY/3 && y_touch<2*maxY/3)
                canvas.drawText("X", 5*maxX/6, maxY/2, paint);
            else if (x_touch<maxX/3 && y_touch>2*maxY/3)
                canvas.drawText("X", maxX/6, 5*maxY/6, paint);
            else if (x_touch>maxX/3 && x_touch<2*maxX/3 && y_touch>2*maxY/3)
                canvas.drawText("X", maxX/2, 5*maxY/6, paint);
            else if (x_touch>2*maxX/3 && y_touch>2*maxY/3)
                canvas.drawText("X", 5*maxX/6, 5*maxY/6, paint);
            Log.v("id3", "maxX="+Float.toString(maxX)+" maxY="+Float.toString(maxY)+
                    " x_touch="+Float.toString(x_touch)+" y_touch="+Float.toString(y_touch));
        }
    }

    public void setXandY(float x, float y) {
        x_touch = x;
        y_touch = y;
        this.invalidate();
    }
}

单击第一条水平线上方将在第一条水平线下方打印“X”，点击第二条水平线上方将在第二条水平线下方打印“X”。

Logcat 显示，单击第一条水平线上方确实会给出大于 maxY/3 的值。

编辑:我尝试从应用程序中删除标题栏，其准确性在一定程度上有所提高，但仍然不是很准确。

Answer 1

问题是您正在使用 Activity ( documentation ) 的 onTouchEvent 接收到的 MotionEvent ，因此您的坐标是接收是基于 Activity 而不是基于 View 。

要解决您的问题，您可以将手势检测移至 DrawView:

public class DrawView extends View implements GestureDetector.OnGestureListener, GestureDetector.OnDoubleTapListener {
    private GestureDetectorCompat g1;

    public DrawView(final Context context) {
        super(context);

        g1 = new GestureDetectorCompat(getContext(), this);
        g1.setOnDoubleTapListener(this);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        g1.onTouchEvent(event);
        return super.onTouchEvent(event);
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
        setXandY(e.getX(), e.getY());
        Log.v("id2","message2");
        return false;
    }
}

此外，要在 DrawView 上接收触摸事件，请不要忘记使其可点击:

drawView.setClickable(true);

根据评论进行编辑:

在此示例中，黑色 X 代表触摸。

当你在View的onTouchEvent上收到MotionEvent时，你收到的坐标是View相关的，所以你会收到(124 ，187)。

当你在Activity的onTouchEvent上接收到MotionEvent时，你接收到的坐标是与Activity相关的，所以你会接收到(324 ，487)。

当你在View上绘制时，坐标是View相关的，所以如果你绘制接收到的Activity相关的坐标，你就会在红点上绘制。