OnTouchEvent无法在Android中正常工作

Question

the problem is is that the touchX and Y are not saving the value taken on ACTION.DOWN, how to keep this last values? I wan to be able to draw a single line with coordinates from ACTION.DOWN to ACTION.U

@Override
public boolean onTouchEvent(MotionEvent event) {
 //detect user touch
    float touchX = 0;// I've try = event.getX();
    float touchY= 0;// = event.getY();
    float upX = 0;// = event.getX();
    float upY = 0;// = event.getX();

    switch (event.getAction()) {

        //case MotionEvent.ACTION_DOWN:
        case MotionEvent.ACTION_DOWN:
            touchX = event.getX();
            touchY = event.getY();
            drawCanvas.drawText("x:"+ touchX + " ,y:"+ touchY,touchX, touchY, canvasPaint);
            break;

        case MotionEvent.ACTION_MOVE:
            //skip
            break;

        case MotionEvent.ACTION_UP:
            upX = event.getX();
            upY = event.getY();

            drawCanvas.drawText("x2:"+ touchX + " ,y2:"+ touchY,upX, upY, canvasPaint);
            drawCanvas.drawLine(touchX, touchY, upX, upY, drawPaint);
            //the problem is is that the touchX and Y are not saving the value taken on ACTION.DOWN, how to keep this last values? 
            break;
        default:
            return false;
    }
    invalidate();
    return true;
}

Answer 1

If you want to save the values you must add the method variables as object attributes, if your method is just what you posted, you just need touchX and touchY :

public class YourView extends View {
    // class attributes   
    float touchX = 0;
    float touchY= 0;

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //detect user touch        
        switch (event.getAction()) {
            // your logic using touchX and touchY now 
            // will keep values assigned here
        }
    }
}

If you need to use it more than once, you can create your own class to save coordinates:

class MyPoint {
    private float x;
    private float y;

    public MyPoint(float x, float y) {
        this.x = x;
        this.y = y;
    }

    public float getX() {
        return x;
    }

    public void setX(float x) {
        this.x = x;
    }

    public float getY() {
        return y;
    }

    public void setY(float y) {
        this.y = y;
    }

    @Override
    public String toString() {
        return "x:"+ x + " ,y:"+ y;
    }
}

And use it like:

public class YourView extends View {
    // class attributes   
    private MyPoint touchPoint;

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()) {

            case MotionEvent.ACTION_DOWN:
                touchPoint = new MyPoint(event.getX(), event.getY());
                drawCanvas.drawText(touchPoint.toString(), canvasPaint);
                break;

            // more!!!