Android (x,y) continuous touch (drag) coordinates

问题

I'm new to android, and I've been trying for a while to find out how can I retrieve the coordinates of a continuous touch on the screen. for example have 2 vars (x,y) that update in real time as finger moves around. I got it how to find it when the touch is made, but I really don;t get it how to make it return the result after that , when the finger is moving.

I've been trying switch statements, while/for loops in different combination with ACTION_MOVE./ UP/ DOWN .. .still nothing.

I've found like the same question on the website, but the answers only fit for the first step(showing the coordination from the touch only) I'd really appreciate a solution to this! Thanks!

回答1:

Without seeing your code I'm just guessing, but essentially if you don't return true to the first call to onTouchEvent, you won't see any of the subsequent events in the gesture (MOVE, UP, etc).

Maybe that is your problem? Otherwise please put code sample up.

回答2:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    final TextView xCoord = (TextView) findViewById(R.id.textView1);
    final TextView yCoord = (TextView) findViewById(R.id.textView2);

    final View touchView = findViewById(R.id.textView3);
    touchView.setOnTouchListener(new View.OnTouchListener() {

        public boolean onTouch(View v, MotionEvent event) {
            final int action = event.getAction();
            switch (action & MotionEvent.ACTION_MASK) {

                case MotionEvent.ACTION_DOWN: {
                    xCoord.setText(String.valueOf((int) event.getX()));
                    yCoord.setText(String.valueOf((int) event.getY()));
                    break;
                }

                case MotionEvent.ACTION_MOVE:{
                    xCoord.setText(String.valueOf((int) event.getX()));
                    yCoord.setText(String.valueOf((int) event.getY()));
                    break;
                }
            }
            return true;

        }

    });
}

回答3:

You need to implement an OnTouchListener for whatever view you want to recognize the drag.

Then in the OnTouchListener you need to display the X and Y coordinates. I believe you can get those via MotionEvent.getRawX() and MotionEvent.getRawY()

You can use the MotionEvent.getAction() method to find out when a drag is occurring. I believe the constant is MotionEvent.ACTION_MOVE. Here is some psuedo-code:

Add OnTouchListener interface

public class XYZ extends Activity implements OnTouchListener

public void onCreate(Bundle savedInstanceState)
{
    //other code

    View onTouchView = findViewById(R.id.whatever_id);
    onTouchView.setOnTouchListener(this);
}

Implement the onTouch method

public boolean onTouch(View view, MotionEvent event) 
{
    if(event.getAction() == MotionEvent.ACTION_MOVE)
    {
        float x = event.getRawX();
        float y = event.getRawY();
        //  Code to display x and y go here
        // you can print the x and y coordinate in a textView for exemple
    }
}

来源：https://stackoverflow.com/questions/10791389/android-x-y-continuous-touch-drag-coordinates

标签

android

touch

coordinates