Java: Breakout game, move player as I swipe?

Question

I'm making a simple Breakout game, and so far I have created the ball and the player. I made the ball so that it moves to the position you touch, but I'd rather have it moving towards the direction I swipe. As in, the player moves along with my finger. Here's the code I have in my MainActivity:

package com.example.breakout;

import android.os.Bundle;
import android.app.Activity;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class MainActivity extends Activity implements OnTouchListener, OnGestureListener{

    BreakoutView bv;
    GestureDetector gs;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        bv = new BreakoutView(this);
        setContentView(bv);
        bv.setOnTouchListener(this);


        gs = new GestureDetector(MainActivity.this, this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);

        return true;
    }

    @Override
    public boolean onTouch(View arg0, MotionEvent arg1) {
        /*if(arg1.getY()<600){
            bv.p1.x = arg1.getX();
            bv.p1.y = 600;
        }*/
        return false;
    }

    @Override
    public boolean onTouchEvent(MotionEvent me){
        return gs.onTouchEvent(me);
    }

    @Override
    public boolean onDown(MotionEvent arg0) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        /*if(e2.getX()>e1.getX()){
            //Move right
            bv.p1.x = e2.getX();

        }*/

        return false;
    }

    @Override
    public void onLongPress(MotionEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public boolean onScroll(MotionEvent arg0, MotionEvent arg1, float arg2,
            float arg3) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public void onShowPress(MotionEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public boolean onSingleTapUp(MotionEvent arg0) {
        // TODO Auto-generated method stub
        return false;
    }

}

So, the two methods I have tried are the onTouch and the onFling ones. The onTouch "teleports" my player where I touch, which isn't what I want. The onFling only moves my player when I'm done swiping, so that doesnt work either. My question is, how can I make it move as I swipe my finger? Do I use onDown? Any help is appreciated.

Thanks!

A fine choice for a game starter project. :-) The trouble I found with "teleporting" the paddle was that it could end up "inside" the ball and confuse the collision detection. Otherwise, it was sort of amusing to wave my finger quickly and see how far the input lagged behind the game, so I left it alone. Code + APK here if you want to compare: https://code.google.com/p/android-breakout/ — fadden, Feb 20 '13 at 02:13

score 1 · Accepted Answer · answered Jan 30 '13 at 16:10

Assuming you have some sort of game loop set up where the UI is updated on intervals:

/**
 * Onclick event for Touch Screen
 */
@Override
public boolean onTouchEvent(MotionEvent input) {
    if (input.getAction() == MotionEvent.ACTION_MOVE) {
        float currX = input.getX();
        float currY = input.getY();

        if (!swiping) {
            swiping = true;
            swipeStartY = currY;
            swipeStartX = currX;
        }

        if (swiping) {          
            double newDirection = Math.atan2((currY-ball.getY()),currX-ball.getX());
            ball.setDirection(newDirection);
        }

    } else if (input.getAction() == MotionEvent.ACTION_UP) {
        if (swiping) {
            swiping = false;
        }
    }
}

This way the ball's direction is updated on each tick of the game thread and moves towards your finger (the touch event X/Y location). I'm not sure how you have set up your drawing/physics/etc. so I can't provide meaningful function calls here. If you need to modify it so it swipes in a straight line after you lift your finger then store the initial X/Y point (swipeStartX/swipeStartY in this case) and only set the new direction after you stop swiping.

EDIT:

I should mention, my class definition that contains this code is as follows:

public class GameView extends SurfaceView implements SurfaceHolder.Callback {
  ....
}

Java: Breakout game, move player as I swipe?

1 Answers1