How to get Touch Location on Screen (Android)

Question

I am developing game in android, in that game I am using canvas to show grid(5*6) of circles. I want to check location of Touch area. For Example if I touch/Tap on screen around two adjacent circles it should return location or if possible it should display line between those circles. For that I used this onTouchEvent() method. But I am not getting any output on my device's screen. I have checked on Stackoverflow there was method given there but it doesn't help me, here is the link(How to get the Touch position in android?). I request you to please check this code and suggest solution. Here is the code file:

   package com.example.tap;

import android.os.Bundle;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.gesture.Gesture;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.Log;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new board(this));
    }

    public class board extends View
    {
        Paint pBack = new Paint();
        Paint pDot  = new Paint();
        int xpos=0;
        int ypos=0;

        int cols = 5;
        int rows = 6;

        public board(Context context)
        {
            super(context);
            pBack.setARGB(255, 15, 102, 0);
            pDot.setARGB(255, 255, 255, 255);
        }

        @SuppressLint("DrawAllocation")
        protected void onDraw(Canvas canvas)
        {
            super.onDraw(canvas);
            canvas.drawPaint(pBack);
            float xStep = canvas.getWidth() / (cols + 1);
            float yStep = canvas.getHeight() / (rows + 1);
            float curCirclXpos, curCirclYpos, lastCirclXpos = 0, lastCirclYpos =0;
            //float vertical= 
//          boolean onTap(Gesture g, Point p)
//          {
//              
//          }

            for (int y = 0; y < rows; y++)
            {
                for (int x = 0; x < cols; x++)
                {
                    canvas.drawCircle((x + 1) * xStep, (y + 1) * yStep, 20, pDot);
                    curCirclXpos=x;
                    curCirclYpos=y;

                    if (y == 0)
                    {
                        //canvas.drawLine((x + 1) * xStep, yStep, (x + 1) * xStep, rows * yStep, pDot);
                        //canvas.drawLine(xpos, ypos, xpos, yStep, pDot);
                        canvas.drawLine(curCirclXpos, curCirclYpos, lastCirclXpos, lastCirclYpos, pDot);
                    }                   
                }

                //canvas.drawLine(xStep, (y + 1) * yStep, cols * xStep, (y + 1) * yStep, pDot);
            }
        }
        public boolean onTouchEvent(MotionEvent e)
        {
            xpos=(int) e.getX();
           ypos=(int) e.getY();
            switch (e.getAction())
            {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_MOVE:
                //Log.d("Umar",String.valueOf(xpos));
                //Log.d("Farooq",String.valueOf(ypos));

            break;

            }
            return false;


        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }


}

You need to add some code to your switch event, currently your code will most likely get the X and Y values but do nothing with with them Try "Log.d("DEBUG", String.valueOf(xpos));" and check Logcat see if it displays the X co-ord on touch. — Pheonix2105, Mar 31 '14 at 11:07
Yes it worked. What would be the print statement for screen. — Umar Farooq, Mar 31 '14 at 11:12
You would need need to use the co-ords from the touch event to draw whatever it is you wish to draw on screen. I'll update my answer below. — Pheonix2105, Mar 31 '14 at 11:16
I need to draw a line either vertically or horizontally. That line should be between only two circles not more then two. — Umar Farooq, Mar 31 '14 at 11:18

Pheonix2105 · Accepted Answer · 2014-03-31T11:39:15.437

public boolean onTouchEvent(MotionEvent e)
        {
            int xpos=(int) e.getX();
            int ypos=(int) e.getY();
            switch (e.getAction())
            {
            case MotionEvent.ACTION_DOWN:
             Log.d("DEBUG", "On touch (down)" + String.valueOf(xpos) + String.valueOf(ypos));
            case MotionEvent.ACTION_UP:
            Log.d("DEBUG", "On touch (up)" + String.valueOf(xpos) + String.valueOf(ypos));
            case MotionEvent.ACTION_MOVE:
            Log.d("DEBUG", "On touch (move)" + String.valueOf(xpos) + String.valueOf(ypos));
            break;
        }
        return true;

    }

Then override the draw method

 @Override
  public void draw(Canvas canvas) {
   super.draw(canvas);
   }

So you try

canvas.drawLine(startX, startY, stopX, stopY, paint);

To make a line go straight up try

canvas.drawLine(xpos, ypos, xpos, getHeight() , new Paint());

Get height should be your screen's height (Since your drawing a line straight up)

For this the variables xpos and ypos should be available to all methods so add

int xpos,ypos = 0;

To the the top of your code (but within the class declaration)

For drawling a between the circles you would need to get the first circles x,y position on touch then set the drawLine method with them, so something like:

currentCircleXpos, lastCircleXpos = 0; //you would set these in the onDraw method when the circle get's drawn.
currentCircleYpos, lastCircleypos = 0;


canvas.drawLine(currentCircleXpos, currentCircleYpos, lastCircleXpos, lastCircleYpos , new Paint());

OnDraw() method-------

 for (int y = 0; y < rows; y++)
    {
        for (int x = 0; x < cols; x++)
        {
            canvas.drawCircle((x + 1) * xStep, (y + 1) * yStep, 20, pDot);
             currentCircleXpos = x;
              currentCircleYpos = y; //gets the circle that is being drawn's location
        if (y == 0)
        {
            //canvas.drawLine((x + 1) * xStep, yStep, (x + 1) * xStep, rows * yStep, pDot);
        }                   
    }

    //canvas.drawLine(xStep, (y + 1) * yStep, cols * xStep, (y + 1) * yStep, pDot);
}

Now I want to show a line between two circles, how I will do that? — Umar Farooq, Mar 31 '14 at 11:15
you can see my question. I tried to draw lines, without using any touch event. — Umar Farooq, Mar 31 '14 at 11:23
and those lines were between 1st circle to last circle horizontally and vertically now I was trying to display line between only two circles after occurrence of touch event. — Umar Farooq, Mar 31 '14 at 11:24
You could use the same code but change the drawLine method, I'll update again to give you a rough idea. — Pheonix2105, Mar 31 '14 at 11:27
Please check code now. Without tapping on screen It shows a small line on my device's upper left corner of screen. — Umar Farooq, Mar 31 '14 at 13:26

How to get Touch Location on Screen (Android)

1 Answers1