TouchingView.java

package com.godoro.androidgraphics;

import android.content.*;
import android.graphics.*;
import android.view.*;

public class TouchingView extends View implements View.OnTouchListener {

    private Paint paintDown=new Paint();
    private Paint paintMove=new Paint();
    private Paint paintUp=new Paint();
    private float touchDownX=-1;
    private float touchDownY=-1;
    private float touchMoveX=-1;
    private float touchMoveY=-1;
    private float touchUpX=-1;
    private float touchUpY=-1;


    public TouchingView(Context context) {
        super(context);
        paintDown.setColor(Color.GREEN);
        paintMove.setColor(Color.YELLOW);
        paintUp.setColor(Color.RED);
        setOnTouchListener(this);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if(touchDownX>-1 && touchDownY>-1){
            canvas.drawCircle(touchDownX, touchDownY, 20.0f, paintDown);
        }
        if(touchMoveX>-1 && touchMoveY>-1){
            canvas.drawCircle(touchMoveX, touchMoveY, 20.0f, paintMove);
        }
        if(touchUpX>-1 && touchUpY>-1){
            canvas.drawCircle(touchUpX, touchUpY, 20.0f, paintUp);
        }
    }

    @Override
    public boolean onTouch(View view, MotionEvent event) {
        if(event.getActionMasked()==MotionEvent.ACTION_DOWN){
            touchDownX=event.getX();
            touchDownY=event.getY();
        }else if(event.getActionMasked()==MotionEvent.ACTION_MOVE){
            touchMoveX=event.getX();
            touchMoveY=event.getY();

        }else if(event.getActionMasked()==MotionEvent.ACTION_UP){
            touchUpX=event.getX();
            touchUpY=event.getY();
        }
        invalidate();
        return true;
    }

}