android 繪圖程式範例

拿這個範例改的（修正原本要畫完放開滑鼠之後才會出現線段）

http://www.tutorialforandroid.com/2009/06/drawing-with-canvas-in-android.html

source code:

package com.cyl.android.draw;



import java.util.ArrayList;

import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Paint;

import android.graphics.Path;

import android.os.Bundle;

import android.view.MotionEvent;

import android.view.SurfaceHolder;

import android.view.SurfaceView;



public class draw extends Activity {

private ArrayList _graphics = new ArrayList();

private Paint mPaint;







@Override

 public void onCreate(Bundle savedInstanceState) {

     super.onCreate(savedInstanceState);

     setContentView(new DrawingPanel(this));

     mPaint = new Paint();

     mPaint.setDither(true);

     mPaint.setColor(0xFFFF0000);

     mPaint.setStyle(Paint.Style.STROKE);

     mPaint.setStrokeJoin(Paint.Join.ROUND);

     mPaint.setStrokeCap(Paint.Cap.ROUND);

     mPaint.setStrokeWidth(3);



}







class DrawingPanel extends SurfaceView implements SurfaceHolder.Callback {

private DrawingThread _thread;

private Path path;



public DrawingPanel(Context context) {

 super(context);

         getHolder().addCallback(this);

         _thread = new DrawingThread(getHolder(), this);

}



@Override

     public boolean onTouchEvent (MotionEvent event) {

         synchronized (_thread.getSurfaceHolder()) {

          if(event.getAction() == MotionEvent.ACTION_DOWN){

           path = new Path();

           path.moveTo(event.getX(), event.getY());

          }else if(event.getAction() == MotionEvent.ACTION_MOVE){

           path.lineTo(event.getX(), event.getY());

           _graphics.add(path);

           path = new Path();

           path.moveTo(event.getX(), event.getY());

          }else if(event.getAction() == MotionEvent.ACTION_UP){

           path.lineTo(event.getX(), event.getY());

           _graphics.add(path);

          }

        

          return true;

         }

}



@Override

     public void onDraw(Canvas canvas) {

 for (Path path : _graphics) {

  canvas.drawPath(path, mPaint);

 }

}







public void surfaceCreated(SurfaceHolder holder) {

 // TODO Auto-generated method stub

 _thread.setRunning(true);

         _thread.start();

}



public void surfaceDestroyed(SurfaceHolder holder) {

 // TODO Auto-generated method stub

 boolean retry = true;

         _thread.setRunning(false);

         while (retry) {

             try {

                 _thread.join();

                 retry = false;

             } catch (InterruptedException e) {

                 // we will try it again and again...

             }

         }

}



@Override

public void surfaceChanged(SurfaceHolder holder, int format, int width,

  int height) {

 // TODO Auto-generated method stub



}

}



class DrawingThread extends Thread {

     private SurfaceHolder _surfaceHolder;

     private DrawingPanel _panel;

     private boolean _run = false;



     public DrawingThread(SurfaceHolder surfaceHolder, DrawingPanel panel) {

         _surfaceHolder = surfaceHolder;

         _panel = panel;

     }



     public void setRunning(boolean run) {

         _run = run;

     }



     public SurfaceHolder getSurfaceHolder() {

         return _surfaceHolder;

     }



     @Override

     public void run() {

         Canvas c;

         while (_run) {

             c = null;

             try {

                 c = _surfaceHolder.lockCanvas(null);

                 synchronized (_surfaceHolder) {

                     _panel.onDraw(c);

                 }

             } finally {

                 // do this in a finally so that if an exception is thrown

                 // during the above, we don't leave the Surface in an

                 // inconsistent state

                 if (c != null) {

                     _surfaceHolder.unlockCanvasAndPost(c);

                 }

             }

         }

     }

 }

}