Andoid实现手动绘图

 public class MainActivity extends Activity
  {
  int width,height;
  private GameView gameview;
  private Canvas canvas;
  private Bitmap map;
  private Paint paint;
  public Path path;
  private int color,pen;
  private boolean isclear=true;
     @SuppressWarnings("deprecation")
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);

     //获得手机屏幕的宽度和高度
         width=getWindowManager().getDefaultDisplay().getWidth();
         height=getWindowManager().getDefaultDisplay().getHeight();

     //设置手机为全屏模式
          requestWindowFeature(Window.FEATURE_NO_TITLE);
          getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

         gameview=new GameView(this, width, height);

         setContentView(gameview);
         canvas=gameview.canvas;
         map=gameview.map;
         paint=gameview.paint;
         path=gameview.dpath;
         color=gameview.color;
     }

 //创建菜单
  public boolean onCreateOptionsMenu(Menu menu) {
             getMenuInflater().inflate(R.menu.activity_main, menu);
             return true;
         }

 //添加菜单事件监听
     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
         switch (item.getItemId()) {
         case R.id.save:
             try
             {
                 Random random=new Random();
                 int a=random.nextInt(100);//产生100以内的数据
                 File f=new File(Environment.getExternalStorageDirectory().getPath()+"/bitmap");
                 f.mkdir();
                     File file=new File(f,a+".jpg");
                     FileOutputStream outstream=new FileOutputStream(file);

                     map.compress(Bitmap.CompressFormat.PNG, 90, outstream);
                     //把bitmap对象保存一张jpg的图片

                     Toast.makeText(this, "保存成功！", Toast.LENGTH_LONG).show();
             }
             catch (FileNotFoundException e)
             {
                 e.printStackTrace();
             }
             break;
         case R.id.Color:
             if(path!=null)
             {
                 canvas.drawPath(path, paint);
                 gameview.invalidate();
             }
             Builder dialog=new AlertDialog.Builder(this);
             dialog.setSingleChoiceItems(new String[]{"红色","绿色","黄色","粉色"}, 0, new OnClickListener()
             {
                 public void onClick(DialogInterface arg0, int arg1) {
                      switch (arg1)
                      {
                     case 0:
                         paint.setColor(Color.RED);
                         break;
                     case 1:
                         paint.setColor(Color.GREEN);
                         break;
                     case 2:
                         paint.setColor(Color.YELLOW);
                         break;
                     case 3:
                         paint.setColor(Color.MAGENTA);
                         break;
                     }
                      pen=paint.getColor();
                 }
             });
             dialog.setPositiveButton("确定", null).create();
             dialog.show();
             gameview.invalidate();
             break;
         case R.id.Paintsize:
             paint.setStrokeWidth(5);
             gameview.invalidate();
             break;
         case R.id.background:
             canvas.drawColor(Color.DKGRAY);
             color=Color.CYAN;
             gameview.invalidate();
             break;
         case R.id.clear:
                 path=new Path();
                 gameview.invalidate();
             break;
         }
         return super.onOptionsItemSelected(item);
     }

 }

 2.绘图操作的GameView类

 public class GameView extends View implements OnTouchListener {
 private float mx,my;//用来存手指移动后的坐标
 public Bitmap map;//对图像的一些操作
 public Canvas canvas;
 public  Path dpath;//主要用来绘制图像的对象，他会把所有绘制的图像保存到path里面
 public Paint paint;//画笔
 public int color;
     public GameView(Context context,int width,int height) {
         super(context);
              map=Bitmap.createBitmap(width,height, Bitmap.Config.ARGB_4444);//绘制一个与手机屏幕大小的BitMap对象
              canvas=new Canvas(map);
              paint=new Paint();
              paint.setAntiAlias(true);//消除锯齿
              paint.setStyle(Style.STROKE);//设置画笔结尾时的样式为圆润
              paint.setStrokeJoin(Paint.Join.ROUND);
              paint.setStrokeCap(Paint.Cap.SQUARE);
              paint.setColor(Color.MAGENTA);
              paint.setStrokeWidth(3);

          this.setOnTouchListener(this);//添加触屏操作
     }

     public void draw(Canvas canvas) {
         super.draw(canvas);
         canvas.drawColor(Color.WHITE);//这里具有清屏的意思
         color=Color.DKGRAY;
         canvas.drawBitmap(map, 0,0, paint);//从 0 0开始到map中的width，height的一块画布，也就是全屏幕的一块画布

         //保存上次绘制的路径，只要他不为空就绘制出上次绘制的图形
         if(dpath!=null)
         {
             canvas.drawPath(dpath, paint);
         }
     }

     public void touch_start(float x,float y)
     {
         dpath.moveTo(x, y);//设置绘制图形的起始点
     }
     public void touch_move(float x,float y)
     {
            // 从x1,y1到x2,y2画一条贝塞尔曲线，更平滑(直接用mPath.lineTo也是可以的)
            dpath.lineTo(x,y);
            mx = x;//把手指移动后的坐标存放到mx,my中，
            my = y;
     }
     public void touch_up()
     {
         dpath.lineTo(mx, my);//设置手指从按下到移动过后之间绘制一条线存放到path中，之后通过下面的方法绘制到屏幕上
         canvas.drawPath(dpath, paint);
     }
     public boolean onTouch(View arg0, MotionEvent event)
     {
           float x = event.getX()获得手指放下的坐标
           float y = event.getY();
           switch (event.getAction())
          {
           case MotionEvent.ACTION_DOWN:
            // 每次down下去重新new一个Path，这是一个要注意的地方，每一次手指从触摸屏幕到离开屏幕，都是一次新的path路径，所以要重新绘制一个新的Path对象
            dpath = new Path();
            touch_start(x, y);//设置起始点
            invalidate();
            break;
           case MotionEvent.ACTION_MOVE:
            touch_move(x, y);
            invalidate();
            break;
           case MotionEvent.ACTION_UP:
            touch_up();
            //invalidate();
            break;
           }
           return true;
     }

 }