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;
    }

}