画画板

public class MainActivity extends Activity {

private ImageView iv;

int startX;
int startY;

private Canvas canvas;

private Paint paint;

private Bitmap bmCopy;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

//加载画画板的背景图
Bitmap bmSrc = BitmapFactory.decodeResource(getResources(), R.drawable.bg);

bmCopy = Bitmap.createBitmap(bmSrc.getWidth(), bmSrc.getHeight(), bmSrc.getConfig());
paint = new Paint();
canvas = new Canvas(bmCopy);
//绘制
canvas.drawBitmap(bmSrc, new Matrix(), paint);

iv = (ImageView) findViewById(R.id.iv);
iv.setImageBitmap(bmCopy);

//设置触摸侦听
iv.setOnTouchListener(new OnTouchListener() {

//触摸屏幕时，触摸事件产生时，此方法调用
@Override
public boolean onTouch(View v, MotionEvent event) {
int action = event.getAction();
switch (action) {
//用户手指摸到屏幕
case MotionEvent.ACTION_DOWN:
startX = (int) event.getX();
startY = (int) event.getY();
break;
//用户手指正在滑动
case MotionEvent.ACTION_MOVE:
int x = (int) event.getX();
int y = (int) event.getY();
canvas.drawLine(startX, startY, x, y, paint);
//每次绘制完毕之后，本次绘制的结束坐标变成下一次绘制的初始坐标
startX = x;
startY = y;
iv.setImageBitmap(bmCopy);
break;
//用户手指离开屏幕
case MotionEvent.ACTION_UP:
break;

}
//true：告诉系统，这个触摸事件由我来处理
//false：告诉系统，这个触摸事件我不处理，这时系统会把触摸事件传递给imageview的父节点
return true;
}
});

}

public void red(View v){
paint.setColor(Color.RED);
}
public void green(View v){
paint.setColor(Color.GREEN);
}
public void brush(View v){
paint.setStrokeWidth(7);
}
public void save(View v){
File file = new File("sdcard/dazuo.png");
FileOutputStream fos = null;
try {
fos = new FileOutputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
bmCopy.compress(CompressFormat.PNG, 100, fos);

//发送sd卡就绪广播
Intent intent = new Intent();
intent.setAction(Intent.ACTION_MEDIA_MOUNTED);
intent.setData(Uri.fromFile(Environment.getExternalStorageDirectory()));
sendBroadcast(intent);
}
}