我想画一个用户触摸屏幕的圆圈.
public class MainActivity extends Activity implements OnTouchListener {
LinearLayout layout;
float x=0;
float y=0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_main);
layout=(LinearLayout)findViewById(R.id.layout);
layout.addView(new CustomView(MainActivity.this));
}
public class CustomView extends View {
Bitmap mBitmap;
Paint paint;
public CustomView(Context context) {
super(context);
mBitmap = Bitmap.createBitmap(400,800,Bitmap.Config.ARGB_8888);
paint=new Paint();
paint.setColor(Color.RED);
paint.setStyle(Style.FILL);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.setBitmap(mBitmap);
canvas.drawCircle(x,y,50,paint);
Toast.makeText(MainActivity.this,"DDD",1).show();
}
}
@Override
public boolean onTouch(View v,MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
layout.invalidate();
}
return false;
}}
解决方法
我会这样做：
public class TestActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new DrawingView(this));
}
class DrawingView extends SurfaceView {
private final SurfaceHolder surfaceHolder;
private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
public DrawingView(Context context) {
super(context);
surfaceHolder = getHolder();
paint.setColor(Color.RED);
paint.setStyle(Style.FILL);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if(event.getAction() == MotionEvent.ACTION_DOWN) {
if (surfaceHolder.getSurface().isValid()) {
Canvas canvas = surfaceHolder.lockCanvas();
canvas.drawColor(Color.BLACK);
canvas.drawCircle(event.getX(),event.getY(),paint);
surfaceHolder.unlockCanvasAndPost(canvas);
}
}
return false;
}
}
}