我正在尝试修改我用于进行相机预览的SurfaceView,以显示重叠的方块。但是,从不调用扩展SurfaceView的onDraw方法。
以下是来源:
public class CameraPreviewView extends SurfaceView {
protected final Paint rectanglePaint = new Paint();
public CameraPreviewView(Context context, AttributeSet attrs) {
super(context, attrs);
rectanglePaint.setARGB(255, 200, 0, 0);
rectanglePaint.setStyle(Paint.Style.FILL);
rectanglePaint.setStrokeWidth(2);
}
@Override
protected void onDraw(Canvas canvas){
canvas.drawRect(new Rect(10,10,200,200), rectanglePaint);
Log.w(this.getClass().getName(), "On Draw Called");
}
}
public class CameraPreview extends Activity implements SurfaceHolder.Callback{
private SurfaceHolder holder;
private Camera camera;
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
// We remove the status bar, title bar and make the application fullscreen
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
// We set the content view to be the layout we made
setContentView(R.layout.camera_preview);
// We register the activity to handle the callbacks of the SurfaceView
CameraPreviewView surfaceView = (CameraPreviewView) findViewById(R.id.camera_surface);
holder = surfaceView.getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
Camera.Parameters params = camera.getParameters();
params.setPreviewSize(width, height);
camera.setParameters(params);
try {
camera.setPreviewDisplay(holder);
} catch (IOException e) {
e.printStackTrace();
}
camera.startPreview();
}
public void surfaceCreated(SurfaceHolder holder) {
camera = Camera.open();
}
public void surfaceDestroyed(SurfaceHolder holder) {
camera.stopPreview();
camera.release();
}
}
答案 0 :(得分:75)
在android-developers Google群组上找到它。你只需要添加:
setWillNotDraw(false)
到构造函数。如果有人能解释我为什么,那将非常感激。
答案 1 :(得分:22)
小修正:
将setWillNotDraw(false)添加到构造函数将导致崩溃,因为尚未创建基础Surface对象。
相反,将setWillNotDraw(false)语句放入surfaceCreated()方法中。这会延迟通话,直到有真正的对象可以使用,并且正常工作。
(非常感谢发布此解决方案的用户,它解决了我的一个主要问题)
答案 2 :(得分:7)
Romain Guy explained它:
为了提高效率,布局不会调用
onDraw()
方法。至 启用它,调用setWillNotDrawEnabled(false)
(或设置等效项 XML属性为false。)
答案 3 :(得分:2)
根据我使用的所有上述评论:
在onAttachedToWindow()事件中添加setWillNotDraw(false)。
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
setWillNotDraw(false);
}
并且有效。