问一下,我做了一个摄像头程序,继承了一个SurfaceView做预览,但用addView(mPreview)将预览添加到FrameLayout时,
报错说Unable to start activity ComponentInfo{com.example.test/com.example.test.CameraActivity}: java.lang.NullPointerException.
之前构造mPreview已经成功了,请问一下这是什么问题?
代码如下:
首先实现了
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback ()
{
//实现了 public CameraPreview(Context context, Camera camera){}
public void surfaceCreated(SurfaceHolder holder) {}
public void surfaceDestroyed(SurfaceHolder holder) {}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {}
}
然后在activity中调用时
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camerapreview);
preview.addView(mPreview);
问题出在preview.addView(mPreview);这句上,提示mPreview为空,请问是怎么回事