Android 4.4-Camera.PreviewCallback从未被调用
我通过了 我试图添加一个Camera.PreviewCallback,但没有调用它。哪些方法/类依赖于PreviewCallback触发Android 4.4-Camera.PreviewCallback从未被调用,android,camera,android-4.4-kitkat,Android,Camera,Android 4.4 Kitkat,我通过了 我试图添加一个Camera.PreviewCallback,但没有调用它。哪些方法/类依赖于PreviewCallback触发 public class MainActivity extends Activity { private Camera mCamera; private CameraPreview mPreview; private final static String TAG = "Main-Activity"; private Cam
public class MainActivity extends Activity {
private Camera mCamera;
private CameraPreview mPreview;
private final static String TAG = "Main-Activity";
private Camera.PreviewCallback countFrameCallback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] bytes, Camera camera) {
Log.d(TAG, "In frame callback");
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create an instance of Camera
mCamera = getCameraInstance();
// Create our Preview view and set it as the content of our activity.
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
mCamera.setPreviewCallback(countFrameCallback);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/** Check if this device has a camera */
private boolean checkCameraHardware(Context context) {
if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance() {
Camera c = null;
try {
c = Camera.open(); // attempt to get a Camera instance
} catch (Exception e) {
// Camera is not available (in use or does not exist)
}
return c; // returns null if camera is unavailable
}
}
和审查:
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
private final static String TAG = "Camera-Preview";
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(TAG, "Error starting camera preview: " + e.getMessage());
}
}
}
相机回调有点特别。从: 大多数长期运行的操作(预览、对焦、照片捕获等) 异步发生,并根据需要调用回调。回调 将在从调用线程打开(int)的事件上调用 要获取回调,并且因为您从主活动中获取相机,只需实现PreviewCallback并重写其方法,如下所示:
public class MainActivity extends Activity implements PreviewCallback
然后,在启动CameraPreview类时,将MainActivity的回调作为参数传递,如下所示:
public class MainActivity extends Activity implements PreviewCallback
main活动
mPreview = new CameraPreview(this, mCamera, this); //This stand for the PreviewCallback
并删除mCamera.setPreviewCallback(countFrameCallback)代码>来自MainActivity
CameraPreview
private Camera.PreviewCallback mCallback;
...
//Constructor
public CameraPreview(Context context, Camera camera, Camera.PreviewCallback callback) {
super(context);
mCallback = callback;
...
}
在SurfaceChanged方法中:
try {
mCamera.setPreviewCallback(mCallback);
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(TAG, "Error starting camera preview: " + e.getMessage());
}
不幸的是,这并没有解决我的问题。它仍然没有被调用。它在运行5.0的HTC m8上工作,但在运行4.4.2的HTC Desire 510上没有工作。除了调用摄像头的静态方法,尝试直接调用camera.open()
onCreate。它仍然不会进入预览回调。我使用了调试器,它显示mCamera对象设置了预览回调,但它从未命中onPreviewFrame方法中的断点。是否有任何配置需要更改?还是这部手机的问题?我编辑我的答案。我使用这种方式运行我的应用程序。不要忘记管理相机资源,并在不需要时释放。