Spy Camera on Android

Make a photo

• For photos in Android meets the class Camera .

<uses-permission android:name="android.permission.CAMERA" /> <uses-feature android:name="android.hardware.camera" /> <uses-feature android:name="android.hardware.camera.autofocus" /> 

1. Find the Id of the desired camera using the getNumberOfCameras and getCameraInfo methods );
2. Get a link to the camera object using the open method.
3. Get the current (default) settings by the getParameters method.
4. If necessary, change the parameters and set them again with the setParameters method;
5. If necessary, set the camera orientation using the setDisplayOrientation method (NO vertical video!);
6. IMPORTANT: Pass a properly initialized SurfaceHolder object to the setPreviewDisplay method . If this is not done, the camera will not be able to start the preview.
7. IMPORTANT: Call the startPreview method), which will begin to update SurfaceHolder. You MUST begin a preview before taking a photo.
8. Finally call the takePicture method and wait for the data to return to onPictureTaken ;
9. After calling the takePicture method, the preview will be stopped. If you need to take another photo, you will have to call startPreview again;
10. If the camera is no longer needed, you must first stop the preview with the stopPreview method;
11. IMPORTANT: Call the release () method to free up camera resources for other applications. The application should immediately release camera resources in the onPause method (and get them back in the onResume method).

1. It is necessary to show a preview.
2. On different devices, the camera can work in different ways.

1. Transparent Activity.
2. FrameLayout size of 1 to 1 pixel in the upper left corner of our Activity.

 <activity android:name=".activities.CameraActivity" android:exported="false" android:launchMode="singleTask" android:excludeFromRecents="true" android:theme="@android:style/Theme.Translucent.NoTitleBar" /> 

 <?xml version="1.0" encoding="utf-8"?> <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/surfaceHolder" android:layout_width="1.0px" android:layout_height="1.0px" /> 

 public class CameraActivity extends Activity implements Camera.PictureCallback, SurfaceHolder.Callback { private static final int NO_FRONT_CAMERA = -1; private Camera mCamera; private boolean mPreviewIsRunning = false; private boolean mIsTakingPicture = false; public class CameraPreview extends SurfaceView { public CameraPreview(Context context) { super(context); } } ... 

 @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.surface_holder); SurfaceView surfaceView = new CameraPreview(this); ((FrameLayout) findViewById(R.id.surfaceHolder)).addView(surfaceView); SurfaceHolder holder = surfaceView.getHolder(); if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); holder.addCallback(this); } @Override protected void onResume() { startPreview(); super.onResume(); } @Override protected void onPause() { stopPreview(); super.onPause(); } @Override public void surfaceCreated(SurfaceHolder surfaceHolder) { final int cameraId = getFrontCameraId(); if (cameraId != NO_FRONT_CAMERA) { try { mCamera = Camera.open(cameraId); Camera.Parameters parameters = mCamera.getParameters(); if (getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) parameters.setRotation(270); List<String> flashModes = parameters.getSupportedFlashModes(); if (flashModes != null && flashModes.contains(Camera.Parameters.FLASH_MODE_OFF)) parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF); List<String> whiteBalance = parameters.getSupportedWhiteBalance(); if (whiteBalance != null && whiteBalance.contains(Camera.Parameters.WHITE_BALANCE_AUTO)) parameters.setWhiteBalance(Camera.Parameters.WHITE_BALANCE_AUTO); List<String> focusModes = parameters.getSupportedFocusModes(); if (focusModes != null && focusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO)) parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO); List<Camera.Size> sizes = parameters.getSupportedPictureSizes(); if (sizes != null && sizes.size() > 0) { Camera.Size size = sizes.get(0); parameters.setPictureSize(size.width, size.height); } List<Camera.Size> previewSizes = parameters.getSupportedPreviewSizes(); if (previewSizes != null) { Camera.Size previewSize = previewSizes.get(previewSizes.size() - 1); parameters.setPreviewSize(previewSize.width, previewSize.height); } mCamera.setParameters(parameters); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) mCamera.enableShutterSound(false); } catch (RuntimeException e) { A.handleException(e, true); finish(); return; } } else { Log.e(Value.LOG_TAG, "Could not find front-facing camera"); finish(); return; } try { mCamera.setPreviewDisplay(surfaceHolder); } catch (IOException ioe) { A.handleException(ioe, true); finish(); } } @Override public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) { startPreview(); } @Override public void surfaceDestroyed(SurfaceHolder surfaceHolder) { releaseCamera(); } @Override public void onPictureTaken(byte[] bytes, Camera camera) { mIsTakingPicture = false; releaseCamera(); //noinspection PrimitiveArrayArgumentToVariableArgMethod new SaveImageTask().execute(bytes); finish(); } private int getFrontCameraId() { final int numberOfCameras = Camera.getNumberOfCameras(); for (int i = 0; i < numberOfCameras; i++) { Camera.CameraInfo info = new Camera.CameraInfo(); Camera.getCameraInfo(i, info); if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) return i; } return NO_FRONT_CAMERA; } private void startPreview() { if (!mPreviewIsRunning && mCamera != null) { try { mCamera.startPreview(); mCamera.autoFocus(new Camera.AutoFocusCallback() { @Override public void onAutoFocus(boolean b, Camera camera) { if (!mIsTakingPicture) { try { mIsTakingPicture = true; mCamera.setPreviewCallback(null); mCamera.takePicture(null, null, CameraActivity.this); } catch (RuntimeException e) { A.handleException(e, true); finish(); } } } }); mPreviewIsRunning = true; } catch (Exception e) { A.handleException(e, true); finish(); } } } private void stopPreview() { if (!mIsTakingPicture && mPreviewIsRunning && mCamera != null) { mCamera.stopPreview(); mPreviewIsRunning = false; } } private void releaseCamera() { if (mCamera != null) { mCamera.setPreviewCallback(null); mCamera.stopPreview(); mCamera.release(); mCamera = null; } } 

1. The most important thing is the procedure for calling methods. The documentation states that you need to call and in what order, but does not specify when. For example, the setPreviewDisplay method. If you initialize the camera and call this method immediately in onCreate or in onResume, the photo will not work. Then how to know when to call this method? The correct answer is from the comments to the setPreviewDisplay method in the source code. Here is a short excerpt from there:
   

   The android.view.SurfaceHolder must already contain this surface when this method is called. If you are usingandroid.view.SurfaceView, android.view.SurfaceHolder.Callback withandroid.view.SurfaceHolder.addCallback (android.view.SurfaceHolder.Callback) android.view.SurfaceHolder) before calling setPreviewDisplay () or starting preview.
   This method must be called before startPreview ().
   

2. The second point is related to the life cycle of the SurfaceHolder object relative to the Activity. The life cycle of the Activity can be found in the documentation, but with SurfaceHolder, everything is not clear, so I had to figure it out empirically:
   
   

    onCreate (Bundle savedInstanceState)
    onResume ()
    onPause ()
    surfaceCreated (SurfaceHolder surfaceHolder)
    surfaceChanged (SurfaceHolder surfaceHolder, int format, int width, int height)
    onStop ()
    surfaceDestroyed (SurfaceHolder surfaceHolder)
   

   
   
3. The next interesting point is related to the order of calls to the Life cycle methods of the Activity. You may ask: “Why are all these checks in the spirit of if (mCamera! = Null) and the variables mPreviewIsRunning, mIsTakingPicture?”. Unfortunately, the only answer I can give in this case is that. And the point is that in some situations, the order of calls to the methods of the life cycle of an Activity may differ from that specified in the official docks (from this diagram, for example ). Most incidents occur when the screen lock is enabled on the phone. I had cases when the onStop method was called twice in a row, and after that, bypassing onStart, as if nothing had happened, onResume was called. In this case, the order of calling methods may differ on different devices, even despite the same version of Android on board. I have long tried to figure it out, to understand why this is happening. As a result, I just spent a lot of time on it and wrote the current implementation.

1. We start the Activity on the desired event (in my case - to turn on the screen).
2. In onCreate, we create a SurfaceHolder and register an Activity to get callbacks.
3. We are waiting for the surfaceCreated call and initialize the camera in it.
4. After the camera is initialized, try to call takePicture. Since the order of calling methods strongly depends on the device, the OS version and the type of screen lock, we try using the onResume | surfaceChanged start a preview, and onPause stop it. At the same time onResume | onPause can happen both before and after surfaceCreated, so everywhere we check the camera for "initialization".
5. The surfaceChanged method, according to the documentation, is guaranteed to be called at least once after the surfaceCreated, but theoretically it can be called as many times as necessary in the process of obtaining a photo. We add the mPreviewIsRunning variable in order not to accidentally start the preview several times. We start the preview, call takePicture, wait.
6. We catch a photo in onPictureTaken. We release the camera, create AsyncTask to save the image, close the Activity.

 onCreate (Bundle savedInstanceState)
 onResume ()
 onPause ()
 surfaceCreated (SurfaceHolder surfaceHolder)
 surfaceChanged (SurfaceHolder surfaceHolder, int format, int width, int height)
 onPictureTaken (byte [] bytes, Camera camera)
 onStop ()
 surfaceDestroyed (SurfaceHolder surfaceHolder)

Conclusion

1. Add profiles for different phone models and take a photo with this profile. For example, for phones that produce a shutter sound when photographing, add a mute immediately before the photograph.
2. Thoroughly drive the application on a large set of test models and try to understand the reason for the difference in the call of the Activity methods.
3. Dig deeper into the source code of Android. Finally, climb into the native part and figure out why takePicture can only be called after initializing the preview. Think how else you can deal with it.