Android take photo on unlock secretly

Question

I am trying to build an app which captures a photo everytime the phone is unlocked. The user should not see that a photo has been taken. So it should basically behave like an anti-theft app.

I have read that I should use a dummy SurfaceTexture, so the preview is not shown on the screen, but I am not able to capture a photo.

Here is what I have written so far. It is just a sample activity to get in touch with the Camera object:

package com.brushmate.chameleon;

import java.io.IOException;

import android.graphics.SurfaceTexture;
import android.hardware.Camera;
import android.os.Bundle;
import android.os.SystemClock;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.util.Log;
import android.view.SurfaceView;

public class SettingsActivity extends Activity {
    private static final String TAG = "Chameleon Wallpaper";

    @SuppressLint("NewApi") protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_settings);

        Log.d(TAG, "Activity created");

        Camera cam = getCamera();

        if (cam != null) {
            Log.d(TAG, "Camera available");

            SurfaceTexture dummy = new SurfaceTexture(0);

            try {
            cam.setPreviewTexture(dummy);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            Log.d(TAG, "Preview texture set");

            cam.startPreview();

            Log.d(TAG, "Preview started");

            cam.takePicture(null, null, new Camera.PictureCallback() {

                @Override
                public void onPictureTaken(byte[] data, Camera camera) {
                    Log.d(TAG, "Image taken");
                }
            });

            cam.stopPreview();

            Log.d(TAG, "Preview stopped");

            cam.release();

            Log.d(TAG, "Camera released");
        }
    }

    private Camera getCamera() {
        Camera cam = null;

        try {
            cam = Camera.open();
        } catch (RuntimeException e) {
            Log.e(TAG, "Camera not available", e);
        }

        return cam;
    }

}

And here is my Logcat output:

05-12 23:54:56.947: D/Chameleon Wallpaper(19614): Activity created
05-12 23:54:56.947: I/AwesomePlayer(161): setDataSource_l(URL suppressed)
05-12 23:54:56.977: I/AwesomePlayer(161): setDataSource_l(URL suppressed)
05-12 23:54:57.007: I/CameraClient(161): Opening camera 0
05-12 23:54:57.117: E/mm-camera(175): sensor_load_chromatix: libchromatix_imx111_preview.so: 30
05-12 23:54:57.217: E/mm-camera(175): vfe_ops_init: E
05-12 23:54:57.237: E/mm-camera(175): vfe_legacy_stats_buffer_init: AEC_STATS_BUFNUM
05-12 23:54:57.237: E/mm-camera(175): vfe_legacy_stats_buffer_init: AEC_STATS_BUFNUM
05-12 23:54:57.247: E/mm-camera(175): mctl_init_stats_proc_info: snap_max_line_cnt =30096
05-12 23:54:57.267: D/Chameleon Wallpaper(19614): Camera available
05-12 23:54:57.267: D/Chameleon Wallpaper(19614): Preview texture set
05-12 23:54:57.267: E/QCameraHWI(161): android::status_t android::QCameraHardwareInterface::setPreviewWindow(preview_stream_ops_t*): mPreviewWindow = 0x0x400b9e98, mStreamDisplay = 0x0x4008c378
05-12 23:54:57.267: D/QCameraHWI(161): android::status_t android::QCameraHardwareInterface::startPreview():  start preview now
05-12 23:54:57.267: I/QCameraHWI(161): android::status_t android::QCameraHardwareInterface::startPreview2():Setting ZSL mode
05-12 23:54:57.267: E/mm-camera(175): config_proc_CAMERA_SET_INFORM_STARTPREVIEW
05-12 23:54:57.267: E/mm-camera(175): config_update_stream_info Storing stream parameters for video inst 1 as : width = 640, height 480, format = 1 inst_handle = 810081 cid = 0
05-12 23:54:57.307: E/mm-camera(175): config_update_stream_info Storing stream parameters for video inst 3 as : width = 640, height 480, format = 1 inst_handle = 830083 cid = 0
05-12 23:54:57.307: E/mm-camera(175): config_update_stream_info Storing stream parameters for video inst 4 as : width = 512, height 384, format = 1 inst_handle = 840084 cid = 0
05-12 23:54:57.307: E/mm-camera(175): config_decide_vfe_outputs: Ports Used 3, Op mode 1
05-12 23:54:57.307: E/mm-camera(175): config_decide_vfe_outputs Current mode 0 Full size streaming : Disabled
05-12 23:54:57.307: E/mm-camera(175): config_decide_vfe_outputs: Primary: 640x480, extra_pad: 0x0, Fmt: 1, Type: 1, Path: 1
05-12 23:54:57.307: E/mm-camera(175): config_decide_vfe_outputs: Secondary: 640x480, extra_pad: 0x0, Fmt: 1, Type: 3, Path: 4
05-12 23:54:57.307: E/mm-camera(175): config_update_inst_handles Updated the inst handles as 810081, 830083, 0, 0 
05-12 23:54:57.387: W/ActivityManager(592): Activity pause timeout for ActivityRecord{420bd848 u0 com.brushmate.chameleon/.SettingsActivity}
05-12 23:54:57.447: E/mm-camera(175): sensor_load_chromatix: libchromatix_imx111_zsl.so: 26
05-12 23:54:57.537: E/mm-camera(175): camif_client_set_params: camif has associated with obj mask 0x1
05-12 23:54:57.537: E/mm-camera(175): config_v2_CAMERA_START_common CAMIF_PARAMS_ADD_OBJ_ID failed -1 
05-12 23:54:57.537: E/mm-camera(175): vfe_operation_config: format 3
05-12 23:54:57.537: E/mm-camera(175): vfe_operation_config:vfe_op_mode=5
05-12 23:54:57.537: E/mm-camera(175): Invalid ASD Set Params Type
05-12 23:54:57.537: E/mm-camera(175): vfe_set_bestshot: Bestshot mode not changed
05-12 23:54:57.567: D/Chameleon Wallpaper(19614): Preview started
05-12 23:54:57.607: E/mm-libcamera2(161): PROFILE HAL: First preview frame received: 1368395697.614272749
05-12 23:54:57.607: E/BufferQueue(19614): [unnamed-19614-0] dequeueBuffer: min undequeued buffer count (2) exceeded (dequeued=6 undequeudCount=0)
05-12 23:54:57.647: E/mm-libcamera2(161): mm_camera_dispatch_buffered_frames: mframe 0x0, sframe = 0x0
05-12 23:54:57.647: E/mm-libcamera2(161): PROFILE HAL: stopPreview(): E: 1368395697.653949232
05-12 23:54:57.647: E/mm-camera(175): config_MSG_ID_STOP_ACK: streamon_mask is not clear. Should not call PP_Release_HW
05-12 23:54:57.667: D/Chameleon Wallpaper(19614): Preview stopped
05-12 23:54:57.667: E/mm-libcamera2(161): PROFILE HAL: stopPreview(): E: 1368395697.676839512
05-12 23:54:57.667: E/QCameraHWI(161): android::status_t android::QCameraHardwareInterface::setPreviewWindow(preview_stream_ops_t*):Received Setting NULL preview window
05-12 23:54:57.677: E/QCameraHWI(161): android::status_t android::QCameraHardwareInterface::setPreviewWindow(preview_stream_ops_t*): mPreviewWindow = 0x0x0, mStreamDisplay = 0x0x4008c378
05-12 23:54:57.677: W/QCameraHWI_Preview(161):  Setting NULL preview window 
05-12 23:54:57.677: I/CameraClient(161): Destroying camera 0
05-12 23:54:57.687: E/mm-camera(175): config_shutdown_pp Camera not in streaming mode. Returning. 
05-12 23:54:57.687: E/mm-camera(175): vfe_ops_deinit: E
05-12 23:54:57.758: D/Chameleon Wallpaper(19614): Camera released
05-12 23:54:57.758: W/AudioFlinger(161): session id 77 not found for pid 161
05-12 23:54:57.758: W/AudioFlinger(161): session id 78 not found for pid 161
05-12 23:54:57.808: D/libEGL(19614): loaded /system/lib/egl/libEGL_adreno200.so
05-12 23:54:57.808: D/libEGL(19614): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
05-12 23:54:57.808: D/libEGL(19614): loaded /system/lib/egl/libGLESv2_adreno200.so
05-12 23:54:57.818: I/Adreno200-EGL(19614): <eglInitialize:269>: EGL 1.4 QUALCOMM build: Nondeterministic AU_full_mako_PARTNER-ANDROID/JB-MR1-DEV_CL2961380_release_AU (CL2961380)
05-12 23:54:57.818: I/Adreno200-EGL(19614): Build Date: 12/10/12 Mon
05-12 23:54:57.818: I/Adreno200-EGL(19614): Local Branch: 
05-12 23:54:57.818: I/Adreno200-EGL(19614): Remote Branch: m/partner-android/jb-mr1-dev
05-12 23:54:57.818: I/Adreno200-EGL(19614): Local Patches: NONE
05-12 23:54:57.818: I/Adreno200-EGL(19614): Reconstruct Branch: NOTHING
05-12 23:54:57.848: D/OpenGLRenderer(19614): Enabling debug mode 0
05-12 23:54:57.888: I/ActivityManager(592): Displayed com.brushmate.chameleon/.SettingsActivity: +1s63ms

As far as I understood, the procedure is correct. So what am I doing wrong?

Answer 1

After days of trying and further reading I found out that it was a timing problem. The Camera object is released before the jpeg callback is called. You just have to release the camera inside the callback.

package com.brushmate.chameleon;

import java.io.IOException;

import android.graphics.SurfaceTexture;
import android.hardware.Camera;
import android.os.Bundle;
import android.os.SystemClock;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.util.Log;
import android.view.SurfaceView;

public class SettingsActivity extends Activity {
    private static final String TAG = "Chameleon Wallpaper";

    @SuppressLint("NewApi") protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_settings);

        Log.d(TAG, "Activity created");

        Camera cam = getCamera();

        if (cam != null) {
            Log.d(TAG, "Camera available");

            SurfaceTexture dummy = new SurfaceTexture(0);

            try {
            cam.setPreviewTexture(dummy);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            Log.d(TAG, "Preview texture set");

            cam.startPreview();

            Log.d(TAG, "Preview started");

            cam.takePicture(null, null, new Camera.PictureCallback() {

                @Override
                public void onPictureTaken(byte[] data, Camera camera) {
                    Log.d(TAG, "Image taken");

                    cam.stopPreview();

                    Log.d(TAG, "Preview stopped");

                    cam.release();

                    Log.d(TAG, "Camera released");
                }
            });
        }
    }

    private Camera getCamera() {
        Camera cam = null;

        try {
            cam = Camera.open();
        } catch (RuntimeException e) {
            Log.e(TAG, "Camera not available", e);
        }

        return cam;
    }

}