android - 当相机拍摄新照片时，Oreo JobScheduler 不工作

Question

在 android 中，Oreo 广播接收器不适用于“android.hardware.action.NEW_PICTURE”，因此我必须将其替换为 JobScheduler。现在的问题是当我重新启动应用程序时，PhotoContentsJob 被调用并显示拍摄的新图像的 toast 但是一旦拍摄新照片它就不会在后台工作。请帮助我如何实现它。附上代码以供引用。

在MainActivity的onCreate方法中

 if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
        scheduleCameraJob();
    }

@RequiresApi(api = Build.VERSION_CODES.O)
private void scheduleCameraJob() {
     final Uri MEDIA_URI = Uri.parse("content://" + MediaStore.AUTHORITY + "/");

    JobInfo.Builder builder = new JobInfo.Builder(11,
            new ComponentName(this, PhotosContentJob.class.getName()));
    // Look for specific changes to images in the provider.
    builder.addTriggerContentUri(new JobInfo.TriggerContentUri(
            MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
            JobInfo.TriggerContentUri.FLAG_NOTIFY_FOR_DESCENDANTS));
    // Also look for general reports of changes in the overall provider.
    builder.addTriggerContentUri(new JobInfo.TriggerContentUri(MEDIA_URI, 0));
    builder.setTriggerContentUpdateDelay(1);
    builder.setTriggerContentMaxDelay(100);
    JobInfo myCameraJob  = builder.build();
    JobScheduler jobScheduler = (JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);
    jobScheduler.schedule(myCameraJob);
}

PhotosContentJob 服务--工作代码

@RequiresApi(api = Build.VERSION_CODES.O)
public class PhotosContentJob extends JobService {

SpreadsheetImage spreadsheetImage;
DatabaseHandler databaseHandler;

// Path segments for image-specific URIs in the provider.
static final List<String> EXTERNAL_PATH_SEGMENTS
        = MediaStore.Images.Media.EXTERNAL_CONTENT_URI.getPathSegments();
// The columns we want to retrieve about a particular image.
static final String[] PROJECTION = new String[] {
        MediaStore.Images.ImageColumns._ID, MediaStore.Images.ImageColumns.DATA
};
static final int PROJECTION_ID = 0;
static final int PROJECTION_DATA = 1;
// This is the external storage directory where cameras place pictures.
static final String DCIM_DIR = Environment.getExternalStoragePublicDirectory(
        Environment.DIRECTORY_DCIM).getPath();


JobParameters mRunningParams;

// Check whether this job is currently scheduled.
public static boolean isScheduled(Context context) {
    JobScheduler js = context.getSystemService(JobScheduler.class);
    List<JobInfo> jobs = js.getAllPendingJobs();
    if (jobs == null) {
        return false;
    }
    for (int i=0; i<jobs.size(); i++) {
        if (jobs.get(i).getId() == 11) {
            return true;
        }
    }
    return false;
}

// Cancel this job, if currently scheduled.
public static void cancelJob(Context context) {
    JobScheduler js = context.getSystemService(JobScheduler.class);
    js.cancel(11);
}

@Override
public boolean onStartJob(JobParameters params) {
    Log.e("PhotosContentJob", "JOB STARTED!");
    mRunningParams = params;
    // Instead of real work, we are going to build a string to show to the user.
    Date addedDate=new Date();
    databaseHandler=new DatabaseHandler(getApplicationContext());
    spreadsheetImage=new SpreadsheetImage();

    StringBuilder sb = new StringBuilder();
    // Did we trigger due to a content change?
    if (params.getTriggeredContentAuthorities() != null) {
        boolean rescanNeeded = false;
        if (params.getTriggeredContentUris() != null) {
            // If we have details about which URIs changed, then iterate through them
            // and collect either the ids that were impacted or note that a generic
            // change has happened.
            ArrayList<String> ids = new ArrayList<>();
            for (Uri uri : params.getTriggeredContentUris()) {
                List<String> path = uri.getPathSegments();
                if (path != null && path.size() == EXTERNAL_PATH_SEGMENTS.size()+1) {
                    // This is a specific file.
                    ids.add(path.get(path.size()-1));
                } else {
                    // Oops, there is some general change!
                    rescanNeeded = true;
                }
            }
            if (ids.size() > 0) {
                // If we found some ids that changed, we want to determine what they are.
                // First, we do a query with content provider to ask about all of them.
                StringBuilder selection = new StringBuilder();
                for (int i=0; i<ids.size(); i++) {
                    if (selection.length() > 0) {
                        selection.append(" OR ");
                    }
                    selection.append(MediaStore.Images.ImageColumns._ID);
                    selection.append("='");
                    selection.append(ids.get(i));
                    selection.append("'");
                }
                // Now we iterate through the query, looking at the filenames of
                // the items to determine if they are ones we are interested in.
                Cursor cursor = null;
                boolean haveFiles = false;
                try {
                    cursor = getContentResolver().query(
                            MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                            PROJECTION, selection.toString(), null, null);
                    while (cursor.moveToNext()) {
                        // We only care about files in the DCIM directory.
                        String dir = cursor.getString(PROJECTION_DATA);
                        if (dir.startsWith(DCIM_DIR)) {
                            if (!haveFiles) {
                                haveFiles = true;
                                sb.append("New photos:\n");
                            }
                            sb.append(cursor.getInt(PROJECTION_ID));
                            sb.append(": ");
                            sb.append(dir);
                            sb.append("\n");

                            spreadsheetImage.ImagePath=dir;
                            spreadsheetImage.AddedOn=addedDate;
                            databaseHandler.AddSpreadSheetImage(spreadsheetImage);
                        }
                    }
                } catch (SecurityException e) {
                    sb.append("Error: no access to media!");
                } finally {
                    if (cursor != null) {
                        cursor.close();
                    }
                }
            }
        } else {
            // We don't have any details about URIs (because too many changed at once),
            // so just note that we need to do a full rescan.
            rescanNeeded = true;
        }
        if (rescanNeeded) {
            sb.append("Photos rescan needed!");
        }
    } else {
        sb.append("(No photos content)");
    }

    Toast.makeText(this, sb.toString(), Toast.LENGTH_LONG).show();
    jobFinished(params, /*reschedule*/false);
    scheduleCameraJob( /*immediate*/false);
    return true;
}
@Override
public boolean onStopJob(JobParameters params) {

    return false;
}

@RequiresApi(api = Build.VERSION_CODES.O)
private void scheduleCameraJob(Boolean Immediate) {
    final Uri MEDIA_URI = Uri.parse("content://" + MediaStore.AUTHORITY + "/");

    JobInfo.Builder builder = new JobInfo.Builder(11,
            new ComponentName(this, PhotosContentJob.class.getName()));
    // Look for specific changes to images in the provider.
    builder.addTriggerContentUri(new JobInfo.TriggerContentUri(
            MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
            JobInfo.TriggerContentUri.FLAG_NOTIFY_FOR_DESCENDANTS));
    // Also look for general reports of changes in the overall provider.
    builder.addTriggerContentUri(new JobInfo.TriggerContentUri(MEDIA_URI, 0));

    if (Immediate) {
        // Get all media changes within a tenth of a second.
        builder.setTriggerContentUpdateDelay(1);
        builder.setTriggerContentMaxDelay(100);
    } else {
        builder.setTriggerContentUpdateDelay(1);
        builder.setTriggerContentMaxDelay(100);
    }

    JobInfo myCameraJob  = builder.build();
    JobScheduler jobScheduler = (JobScheduler) getSystemService(Context.JOB_SCHEDULER_SERVICE);
    int result =jobScheduler.schedule(myCameraJob);
    if (result == JobScheduler.RESULT_SUCCESS) {
        Log.e("JobScheduler"," JobScheduler OK");
    } else {
        Log.e("JobScheduler"," JobScheduler fails");
    }
}
}

Answer 1

根据内容观察器 URI 调度一个 JobScheduler 只是一个时间任务。当您收到对 PhotosContentJob 的更改时，您需要在 onStartJob(JobParameters params) 结束时再次重新安排作业以继续接收更新。

基于文档:

Note: TriggerContentUri() cannot be used in combination with setPeriodic() or setPersisted(). To continually monitor for content changes, schedule a new JobInfo before the app’s JobService finishes handling the most recent callback.

注意:

记得在设备重启时重新安排作业。由于计划的作业不会在重启后持续存在。