How to get notified of each new image being visibl

问题:

Background

When the user downloads a new image or captures one using the camera, the gallery app will get updated to show the new images.

I need to be notified of each new image as soon as it was created, no matter how it was created (camera, browser,...) , just as the gallery app shows.

The problem

As it turns out there is a mediaScanner Android component that is responsible for scanning all types of media files, and when it finishes, it's supposed to send an intent "MEDIA_SCANNER_FINISHED" (as shown on this example) .

So I've added the next code , hoping it will show a toast each time the user takes a photo from the camera app:

manifest:

    ...
    <receiver android:name="com.example.newgalleryimagereceivertest.MediaScannerBroadcastReceiver" >
        <intent-filter>
            <action android:name="android.intent.action.MEDIA_SCANNER_FINISHED" />
            <data android:scheme="file" />
        </intent-filter>
    </receiver>
    ...

java file:

package com.example.newgalleryimagereceivertest;
...
public class MediaScannerBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, final Intent intent) {
        android.util.Log.d("AppLog", "gallery has new images");
    }

For some reason , this code doesn't work ...

The question

What's wrong with the code?

Will the broadcastReceiver ever be called after taking a photo?

What is the correct way to do it?

Do I really need to use a contentObserver and monitor its changes (using something like this), and keep the app running just for this? I really hope not...

回答1:

ACTION_MEDIA_SCANNER_FINISHED is used for adding new directories to the gallery:

Broadcast Action: The media scanner has finished scanning a directory. The path to the scanned directory is contained in the Intent.mData field.

Constant Value: "android.intent.action.MEDIA_SCANNER_FINISHED"

You should use ACTION_MEDIA_SCANNER_SCAN_FILE, which is used to add new files - not just directories:

Broadcast Action: Request the media scanner to scan a file and add it to the media database. The path to the file is contained in the Intent.mData field.

Constant Value: "android.intent.action.MEDIA_SCANNER_SCAN_FILE"

You can test this Intent using the code discussed here.

Additionally, some have reportedly needed to include mime type and file extensions, such as:

<data android:mimeType="*/*"/>
<data android:pathPattern=".*\\.png" />

回答2:

You may want to look into adding these to your filter as well:

com.android.camera.NEW_PICTURE
com.android.camera.NEW_VIDEO
android.hardware.action.NEW_PICTURE
android.hardware.action.NEW_VIDEO

The android.hardware.x actions are the "official" current broadcasts, but the com.android.x ones are sent by Samsung devices and older versions of Android.

回答3:

i think you can acheive this using the FileObserver .

as mentioned in the documentation :

Monitors files to fire an event after files are accessed or changed by by any process on the device . Each FileObserver instance monitors a single file or directory. If a directory is monitored, events will be triggered for all files and subdirectories inside the monitored directory.

but you have to keep in mind :

If a FileObserver is garbage collected, it will stop sending events. To ensure you keep receiving events, you must keep a reference to the FileObserver instance from some other live object.

Please give me some feedback . Hope That helps .