Save Image to Android device



  • Hey!

    I have an app where I take a screen shot of a live video stream. The image is a QUrl. How can I save it to the gallery of the Android device?

    Cant find anywhere that says what I can do.

    Also, I have not written any code yet for saving as I cannot find any.

    Please help!



  • @eiriham

    Hi.

    You can use a QStandardPaths.

    like this:

    QString path = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation);
    
    if (path.isEmpty())
        return;
    
    path.append("/yourImage.png");
    yourImage.save(path);
    


  • Thanks! But I cant really get that to work. The pictures dont show in the photo album.

    This is my code:
    @
    void SnapshotController::savePicture()
    {
    QString path = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation);

    if(path.isEmpty()){
        return;
    }
    path.append("/yourImage.png");
    m_img.save(path);
    

    }
    @

    The standard path gives this string: "/storage/emulated/0/Pictures"

    I am on a Nexus 7


  • Moderators

    @eiriham said:

    Thanks! But I cant really get that to work. The pictures dont show in the photo album.

    Now the search begins.

    1. on Android you need to trigger the Media scanner to add it to the systems media database so other apps can access it. If it's working after a device restart, then thats the cause.

    2. you should make sure that your app has the correct permission to write to the filesystem. Change your code to the following and check the error (in console):

    QBuffer buffer;
    buffer.open(QIODevice::WriteOnly);
    img.save(&buffer, "PNG");
    buffer.close();
    
    QString path = QStandardPaths::writableLocation(QStandardPaths::PicturesLocation) + "/image.png";
    QFile f( path  );
    if( file.open( QIODevice::WriteOnly ) )
    {
        file.write( buffer.buffer() );
        file.close();
    }
    if( file.error() != QFileDevice::NoError )
         qFatal() << QString("Error writing file '%1':").arg(path) <<  file.errorString();
    


  • Thanks!
    I found my pictures after a device restart. Since it did, do I still need step 2?

    Because I get the following error:
    OpenOnly is not a member of QIODevice.

    And I have included QIODevice


  • Moderators

    @eiriham said:

    I found my pictures after a device restart. Since it did, do I still need step 2?

    if you want to have it in the media database immediately, then yes.
    If you can live with it being available after a device restart, then no

    Because I get the following error:
    OpenOnly is not a member of QIODevice.

    my mistake. should be "ReadOnly". (Changed it already in my code)



  • Thanks!

    I ran your code and got this error message:
    "Error writing file '/storage/emulated/0/Pictures/image.png':" "No such file or directory"

    That was not a problem earlier? What happened?


  • Moderators

    @eiriham
    seems i need some sleep :P
    Should be "WriteOnly" instead of "ReadOnly" unlike i said before...



  • Thanks!

    Well, I have not fixed step 1 yet, but I did exactly as in step 2. Again, the picture was showing only after a restart. What is the difference between the code in step 2 that you presented and the code I wrote in the original post?

    They both seem to do the same thing? Or would your code work with the mediascanner, and mine wont?


  • Moderators

    @eiriham
    i just added my code, so we can check the error message

    Are you triggering the media scanner already?!



  • No, I am not triggering it! Still trying to understand how one does that.


  • Moderators

    @eiriham
    because you were wondering why it still shows up after a device restart.
    There is no way around using the media scanner if you want to have it immediately listed in the media db.



  • Any help would be appreciated. I am looking at this post now, but it is not solved: http://lists.qt-project.org/pipermail/interest/2015-April/016263.html.

    Also, I saw your post about the Android Extra JNI, but how do I call the scanFile from there?

    This is the start of the code I am trying to write:
    @
    void SnapshotController::trigMediaScanner(QString path)
    {
    QAndroidJniObject string = QAndroidJniObject::fromString(path);

    QAndroidJniEnvironment test2;
    

    }
    @



  • Any help? Tried a lot of stuff, but could not make it work



  • This is a funny issue. People claim that calling scanFile should work, but I have seen no sign that anyone has actually managed to make it work from Qt...

    Yes, I am trying the same thing, but currently, on a personal app, just use Android app media.re.Scan: as needed.



  • Using an app wont solve my problem, but thanks for the advice.



  • I had the same issue to show a picture taken by my app immediatly after saving it. And scanFile works for me.

    I wrote a java class extending org.qtproject.qt5.android.bindings.QtActivity and declared it in the manifest file.

    public class AndroidAccess extends org.qtproject.qt5.android.bindings.QtActivity
    {
      public static MediaScannerConnection s_mMs;
    
      @Override
      public void onCreate(Bundle savedInstanceState)
      {
         ...
         s_mMs = new MediaScannerConnection(getApplicationContext(), null);
         s_mMs.connect();
      }
    
      public static void scanForPicture(String name)
      {
         s_mMs.scanFile(name, null);
      }
    }
    

    and then in my Qt class i simply call:

    QAndroidJniObject::callStaticMethod<void>("org/tud/qpcam/AndroidAccess",
                                               "scanForPicture",
                                               "(Ljava/lang/String;)V",
                                               QAndroidJniObject::fromString(this->getSavePicturesDir().absolutePath()).object<jstring>());
    

    whereas getSavePicturesDir() returns the directory where the pictures were saved to.
    Works like charm with Qt 5.6 and android 4.4 - 6.0.



  • Thanks! I am trying to get this to work now.
    How did you register it in the manifest file?
    And how do I know the path? I mean, how did you know you had to put in "org/tud/qpcam/AndroidAccess"?

    I try this but the isAvailable returns false:

    
        qDebug()<< "Is available: " << QAndroidJniObject::isClassAvailable("MediaScanner");
    
        QAndroidJniObject::callStaticMethod<void>("MediaScanner",
                                                   "scanForPicture",
                                                   "(Ljava/lang/String;)V",
                                                   QAndroidJniObject::fromString(this->getSavePicturesDir().absolutePath()).object<jstring>());
    


  • @eiriham

    You can use the sendBroadcast(). MediaScanner is simple to implement only JNI without JAVA code.



  • Well, i tried a lot of ways and sendBroadcast() did not work for me. So maybe my way isnt the shortest one, but it works and thats what matters, doesnt it?

    • Create the android files "create Android APK"

    • set the package name, e.g. "aha.androscanner" in manifest

    • open manifest in text mode and replace android:name="org.qtproject.qt5.android.bindings.QtActivity" with android:name="aha.androscanner.AndroScannerInJava"

    • Create a subdirectory below the android folder, e.g. ...android/src/aha/androscanner
    • Put in a java file, named exactly like in point 3, e.g. AndroScannerInJava.java and add it to project
    • add "android: QT += androidextras" to your .pro file

    • Fill in the code

    AndroScannerInJava.java

    package aha.androscanner;
    
    import android.media.MediaScannerConnection;
    import android.os.Bundle;
    
    public class AndroScannerInJava extends org.qtproject.qt5.android.bindings.QtActivity
    {
        public static MediaScannerConnection s_mMs;
    
        @Override
        public void onCreate(Bundle savedInstanceState)
        {
            System.out.println("in the activity");
    
            super.onCreate(savedInstanceState);
    
            s_mMs = new MediaScannerConnection(getApplicationContext(), null);
            s_mMs.connect();
    
        }
    
        public static void scanForPicture(String name)
        {
            System.out.print("scan for picture -> ");
            System.out.println(name);
    
            s_mMs.scanFile(name, null);
        }
    }
    

    Within Qt code you call:

    void MainWindow::saveThatPicture()
    {
        qDebug() << "saveThatPicture!";
    
        QPixmap pix(700,700);
        pix.fill(Qt::red);
    
        QDir picDir = QDir(QStandardPaths::writableLocation(QStandardPaths::PicturesLocation));
        QDir saveDir = QDir(picDir.filePath("aha"));
        if(!saveDir.exists())
            picDir.mkdir("aha");
    
        QString filePath = saveDir.filePath("test.jpg");
        pix.save(filePath);
    
    
        QAndroidJniObject::callStaticMethod<void>("aha/androscanner/AndroScannerInJava",
                                                   "scanForPicture",
                                                   "(Ljava/lang/String;)V",
                                                   QAndroidJniObject::fromString(filePath).object<jstring>());
    }
    

    Manifest.xml

    <?xml version='1.0' encoding='utf-8'?>
    <manifest package="aha.androscanner" xmlns:android="http://schemas.android.com/apk/res/android" android:versionName="1.0" android:versionCode="1" android:installLocation="auto">
        <application android:hardwareAccelerated="true" android:name="org.qtproject.qt5.android.bindings.QtApplication" android:label="-- %%INSERT_APP_NAME%% --">
            <activity android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|layoutDirection|locale|fontScale|keyboard|keyboardHidden|navigation"
                      android:name="aha.androscanner.AndroScannerInJava"
                      android:label="-- %%INSERT_APP_NAME%% --"
                      android:screenOrientation="unspecified"
                      android:launchMode="singleTop">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN"/>
                    <category android:name="android.intent.category.LAUNCHER"/>
                </intent-filter>
                <meta-data android:name="android.app.lib_name" android:value="-- %%INSERT_APP_LIB_NAME%% --"/>
                <meta-data android:name="android.app.qt_sources_resource_id" android:resource="@array/qt_sources"/>
                <meta-data android:name="android.app.repository" android:value="default"/>
                <meta-data android:name="android.app.qt_libs_resource_id" android:resource="@array/qt_libs"/>
                <meta-data android:name="android.app.bundled_libs_resource_id" android:resource="@array/bundled_libs"/>
                <!-- Deploy Qt libs as part of package -->
                <meta-data android:name="android.app.bundle_local_qt_libs" android:value="-- %%BUNDLE_LOCAL_QT_LIBS%% --"/>
                <meta-data android:name="android.app.bundled_in_lib_resource_id" android:resource="@array/bundled_in_lib"/>
                <meta-data android:name="android.app.bundled_in_assets_resource_id" android:resource="@array/bundled_in_assets"/>
                <!-- Run with local libs -->
                <meta-data android:name="android.app.use_local_qt_libs" android:value="-- %%USE_LOCAL_QT_LIBS%% --"/>
                <meta-data android:name="android.app.libs_prefix" android:value="/data/local/tmp/qt/"/>
                <meta-data android:name="android.app.load_local_libs" android:value="-- %%INSERT_LOCAL_LIBS%% --"/>
                <meta-data android:name="android.app.load_local_jars" android:value="-- %%INSERT_LOCAL_JARS%% --"/>
                <meta-data android:name="android.app.static_init_classes" android:value="-- %%INSERT_INIT_CLASSES%% --"/>
                <!--  Messages maps -->
                <meta-data android:value="@string/ministro_not_found_msg" android:name="android.app.ministro_not_found_msg"/>
                <meta-data android:value="@string/ministro_needed_msg" android:name="android.app.ministro_needed_msg"/>
                <meta-data android:value="@string/fatal_error_msg" android:name="android.app.fatal_error_msg"/>
                <!--  Messages maps -->
    
                <!-- Splash screen -->
                <!--
                <meta-data android:name="android.app.splash_screen_drawable" android:resource="@drawable/logo"/>
                -->
                <!-- Splash screen -->
    
                <!-- Background running -->
                <!-- Warning: changing this value to true may cause unexpected crashes if the
                              application still try to draw after
                              "applicationStateChanged(Qt::ApplicationSuspended)"
                              signal is sent! -->
                <meta-data android:name="android.app.background_running" android:value="false"/>
                <!-- Background running -->
    
                <!-- auto screen scale factor -->
                <meta-data android:name="android.app.auto_screen_scale_factor" android:value="false"/>
                <!-- auto screen scale factor -->
            </activity>
        </application>
        <uses-sdk android:minSdkVersion="9" android:targetSdkVersion="14"/>
        <supports-screens android:largeScreens="true" android:normalScreens="true" android:anyDensity="true" android:smallScreens="true"/>
    
        <!-- The following comment will be replaced upon deployment with default permissions based on the dependencies of the application.
             Remove the comment if you do not require these default permissions. -->
        <!-- %%INSERT_PERMISSIONS -->
    
        <!-- The following comment will be replaced upon deployment with default features based on the dependencies of the application.
             Remove the comment if you do not require these default features. -->
        <!-- %%INSERT_FEATURES -->
    
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    
    </manifest>
    

    Works fine.



  • Thanks! While following your steps I get an error. In the application output it says; "Unable to start "pdapp.mediascanner"."

    Using logcat I get:

    I/ActivityManager(  712): START u0 {flg=0x10000000 cmp=pdapp.mediascanner/.MediaScanner} from uid 2000 on display 0
    W/ActivityManager(  712): Permission Denial: starting Intent { flg=0x10000000 cmp=pdapp.mediascanner/.MediaScanner } from null (pid=21117, uid=2000) not exported from uid 10104
    I/art     (21117): System.exit called, status: 1
    I/AndroidRuntime(21117): VM exiting with result code 1.
    
    

    And also this:

    W/PackageManager( 1369): Failure retrieving resources for pdapp.mediascanner: Resource ID #0x0
    
    

    I followed your steps to the point.



  • Please make sure that you set the permissions to read and write external storage. Furthermore check consitent naming of your package and class names.
    Which android version ar you targeting? Do you have installed the android sdk?



  • Thanks!

    I had forgotten permissions for reading externally.
    Your solution works perfectly.



  • @Qojote Thank you and congratulations for giving all the details for solving this old and apparently common problem! Without the smallest details, this kind of things are never solved.


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