Manual media scan trigger via JNI MediaScannerConnection

[PowerNow]

Hi,
I'm looking for a way to manually trigger a media scan after saving an image e.g. in the folder /DCIM or /Picture. Although the images are correctly saved they are only visible for other apps (gallery, facebook,...) after a refresh via e.g. google+/fotos.

I tried it described like here https://developer.android.com/reference/android/media/MediaScannerConnection.html
but I only get an error.

QAndroidJniObject jCtx("android.content.Context");
QAndroidJniObject jCtxD = jCtx.callMethod<QAndroidJniObject>("getApplicationContext");
QAndroidJniObject jCty("android.media.MediaScannerConnection.MediaScannerConnectionClient");
QAndroidJniObject jMsc("android.media.MediaScannerConnection", "(Landroid.content.Context; Landroid.media.MediaScannerConnection.MediaScannerConnectionClient)V", jCtxD, jCty);

Error:
313: error: cannot pass objects of non-trivially-copyable type 'class QAndroidJniObject' through '...'
         QAndroidJniObject jMsc("android.media.MediaScannerConnection", "(Landroid.content.Context; Landroid.media.MediaScannerConnection.MediaScannerConnectionClient)V", jCtxD, jCty);

Can maybe someone give me a hint what I'm doing wrong?

I already read Save Image to Android device , but I want to use only JNI without Java.

Thxs in andvance...

[Pablo J. Rogina]

@PowerNow I have a media scan working on a camera application. So far I couldn't avoid the Java part, so this is C++ code in a class receiving the signal of an image already processed by the camera:

...
connect(someObject, &SomeObject::imageProcessed, [this](QString fname)
    {
        QAndroidJniObject::callStaticMethod<void>("com/ path/application/MyActivity,
            "scanFile",
            "(Ljava/lang/String;)V",
            QAndroidJniObject::fromString(fname).object<jstring>()
        );
    });

Then on the Java side I have something like this:

...
public class MyActivity extends QtActivity {
...
public static void scanFile(String path) {
        MediaScannerConnection.scanFile(m_instance,
            new String[] { path }, null,
            new MediaScannerConnection.OnScanCompletedListener() {
                public void onScanCompleted(String path, Uri uri) {
                    // No need to do anything on file actually scanned or not
                }
            }
        );
    }
...
}

[PowerNow]

@Pablo-J.-Rogina Thxs Pablo for your fast response! I'm just trying your proposal but my Android/Java knowledge is moderate. Please can you explain me how you get the current application context? How is your m_instance defined?

[Devopia53]

@PowerNow

The following example shows how to auto-register an image for the Android Image Gallery app, tested on the Android kitcat.

First, append permission:
android.permission.READ_EXTERNAL_STORAGE
android.permission.WRITE_EXTERNAL_STORAGE

Java Code:

android.content.Context.sendBroadcast(Intent intent)

To conversion C++/JNI

auto    imagePath = QString(QStandardPaths::writableLocation(QStandardPaths::PicturesLocation) + "/myImage.jpeg");
QAndroidJniEnvironment  env;
QAndroidJniObject   activity = QtAndroid::androidActivity();
QAndroidJniObject   context = activity.callObjectMethod("getApplicationContext", "()Landroid/content/Context;");
QAndroidJniObject   intent("android/content/Intent");
QAndroidJniObject   action = QAndroidJniObject::fromString("android.intent.action.MEDIA_SCANNER_SCAN_FILE");
QAndroidJniObject   jpath = QAndroidJniObject::fromString(QUrl::fromLocalFile(imagePath).toString());
QAndroidJniObject   uri = QAndroidJniObject::callStaticObjectMethod("android/net/Uri", "parse", "(Ljava/lang/String;)Landroid/net/Uri;", jpath.object<jstring>());
	
intent = intent.callObjectMethod("setData", "(Landroid/net/Uri;)Landroid/content/Intent;", uri.object());
intent = intent.callObjectMethod("setAction", "(Ljava/lang/String;)Landroid/content/Intent;", action.object());
	
context.callMethod<void>("sendBroadcast", "(Landroid/content/Intent;)V", intent.object());
	
if (env->ExceptionCheck()) {
    env->ExceptionDescribe();
    env->ExceptionClear();
}

(*) A validation check on all JNI objects is required.

[Pablo J. Rogina]

@PowerNow this is the whole Java code:

package com.yourname.yourproject;

import org.qtproject.qt5.android.bindings.QtActivity;
import org.qtproject.qt5.android.bindings.QtApplication;
import android.os.Bundle;
import android.media.MediaScannerConnection;
import android.net.Uri;

public class MyActivity extends QtActivity
{
    private static MyActivity m_instance;

    public MyActivity()
    {
        m_instance = this;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    public static void scanFile(String path) {
        MediaScannerConnection.scanFile(m_instance,
            new String[] { path }, null,
            new MediaScannerConnection.OnScanCompletedListener() {
                public void onScanCompleted(String path, Uri uri) {
                    // No need to do anything on file actually scanned or not
                }
            }
        );
    }
}

[PowerNow]

Thxs a lot to @Pablo-J-Rogina and @Devopia53 !!!

@Devopia53 This was exactly I was looking for...

Afterwards only a littlebit simplified version.

QString ImgFilePath = "/.../Image.jpg";

QAndroidJniEnvironment env;
QAndroidJniObject context = QtAndroid::androidContext();
QAndroidJniObject intent("android/content/Intent");
QAndroidJniObject action = QAndroidJniObject::fromString("android.intent.action.MEDIA_SCANNER_SCAN_FILE");
QAndroidJniObject jpath = QAndroidJniObject::fromString(QUrl::fromLocalFile(ImgFilePath).toString());
QAndroidJniObject uri = QAndroidJniObject::callStaticObjectMethod("android/net/Uri", "parse", "(Ljava/lang/String;)Landroid/net/Uri;", jpath.object<jstring>());

intent = intent.callObjectMethod("setData", "(Landroid/net/Uri;)Landroid/content/Intent;", uri.object());
intent = intent.callObjectMethod("setAction", "(Ljava/lang/String;)Landroid/content/Intent;", action.object());

context.callMethod<void>("sendBroadcast", "(Landroid/content/Intent;)V", intent.object());

if (env->ExceptionCheck()) {
      env->ExceptionDescribe();
      env->ExceptionClear();
}