Multiple instances of android application

[hexo]

I am trying to write an android application that opens PDF files (that is, it responds to PDF viewing intents). However, when I open the application while another instance is already open by clicking on a PDF file, the application crashes. It appears that the android version of Qt is not capable of handling multiple instances?
Here is a minimal reproducible code sample:

main.cpp file:

#include <QApplication>
#include <QPushButton>


int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QWidget container;
    QPushButton button("Click me", &container);
    container.show();
    return a.exec();
}

AndroidManifest.xml file. This is the same as the default autogenerated manifest file by qt, except the intent-filters for PDF files:

<?xml version="1.0"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.qtproject.example"
    android:installLocation="auto"
    android:versionCode="-- %%INSERT_VERSION_CODE%% --"
    android:versionName="-- %%INSERT_VERSION_NAME%% --">
    <!-- %%INSERT_PERMISSIONS -->
    <!-- %%INSERT_FEATURES -->
    <supports-screens
        android:anyDensity="true"
        android:largeScreens="true"
        android:normalScreens="true"
        android:smallScreens="true" />
    <application
        android:name="org.qtproject.qt.android.bindings.QtApplication"
        android:hardwareAccelerated="true"
        android:label="-- %%INSERT_APP_NAME%% --"
        android:requestLegacyExternalStorage="true"
        android:allowNativeHeapPointerTagging="false"
        android:allowBackup="true"
        android:fullBackupOnly="false">
        <activity
            android:name="org.qtproject.qt.android.bindings.QtActivity"
            android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|layoutDirection|locale|fontScale|keyboard|keyboardHidden|navigation|mcc|mnc|density"
            android:label="-- %%INSERT_APP_NAME%% --"
            android:launchMode="singleTop"
            android:screenOrientation="unspecified"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

            <intent-filter >
                <action android:name="android.intent.action.OPEN_DOCUMENT" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:mimeType="application/pdf" />
            </intent-filter>
            <intent-filter >
                <action android:name="android.intent.action.VIEW" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:mimeType="application/pdf" />
            </intent-filter>

          <meta-data
                android:name="android.app.lib_name"
                android:value="-- %%INSERT_APP_LIB_NAME%% --" />

          <meta-data
                android:name="android.app.arguments"
                android:value="-- %%INSERT_APP_ARGUMENTS%% --" />

            <meta-data
                android:name="android.app.extract_android_style"
                android:value="minimal" />
        </activity>
    </application>
</manifest>

If you open the app and then try to open another instance by clicking on a PDF file, it freezes and the only way to open it again is to close it from system menu. This blog post suggests setting android:launchMode:"singleInstance" in the manifest file, but it is only a partial solution, because even with that when opening a PDF file from another application (e.g. google drive or telegram) still a new version of the application is created and it still crashes.

[hexo]

Should I open a feature request for this? Even the author of the previous blog mentions this in the next part of the series here:

If the App was open, onNewIntent() from our customized Activity should be called, but Google Docs always calls onCreate() - doesn‘t matter if the Target App is already running or not. Then a white screen comes up, the App hangs and must be closed. The Debug Log reports:

E Qt JAVA : Surface 2 not found!

I haven‘t found a way to workaround this yet - perhaps anyone else has an idea HowTo fix ?

That blog post was from 2018! I find it very surprising that there doesn't seem to be any discussion on this issue on the web. It seems like a pretty huge problem. Am I doing something wrong maybe?

[JoeCFD]

@hexo I have a small test program with poppler on Ubuntu.
it works like the following:

    auto new_document = Poppler::Document::load( file_name );
    if ( nullptr == new_document ) { /* check open is ok first */
        std::cout << " can not open pdf file " << qPrintable( file_name ) <<std::endl;
        return;
    }
    closeDocument();  /* close it for other apps  */

   //use new_document

no crash.

[hexo]

@JoeCFD This issue is specific to android. My application already works on linux/mac/windows with no problem.

[Aliciasmith]

This post is deleted!