[Android-development] [Interest] Android-6 File Opening Permissions

[ekke]

here's also an example app demonstrating HowTo ask for permissions if
Camera is needed
https://github.com/ftylitak/qzxing/tree/master/examples/QZXingLive
haven't tested by myself yet, but will soon integrate into QtWorldSummit
Conference APP to read QR Codes

ekke

Am 06.04.17 um 10:31 schrieb Robert Iakobashvili:
> Hi,
> Replying to my own email hoping it will help somebody
> not to waist time.
>
> The issue was related to Android-6 and above file treatment permissions.
>
> It is well covered by the excellent link below:
> http://www.bytran.org/androidmpermissions.htm
>
> IMHO, I would believe that it could be explained in Qt-documentation
> for Android-Extras - note for the maintainer. Thanks.
>
> Kind regards,
> Robert
>
>
> On Thu, Mar 23, 2017 at 7:23 PM, Robert Iakobashvili
> <coroberti at gmail.com> wrote:
>> Hello,
>>
>> Qt-5.7, Nexus-7, Android-6, API 25 or 22.
>>
>> 1. Running Intent from Qt widget app to ask for a new file rather in a
>> standard way works properly:
>>
>> QAndroidJniObject intent("android/content/Intent");
>> QAndroidJniObject ACTION_CREATE_DOCUMENT =
>> QAndroidJniObject::fromString("android.intent.action.CREATE_DOCUMENT");
>>
>>         if (ACTION_CREATE_DOCUMENT.isValid() && intent.isValid())
>>         {
>>             intent.callObjectMethod("setAction",
>>
>> "(Ljava/lang/String;)Landroid/content/Intent;",
>>                                     ACTION_CREATE_DOCUMENT.object<jstring>());
>>             intent.callObjectMethod("setType",
>>
>> "(Ljava/lang/String;)Landroid/content/Intent;",
>>
>> QAndroidJniObject::fromString("text/html").object<jstring>());
>>             intent.callObjectMethod("putExtra",
>>
>> "(Ljava/lang/String;Z)Landroid/content/Intent;",
>>
>> QAndroidJniObject::fromString("android.intent.extra.LOCAL_ONLY").object<jstring>(),
>>                                     jboolean(true));
>>             QtAndroid::startActivity(intent.object<jobject>(),
>>
>> AndroidOpenFileReceiver::NEW_FILE_NAME_REQUEST,
>>                                      this->android_receiver_);
>>         }
>>
>> 2. File could be selected and seen as immediately created in a
>> derivative of a QAndroidActivityResultReceiver
>>
>> handleActivityResult
>>
>> const QString fileURI =
>> data.callObjectMethod("getData","()Landroid/net/Uri;").toString();
>>
>> and that could be translated by calling Java to the absolute file path
>> for the file selected, i.e. first.htm:
>>
>> /storage/emulated/0/Download/first.htm
>>
>> 3. The file content could be written or read in Java using Java I/O Streams.
>> Further the stream and file are closed in Java.
>>
>> 4. Unfortunately, returning to C++ the file is found existing, but open fails.
>> That happens in all cases consistently: whenever dealing with it in
>> Java before or not.
>>
>> if (!QFile::exists(filename)) - it exists
>>         return false;
>>
>> QFile file(filename);
>> if (!file.open(QFile::ReadWrite)) - fails
>> {
>>      if (!file.open(QFile::ReadOnly)) - fails.
>>             return false;
>> }
>>
>> 5. The C++ code above works fine if the location of the files is in
>> /data/data/<app-path>
>>     or any writable standard path returned by Qt.
>>
>> 6. My conclusion is that on Nexus-7 the Intent returned path in
>> /storage/emulated/0/Download/
>>     is considered to be an External Storage.
>>
>>     But the manifest has appropriate Write and Read permissions for
>> External Storage.
>>
>> The question is what I am missing like
>> permission for that specific thread or running something on the GUI
>> thread, or etc.
>>
>> Thanks in advance for any help or ideas.
>>
>> Kind regards,
>> Robert
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