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Qt5.13 on android alternative to Qcameraviewfinder

  • hi,

    I testing the sample from QTCreator Called "Camera Example" on android, but when i deploy to my android phone I get no preview image of the camera, some how the QcameraViewfinder is not compatible with android,
    there is some alternative to solve this?


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    @dedetuga said in Qt5.13 on android alternative to Qcameraviewfinder:

    there is some alternative to solve this?

    More recent Qt version maybe?

  • Didn't work I try the same example with QT5.15

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    @dedetuga Is that the widget example?

    yeah, that was never ported properly to android, use the QML example, that one works

  • hi @jsulm,
    It works in QML but I don't know programe in QML and my project is in c++ (QTWidgets),
    I will use opencv but I have no choise I'm forced to use a vewfinder i get an error if i dont set a view finder.

    This is why I'm looking for alternatives

  • @J-Hilk I tried qml example (i.e. declarative_camera) for QT Android. but its giving same issue to me.

  • @dedetuga said in Qt5.13 on android alternative to Qcameraviewfinder:

    It works in QML but I don't know programe in QML and my project is in c++ (QTWidgets),

    I'm trying to use the Java native alternative but I don't know much of JNI and I'm stuck. Googling quite a lot didn't help much yet. It throw an exception just after on cursor
    Probably it is already on uri.

    QAndroidJniObject uri = data.callObjectMethod("getData", "()Landroid/net/Uri;")

    Because logging statement __DV(uri.isValid()); already prints false:

    D myapp: CImageCaptureAndroid::shootPicture
    D myapp: CImageCaptureAndroid::handleActivityResult
    D myapp: data.isValid()  = > true <
    D myapp: data.toString()  = > Intent { act=inline-data (has extras) } <
    D myapp: uri.isValid()  = > false <   /// <== Already wrong here
    D myapp: uri.toString()  = >  <    /// <== thus, meaningless
    D myapp: data_android.isValid()  = > true <
    D myapp: data_android.toString()  = > _data <
    D myapp: object_data_android  = > 0x95 <
    D myapp: contentResolver.isValid()  = > true <
    D myapp: contentResolver.toString()  = >$ApplicationContentResolver@b813db1 <
    D myapp: cursor.isValid()  = > false < /// <== Wrong here too
    D myapp: cursor.toString()  = >  < /// <== Meaningless too
    D myapp: In If9
    F mple.myapp:] JNI DETECTED ERROR IN APPLICATION: JNI GetMethodID called with pending exception java.lang.NullPointerException: uri
    F mple.myapp:]   at java.lang.Object, java.lang.Object) (


    My current header file is:

    #pragma once
    #include <QObject>
    #include <QtAndroidExtras/QAndroidActivityResultReceiver>
    #include <QtAndroidExtras/QtAndroid>
    #include <QtAndroidExtras/QAndroidJniEnvironment>
    #include <QtAndroidExtras/QAndroidJniObject>
    #include <QDebug>
    class CImageCaptureAndroid : public QObject, public QAndroidActivityResultReceiver
          void shootPicture();
          void handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject & data) override;
          void picturePath(QString);

    And then the source file:

    #include "cimagecaptureandroid.h"
    #include "qt_utils.h"
    #include <QFile>
    #include <QDir>
    #include <QStandardPaths>
    void CImageCaptureAndroid::shootPicture()
       QAndroidJniObject ACTION_CAPTURE = QAndroidJniObject::fromString("android.provider.MediaStore.ACTION_IMAGE_CAPTURE");
       QAndroidJniObject ACTION_IMAGE_CAPTURE = QAndroidJniObject::getStaticObjectField("android/provider/MediaStore", "ACTION_IMAGE_CAPTURE", "Ljava/lang/String;");
       QAndroidJniObject intent("android/content/Intent", "(Ljava/lang/String;)V", ACTION_IMAGE_CAPTURE.object<jstring>());
       if (ACTION_CAPTURE.isValid() && intent.isValid()) {
          QtAndroid::startActivity(intent.object<jobject>(), 101, this);
       } else {
          assert( false );
    void CImageCaptureAndroid::handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject &data)
       jint RESULT_OK = QAndroidJniObject::getStaticField<jint>("android/app/Activity", "RESULT_OK");
       if (receiverRequestCode == 101 && resultCode == RESULT_OK)  {
          QAndroidJniObject uri = data.callObjectMethod("getData", "()Landroid/net/Uri;");
          QAndroidJniObject data_android = QAndroidJniObject::getStaticObjectField("android/provider/MediaStore$MediaColumns", "DATA", "Ljava/lang/String;");
          QAndroidJniEnvironment env;
          jobjectArray object = (jobjectArray)env->NewObjectArray(1, env->FindClass("java/lang/String"), NULL);
          jobject object_data_android = env->NewStringUTF(data_android.toString().toStdString().c_str());
          env->SetObjectArrayElement(object, 0, object_data_android);
          QAndroidJniObject contentResolver = QtAndroid::androidActivity().callObjectMethod("getContentResolver", "()Landroid/content/ContentResolver;");
          QAndroidJniObject cursor = contentResolver.callObjectMethod("query", "(Landroid/net/Uri;[Ljava/lang/String;Ljava/lang/String;[Ljava/lang/String;Ljava/lang/String;)Landroid/database/Cursor;", uri.object<jobject>(), object, NULL, NULL, NULL);
          __DL("In If9");
          jint columnIndex = cursor.callMethod<jint>("getColumnIndex", "(Ljava/lang/String;)I", data_android.object<jstring>());
          __DL("In If10");
          cursor.callMethod<jboolean>("moveToFirst", "()Z");
          __DL("In If11");
          QAndroidJniObject result = cursor.callObjectMethod("getString", "(I)Ljava/lang/String;", columnIndex);
          __DL("In If12");
          QFile imageFile(result.toString());
          QDir dir;
             __DL("Folder already exists");
          }else {
          QStringList splitedImagePath = result.toString().split("/");
          QString imageName = splitedImagePath.value(splitedImagePath.length() - 1);
          QString dataimgFile = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation) + "/images/" + imageName;
          // /data/data/org.qtproject.feather/files/images/offLight_Button.png
          if (imageFile.exists()) {
             QFile cdbfile(dataimgFile);
             if (!cdbfile.exists()) {
                   __DL("Error :copy failed");
                QFile::setPermissions(dataimgFile, QFile::WriteOwner | QFile::ReadOwner);
             } else {
                __DL("image exits already no need to copy");
                QFile::setPermissions(dataimgFile, QFile::WriteOwner | QFile::ReadOwner);
          } else {
             __mDV("img Not exit in Assert ", dataimgFile);
          QString imagePath = "file://" + dataimgFile;
    //      this->deleteLater();
          emit picturePath(imagePath);

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