Start an external activity to scan barcode

Question

I want to start the barcode scanner from my app and get the tag

Here is what I have so far :

scan.h

class DecodeBarCode : public QObject
{
    Q_OBJECT

    BarCodeReceiver *m_receiver;

public:
    explicit DecodeBarCode(QObject *parent = 0);
    ~DecodeBarCode();

    Q_INVOKABLE void useZXingApp();

signals:
    void tagFound(QString tag);
};

class BarCodeReceiver : public QAndroidActivityResultReceiver
{
    DecodeBarCode *m_decoder;
public:
    BarCodeReceiver(DecodeBarCode *decoder) : m_decoder(decoder) {}

    virtual void handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject &data) {
        emit m_decoder->tagFound("Receiver worked");
    }

};

scan.cpp

DecodeBarCode::DecodeBarCode(QObject *parent) : QObject(parent)
{
    m_receiver = new BarCodeReceiver(this);
}

DecodeBarCode::~DecodeBarCode()
{
    delete m_receiver;
}

void DecodeBarCode::useZXingApp()
{
    QAndroidJniObject intent = QAndroidJniObject::fromString("com/google/zxing/client/android/SCAN");
    if (intent.isValid()) {
        QtAndroid::startActivity(intent,0,m_receiver); // CRASH HERE
    } else {
        emit tagFound("Invalid"); // TEMP
    }
}

That is the first time I use JNI, never used it in java nor c++/Qt

There must be something very wrong, what is it ?

Answer 1

I finally got it to work, here is the full code :

decodebarcode.h

#ifndef DECODEBARCODE_H
#define DECODEBARCODE_H

#include <QObject>
#ifdef Q_OS_ANDROID
#include <QtAndroidExtras/QtAndroid>
#include <QtAndroidExtras/QAndroidJniObject>
#include <QtAndroidExtras/QAndroidJniEnvironment>
#include <QtAndroidExtras/QAndroidActivityResultReceiver>
#endif

class BarCodeReceiver;

class DecodeBarCode : public QObject
{
    Q_OBJECT

    BarCodeReceiver *m_receiver;

public:
    explicit DecodeBarCode(QObject *parent = 0);
    ~DecodeBarCode();

    Q_INVOKABLE void useZXingApp();

signals:
    void tagFound(QString tag);
};

#ifdef Q_OS_ANDROID
class BarCodeReceiver : public QAndroidActivityResultReceiver
{
    DecodeBarCode *m_decoder;
public:
    BarCodeReceiver(DecodeBarCode *decoder);

    virtual void handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject &data);

};
#else
class BarCodeReceiver
{
public:
    BarCodeReceiver(DecodeBarCode *decoder) {Q_UNUSED(decoder)};
};
#endif

#endif // DECODEBARCODE_H

decodebarcode.cpp

#include "decodebarcode.h"

DecodeBarCode::DecodeBarCode(QObject *parent) : QObject(parent)
{
    m_receiver = new BarCodeReceiver(this);
}

DecodeBarCode::~DecodeBarCode()
{
    delete m_receiver;
}

void DecodeBarCode::useZXingApp()
{
#ifdef Q_OS_ANDROID
    QAndroidJniObject action = QAndroidJniObject::fromString("com.google.zxing.client.android.SCAN");

    // Intent intent = new Intent(action)
    QAndroidJniObject intent("android/content/Intent","(Ljava/lang/String;)V", action.object<jstring>());

    jint flagCategorieDefault = QAndroidJniObject::getStaticField<jint>("android/content/Intent", "CATEGORY_DEFAULT");
    jint flagActivityClearTop = QAndroidJniObject::getStaticField<jint>("android/content/Intent", "FLAG_ACTIVITY_CLEAR_TOP");
    jint flagActivityClearTaskReset = QAndroidJniObject::getStaticField<jint>("android/content/Intent", "FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET");

    // intentScan.addCategory(Intent.CATEGORY_DEFAULT);
    intent.callObjectMethod("addCategory", "(I)V", flagCategorieDefault);

    //intentScan.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    intent.callObjectMethod("addFlags", "(I)V", flagActivityClearTop);

    //intentScan.addFlags(Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET);
    intent.callObjectMethod("addFlags", "(I)V", flagActivityClearTaskReset);

    QtAndroid::startActivity(intent, 0, m_receiver);
#endif
}


#ifdef Q_OS_ANDROID
BarCodeReceiver::BarCodeReceiver(DecodeBarCode *decoder)
    : m_decoder(decoder)
{

}

void BarCodeReceiver::handleActivityResult(int receiverRequestCode, int resultCode, const QAndroidJniObject &data)
{
    QAndroidJniObject stringExtraScanResult = QAndroidJniObject::fromString("SCAN_RESULT");
    QAndroidJniObject scanResult = data.callObjectMethod("getStringExtra", "(Ljava/lang/String;)Ljava/lang/String;", stringExtraScanResult.object<jstring>());
    emit m_decoder->tagFound(scanResult.toString());
}
#endif

If you have the same problem, I hope that help