android - C++ Builder - 获取 Activity 的结果

Question

我正在使用 C++Builder 10.1 Berlin 开发一个扫描条形码的 Android 应用程序。为此，当用户单击我的应用程序中的按钮时，我将调用另一个应用程序 (Zxing)，如下所示:

_di_JIntent intent;
if(Global->ClipService != NULL){
    Global->ClipService->SetClipboard(TValue::_op_Implicit(NULL));

    intent = TJIntent::Create();
    intent->setAction(StringToJString("com.google.zxing.client.android.SCAN"));
    SharedActivity()->startActivityForResult(intent,0);
    scanCalled = true;    
}
else{
    ShowMessage("Presse Papier non disponible!");
}

为了获取读取的条码，我使用了剪贴板服务。到现在为止，这对我来说已经足够了。

现在，我想获取条形码的类型。我需要处理 Android 的 onActivityResult 事件。我在 Delphi 中找到了一个解决方案，但我无法将其转换为 C++:

Launching activities and handling results in Delphi XE6 Android apps

特别是标题为 "Communication from the launched activity" 的部分.

确实，TMessageManager.DefaultManager.SubscribeToMessage()函数在C++中需要一个TMessageListener，但我不知道如何使用它。

Answer 1

所以，真正的问题只是你不明白如何调用TMessageManager::SubscribeToMessage()在 C++ 中。您应该先阅读文档，其中包括 C++ 示例。

Sending and Receiving Messages Using the RTL .

Brian Long's Delphi example在 C++ 中将转换为以下内容:

#include <System.Messaging.hpp>
//...

class TMainForm : public TForm
{
    //...
private:
    static const int ScanRequestCode = 0;
    int FMessageSubscriptionID;
    void __fastcall HandleActivityMessage(TObject* const Sender, TMessageBase* const M);
    bool __fastcall OnActivityResult(int RequestCode, int ResultCode, _di_JIntent Data);
    //...
};

#include <FMX.Platform.Android.hpp>
#include <Androidapi.Helpers.hpp>
#include <Androidapi.JNI.App.hpp>
#include <Androidapi.JNI.Toast.hpp>
#include <LaunchActivities.hpp>

// ...

void __fastcall TMainForm::BarcodeScannerButtonClick(TObject *Sender)
{
    FMessageSubscriptionID = TMessageManager::DefaultManager->SubscribeToMessage(__classid(TMessageResultNotification), &HandleActivityMessage);
    LaunchQRScanner(ScanRequestCode);
}

void __fastcall TMainForm::HandleActivityMessage(TObject* const Sender, TMessageBase* const M)
{
    TMessageResultNotification *msg = dynamic_cast<TMessageResultNotification*>(M);
    if (msg)
        OnActivityResult(msg->RequestCode, msg->ResultCode, msg->Value);
}

bool __fastcall TMainForm::OnActivityResult(int RequestCode, int ResultCode, _di_JIntent Data)
{
    String ScanContent, ScanFormat;

    TMessageManager::DefaultManager->Unsubscribe(__classid(TMessageResultNotification), FMessageSubscriptionID);
    FMessageSubscriptionID = 0;

    // For more info see https://github.com/zxing/zxing/wiki/Scanning-Via-Intent
    if (RequestCode == ScanRequestCode)
    {
        if (ResultCode == TJActivity::JavaClass->RESULT_OK)
        {
            if (Data)
            {
                ScanContent = JStringToString(Data->getStringExtra(StringToJString("SCAN_RESULT")));
                ScanFormat = JStringToString(Data.getStringExtra(StringToJString("SCAN_RESULT_FORMAT")));
                Toast(Format("Found %s format barcode:\n%s", ARRAYOFCONST(( ScanFormat, ScanContent ))), LongToast);
            }
        }
        else if (ResultCode == TJActivity::JavaClass->RESULT_CANCELED)
        {
            Toast("You cancelled the scan", ShortToast);
        }

        return true;
    }

    return false;
}