QT6 Android应用文件分享故障：文件无法成功附加

我在QT6 Android应用中尝试将文本文件分享至Google Drive、WhatsApp或邮件等应用，目前能唤起可选的分享应用，但文件始终无法被附加，消息为空。已确认文件可读，怀疑问题和JNI路径处理有关。

初始实现代码 #

void myapp::shareTextDocument(const QString& documentPath)
{

    qDebug() << documentPath;
    QString m_downloadfilename;
    m_downloadfilename = QStandardPaths::writableLocation(QStandardPaths::DocumentsLocation);

//test if file is readable -> result is positive 
    QFile inputFile(documentPath);
    if (inputFile.open(QIODevice::ReadOnly))
    {
        QTextStream in(&inputFile);
        while (!in.atEnd())
        {
            QString line = in.readLine();
            qDebug() << line;
        }
        inputFile.close();
    }
//text is readable.

  
    QJniObject jniDocumentPath = QJniObject::fromString(documentPath);

    // Create an Intent to share the text document
    QJniObject intent("android/content/Intent",
                             "(Ljava/lang/String;)V",
                             jniDocumentPath.object<jstring>());

    // Set the action and MIME type
    QJniObject action = QJniObject::getStaticObjectField<jstring>(
        "android/content/Intent", "ACTION_SEND");
    QJniObject mimeType = QJniObject::fromString("text/plain");
    intent.callObjectMethod(
        "setAction", "(Ljava/lang/String;)Landroid/content/Intent;", action.object());
    intent.callObjectMethod(
        "setType", "(Ljava/lang/String;)Landroid/content/Intent;", mimeType.object());

    // Get the current QtActivity and start the sharing activity
    QNativeInterface::QAndroidApplication::runOnAndroidMainThread
    ([intent]() {
        QJniObject currentActivity = QtAndroidPrivate::activity();
        QJniObject chooserIntent = QJniObject::callStaticObjectMethod(
            "android/content/Intent", "createChooser",
            "(Landroid/content/Intent;Ljava/lang/CharSequence;)Landroid/content/Intent;",
            intent.object(), QJniObject::fromString("Share via").object());
        currentActivity.callMethod<void>(
            "startActivity", "(Landroid/content/Intent;)V", chooserIntent.object());
    });
}

问题现象：分享应用可正常唤起、选择及发送，但文件未被附加。

改用FileProvider后的配置与代码 #

AndroidManifest.xml 配置 #

<application .......

        <provider android:name="androidx.core.content.FileProvider" android:authorities="org.my.myap.authority" android:exported="false" android:grantUriPermissions="true">
            <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/filepaths"/>
        </provider>
        
</application>

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />

C++ 代码实现 #

void myApp::shareTextDocument(const QString& documentPath)
{
    QJniObject activity = QtAndroidPrivate::activity();
    QJniObject context = QtAndroidPrivate::context();

    QJniEnvironment env;
    QJniObject file = QJniObject::fromString(QDir::toNativeSeparators(documentPath));


    QString providerAuthority = "org.my.myap.authority";
    QJniObject provider = QJniObject::callStaticObjectMethod("androidx/core/content/FileProvider",
                                                             "getUriForFile",
                                                             "(Landroid/content/Context;Ljava/lang/String;Ljava/io/File;)Landroid/net/Uri;",
                                                             context.object(),
                                                             QJniObject::fromString(providerAuthority).object(),
                                                             file.object<jobject>());

    QJniObject intent("android/content/Intent");
    intent.callObjectMethod("setAction", "(Ljava/lang/String;)Landroid/content/Intent;", QJniObject::fromString("android.intent.action.SEND").object());
    intent.callObjectMethod("putExtra", "(Ljava/lang/String;Landroid/os/Parcelable;)Landroid/content/Intent;", QJniObject::fromString("android.intent.extra.STREAM").object(), provider.object());
    intent.callObjectMethod("setType", "(Ljava/lang/String;)Landroid/content/Intent;", QJniObject::fromString("application/octet-stream").object());


    QtAndroidPrivate::startActivity(intent.object(), 0);
}

CMakeLists.txt 配置 #

if(ANDROID)
    set(ANDROID_XML_FILES android/res/xml/filepaths.xml)
    qt_add_resources(TARGET HyundaiMeteoQML SOURCES ${ANDROID_XML_FILES})
endif()

filepaths.xml 配置 #

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external_files" path="."/>
</paths>

问题现象：接收应用（Drive、邮件、WhatsApp等）提示无数据，问题依旧。

问题排查与修复方案 #

1. 修复FileProvider的文件对象创建错误 #

原代码中用QJniObject::fromString直接创建File对象是错误的，需通过Java File类的构造函数传入路径字符串：

// 替换原有的file创建代码
QJniObject filePathStr = QJniObject::fromString(QDir::toNativeSeparators(documentPath));
QJniObject file("java/io/File", "(Ljava/lang/String;)V", filePathStr.object<jstring>());

2. 正确授予URI权限 #

在启动Intent前，必须给目标应用授予URI的读权限，避免因权限不足导致无法访问文件：

// 添加权限标记
QJniObject readFlag = QJniObject::getStaticObjectField<jint>("android/content/Intent", "FLAG_GRANT_READ_URI_PERMISSION");
intent.callObjectMethod("addFlags", "(I)Landroid/content/Intent;", readFlag.object<jint>());

3. 匹配正确的MIME类型 #

对于文本文件，优先使用text/plain而非通用的application/octet-stream，部分应用对二进制类型的支持有限：

intent.callObjectMethod("setType", "(Ljava/lang/String;)Landroid/content/Intent;", QJniObject::fromString("text/plain").object());

4. 完善FileProvider路径配置 #

如果文件存放在应用私有Documents目录，需在filepaths.xml中添加对应路径配置：

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external_files" path="."/>
    <files-path name="app_documents" path="Documents/"/> <!-- 适配应用私有Documents目录 -->
</paths>

5. 规范Intent初始化与Chooser调用 #

使用系统常量而非硬编码字符串创建Intent，并通过Chooser唤起分享选择器：

// 用系统常量创建Intent
QJniObject actionSend = QJniObject::getStaticObjectField<jstring>("android/content/Intent", "ACTION_SEND");
QJniObject intent("android/content/Intent", "(Ljava/lang/String;)V", actionSend.object<jstring>());

// 创建分享选择器
QJniObject chooser = QJniObject::callStaticObjectMethod("android/content/Intent", "createChooser",
    "(Landroid/content/Intent;Ljava/lang/CharSequence;)Landroid/content/Intent;",
    intent.object(), QJniObject::fromString("分享文件").object());

QtAndroidPrivate::startActivity(chooser.object(), 0);

内容的提问来源于stack exchange，提问作者Kurt Dewulf