Qt Android目录操作技术咨询：文件存储路径修正与QProcess调用可行性问题

Hey there! Let's tackle your two Qt-on-Android questions one by one:

The problem here is that hardcoding absolute paths like /storage/emulated/0/Android/data/ doesn't work reliably on Android, thanks to scoped storage (introduced in Android 10) and Qt's path virtualization for Android apps. When you use a hardcoded external path without proper permissions or Qt's standard path utilities, Android redirects the write operation to your app's private internal storage (/data/user/0/org.qtproject.example.NameApp), which is why you're seeing files end up there.

Here's how to fix it:

• Use Qt's QStandardPaths for platform-safe paths: For Android, QStandardPaths::ExternalDataLocation points directly to your app's dedicated external storage directory: /storage/emulated/0/Android/data/<your_package_name>/files/. This directory is private to your app (no extra permissions needed on Android 11+), and Qt handles all platform-specific path resolution automatically.
• Never hardcode paths: Absolute paths can vary across devices or Android versions, so always rely on Qt's path utilities.

Example code to build your target zip path:

#include <QStandardPaths>
#include <QDir>

// Get the app's external data directory
QString externalDataPath = QStandardPaths::writableLocation(QStandardPaths::ExternalDataLocation);
// Create the directory if it doesn't exist
QDir().mkpath(externalDataPath);
// Build your target zip path
QString zipPath = externalDataPath + "/cache.zip";

// Now use this path for your QuaZip operations or rename
m_file.rename(zipPath);

If you specifically need to write to /storage/emulated/0/Android/data/ (not your app's subdirectory):

1. Add the WRITE_EXTERNAL_STORAGE permission to your AndroidManifest.xml (for Android 9 and below).
2. For Android 10+, add android:requestLegacyExternalStorage="true" to your <application> tag in AndroidManifest.xml to temporarily bypass scoped storage (note this is deprecated in Android 11+—stick to your app's dedicated directory whenever possible).

Unfortunately, QProcess won't work for opening files on Android the way it does on Windows. Android uses an Intent-based system to launch apps that can handle specific file types, rather than directly executing commands like desktop systems.

To open a file, you'll need to use Qt's Android Extras module to call Android's native Intent system. Here's how:

Step 1: Add Qt Android Extras to your project #

Add this line to your .pro file:

QT += androidextras

Step 2: Code to open a file using Intent #

This example handles Android 7+'s FileProvider requirement (to avoid FileUriExposedException):

#include <QAndroidJniObject>
#include <QAndroidIntent>
#include <QFile>

void openFile(const QString& filePath) {
    QFile file(filePath);
    if (!file.exists()) {
        // Handle file not found error
        return;
    }

    // Convert Qt file path to Android File object
    QAndroidJniObject javaFile = QAndroidJniObject::fromString(filePath);
    QAndroidJniObject fileUri;

    // Use FileProvider for Android 7.0 (API 24) and above
    if (QAndroidJniEnvironment().version() >= JNI_VERSION_1_6 && 
        QAndroidJniObject::callStaticMethod<jint>("android/os/Build$VERSION", "SDK_INT") >= 24) {
        QAndroidJniObject authority = QAndroidJniObject::fromString("org.qtproject.example.NameApp.fileprovider"); // Replace with your package name + .fileprovider
        fileUri = QAndroidJniObject::callStaticObjectMethod("androidx/core/content/FileProvider", "getUriForFile",
                                                            "(Landroid/content/Context;Ljava/lang/String;Ljava/io/File;)Landroid/net/Uri;",
                                                            QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/android/QtNative", "activity", "()Landroid/app/Activity;").object(),
                                                            authority.object(),
                                                            javaFile.object());
    } else {
        // Use file:// URI for older Android versions
        fileUri = QAndroidJniObject::callStaticObjectMethod("android/net/Uri", "fromFile", "(Ljava/io/File;)Landroid/net/Uri;", javaFile.object());
    }

    // Create ACTION_VIEW Intent to open the file
    QAndroidIntent intent(QAndroidJniObject::getStaticObjectField("android/content/Intent", "ACTION_VIEW", "Ljava/lang/String;"));
    intent.setData(fileUri);
    intent.setFlags(QAndroidJniObject::getStaticField<jint>("android/content/Intent", "FLAG_GRANT_READ_URI_PERMISSION"));

    // Launch the Intent
    QAndroidJniObject activity = QAndroidJniObject::callStaticObjectMethod("org/qtproject/qt5/android/QtNative", "activity", "()Landroid/app/Activity;");
    activity.callMethod<void>("startActivity", "(Landroid/content/Intent;)V", intent.handle());
}

Step 3: Configure FileProvider (for Android 7+) #

1. Create res/xml/file_paths.xml in your Android resources directory:

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

This tells FileProvider to share files from your app's external files directory.

2. Add the FileProvider to your AndroidManifest.xml:

<application ...>
    <provider
        android:name="androidx.core.content.FileProvider"
        android:authorities="org.qtproject.example.NameApp.fileprovider" <!-- Match the authority in your code -->
        android:exported="false"
        android:grantUriPermissions="true">
        <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/file_paths"/>
    </provider>
</application>

Replace org.qtproject.example.NameApp with your actual app's package name.

内容的提问来源于stack exchange，提问作者Ed Vestorn