应用程序权限

当今设备和 OS (操作系统) 的许多特征可能对隐私、安全性、及性能有显著影响，若滥用。因此，要求用户明确同意的平台越来越普遍，在访问这些特征之前。

Qt 权限 API 允许应用程序以跨平台方式，校验 (或请求) 这些特性的权限。

用法

A feature that commonly requires user consent is access to the microphone of the device. An application for recording voice memos would perhaps look something like this initially:

void VoiceMemoWidget::onRecordingInitiated()
{
    m_microphone->startRecording();
}

To ensure this application works well on platforms that require user consent for microphone access we would extend it like this:

void VoiceMemoWidget::onRecordingInitiated()
{
    QMicrophonePermission microphonePermission;
    switch (qApp->checkPermission(microphonePermission)) {
    case Qt::PermissionStatus::Undetermined:
        qApp->requestPermission(microphonePermission, this,
                    &VoiceMemoWidget::onRecordingInitiated);
        return;
    case Qt::PermissionStatus::Denied:
        m_permissionInstructionsDialog->show();
        return;
    case Qt::PermissionStatus::Granted:
        m_microphone->startRecording();
    }
}

We first check if we already know the status of the microphone permission. If we don't we initiate a permission request to determine the current status, which will potentially ask the user for consent. We connect the result of the request to the slot we're already in, so that we get another chance at evaluating the permission status.

Once the permission status is known, either because we had been granted or denied permission at an earlier time, or after getting the result back from the request we just initiated, we redirect the user to a dialog explaining why we can not record voice memos at this time (if the permission was denied), or proceed to using the microphone (if permission was granted).

注意： On macOS and iOS permissions can currently only be requested for GUI applications.

声明权限

Some platforms require that the permissions you request are declared up front at build time.

Apple 平台

请求的每个权限都必须附有所谓的 用法描述 字符串在应用程序的 Info.plist 文件，描述应用程序为什么需要访问给定权限。例如：

<key>NSMicrophoneUsageDescription</key>
<string>The microphone is used to record voice memos.</string>

每种权限类型的相关用法描述键，在文档编制中有描述。

要确保相关权限后端包括在应用程序中，请把构建系统指向自定义 Info.plist .

Android

请求的每个权限都必须附有 uses-permission 条目在应用程序的 AndroidManifest.xml 文件。例如：

<manifest ...>
    <uses-permission android:name="android.permission.RECORD_AUDIO"/>
</manifest>

要确保相关权限后端包括在应用程序中，请把构建系统指向自定义 AndroidManifest.xml 或使用 qt_add_android_permission()。

每种权限类型的相关权限名称，在文档编制中有描述。

可用权限

下列权限类型可用：

QBluetoothPermission	访问蓝牙外围设备
QCalendarPermission	访问用户的日历
QCameraPermission	访问摄像头为取得图片 (或视频)
QContactsPermission	访问用户的联系人
QLocationPermission	访问用户的位置
QMicrophonePermission	为监视访问麦克风 (或录制声音)

注意： The available permission types cover core functionality of Qt modules like Qt Multimedia and Qt Positioning, but do not encompass all platform-specific permissions. Custom permission types are not currently supported.

最佳实践

To ensure the best possible user experience for the end user we recommend adopting the following best practices for managing application permissions:

Request the minimal set of permissions needed. For example, if you only need access to the microphone, do not request camera permission just in case. Use the properties of individual permission types to limit the permission scope even further, for example QContactsPermission::setAccessMode () to request read only access.
Request permissions in response to specific actions by the user. For example, defer requesting microphone permission until the user presses the button to record audio. Associating the permission request to a specific action gives the user a clearer context of why the permission is needed. Do not request all needed permission on startup.
Present extra context and explanation if needed. Sometimes the action by the user is not enough context. Consider presenting an explanation-dialog after the user has initiated the action, but before requesting the permission, so the user is aware of what's about to happen when the system permission dialog subsequently pops up.
Be transparent and explicit about why permissions are needed. In explanation dialogs and usage descriptions, be transparent about why the particular permission is needed for your application to provide a specific feature, so users can make informed decisions.
Account for denied permissions. The permissions you request may be denied for various reasons. You should always account for this situation, by gracefully degrading the experience of your application, and presenting clear explanations the user about the situation.
Never request permissions from a library. The request of permissions should be done as close as possible to the user, where the information needed to make good decisions on the points above is available. Libraries can check permissions, to ensure they have the prerequisites for doing their work, but if the permission is undetermined or denied this should be reflected through the library's API, so that the application in turn can request the necessary permissions.

另请参阅 信息特性列表文件 and Qt Creator：编辑清单文件 .

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