无法通过其他应用程序访问我使用Android FileProvider公开的文件

Question

我正试图使用文件提供程序公开一个文件，然后在我开发的另一个应用程序中读取该文件。

以下是暴露文件并触发意图的应用程序的代码：

val intent = Intent(ACTION_INSTALL)
intent.setPackage(servicePackage)
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
intent.putExtra(EXTRA_URI, 
"content://com.mma.apkprovider/apks//storage/emulated/0/main_app-release.apk")
// Launch the installer service
context.startForegroundService(intent)

连同以下AndroidManifest.xml：

<permission
android:name="com.mma.permissions.APK_PROVIDER"
android:protectionLevel="signature" />
<application>
<provider
android:name=".ApkProvider"
android:authorities="com.mma.mainapp.ApkProvider"
android:exported="false"
android:grantUriPermissions="true"
android:permission="com.mma.permissions.APK_PROVIDER" >
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/apk_paths" />
</provider>
</application>

以下是应用程序的代码，该应用程序从读取文件的意图中被触发：

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
log("onStartCommand called...")
log("action: ${intent?.action}")
log("flags: $flags")
log("action: $startId")
val action = intent?.action
val uri = intent?.getStringExtra(EXTRA_URI) ?: return START_NOT_STICKY
if (action == ACTION_INSTALL) {
log("Install APK $uri...")
executor.submit {
performInstallation(Uri.parse(uri))
}
}
return START_NOT_STICKY
}
private fun performInstallation(uri: Uri) {
try {
val packageInstaller = packageManager.packageInstaller
val sessionId = packageInstaller.createSession(
PackageInstaller.SessionParams(
PackageInstaller.SessionParams.MODE_FULL_INSTALL
)
)
val session = packageInstaller.openSession(sessionId)
val uniqueName = UUID.randomUUID().toString()
//
val file = contentResolver.openFileDescriptor(uri, "r")
val size = file?.statSize ?: throw IOException("Couldn't read file from provider!")
file.close()
val outputStream = session.openWrite(uniqueName, 0, size)
val inputStream = contentResolver.openInputStream(uri)
?: throw IOException("Couldn't read file from provider!")
} catch (e: Exception) {
val intent = Intent(ACTION_RESULT).also { it.putExtra(EXTRA_RESULT, e.message) }
sendBroadcast(intent)
loge("Error installing $uri", e)
}
//...
}

以下是我从安装程序应用程序中得到的堆栈跟踪：

D Installer: onStartCommand called...
10-19 16:27:57.310  3814  3814 D Installer: action: com.mma.INSTALL
10-19 16:27:57.310  3814  3814 D Installer: flags: 0
10-19 16:27:57.310  3814  3814 D Installer: action: 3
10-19 16:27:57.324  3814  3814 D Installer: Install APK content://com.mma.main_app.ApkProvider/apks//storage/emulated/0/main_app-release.apk...
10-19 16:27:57.332  2607  2607 W Binder:2607_8: type=1400 audit(0.0:45866): avc: denied { dac_read_search } for capability=2 scontext=u:r:installd:s0 tcontext=u:r:installd:s0 tclass=capability permissive=0
10-19 16:27:57.576  3814  7880 E ActivityThread: Failed to find provider info for com.mma.main_app.ApkProvider
10-19 16:27:57.336  2607  2607 I chatty  : uid=0(root) Binder:2607_2 identical 3 lines
10-19 16:27:57.336  2607  2607 W Binder:2607_8: type=1400 audit(0.0:45870): avc: denied { dac_read_search } for capability=2 scontext=u:r:installd:s0 tcontext=u:r:installd:s0 tclass=capability permissive=0
10-19 16:27:57.588  3814  7880 E Installer: Error installing content://com.mma.main_app.ApkProvider/apks//storage/emulated/0/main_app-release.apk
10-19 16:27:57.588  3814  7880 E Installer: java.io.FileNotFoundException: No content provider: content://com.mma.main_app.ApkProvider/apks//storage/emulated/0/main_app-release.apk
10-19 16:27:57.588  3814  7880 E Installer:     at android.content.ContentResolver.openTypedAssetFileDescriptor(ContentResolver.java:1445)
10-19 16:27:57.588  3814  7880 E Installer:     at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:1296)
10-19 16:27:57.588  3814  7880 E Installer:     at android.content.ContentResolver.openFileDescriptor(ContentResolver.java:1149)
10-19 16:27:57.588  3814  7880 E Installer:     at android.content.ContentResolver.openFileDescriptor(ContentResolver.java:1103)
10-19 16:27:57.588  3814  7880 E Installer:     at com.mma.installer.InstallerService.performInstallation(InstallerService.kt:74)
10-19 16:27:57.588  3814  7880 E Installer:     at com.mma.installer.InstallerService.access$performInstallation(InstallerService.kt:18)
10-19 16:27:57.588  3814  7880 E Installer:     at com.mma.installer.InstallerService$onStartCommand$1.run(InstallerService.kt:46)
10-19 16:27:57.588  3814  7880 E Installer:     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:458)
10-19 16:27:57.588  3814  7880 E Installer:     at java.util.concurrent.FutureTask.run(FutureTask.java:266)
10-19 16:27:57.588  3814  7880 E Installer:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
10-19 16:27:57.588  3814  7880 E Installer:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
10-19 16:27:57.588  3814  7880 E Installer:     at java.lang.Thread.run(Thread.java:764)

因此，我在从安装程序应用程序中查找内容提供商时遇到问题。我在这件事上被困了好几天。我是使用提供商/内容解析器的新手，这对我来说相当复杂。

编辑

ApkProvider是一个FileProvider子类：

import androidx.core.content.FileProvider
class ApkProvider : FileProvider() {}

Answer 1

我最终没有使用FileProvider/ContentResolver/Uri API，这些API非常容易出错，并且不能提供明确的警告/错误消息。

要共享的文件可以简单地保存到/data/local/tmp("${Environment.getDataDirectory((}/local/tmp&"(中并且在没有特定权限的情况下从其他活动中检索。

触发的应用程序可以简单地从绝对路径读取文件：

val file = File(apkPath)
val inputStream = FileInputStream(file)