默认情况下，如果应用以 Android Q 为目标平台，则在访问外部存储设备中的文件时会进入过滤视图。应用可以使用 Context.getExternalFilesDir() 将专用于自己的文件存储在特定于自己的目录中。
1. 临时停用分区存储行为:
以 Android 9（API 级别 28）或更低版本为目标平台。
如果您以 Android Q 为目标平台，请在应用的清单文件中将 requestLegacyExternalStorage 的值设为 true。
<manifest ... > <!-- This attribute is "false" by default on apps targeting Android Q. --> <application android:requestLegacyExternalStorage="true" ... > ... </application> </manifest>
2. 如何实现隔离存储:
2.1 ApplicationInfo新增PRIVATE_FLAG_REQUEST_LEGACY_EXTERNAL_STORAGE标记
PackageParser.java:
if (sa.getBoolean(
R.styleable.AndroidManifestApplication_requestLegacyExternalStorage,
owner.applicationInfo.targetSdkVersion < Build.VERSION_CODES.Q)) {
ai.privateFlags |= ApplicationInfo.PRIVATE_FLAG_REQUEST_LEGACY_EXTERNAL_STORAGE;
}
ApplicationInfo.java:
public boolean hasRequestedLegacyExternalStorage() {
return (privateFlags & PRIVATE_FLAG_REQUEST_LEGACY_EXTERNAL_STORAGE) != 0;
}
2.2 grantRuntimePermission()重新挂载视图
apk启动时默认挂载runtime/default视图，grantRuntimePermission()时如果是READ_EXTERNAL_STORAGE或WRITE_EXTERNAL_STORAGE，则会获取挂载模式重新挂载对应视图。
PermissionManagerService.java:
private void grantRuntimePermission(String permName, String packageName, boolean overridePolicy,
int callingUid, final int userId, PermissionCallback callback) {
......
if (READ_EXTERNAL_STORAGE.equals(permName)
|| WRITE_EXTERNAL_STORAGE.equals(permName)) {
final long token = Binder.clearCallingIdentity();
try {
if (mUserManagerInt.isUserInitialized(userId)) {
StorageManagerInternal storageManagerInternal = LocalServices.getService(
StorageManagerInternal.class);
storageManagerInternal.onExternalStoragePolicyChanged(uid, packageName);
}
} finally {
Binder.restoreCallingIdentity(token);
}
}
}
获取挂载模式这块android10有修改，没有设置Legacy标志的话，总是获取default挂载模式，没有读写权限。
android 10会设置属性[persist.sys.isolated_storage]: [true]，因此走到if(ENABLE_ISOLATED_STORAGE)中的getMountMode()。
public static boolean hasIsolatedStorage() {
//[persist.sys.isolated_storage]: [true]
//[sys.isolated_storage_snapshot]: [true]
return SystemProperties.getBoolean("sys.isolated_storage_snapshot",
SystemProperties.getBoolean("persist.sys.isolated_storage", true));
}
private static final boolean ENABLE_ISOLATED_STORAGE = StorageManager.hasIsolatedStorage();
public int getExternalStorageMountMode(int uid, String packageName) {
+ //android 10新增逻辑
+ if (ENABLE_ISOLATED_STORAGE) {
+ return getMountMode(uid, packageName);
+ }
......
int mountMode = Integer.MAX_VALUE;
for (ExternalStorageMountPolicy policy : mPolicies) {
final int policyMode = policy.getMountMode(uid, packageName);
if (policyMode == Zygote.MOUNT_EXTERNAL_NONE) {
return Zygote.MOUNT_EXTERNAL_NONE;
}
mountMode = Math.min(mountMode, policyMode);
}
if (mountMode == Integer.MAX_VALUE) {
return Zygote.MOUNT_EXTERNAL_NONE;
}
return mountMode;
}
正常模式下hasLegacy=false，走到if判断的DEFAULT分支；legacy模式hasLegacy=true，与之前保持一致，有write权限就走到WRITE模式分支。
private int getMountModeInternal(int uid, String packageName) {
try {
......
final boolean hasRead = StorageManager.checkPermissionAndCheckOp(mContext, false, 0,
uid, packageName, READ_EXTERNAL_STORAGE, OP_READ_EXTERNAL_STORAGE);
final boolean hasWrite = StorageManager.checkPermissionAndCheckOp(mContext, false, 0,
uid, packageName, WRITE_EXTERNAL_STORAGE, OP_WRITE_EXTERNAL_STORAGE);
......
final boolean hasLegacy = mIAppOpsService.checkOperation(OP_LEGACY_STORAGE,
uid, packageName) == MODE_ALLOWED;
if (hasLegacy && hasWrite) {
return Zygote.MOUNT_EXTERNAL_WRITE;
} else if (hasLegacy && hasRead) {
return Zygote.MOUNT_EXTERNAL_READ;
} else {
return Zygote.MOUNT_EXTERNAL_DEFAULT;
}
} catch (RemoteException e) {
// Should not happen
}
return Zygote.MOUNT_EXTERNAL_NONE;
}
2.3 Legacy Storage属性对权限的影响
安装apk时，就会根据requestLegacyExternalStorage属性来对ops state进行设置，修改OP_LEGACY_STORAGE的默认状态。
<manifest ... > <application android:requestLegacyExternalStorage="true" ... > </application> </manifest> //Q 正常模式 LEGACY_STORAGE: mode=ignore //Q legacy模式 LEGACY_STORAGE: mode=allow
PermissionPolicyService启动时首先进行权限变化监听：
public void onStart() {
permManagerInternal.addOnRuntimePermissionStateChangedListener(
this::synchronizePackagePermissionsAndAppOpsAsyncForUser);
}
private void synchronizePackagePermissionsAndAppOpsAsyncForUser(@NonNull String packageName,
@UserIdInt int changedUserId) {
if (isStarted(changedUserId)) {
synchronized (mLock) {
if (mIsPackageSyncsScheduled.add(new Pair<>(packageName, changedUserId))) {
FgThread.getHandler().sendMessage(PooledLambda.obtainMessage(
PermissionPolicyService
::synchronizePackagePermissionsAndAppOpsForUser,
this, packageName, changedUserId));
}
......
}
}
}
APK安装时，会根据requestLegacyExternalStorage属性来通知storage权限变化，调用关系如下：
//调用关系：
1.PackageManagerService.java:
installPackagesLI()
commitPackagesLocked()
updateSettingsLI()
updateSettingsInternalLI()
2.PermissionManagerService.java:
mPermissionManager.updatePermissions()
restorePermissionState()
//关键代码：
private void restorePermissionState(@NonNull PackageParser.Package pkg, boolean replace,
@Nullable String packageOfInterest, @Nullable PermissionCallback callback) {
......
//判断requestLegacyExternalStorage属性
updatedUserIds = checkIfLegacyStorageOpsNeedToBeUpdated(pkg, replace, updatedUserIds);
......
for (int userId : updatedUserIds) {
notifyRuntimePermissionStateChanged(pkg.packageName, userId);
}
}
最终调用到PermissionPolicyService的监听函数synchronizePackagePermissionsAndAppOpsForUser()，进行默认权限获取和设置。
当apk安装时，声明了requestLegacyExternalStorage="true"属性，并且声明了READ_EXTERNAL_STORAGE、WRITE_EXTERNAL_STORAGE，那么addOpIfRestricted()就会将LEGACY_STORAGE设置为allow模式。
//调用关系：
synchronizePackagePermissionsAndAppOpsForUser()：
synchroniser.addPackage()
addOpIfRestricted()//LEGACY_STORAGE加入到mOpsToAllow
synchroniser.syncPackages()
setUidModeAllowed()
setUidMode()//设置LEGACY_STORAGE为allow
//关键代码：
private void addOpIfRestricted(@NonNull PermissionInfo permissionInfo,
@NonNull PackageInfo pkg) {
......
//forPermission()会根据requestLegacyExternalStorage的值进行返回
final SoftRestrictedPermissionPolicy policy =
SoftRestrictedPermissionPolicy.forPermission(mContext, pkg.applicationInfo,
mContext.getUser(), permission);
final int op = policy.resolveAppOp();
if (op != OP_NONE) {
switch (policy.getDesiredOpMode()) {
case MODE_DEFAULT:
mOpsToDefault.add(new OpToChange(uid, pkg.packageName, op));
break;
case MODE_ALLOWED:
//在声明READ_EXTERNAL_STORAGE权限下，会将LEGACY_STORAGE加入到mOpsToAllow
if (policy.shouldSetAppOpIfNotDefault()) {
mOpsToAllow.add(new OpToChange(uid, pkg.packageName, op));
} else {
mOpsToAllowIfDefault.add(
new OpToChange(uid, pkg.packageName, op));
}
break;
......
}
public static @NonNull SoftRestrictedPermissionPolicy forPermission(@NonNull Context context,
@Nullable ApplicationInfo appInfo, @Nullable UserHandle user,
@NonNull String permission) {
switch (permission) {
case READ_EXTERNAL_STORAGE: {
if (appInfo != null) {
boolean hasAnyRequestedLegacyExternalStorage =
appInfo.hasRequestedLegacyExternalStorage();
hasRequestedLegacyExternalStorage = hasAnyRequestedLegacyExternalStorage;
}
return new SoftRestrictedPermissionPolicy() {
@Override
public int getDesiredOpMode() {
if (applyRestriction) {
return MODE_DEFAULT;
} else if (hasRequestedLegacyExternalStorage) {
//声明了requestLegacyExternalStorage就返回allow
return MODE_ALLOWED;
} else {
return MODE_IGNORED;
}
}
@Override
public boolean shouldSetAppOpIfNotDefault() {
return getDesiredOpMode() != MODE_IGNORED;
}
};
}
3. sdcard路径权限说明:
- rwx:421，umask默认为八进制022(----w--w-)
- /mnt/runtime/default的gid为1015，也就是sdcard_rw；mask 为6，八进制006，group sdcard_rw可读写，也就是other没有rw权限
- /mnt/runtime/read的gid为9997，也就是everybody；mask 为23，八进制027，group everybody可读、不可写，other没有读写执行权限
- /mnt/runtime/write的gid为9997，也就是everybody；mask 为7，八进制007，group everybody可读写，other没有读写可执行权限
- /data/media on /mnt/runtime/default/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal)
/data/media on /mnt/runtime/read/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23,derive_gid,default_normal)
/data/media on /mnt/runtime/write/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal)
/mnt/runtime/default:
drwxrwx--x 3 root sdcard_rw 4096 2018-12-18 03:41 Android drwxrwx--x 3 root sdcard_rw 4096 2018-12-18 06:11 DCIM
/mnt/runtime/read:
drwxr-x--- 3 root everybody 4096 2018-12-18 03:41 Android drwxr-x--- 3 root everybody 4096 2018-12-18 06:11 DCIM
/mnt/runtime/write:
drwxrwx--- 3 root everybody 4096 2018-12-18 03:41 Android drwxrwx--- 3 root everybody 4096 2018-12-18 06:11 DCIM
/sdcard/Android/data:
drwxrwx--- 4 u0_a64 everybody 4096 2018-12-18 06:11 com.android.camera2 drwxrwx--- 3 u0_a15 everybody 4096 2018-12-18 03:41 com.google.android.gms drwxrwx--- 4 u0_a84 everybody 4096 2018-12-18 03:41 com.google.android.youtube
4. sdcard文件存储示例:
4.1 getExternalFilesDir()随卸载而删除
///storage/emulated/0/Android/data/com.xx.xx/files File file = File(context.getExternalFilesDir(null), "test.txt");
4.2 媒体文件
媒体文件使用MediaStore操作，卸载后不会删除。
访问其他应用生成的照片、视频、音频，需要READ_EXTERNAL_STORAGE权限。
4.3 存储访问框架(SAF)
访问其他应用创建的文件，例如"Download"目录，必须使用存储访问框架，用户通过框架选择特定文件。
4.4 照片中的位置信息
需要ACCESS_MEDIA_LOCATION权限，才能获取元数据中的位置信息。
<permission android:name="android.permission.ACCESS_MEDIA_LOCATION" android:permissionGroup="android.permission-group.UNDEFINED" android:label="@string/permlab_mediaLocation" android:description="@string/permdesc_mediaLocation" android:protectionLevel="dangerous" />
到此这篇关于androidQ sd卡权限使用详解的文章就介绍到这了,更多相关androidQ sd卡权限内容请搜索易盾网络以前的文章或继续浏览下面的相关文章希望大家以后多多支持易盾网络！