Android系统开发之在PMS里面限制应用的卸载

在日常开发中，尤其是定制ROM,有些设备里面的应用不想被卸载，就需要限制用户，当然如果将不能卸载的应用预置到system/app目录下也不会被卸载，但是我们还有其他方式，比如在PMS里面假如卸载限制，这样也可以实现这个功能，而且adb 命令或者代码都不能卸载该应用，接下来我们看下实现方法。
首先我们先看下PMS的源码如下：

 private static boolean isPrivilegedApp(PackageParser.Package pkg) {
        return (pkg.applicationInfo.flags & ApplicationInfo.FLAG_PRIVILEGED) != 0;
    }

    private static boolean isSystemApp(ApplicationInfo info) {
        return (info.flags & ApplicationInfo.FLAG_SYSTEM) != 0;
    }

    private static boolean isSystemApp(PackageSetting ps) {
        return (ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) != 0;
    }

    private static boolean isUpdatedSystemApp(PackageSetting ps) {
        return (ps.pkgFlags & ApplicationInfo.FLAG_UPDATED_SYSTEM_APP) != 0;
    }

    private static boolean isUpdatedSystemApp(PackageParser.Package pkg) {
        return (pkg.applicationInfo.flags & ApplicationInfo.FLAG_UPDATED_SYSTEM_APP) != 0;
    }

    private int packageFlagsToInstallFlags(PackageSetting ps) {
        int installFlags = 0;
        if (isExternal(ps)) {
            installFlags |= PackageManager.INSTALL_EXTERNAL;
        }
        if (isForwardLocked(ps)) {
            installFlags |= PackageManager.INSTALL_FORWARD_LOCK;
        }
        return installFlags;
    }

    private void deleteTempPackageFiles() {
        final FilenameFilter filter = new FilenameFilter() {
            public boolean accept(File dir, String name) {
                return name.startsWith("vmdl") && name.endsWith(".tmp");
            }
        };
        deleteTempPackageFilesInDirectory(mAppInstallDir, filter);
        deleteTempPackageFilesInDirectory(mDrmAppPrivateInstallDir, filter);
    }

    private static final void deleteTempPackageFilesInDirectory(File directory,
            FilenameFilter filter) {
        final String[] tmpFilesList = directory.list(filter);
        if (tmpFilesList == null) {
            return;
        }
        for (int i = 0; i < tmpFilesList.length; i++) {
            final File tmpFile = new File(directory, tmpFilesList[i]);
            tmpFile.delete();
        }
    }

    private File createTempPackageFile(File installDir) {
        File tmpPackageFile;
        try {
            tmpPackageFile = File.createTempFile("vmdl", ".tmp", installDir);
        } catch (IOException e) {
            Slog.e(TAG, "Couldn't create temp file for downloaded package file.");
            return null;
        }
        try {
            FileUtils.setPermissions(
                    tmpPackageFile.getCanonicalPath(), FileUtils.S_IRUSR|FileUtils.S_IWUSR,
                    -1, -1);
            if (!SELinux.restorecon(tmpPackageFile)) {
                return null;
            }
        } catch (IOException e) {
            Slog.e(TAG, "Trouble getting the canoncical path for a temp file.");
            return null;
        }
        return tmpPackageFile;
    }

    @Override
    public void deletePackageAsUser(final String packageName,
                                    final IPackageDeleteObserver observer,
                                    final int userId, final int flags) {
        mContext.enforceCallingOrSelfPermission(
                android.Manifest.permission.DELETE_PACKAGES, null);
        final int uid = Binder.getCallingUid();
        if (UserHandle.getUserId(uid) != userId) {
            mContext.enforceCallingPermission(
                    android.Manifest.permission.INTERACT_ACROSS_USERS_FULL,
                    "deletePackage for user " + userId);
        }
		
        if (isUserRestricted(userId, UserManager.DISALLOW_UNINSTALL_APPS)||packageName.contains("packageName")) {
            try {
                observer.packageDeleted(packageName, PackageManager.DELETE_FAILED_USER_RESTRICTED);
            } catch (RemoteException re) {
            }
            return;
        }

        if (DEBUG_REMOVE) Slog.d(TAG, "deletePackageAsUser: pkg=" + packageName + " user=" + userId);
        // Queue up an async operation since the package deletion may take a little while.
        mHandler.post(new Runnable() {
            public void run() {
                mHandler.removeCallbacks(this);
                final int returnCode = deletePackageX(packageName, userId, flags);
                if (observer != null) {
                    try {
                        observer.packageDeleted(packageName, returnCode);
                    } catch (RemoteException e) {
                        Log.i(TAG, "Observer no longer exists.");
                    } //end catch
                } //end if
            } //end run
        });
    }

    private boolean isPackageDeviceAdmin(String packageName, int userId) {
        IDevicePolicyManager dpm = IDevicePolicyManager.Stub.asInterface(
                ServiceManager.getService(Context.DEVICE_POLICY_SERVICE));
        try {
            if (dpm != null && (dpm.packageHasActiveAdmins(packageName, userId)
                    || dpm.isDeviceOwner(packageName))) {
                return true;
            }
        } catch (RemoteException e) {
        }
        return false;
    }

上面代码中，系统卸载应用的API就是如下代码：

@Override
    public void deletePackageAsUser(final String packageName,
                                    final IPackageDeleteObserver observer,
                                    final int userId, final int flags) {
        mContext.enforceCallingOrSelfPermission(
                android.Manifest.permission.DELETE_PACKAGES, null);
        final int uid = Binder.getCallingUid();
        if (UserHandle.getUserId(uid) != userId) {
            mContext.enforceCallingPermission(
                    android.Manifest.permission.INTERACT_ACROSS_USERS_FULL,
                    "deletePackage for user " + userId);
        }
		
        if (isUserRestricted(userId, UserManager.DISALLOW_UNINSTALL_APPS)||packageName.contains("packageName")) {
            try {
                observer.packageDeleted(packageName, PackageManager.DELETE_FAILED_USER_RESTRICTED);
            } catch (RemoteException re) {
            }
            return;
        }

        if (DEBUG_REMOVE) Slog.d(TAG, "deletePackageAsUser: pkg=" + packageName + " user=" + userId);
        // Queue up an async operation since the package deletion may take a little while.
        mHandler.post(new Runnable() {
            public void run() {
                mHandler.removeCallbacks(this);
                final int returnCode = deletePackageX(packageName, userId, flags);
                if (observer != null) {
                    try {
                        observer.packageDeleted(packageName, returnCode);
                    } catch (RemoteException e) {
                        Log.i(TAG, "Observer no longer exists.");
                    } //end catch
                } //end if
            } //end run
        });
    }

具体实现可以参考如下代码：

if (isUserRestricted(userId, UserManager.DISALLOW_UNINSTALL_APPS)||packageName.contains("packageName")) {
            try {
                observer.packageDeleted(packageName, PackageManager.DELETE_FAILED_USER_RESTRICTED);
            } catch (RemoteException re) {
            }
            return;
        }

这只是单一的功能，我们可以将需要限制的应用包名存放一个集合，再通过比对的方式限制

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