How to take CLEAR_APP_CACHE permission in Android Marshmallow at runtime?

问题

Code:

void clearCache() {

    if (mClearCacheObserver == null) {
        mClearCacheObserver = new CachePackageDataObserver();
    }

    PackageManager mPM = getPackageManager();

    @SuppressWarnings("rawtypes")
    final Class[] classes = {Long.TYPE, IPackageDataObserver.class};

    Long localLong = Long.valueOf(CACHE_APP);


    try {
        Method localMethod =
                mPM.getClass().getMethod("freeStorageAndNotify", classes);

        localMethod.setAccessible(true);
        // Start of inner try-catch block

        try {
            localMethod.invoke(mPM, localLong, mClearCacheObserver);

        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.getCause().printStackTrace();
        }

        // End of inner try-catch block

    } catch (NoSuchMethodException e1) {

        e1.printStackTrace();
    }

}

Logcat:

java.lang.SecurityException: Neither user 10206 nor current process has android.permission.CLEAR_APP_CACHE.
     at android.os.Parcel.readException(Parcel.java:1620)
     at android.os.Parcel.readException(Parcel.java:1573)
     at android.content.pm.IPackageManager$Stub$Proxy.freeStorageAndNotify(IPackageManager.java:5081)
     at android.app.ApplicationPackageManager.freeStorageAndNotify(ApplicationPackageManager.java:2500)
     at android.content.pm.PackageManager.freeStorageAndNotify(PackageManager.java:4710)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.onexsoftech.clearcacheapp.MainActivity.clearCache(MainActivity.java:278)
     at com.onexsoftech.clearcacheapp.MainActivity.insertDummyContactWrapper1(MainActivity.java:495)
     at com.onexsoftech.clearcacheapp.MainActivity.insertDummyContact(MainActivity.java:472)

回答1:

Prior to Android 6.0, CLEAR_APP_CACHE had a protectionLevel of dangerous, so ordinary SDK apps could request it in the manifest.

As of Android 6.0, CLEAR_APP_CACHE has a protectionLevel of signature|privileged. Ordinary Android apps cannot hold this permission. You can only hold this permission if your app is signed with the firmware's signing key or you are installed on the privileged system partition.

回答2:

From Android M -> CLEAR_APP_CACHE, Protection level: system|signature

Android 6.0 does not change the behavior of normal permissions (all non-dangerous permissions including normal, system, and signature permissions).

So it is not possible to ask for that permission in runtime. To be more precise

A signature|system permission, meaning that it can only be held by apps that are signed with the firmware's signing key or are installed on the system partition (e.g., by a rooted device user). From this stackoverflow Q/A.

Docs: https://source.android.com/devices/tech/config/runtime_perms.html#affected-permissions

回答3:

Add Permission in AndroidManifest.xml

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

Make a Constant for Request Code.

Constants.java

public static final int REQUEST_CODE_FOR_PERMISSION = 501;

Request Permission :-

public static void requestPermissionForClearCache(Activity activity) {
    if (ActivityCompat.checkSelfPermission(activity, Manifest.permission.CLEAR_APP_CACHE) != PackageManager.PERMISSION_GRANTED) {
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.CLEAR_APP_CACHE)) {
            ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.CLEAR_APP_CACHE}, Constatnts.REQUEST_CODE_FOR_PERMISSION);
        } else {
            ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.CLEAR_APP_CACHE}, Constatnts.REQUEST_CODE_FOR_PERMISSION);
        }
    }
}

Override Below method in Fragment.

@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    if (requestCode == Constatnts.REQUEST_CODE_FOR_PERMISSION && grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        // permission was granted successfully
    } else {
        // permission was NOT granted successfully
    }
}

来源：https://stackoverflow.com/questions/40261139/how-to-take-clear-app-cache-permission-in-android-marshmallow-at-runtime