public boolean enableSystemApp(final String pkg) {
		try {
			mDevicePolicyManager.enableSystemApp(sCachedComponent, pkg);
			return true;
		} catch (final RuntimeException e) {
			// May throw NPE if package not found (on Android 5.x, see commit 637baaf0db76f9e1e51eeab077ffb85da0ff9308 in platform_frameworks_base)
			// 	 or IllegalArgumentException (on Android 6+) if package is not present on this device.
			if (e instanceof NullPointerException || e instanceof IllegalArgumentException) return false;
			throw e;
		}
	}
@return true if successfully enabled, false if package not found or not system app.
 @see DevicePolicyManager#enableSystemApp(ComponentName, String)
shared/src/main/java/com/oasisfeng/island/util/DevicePolicies.java