Android WifiManager getScanResult抱怨虽然声明了权限，但需要ACCESS_COARSE_LOCATION或ACCESS_FINE_LOCATION权限

Question

I am developing an App to check Wifi points.

I am getting error "java.lang.SecurityException: Need ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission to get scan results" at wifiManager.getScanResults() even though I already declared those permissions.

main activity

public class MainActivity extends AppCompatActivity {

WifiManager wifiManager;
String[] wifis;
WifiReceiver wifiReceiver;

ListView wifiListView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    wifiListView = (ListView) findViewById(R.id.wifi_list);

    wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    wifiReceiver = new WifiReceiver();
    wifiManager.startScan();
}

protected void onPause() {
    unregisterReceiver(wifiReceiver);
    super.onPause();
}

protected void onResume() {
    registerReceiver(wifiReceiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
    super.onResume();
}

private class WifiReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        List<ScanResult> wifiScanList = wifiManager.getScanResults();
        wifis = new String[wifiScanList.size()];

        for (int i = 0; i < wifiScanList.size(); i++) {
            wifis[i] = wifiScanList.get(i).toString();
        }

        wifiListView.setAdapter(new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_list_item_1, wifis));
    }
}

manifest

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sample">

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

I am on SDK 6.0

I observed similar question , but solution does not apply since I already declared permission.

Anyone know what might be problem? Thank you.

Answer 1

In Android M, you need to ask for the permission which is defined as dangerous in PermissionModel to the user before start using each time, it as such:

private boolean mayRequestLocation() {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            return true;
        }
        if (checkSelfPermission(ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            return true;
        }
        if (shouldShowRequestPermissionRationale(ACCESS_FINE_LOCATION)) {
            Snackbar.make(mView, R.string.permission_rationale, Snackbar.LENGTH_INDEFINITE)
                    .setAction(android.R.string.ok, new View.OnClickListener() {
                        @Override
                        @TargetApi(Build.VERSION_CODES.M)
                        public void onClick(View v) {
                            requestPermissions(new String[]{ACCESS_FINE_LOCATION}, REQUEST_FINE_LOCATION);
                        }
                    });
        } else {
            requestPermissions(new String[]{ACCESS_FINE_LOCATION}, REQUEST_FINE_LOCATION);
        }
        return false;
    }

Add this to your Activity:

private static final int REQUEST_FINE_LOCATION=0

and load it during runtime with:

loadPermissions(Manifest.permission.ACCESS_FINE_LOCATION,REQUEST_FINE_LOCATION);

To evaluate the results of your permission request, you can override onRequestPermissionsResult method:

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case REQUEST_FINE_LOCATION: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // The requested permission is granted.
            }
            else{
                // The user disallowed the requested permission.
            }
            return;
        }

}

Answer 2

MADAO is right : you should turn on GPS to get the WIFI access point list.

But I'm not sure about PEERS_MAC_ADDRESS. If you look at the source code (line 957):

/**
 * Return the results of the most recent access point scan, in the form of
 * a list of {@link ScanResult} objects.
 * @return the list of results
 */
public List<ScanResult> getScanResults(String callingPackage) {
    enforceAccessPermission();
    int userId = UserHandle.getCallingUserId();
    int uid = Binder.getCallingUid();
    boolean canReadPeerMacAddresses = checkPeersMacAddress();
    boolean isActiveNetworkScorer =
            NetworkScorerAppManager.isCallerActiveScorer(mContext, uid);
    boolean hasInteractUsersFull = checkInteractAcrossUsersFull();
    long ident = Binder.clearCallingIdentity();
    try {
        if (!canReadPeerMacAddresses && !isActiveNetworkScorer
                && !isLocationEnabled()) {
            return new ArrayList<ScanResult>();
        }
        if (!canReadPeerMacAddresses && !isActiveNetworkScorer
                && !checkCallerCanAccessScanResults(callingPackage, uid)) {
            return new ArrayList<ScanResult>();
        }
        if (mAppOps.noteOp(AppOpsManager.OP_WIFI_SCAN, uid, callingPackage)
                != AppOpsManager.MODE_ALLOWED) {
            return new ArrayList<ScanResult>();
        }
        if (!isCurrentProfile(userId) && !hasInteractUsersFull) {
            return new ArrayList<ScanResult>();
        }
        return mWifiStateMachine.syncGetScanResultsList();
    } finally {
        Binder.restoreCallingIdentity(ident);
    }
}

The first if is checking canReadPeerMacAddresses which the code for checkPeersMacAddress() is:

/**
 * Returns true if the caller holds PEERS_MAC_ADDRESS.
 */
private boolean checkPeersMacAddress() {
    return mContext.checkCallingOrSelfPermission(
            android.Manifest.permission.PEERS_MAC_ADDRESS) == PackageManager.PERMISSION_GRANTED;
}

If you add the permission you can bypass if (!canReadPeerMacAddresses && !isActiveNetworkScorer && !isLocationEnabled()) { . I've tested but I cannot get WIFI MAC list by just using the permission and disabling location.

Answer 3

ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION is necessary. To get a valid result, you also have to turn on GPS or get a PEERS_MAC_ADDRESS permission like Setting .