WiFi getSSID() 总是返回“<unknown ssid> ”

Question

This question has already been asked by many people, but the solution that worked for them is not working for me. I have tested on Android 8.1 and Android 9.0 and cannot get the name of the SSID.

Broadcast receiver for getting WiFi state changes:

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if(intent.getAction().equals(WifiManager.WIFI_STATE_CHANGED_ACTION) ||
                intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION) ||
                intent.getAction().equals(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION) ||
                intent.getAction().equals(WifiManager.SUPPLICANT_CONNECTION_CHANGE_ACTION) ||
                intent.getAction().equals(WifiManager.NETWORK_STATE_CHANGED_ACTION)) {
            setWifiIndicator();
        }
    }
};

The receiver is registered onCreate and unregistered in onDestroy , which I think is proper, and I'm seeing the log lines when the receiver is called.

in onCreate :

IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(ScannerService.ACTION_READ_SCANNER);
intentFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
intentFilter.addAction(WifiManager.SUPPLICANT_CONNECTION_CHANGE_ACTION);
intentFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
intentFilter.addAction(WifiManager.SUPPLICANT_STATE_CHANGED_ACTION);
registerReceiver(mReceiver, intentFilter);
setWifiIndicator();

setWifiIndicator is implemented thusly:

private void setWifiIndicator() {
    ConnectivityManager connMgr = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
    //getApplicationContext solves memory leak issues prior to Android N (must use Application Context to get wifi system service.
    WifiManager wifiMgr = (WifiManager)getApplicationContext().getSystemService(Context.WIFI_SERVICE);
    ImageView wifiIndicator = (ImageView)findViewById(R.id.wifi_indicator);
    TextView wifiSSID = (TextView)findViewById(R.id.wifi_ssid);

    try {
        if (wifiMgr != null) {
            if (wifiMgr.isWifiEnabled()) {
                //wifi is enabled.  toggle on wifi indicator.
                wifiIndicator.setImageResource(R.drawable.wifi_indicator);
                String ssid = wifiMgr.getConnectionInfo().getSSID();
                if (ssid != null) {
                    Log.v(this.getClass().getSimpleName(), "SSID: " + ssid + "  Supplicant State: " + info.getSupplicantState());
                    wifiSSID.setText(ssid);
                }
            } else {
                //wifi is disabled.  toggle off wifi indicator.
                wifiSSID.setText("");

                //check for 3G
                NetworkInfo mobileInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
                if (mobileInfo != null && mobileInfo.getState().equals(NetworkInfo.State.CONNECTED)) {
                    wifiIndicator.setImageResource(R.drawable.cellular_indicator);
                } else {
                    wifiIndicator.setImageResource(R.drawable.down_indicator);
                }
            }
        } else {
            //check for 3G
            NetworkInfo mobileInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
            if (mobileInfo != null && mobileInfo.getState().equals(NetworkInfo.State.CONNECTED)) {
                wifiIndicator.setImageResource(R.drawable.cellular_indicator);
            } else {
                wifiIndicator.setImageResource(R.drawable.down_indicator);
            }
        }
    } catch(Exception e) {
        //catching anything thrown in this block just so it doesn't crash the program unnecessarily
        e.printStackTrace();
    }
}

My app already had permission for ACCESS_COARSE_LOCATION but I aslo added ACCESS_FINE_LOCATION just in case. getSSID() is till returning <unknown ssid> .

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_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" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.GET_TASKS" />

Perhaps it has to do with compile target SDK? I'm really clueless here.

gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.noneofyour.business"
        minSdkVersion 15
        targetSdkVersion 28
        versionCode 59
        versionName "1.44"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:28.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation files('libs/android.jar')
}

Answer 1

Wi-Fi Permissions

Android 8.0 and Android 8.1:

A successful call to WifiManager.getScanResults() requires any one of the following permissions:

• ACCESS_FINE_LOCATION • ACCESS_COARSE_LOCATION • CHANGE_WIFI_STATE

If the calling app does not have any of these permissions, the call fails with a SecurityException.

Android 9:

A successful call to WifiManager.startScan() requires all of the following conditions to be met:

• Your app has the ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION permission. • Your app has the CHANGE_WIFI_STATE permission. • Location services are enabled on the device (under Settings > Location).

Android 10 (API level 29) and higher:

A successful call to WifiManager.startScan() requires all of the following conditions to be met:

• If your app is targeting Android 10 (API level 29) SDK or higher, your app has the ACCESS_FINE_LOCATION permission.

• If your app is targeting SDK lower than Android 10 (API level 29), your app has the ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission.

• Your app has the CHANGE_WIFI_STATE permission.

• Location services are enabled on the device (under Settings > Location).

And Request User level permission to achieve

See this link for more information: https://developer.android.com/guide/topics/connectivity/wifi-scan#wifi-scan-permissions

XAMARIN FORMS Code Change:

if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.O){
status = await CrossPermissions.Current.CheckPermissionStatusAsync(Permission.Location);
if (status != PermissionStatus.Granted)
{   
var results = await CrossPermissions.Current.RequestPermissionsAsync(new[] { Permission.Location });
status = results[Permission.Location];
}
}

Answer 2

Have you tried to check if getSupplicantState() is COMPLETED ?

if(wifiInfo.getSupplicantState() == SupplicantState.COMPLETED){
        String ssid = wifiInfo.getSSID();
        wifiSSID.setText(ssid);
}

Also, have you asked for this before running the BroadcastReceiver or even inside you can do it :

 if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, LOCATION);
}else{setWifiIndicator();