java - WiFi getSSID() 总是返回 ""

Question

很多人已经问过这个问题，但对他们有用的解决方案对我来说并不适用。我在Android 8.1和Android 9.0上测试过，无法获取到SSID的名称。

用于获取 WiFi 状态更改的广播接收器:

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();
        }
    }
};

接收者已注册onCreate并在 onDestroy 中未注册，我认为这是正确的，并且在调用接收器时我看到了日志行。

在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是这样实现的:

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();
    }
}

我的应用程序已经获得了 ACCESS_COARSE_LOCATION 的许可但我还添加了 ACCESS_FINE_LOCATION万一。 getSSID()直到回来<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" />

可能跟编译目标SDK有关？我在这里真的一无所知。

渐变文件:

应用插件:'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

无线网络权限

Android 8.0 和 Android 8.1:

成功调用 WifiManager.getScanResults() 需要以下任一权限:

• ACCESS_FINE_LOCATION• ACCESS_COARSE_LOCATION• CHANGE_WIFI_STATE

如果调用应用程序没有任何这些权限，调用将失败并出现 SecurityException。

安卓 9:

成功调用 WifiManager.startScan() 需要满足以下所有条件:

• 您的应用具有 ACCESS_FINE_LOCATION 或 ACCESS_COARSE_LOCATION 权限。• 您的应用程序具有CHANGE_WIFI_STATE 权限。• 设备上启用了位置服务(在“设置”>“位置”下)。

Android 10(API 级别 29)及更高版本:

成功调用 WifiManager.startScan() 需要满足以下所有条件:

• 如果您的应用以 Android 10(API 级别 29)SDK 或更高版本为目标平台，则您的应用具有 ACCESS_FINE_LOCATION 权限。

• 如果您的应用的目标 SDK 低于 Android 10(API 级别 29)，则您的应用具有 ACCESS_COARSE_LOCATION 或 ACCESS_FINE_LOCATION 权限。

• 您的应用具有 CHANGE_WIFI_STATE 权限。

• 设备上启用了位置服务(在“设置”>“位置”下)。

并Request User级权限实现

有关详细信息，请参阅此链接:https://developer.android.com/guide/topics/connectivity/wifi-scan#wifi-scan-permissions

XAMARIN FORMS 代码更改:

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];}}