Trying to connect to a wifi I get ClassNotFoundException for WifiNetworkSpecifier$Builder

相关文章推荐

坚强的山楂 · Java8 中map中删除元素的简单方法 ...· 3 月前 ·

忐忑的机器猫 · pyecharts可视化大屏模板套用方法 ...· 4 月前 ·

独立的灭火器 · JAVA中如何对父类对象强制转换子类对象的引 ...· 1 年前 ·

聪明伶俐的大熊猫 · python获取cpu温度-掘金· 1 年前 ·

冷冷的遥控器 · CUDA环境变量配置 - 简书· 1 年前 ·

I need to connect a smartphone to specific WiFi network that is created by other device. I'm using Xamarin.Forms to develop my app. The goal is to connect the smartphone automatically, that is, programmatically. I just need to do Android development.

This is the connection code:

public class WifiConnector : IWifiConnector
    public void ConnectToWifi(string ssid, string password)
            WifiNetworkSpecifier.Builder wifiNetworkSpecifierBuilder = new WifiNetworkSpecifier.Builder();
            wifiNetworkSpecifierBuilder.SetSsid(ssid);
            wifiNetworkSpecifierBuilder.SetWpa2Passphrase(password);
            WifiNetworkSpecifier wifiNetworkSpecifier = wifiNetworkSpecifierBuilder.Build();
            NetworkRequest.Builder networkRequestBuilder = new NetworkRequest.Builder();
            networkRequestBuilder.AddTransportType(TransportType.Wifi);
            networkRequestBuilder.AddCapability(NetCapability.Internet);
            networkRequestBuilder.SetNetworkSpecifier(wifiNetworkSpecifier);
            NetworkRequest networkRequest = networkRequestBuilder.Build();
            ConnectivityManager connectivityManager = (ConnectivityManager)Android.App.Application.Context.GetSystemService(Context.ConnectivityService);
            connectivityManager.RequestNetwork(networkRequest, new NetworkCallback());
        catch (Exception ex)
            Console.WriteLine(ex.Message);
            Console.WriteLine(ex.StackTrace);
    class NetworkCallback : ConnectivityManager.NetworkCallback
        public override void OnAvailable(Network network)
            base.OnAvailable(network);
            Log.Debug("WifiConnector", "OnAvailable(): " + network.ToString());
I don't have any compilation errors, but at runtime I get this error:
Didn't find class "android.net.wifi.WifiNetworkSpecifier$Builder" on path: DexPathList[[zip file "/data/app/com.companyname.connecttowifi-i0OpZvWjDZqiRX01MQJcMA==/base.apk"],nativeLibraryDirectories=[/data/app/com.companyname.connecttowifi-i0OpZvWjDZqiRX01MQJcMA==/lib/arm64, /data/app/com.companyname.connecttowifi-i0OpZvWjDZqiRX01MQJcMA==/base.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64]]
  at Java.Interop.JniEnvironment+Types.FindClass (System.String classname) [0x0015a] in <00c315a988634383b446eff646084784>:0 
  at Java.Interop.JniType..ctor (System.String classname) [0x00006] in <00c315a988634383b446eff646084784>:0 
  at Java.Interop.JniType.GetCachedJniType (Java.Interop.JniType& cachedType, System.String classname) [0x00018] in <00c315a988634383b446eff646084784>:0 
  at Java.Interop.JniPeerMembers.get_JniPeerType () [0x0000c] in <00c315a988634383b446eff646084784>:0 
  at Java.Interop.JniPeerMembers+JniInstanceMethods.get_JniPeerType () [0x00014] in <00c315a988634383b446eff646084784>:0 
  at Java.Interop.JniPeerMembers+JniInstanceMethods.StartCreateInstance (System.String constructorSignature, System.Type declaringType, Java.Interop.JniArgumentValue* parameters) [0x0003f] in <00c315a988634383b446eff646084784>:0 
  at Android.Net.Wifi.WifiNetworkSpecifier+Builder..ctor () [0x0001f] in /Users/builder/azdo/_work/1/s/xamarin-android/src/Mono.Android/obj/Release/monoandroid10/android-30/mcw/Android.Net.Wifi.WifiNetworkSpecifier.cs:82 
  at ConnectToWifi.Droid.Services.WifiConnector.ConnectToWifi (System.String ssid, System.String password) [0x00002] in C:\DATA\Code tests\Xamarin\ConnectToWifi\ConnectToWifi\ConnectToWifi.Android\Services\WifiConnector.cs:27 
  --- End of managed Java.Lang.ClassNotFoundException stack trace ---
java.lang.ClassNotFoundException: Didn't find class "android.net.wifi.WifiNetworkSpecifier$Builder" on path: DexPathList[[zip file "/data/app/com.companyname.connecttowifi-i0OpZvWjDZqiRX01MQJcMA==/base.apk"],nativeLibraryDirectories=[/data/app/com.companyname.connecttowifi-i0OpZvWjDZqiRX01MQJcMA==/lib/arm64, /data/app/com.companyname.connecttowifi-i0OpZvWjDZqiRX01MQJcMA==/base.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64]]
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
    at crc64ee486da937c010f4.ButtonRenderer.n_onClick(Native Method)
    at crc64ee486da937c010f4.ButtonRenderer.onClick(ButtonRenderer.java:104)
    at android.view.View.performClick(View.java:7339)
    at android.widget.TextView.performClick(TextView.java:14275)
    at android.view.View.performClickInternal(View.java:7305)
    at android.view.View.access$3200(View.java:846)
    at android.view.View$PerformClick.run(View.java:27787)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7078)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)
I added this permissions in AndroidManifest.xml file:
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
Details about project, libraries and development environment:
   Microsoft Visual Studio Professional 2019 Version 16.11.12
   Xamarin.Forms 5.0.0.2012
   Android target version: Android 11 API 30
   Smartphone Android version: Android 9 API 28
Why is this error happening?
Smartphone Android version: Android 9 API 28
Referring to the Android official documentation WifiNetworkSpecifier, we can find it was added in API 29.
Therefore, you will get ClassNotFoundException for WifiNetworkSpecifier$Builder in using API 28.
If you want to implement this function in API 28, you could refer to WifiManager.
You can use if(Build.VERSION.SdkInt >= BuildVersionCodes.Q) //use WifiNetworkSpecifier; else //use WifiManager to implement this function for both API 29 below or above.
Best Regards,
Alec Liu.
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.