Unable to listen to android wi-fi manager's state?

问题

I am having some trouble with BroadCast receiver for checking the Wi-fi state. Could you please help?

This is my manifest file.

<uses-permission android:name="android.permission.READ_PHONE_STATE"> </uses-permission>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"> </uses-permission>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"> </uses-permission>
<uses-permission android:name="android.permission.INTERNET"> </uses-permission>
<application 
        android:icon="@drawable/icon" 
        android:label="@string/app_name">
    <activity 
        android:name=".MainActivity"
            android:label="@string/app_name">
    <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
    </activity>
           <receiver android:name=".MainActivity">
<intent-filter android:name="android.net.wifi.WIFI_STATE_CHANGED"/>
       </receiver>  
   </application>
</manifest>

And this is the MainActivity.java

public class MainActivity extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        int state = intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE, -1);
        String msg = null;
        switch (state) {
        case WifiManager.WIFI_STATE_DISABLED:
            msg = "it is disabled";
            break;
        case WifiManager.WIFI_STATE_ENABLED:
            msg = "it is enabled";
            break;
        case WifiManager.WIFI_STATE_DISABLING:
            msg = "it is switching off";
            break;
        case WifiManager.WIFI_STATE_ENABLING:
            msg = "wifi is getting enabled";
            break;
        default:
            msg = "not working properly";
            break;
        }
        if (msg != null) {
            Log.d("************%%%%%%%%wifi state ", "WIFI" + msg);
            Toast.makeText(context, "Wifi state is" + msg, Toast.LENGTH_LONG)
                    .show();
        }
    }
}

I am unsure where am I making my mistake. Any input would be appreciated.
I am not getting any errors just that the log file doesn't show the required message.

回答1:

You have had not added the parameters for the intent filter, the final manifest should look like this

<uses-permission android:name="android.permission.READ_PHONE_STATE"> </uses-permission>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"> </uses-permission>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"> </uses-permission>
<uses-permission android:name="android.permission.INTERNET"> </uses-permission>
<application 
            android:icon="@drawable/icon" 
            android:label="@string/app_name">
<activity 
            android:name=".MainActivity"
            android:label="@string/app_name">
<intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
    </activity>
    <receiver android:name=".MainActivity">
    <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" /> 
            <action android:name="android.net.wifi.WIFI_STATE_CHANGED"/>
    </intent-filter>
    </receiver>
</application>

Hope this helps.

回答2:

If you did not add the following permissions then try again after adding those.

<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>

回答3:

First, you should make sure you request the permission to get access to view WIFI state. Just do as Anup Rojekar said.

Second, I believe you make mistake in using a BroadcastReceiver. In your manifest.xml, you declare the MainActivity.

<activity 
        android:name=".MainActivity"
            android:label="@string/app_name">
    <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
    </activity>

so the MainActivy is an Activity. Also, you declare the MainActivity as a broadcastReceiver. This is illegal. You should use a standalone broadcast to do so. Like this:

           <receiver android:name=".WifiBroadcastReceiver">
<intent-filter> 
     <action android:name="android.net.wifi.WIFI_STATE_CHANGED"/>
</intent-filter>
       </receiver>  

Please notice that I changed the name for the broadcastReceiver and inside the node, you should add a <action> node like above.

Third, create a WifiBroadcastReceiver.java and copy the codes from your original MainActivity.java to it. Remember to change the class declaration to public class WifiBroadcastReceiver extends BroadcastReceiver

Hope I could help. Please tell me if it works. I don't have a pc on hand; thus I don' t test the codes either.

Also, you need a new MainActivity.java file. It could be generated automatically in Eclipse. This class should be declared like: public class MainActivity extends Activity.

回答4:

Add this permission also in order to check the network state of your device.

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

回答5:

a mix-and-match of various previous answers, these snippets worked for me to check IF I AM CONNECTED TO A WIFI NETWORK (this does not tell me if i am connected to internet):

create a WifiMonitor.java class

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.wifi.WifiManager;
import android.util.Log;

public class WifiMonitor extends BroadcastReceiver {
    private String TAG = "TGtracker";

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.e(TAG,"entered  wifimonitor");
         // Process the Intent here
        WifiManager wifi = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        if (wifi.isWifiEnabled()==true) {
          Log.d(TAG, "You are connected to WIFI "+wifi.getConnectionInfo());
        } else {
          Log.e(TAG,"You are NOT connected to WIFI");
        }
    }
}

now go to your Manifest file and include

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

and finally, place the receiver right before the < / application > tag (still in Manifest file)

<application...
    <receiver android:name=".WifiMonitor" android:enabled="true">
        <intent-filter>
            <action android:name="android.net.ConnectivityManager.CONNECTIVITY_ACTION" />
            <action android:name="android.net.wifi.STATE_CHANGE" />
            <action android:name="android.net.wifi.supplicant.CONNECTION_CHANGE" />
        </intent-filter>
    </receiver>
</application>

when applying your code, DO NOT COPY < application... or < / application > tags in the code above (i just put them there so that you will know where to place the receiver).

NOTE: please fix your MainActivity to extend Activity and not BroadcastReceiver.

回答6:

For me the changes in the AndroidManifiest.xml did not work. I have the same problem, the application stopped suddenly.

I used the registerReceiver in the main activity and it works:) For me the WifiStateTester is the class that extends from BroadcastReceiver.

 WifiStateTester wfs= new WifiStateTester();
 IntentFilter iFilter= new IntentFilter();
 iFilter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
 iFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
 this.registerReceiver(wfs, iFilter);

Other different thing I did, is that in the onReceiver method I directly checked the wifi status.

来源：https://stackoverflow.com/questions/7329682/unable-to-listen-to-android-wi-fi-managers-state