Question

This is my first post, hope to do it right. I’m trying to create an application using the new android technology Wi-Fi Direct. To do so I was following the tutorial you can find in:

http://developer.android.com/guide/topics/connectivity/wifip2p.html

It’s really useful, but when I copy the code, there is something wrong. Exactly with step number 3:

WifiP2pManager mManager;
Channel mChannel;
BroadcastReceiver mReceiver;
...
@Override
protected void onCreate(Bundle savedInstanceState){
    ...
    mManager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
    mChannel = mManager.initialize(this, getMainLooper(), null);
    mReceiver = new WiFiDirectBroadcastReceiver(manager, channel, this);
    ...
}

The error is on line:

mChannel = mManager.initialize(this, getMainLooper(), null);

And the error message is:

Type mismatch: cannot convert from WifiPesManager.Channel to Channel

The recommendation is to make a cast like this:

mChannel =  (Channel) mManager.initialize(this, getMainLooper(), null);

But when I change my code for that, I have another error while running the application:

10-25 12:08:34.845: E/AndroidRuntime(26634): java.lang.RuntimeException: Unable to start activity ComponentInfo{android.nacho.WifiDirect/android.nacho.WifiDirect.WifiDirect}: java.lang.ClassCastException: android.net.wifi.p2p.WifiP2pManager$Channel cannot be cast to java.nio.channels.Channel

Just add the rest of the code is exactly how it appear in the tutorial, but just in case I’m going to add the Activity and also the Broadcast class:

Main Activity

package android.nacho.WifiDirect;

import java.nio.channels.Channel;

import android.net.wifi.p2p.WifiP2pManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.IntentFilter;
import android.view.Menu;

public class WifiDirect extends Activity {

    
    WifiP2pManager mManager;
    Channel mChannel;
    BroadcastReceiver mReceiver;
    
    IntentFilter mIntentFilter;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wifi_direct);
        
        
        //To register the BroadastReceiver
        mManager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
        mChannel =  (Channel) mManager.initialize(this, getMainLooper(), null); //It was necessary to make a cast (Channel)
        mReceiver = new WiFiBroadcastReceiver(mManager, mChannel, this, this);
        
        
        //To define the filter in the BroadcastReceiver
        mIntentFilter = new IntentFilter();
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
        mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
        
       
    }

    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_wifi_direct, menu);
        return true;
    }
   
    //
    
    
    @Override
    protected void onResume() {
        super.onResume();
        registerReceiver(mReceiver, mIntentFilter);
    }
    
   // unregister the broadcast receiver
    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(mReceiver);
    }
    
}

WiFiBroadcastReceiver

package android.nacho.WifiDirect;

import java.nio.channels.Channel;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.wifi.p2p.WifiP2pManager;
import android.widget.Toast;



/**
 * A BroadcastReceiver that notifies of important Wi-Fi p2p events.
 */

public class WiFiBroadcastReceiver extends BroadcastReceiver {

    private WifiP2pManager manager;
    private Channel channel;
    private WifiDirect activity;
    //For toast, add also context
    private Context context;

    public WiFiBroadcastReceiver(WifiP2pManager manager, Channel channel, WifiDirect activity, Context context) {
        super();
        this.manager = manager;
        this.channel = channel;
        this.activity = activity;
        this.context= context;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        
        String action = intent.getAction();
        
        
        if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
            
            // Check to see if Wi-Fi is enabled and notify appropriate activity
             int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1);
             if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) {
                            
                Toast.makeText(context, "Wi-Fi Direct is enable", Toast.LENGTH_LONG).show();
                
             } else {
                 
                Toast.makeText(context, "Wi-Fi Direct is not enable", Toast.LENGTH_LONG).show();
             }      
            
        } else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {
            // Call WifiP2pManager.requestPeers() to get a list of current peers
        } else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {
            // Respond to new connection or disconnections
        } else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {
            // Respond to this device's wifi state changing
        }
    }
}

AndroidManifest

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="android.nacho.WifiDirect"
    android:versionCode="1"
    android:versionName="1.0" >
    
    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="15" />
    
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
    <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    

   

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".WifiDirect"
            android:label="@string/title_activity_wifi_direct" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

Thank you very much for your help!!!

Answer 1

You are using a Channel class coming from the wrong package.

Do import android.net.wifi.p2p.WifiP2pManager.Channel;

instead of

import java.nio.channels.Channel;