Android comes with a complete support for the WiFi connectivity. The main component is the system-provided WiFiManager. As usual, we obtain it via getSystemServices() call to the current context.

Once we have the WiFiManager, we can ask it for the current WIFi connection in form of WiFiInfo object. We can also ask for all the currently available networks via getConfiguredNetworks(). That gives us the list of WifiConfigurations.

In this example we are also registering a broadcast receiver to perform the scan for new networks. 


WiFiDemo.java

Code:
 


package com.example;


import java.util.List;


import android.app.Activity;

import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.IntentFilter;

import android.net.wifi.WifiConfiguration;

import android.net.wifi.WifiInfo;

import android.net.wifi.WifiManager;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

import android.widget.Toast;


public class WiFiDemo extends Activity implements OnClickListener {

	private static final String TAG = "WiFiDemo";

	WifiManager wifi;

	BroadcastReceiver receiver;


	TextView textStatus;

	Button buttonScan;


	/** Called when the activity is first created. */

	@Override

	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);


		// Setup UI

		textStatus = (TextView) findViewById(R.id.textStatus);

		buttonScan = (Button) findViewById(R.id.buttonScan);

		buttonScan.setOnClickListener(this);


		// Setup WiFi

		wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);


		// Get WiFi status

		WifiInfo info = wifi.getConnectionInfo();

		textStatus.append("\n\nWiFi Status: " + info.toString());


		// List available networks

		List<WifiConfiguration> configs = wifi.getConfiguredNetworks();

		for (WifiConfiguration config : configs) {

			textStatus.append("\n\n" + config.toString());

		}


		// Register Broadcast Receiver

		if (receiver == null)

			receiver = new WiFiScanReceiver(this);


		registerReceiver(receiver, new IntentFilter(

				WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

		Log.d(TAG, "onCreate()");

	}


	@Override

	public void onStop() {

		unregisterReceiver(receiver);

	}


	public void onClick(View view) {

		Toast.makeText(this, "On Click Clicked. Toast to that!!!",

				Toast.LENGTH_LONG).show();


		if (view.getId() == R.id.buttonScan) {

			Log.d(TAG, "onClick() wifi.startScan()");

			wifi.startScan();

		}

	}


}



The WiFiScanReceiver is registered by WiFiDemo as a broadcast receiver to be invoked by the system when new WiFi scan results are available. WiFiScanReceiver gets the callback via onReceive(). It gets the new scan result from the intent that activated it and compares it to the best known signal provider. It then outputs the new best network via a Toast.

WiFiScanReceiver.java

Code:
 


package com.example;


import java.util.List;


import android.content.BroadcastReceiver;

import android.content.Context;

import android.content.Intent;

import android.net.wifi.ScanResult;

import android.net.wifi.WifiManager;

import android.util.Log;

import android.widget.Toast;


public class WiFiScanReceiver extends BroadcastReceiver {

  private static final String TAG = "WiFiScanReceiver";

  WiFiDemo wifiDemo;


  public WiFiScanReceiver(WiFiDemo wifiDemo) {

    super();

    this.wifiDemo = wifiDemo;

  }


  @Override

  public void onReceive(Context c, Intent intent) {

    List<ScanResult> results = wifiDemo.wifi.getScanResults();

    ScanResult bestSignal = null;

    for (ScanResult result : results) {

      if (bestSignal == null

          || WifiManager.compareSignalLevel(bestSignal.level, result.level) < 0)

        bestSignal = result;

    }


    String message = String.format("%s networks found. %s is the strongest.",

        results.size(), bestSignal.SSID);

    Toast.makeText(wifiDemo, message, Toast.LENGTH_LONG).show();


    Log.d(TAG, "onReceive() message: " + message);

  }


}



The layout file for this example is fairly simple. It has one TextView wrapped in a ScrollView for scrolling purposes.

/res/layout/main.xml

Code:
 


<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

  android:orientation="vertical" android:layout_width="fill_parent"

  android:layout_height="fill_parent">


  <Button android:layout_width="wrap_content"

    android:layout_height="wrap_content" android:id="@+id/buttonScan"

    android:text="Scan"></Button>

  <ScrollView android:id="@+id/ScrollView01"

    android:layout_width="wrap_content" android:layout_height="wrap_content">

    <TextView android:layout_width="fill_parent"

      android:layout_height="wrap_content" android:id="@+id/textStatus"

      android:text="WiFiDemo" />

  </ScrollView>


</LinearLayout>



For the AndroidManifest.xml file, just remember to add the permissions to use WiFi:

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

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

程式碼下載

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