1、 WIFI网卡的状态
WIFI网卡的状态信息都以整型变量的形式存放在 android.net.wifi.WifiManager 类中，有以下状态：
WIFI_STATE_DISABLED
WIFI网卡不可用
WIFI_STATE_DISABLING
WIFI网卡正在关闭
WIFI_STATE_ENABLED
WIFI网卡可用
WIFI_STATE_ENABLING
WIFI网卡正在打开
WIFI_STATE_UNKNOWN
WIFI网卡状态未知
2、 操作WIFI 网卡所需的权限
CHANGE_NETWORK_STATE
允许应用程序改变网络连接状态
CHANGE_WIFI_STATE
允许应用程序改变WIFI 连接状态
ACCESS_NETWORK_STATE
允许应用程序获取网络的状态信息
ACCESS_WIFI_STATE
允许应用程序获得WIFI 的状态信息

3、 改变WIFI 网卡的状态
对WIFI 网卡进行操作需要通过对 WifiManager 对象来进行，获取该对象的方法如下：
复制代码 代码如下:
WifiManager wifiManager=(WifiManager) Context.getSystemService(Service.WIFI_SERVICE); 

打开WIFI 网卡：
复制代码 代码如下:
wifiManager.setWifiEnabled(true); 

关闭WIFI 网卡
复制代码 代码如下:
wifiManager.setWifiEnabled(false); 

获取网卡的当前状态：
复制代码 代码如下:
wifiManager.getWifiState(); 

示例代码：由于Android模拟器不支持wifi操作，所以例子需要在实体手机上运行
AndroidManifest.xml
复制代码 代码如下:
<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="me.bym" android:versionCode="1" android:versionName="1.0"> 
    <application android:icon="@drawable/icon" android:label="@string/app_name"> 
        <activity android:name=".WifiActivity" android:label="@string/app_name"> 
            <intent-filter> 
                <action android:name="android.intent.action.MAIN" /> 
                <category android:name="android.intent.category.LAUNCHER" /> 
            </intent-filter> 
        </activity> 
    </application> 
    <uses-sdk android:minSdkVersion="4" /> 
    <!-- 以下是使用wifi访问网络所需要的权限 --> 
    <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.ACCESS_NETWORK_STATE"></uses-permission> 
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission> 
</manifest>

Activity
复制代码 代码如下:
package me.bym; 
import android.app.Activity; 
import android.content.Context; 
import android.net.wifi.WifiManager; 
import android.os.Bundle; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.Toast; 
public class WifiActivity extends Activity { 
    private Button startWifiButton = null; 
    private Button shutdownWifiButton = null; 
    private Button checkStateButton = null; 
    private WifiManager wifiManager = null; 
    private String res = ""; // 用来存放操作结果信息的字符串 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
        startWifiButton = (Button) findViewById(R.id.StartWifiButton); 
        shutdownWifiButton = (Button) findViewById(R.id.ShutdownWifiButton); 
        checkStateButton = (Button) findViewById(R.id.CheckStateButton); 
        startWifiButton.setOnClickListener(new StartWifiListener()); 
        shutdownWifiButton.setOnClickListener(new ShutdownWifiListener()); 
        checkStateButton.setOnClickListener(new CheckStateListener()); 
    } 
    class StartWifiListener implements OnClickListener { 
        @Override 
        public void onClick(View v) { 
            wifiManager = (WifiManager) WifiActivity.this 
                    .getSystemService(Context.WIFI_SERVICE); 
            if (wifiManager.setWifiEnabled(true)) { 
                res = "启动wifi服务成功"; 
            } else { 
                res = "启动wifi服务失败"; 
            } 
            Toast.makeText(WifiActivity.this, res, Toast.LENGTH_SHORT).show(); 
        } 
    } 
    class ShutdownWifiListener implements OnClickListener { 
        @Override 
        public void onClick(View v) { 
            wifiManager = (WifiManager) WifiActivity.this 
                    .getSystemService(Context.WIFI_SERVICE); 
            if (wifiManager.setWifiEnabled(false)) { 
                res = "关闭wifi服务成功"; 
            } else { 
                res = "关闭wifi服务失败"; 
            } 
            Toast.makeText(WifiActivity.this, res, Toast.LENGTH_SHORT).show(); 
        } 
    } 
    class CheckStateListener implements OnClickListener { 
        @Override 
        public void onClick(View v) { 
            wifiManager = (WifiManager) WifiActivity.this 
                    .getSystemService(Context.WIFI_SERVICE); 
            switch (wifiManager.getWifiState()) { 
            case WifiManager.WIFI_STATE_DISABLED: 
                res = "WIFI已关闭"; 
                break; 
            case WifiManager.WIFI_STATE_DISABLING: 
                res = "WIFI正在关闭中"; 
                break; 
            case WifiManager.WIFI_STATE_ENABLED: 
                res = "WIFI已启用"; 
                break; 
            case WifiManager.WIFI_STATE_ENABLING: 
                res = "WIFI正在启动中"; 
                break; 
            case WifiManager.WIFI_STATE_UNKNOWN: 
                res = "未知WIFI状态"; 
                break; 
            } 
            Toast.makeText(WifiActivity.this, res, Toast.LENGTH_SHORT).show(); 
        } 
    } 
}