Android學習筆記之WI-FI（1）

<1>什麼是Wi-Fi？

Wi-Fi是一種可以將個人電腦、手持功能（如PDA、手機）等終端以無線方式互相串連的技術。Wi-Fi是一個無線網路通訊技術的品牌，由Wi-Fi聯盟(Wi-FiAlliance)所持有。

Wi-Fi 原先是無線保真的縮寫，Wi-Fi 的英文全稱為wireless fidelity,在無線區域網路的範疇是指“無線相容性認證”，實質上是一種商業認證，同時也是一種無線連網的技術，以前通過網線串連電腦，而現在則是通過無線電波來連網；常見的就是一個無線路由器，那麼在這個無線路由器的電波覆蓋的有效範圍都可以採用WIFI串連方式進行連網，如果無線路由器串連了一條ADSL線路或者別的上網線路，則又被稱為“熱點”。

<2>擷取WI-FI網卡的狀態（常量）

public    static    final    int    WIFI_STATE_DISABLED

Wi-Fi is disabled.      WI-FI網卡不可用

Constant Value（常量值）:        1         (0x00000001)                   

 

 public    static    final   int     WIFI_STATE_DISABLING   

Wi-Fi is currently being disabled.   WI-FI網卡正在關閉

The state will change to WIFI_STATE_DISABLED if it finishes successfully. 

 最終狀態會變成WI-FI網卡不可用

Constant Value（常量值）:         0          (0x00000000)                   

 

 public   static    final      int     WIFI_STATE_ENABLED   

Wi-Fi is enabled.  WI-FI網卡可用

Constant Value（常量值）:        3         (0x00000003)                   

 

 public   static    final    int      WIFI_STATE_ENABLING   

Wi-Fi is currently being enabled.   WI-FI網卡正在開啟

The state will change to WIFI_STATE_ENABLED if it finishes successfully.

最終狀態會變成WI-FI網卡可用

Constant Value（常量值）:         2         (0x00000002)                   

 

 public    static    final    int       WIFI_STATE_UNKNOWN   

Wi-Fi is in an unknown state.  未知 網卡狀態

This state will occur when an error happens while enabling or disabling.

Constant Value（常量值）:         4          (0x00000004)                   

 

<3>操作WI-FI的所需的許可權

可以在協助文檔裡找到詳細的許可權，這裡只列出一部分。

Manifest.permission（許可權）

public         static         final        
String        CHANGE_WIFI_MULTICAST_STATE   

Allows applications to enter Wi-Fi Multicast mode

Constant Value:                             "android.permission.CHANGE_WIFI_MULTICAST_STATE"                   

 

public         static         final        
String        CHANGE_WIFI_STATE   

Allows applications to change Wi-Fi connectivity state

Constant Value:                             "android.permission.CHANGE_WIFI_STATE"                   

 

public         static         final        
String        CHANGE_NETWORK_STATE   

Allows applications to change network connectivity state

Constant Value:                             "android.permission.CHANGE_NETWORK_STATE

 

<4>改變WI-FI網卡的狀態

對WI-FI網卡進行操作需要通過WifiManager對象進行

WifiManager  wifiManager = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);

開啟WI-FI網卡

wifiManager.setWifiEnabled(true);   

關閉WI-FI網卡

wifiManager.setWifiEnabled(false);   

擷取網卡目前狀態

wifiManager..getWifiState()

package mars.wifi;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 {    /** Called when the activity is first created. */private Button startButton = null;private Button stopButton = null;private Button checkButton = null;private WifiManager wifiManager = null;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        startButton = (Button)findViewById(R.id.startWifi);        stopButton = (Button)findViewById(R.id.stopWifi);        checkButton = (Button)findViewById(R.id.checkWifi);        startButton.setOnClickListener(new StartWifiListener());        stopButton.setOnClickListener(new StopWifiListener());        checkButton.setOnClickListener(new CheckWifiListener());    }    class StartWifiListener implements OnClickListener{public void onClick(View v) {wifiManager = (WifiManager)WifiActivity.this.getSystemService(Context.WIFI_SERVICE);wifiManager.setWifiEnabled(true);System.out.println("wifi state --->" + wifiManager.getWifiState());Toast.makeText(WifiActivity.this, "當前Wifi網卡狀態為" + wifiManager.getWifiState(), Toast.LENGTH_SHORT).show();}    }    class StopWifiListener implements OnClickListener{public void onClick(View arg0) {// TODO Auto-generated method stubwifiManager = (WifiManager)WifiActivity.this.getSystemService(Context.WIFI_SERVICE);wifiManager.setWifiEnabled(false);switch (wifiManager.getWifiState())             {                 case WifiManager.WIFI_STATE_DISABLED:                 System.out.println("wifi state --->" + "WIFI已關閉");                    break;                 case WifiManager.WIFI_STATE_DISABLING:                 System.out.println("wifi state --->" + "WIFI正在關閉中");                     break;                 case WifiManager.WIFI_STATE_ENABLED:                 System.out.println("wifi state --->" + "WIFI已啟用");                     break;                 case WifiManager.WIFI_STATE_ENABLING:                 System.out.println("wifi state --->" + "WIFI正在啟動中");                     break;                 case WifiManager.WIFI_STATE_UNKNOWN:                 System.out.println("wifi state --->" + "未知WIFI狀態");                     break;             } Toast.makeText(WifiActivity.this, "當前Wifi網卡狀態為" + wifiManager.getWifiState(), Toast.LENGTH_SHORT).show();}        }        class CheckWifiListener implements OnClickListener{public void onClick(View v) {wifiManager = (WifiManager)WifiActivity.this.getSystemService(Context.WIFI_SERVICE);System.out.println("wifi state --->" + wifiManager.getWifiState());Toast.makeText(WifiActivity.this, "當前Wifi網卡狀態為" + wifiManager.getWifiState(), Toast.LENGTH_SHORT).show();}        }}

 

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"package="mars.wifi" 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訪問網路所需要的許可權 --><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>