Android學習筆記之WI-FI（1）
<1>什么是Wi-Fi？
Wi-Fi是一種可以將個人電腦、手持設備（如PDA、手機）等終端以無線方式互相連接的技術。Wi-Fi是一個無線網路通信技術的品牌，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,在無線局域網的范疇是指“無線相容性認證”，實質上是一種商業認證，同時也是一種無線聯網的技術，以前通過網線連接電腦，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，那么在這個無線路由器的電波覆蓋的有效范圍都可以采用WIFI連接方式進行聯網，如果無線路由器連接了一條ADSL線路或者別的上網線路，則又被稱為“熱點”。
<2>獲取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
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
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網卡正在打開
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
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.
<3>操作WI-FI的所需的權限
可以在幫助文檔里找到詳細的權限，這里只列出一部分。
Manifest.permission（權限）
public static final String CHANGE_WIFI_MULTICAST_STATE
Allows applications to enter Wi-Fi Multicast mode
public static final String CHANGE_WIFI_STATE
Allows applications to change Wi-Fi connectivity state
public static final String CHANGE_NETWORK_STATE
Allows applications to change network connectivity 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);
打開WI-FI網卡
wifiManager.setWifiEnabled(true);
關閉WI-FI網卡
wifiManager.setWifiEnabled(false);
獲取網卡當前狀態
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 stub wifiManager = (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(); } }}</pre>
<?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訪問網絡所需要的權限 --> <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> </pre>