Android学习笔记之WI-FI（1）

<1>什么是Wi-Fi？
Wi-Fi是一种可以将个人电脑、手持设备（如PDA、手机）等终端以无线方式互相连接的技术。Wi-Fi是一个无线网路通信技术的品牌，由Wi-Fi联盟(Wi-FiAlliance)所持有。
Wi-Fi 原先是无线保真的缩写，Wi-Fi 的英文全称为wireless fidelity,在无线局域网的范畴是指“无线相容性认证”，实质上是一种商业认证，同时也是一种无线联网的技术，以前通过网线连接电脑，而现在则是通过无线电波来连网；常见的就是一个无线路由器，那么在这个无线路由器的电波覆盖的有效范围都可以采用WIFI连接方式进行联网，如果无线路由器连接了一条ADSL线路或者别的上网线路，则又被称为“热点”。
<2>获取WI-FI网卡的状态（常量）
public static final int WIFI_STATE_DISABLED
Wi-Fi is disabled. WI-FI网卡不可用
Constant Value（常量值）: 1 (0x00000001)

public static final int WIFI_STATE_DISABLING
Wi-Fi is currently being disabled. WI-FI网卡正在关闭
The state will change to WIFI_STATE_DISABLED if it finishes successfully.
最终状态会变成WI-FI网卡不可用
Constant Value（常量值）: 0 (0x00000000)

public static final int WIFI_STATE_ENABLED
Wi-Fi is enabled. WI-FI网卡可用
Constant Value（常量值）: 3 (0x00000003)

public static final int WIFI_STATE_ENABLING
Wi-Fi is currently being enabled. WI-FI网卡正在打开
The state will change to WIFI_STATE_ENABLED if it finishes successfully.
最终状态会变成WI-FI网卡可用
Constant Value（常量值）: 2 (0x00000002)

public static final int WIFI_STATE_UNKNOWN
Wi-Fi is in an unknown state. 未知 网卡状态
This state will occur when an error happens while enabling or disabling.
Constant Value（常量值）: 4 (0x00000004)

<3>操作WI-FI的所需的权限
可以在帮助文档里找到详细的权限，这里只列出一部分。
Manifest.permission（权限）
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>改变WI-FI网卡的状态
对WI-FI网卡进行操作需要通过WifiManager对象进行
WifiManager wifiManager = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
打开WI-FI网卡
wifiManager.setWifiEnabled(true);
关闭WI-FI网卡
wifiManager.setWifiEnabled(false);
获取网卡当前状态
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, "当前Wifi网卡状态为" + 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已关闭");
                    break; 

                case WifiManager.WIFI_STATE_DISABLING: 
                	System.out.println("wifi state --->" + "WIFI正在关闭中"); 
                    break; 
                case WifiManager.WIFI_STATE_ENABLED: 
                	System.out.println("wifi state --->" + "WIFI已启用"); 
                    break; 
                case WifiManager.WIFI_STATE_ENABLING: 
                	System.out.println("wifi state --->" + "WIFI正在启动中"); 
                    break; 
                case WifiManager.WIFI_STATE_UNKNOWN: 
                	System.out.println("wifi state --->" + "未知WIFI状态"); 
                    break; 
            } 
			Toast.makeText(WifiActivity.this, "当前Wifi网卡状态为" + 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, "当前Wifi网卡状态为" + 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>