Android学习笔记之WI-FI（1）

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<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 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>