如何检查Android网络连接状态

在发送任何HTTP请求前最好检查下网络连接状态，这样可以避免异常。这个教程将会介绍怎样在你的应用中检测网络连接状态。

创建新的项目

1.在Eclipse IDE中创建一个新的项目并把填入必须的信息。 File->New->Android Project

2.创建新项目后的第一步是要在AndroidManifest.xml文件中添加必要的权限。

• 为了访问网络我们需要 INTERNET 权限
• 为了检查网络状态我们需要 ACCESS_NETWORK_STATE 权限

AndroidManifest.xml

01	<?xml version="1.0" encoding="utf-8"?>

02	<manifest xmlns:android="http://schemas.android.com/apk/res/android"

03	package="com.example.detectinternetconnection"

04	android:versionCode="1"

05	android:versionName="1.0" >

06

07	<uses-sdk android:minSdkVersion="8" />

08

09	<application

10	android:icon="@drawable/ic_launcher"

11	android:label="@string/app_name" >

12

<activity

13	android:name=".AndroidDetectInternetConnectionActivity"

14	android:label="@string/app_name" >

15	<intent-filter>

16	<action android:name="android.intent.action.MAIN" />

17

18	<category android:name="android.intent.category.LAUNCHER" />

19	</intent-filter>

20	</activity>

21	</application>

22

23	<!-- Internet Permissions -->

24	<uses-permission android:name="android.permission.INTERNET" />

25

26	<!-- Network State Permissions -->

27	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

28

29	</manifest>

3.创建一个新的类，名为ConnectionDetector.java，并输入以下代码。

ConnectionDetector.java

01	package com.example.detectinternetconnection;

02

03	import android.content.Context;

04	import android.net.ConnectivityManager;

05	import android.net.NetworkInfo;

06

07	public class ConnectionDetector {

08

09	private Context _context;

10

11	public ConnectionDetector(Context context){

12	this._context = context;

13

}

14

15	public boolean isConnectingToInternet(){

16	ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE);

17	if (connectivity != null)

18

{

19	NetworkInfo[] info = connectivity.getAllNetworkInfo();

20	if (info != null)

21	for (int i = 0; i < info.length; i++)

22	if (info[i].getState() == NetworkInfo.State.CONNECTED)

23

{

24	return true;

25

}

26

27

}

28	return false;

29

}

30

}

4.当你需要在你的应用中检查网络状态时调用isConnectingToInternet()函数，它会返回true或false。

1	ConnectionDetector cd = new ConnectionDetector(getApplicationContext());

2

3	Boolean isInternetPresent = cd.isConnectingToInternet(); // true or false

5.在这个教程中为了测试我仅仅简单的放置了一个按钮。只要按下这个按钮就会弹出一个 alert dialog 显示网络连接状态。

6.打开 res/layout 目录下的 main.xml 并创建一个按钮。

main.xml

01	<?xml version="1.0" encoding="utf-8"?>

02	<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

03	android:layout_width="fill_parent"

04	android:layout_height="fill_parent"

05	android:orientation="vertical" >

06

07

<TextView

08	android:layout_width="fill_parent"

09	android:layout_height="wrap_content"

10	android:text="Detect Internet Status" />

11

12	<Button android:id="@+id/btn_check"

13	android:layout_height="wrap_content"

14	android:layout_width="wrap_content"

15	android:text="Check Internet Status"

16	android:layout_centerInParent="true"/>

17

18	</RelativeLayout>

7.最后打开你的 MainActivity 文件并粘贴下面的代码。在下面的代码中我用一个 alert dialog 来显示预期的状态信息。

01	package com.example.detectinternetconnection;

02

03	import android.app.Activity;

04	import android.app.AlertDialog;

05	import android.content.Context;

06	import android.content.DialogInterface;

07	import android.os.Bundle;

08	import android.view.View;

09	import android.widget.Button;

10

11	public class AndroidDetectInternetConnectionActivity extends Activity {

12

13	// flag for Internet connection status

14	Boolean isInternetPresent = false;

15

16	// Connection detector class

17	ConnectionDetector cd;

18

19

@Override

20	public void onCreate(Bundle savedInstanceState) {

21	super.onCreate(savedInstanceState);

22	setContentView(R.layout.main);

23

24	Button btnStatus = (Button) findViewById(R.id.btn_check);

25

26	// creating connection detector class instance

27	cd = new ConnectionDetector(getApplicationContext());

28

29

/**

30	* Check Internet status button click event

31

* */

32	btnStatus.setOnClickListener(new View.OnClickListener() {

33

34

@Override

35	public void onClick(View v) {

36

37	// get Internet status

38	isInternetPresent = cd.isConnectingToInternet();

39

40	// check for Internet status

41	if (isInternetPresent) {

42	// Internet Connection is Present

43	// make HTTP requests

44	showAlertDialog(AndroidDetectInternetConnectionActivity.this, "Internet Connection",

45	"You have internet connection", true);

46

} else {

47	// Internet connection is not present

48	// Ask user to connect to Internet

49	showAlertDialog(AndroidDetectInternetConnectionActivity.this, "No Internet Connection",

50	"You don't have internet connection.", false);

51

}

52

}

53

54

});

55

56

}

57

58

/**

59	* Function to display simple Alert Dialog

60	* @param context - application context

61	* @param title - alert dialog title

62	* @param message - alert message

63	* @param status - success/failure (used to set icon)

64

* */

65	public void showAlertDialog(Context context, String title, String message, Boolean status) {

66	AlertDialog alertDialog = new AlertDialog.Builder(context).create();

67

68	// Setting Dialog Title

69	alertDialog.setTitle(title);

70

71	// Setting Dialog Message

72	alertDialog.setMessage(message);

73

74	// Setting alert dialog icon

75	alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);

76

77	// Setting OK Button

78	alertDialog.setButton("OK", new DialogInterface.OnClickListener() {

79	public void onClick(DialogInterface dialog, int which) {

80

}

81

});

82

83	// Showing Alert Message

84	alertDialog.show();

85

}

86

}

运行并测试下你的程序吧！你将会得到类似下面的结果。