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如何检查Android网络连接状态

2012-10-22 16:33 435 查看
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。




                                            

                                        

                        
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