怎么检查Android网络连接状态_Android

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?

01package?com.example.detectinternetconnection;
02??
03import?android.content.Context;
04import?android.net.ConnectivityManager;
05import?android.net.NetworkInfo;
06??
07public?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。

1ConnectionDetector cd =?new?ConnectionDetector(getApplicationContext());
2??
3Boolean 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。

01package?com.example.detectinternetconnection;
02??
03import?android.app.Activity;
04import?android.app.AlertDialog;
05import?android.content.Context;
06import?android.content.DialogInterface;
07import?android.os.Bundle;
08import?android.view.View;
09import?android.widget.Button;
10??
11public?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。