怎么检查Android网络连接状态

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

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 Project2.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.xml01<?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????<application10????????android:icon="@drawable/ic_launcher"11????????android:label="@string/app_name"?>12????????<activity13????????????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????24????<uses-permission?android:name="android.permission.INTERNET"?/>25??26????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.xml01<?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????<TextView08????????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 status14????Boolean isInternetPresent =?false;15??16????// Connection detector class17????ConnectionDetector cd;18??19????@Override20????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 instance27????????cd =?new?ConnectionDetector(getApplicationContext());28??29????????/**30?????????* Check Internet status button click event31?????????* */32????????btnStatus.setOnClickListener(new?View.OnClickListener() {33??34????????????@Override35????????????public?void?onClick(View v) {36??37????????????????// get Internet status38????????????????isInternetPresent = cd.isConnectingToInternet();39??40????????????????// check for Internet status41????????????????if?(isInternetPresent) {42????????????????????// Internet Connection is Present43????????????????????// make HTTP requests44????????????????????showAlertDialog(AndroidDetectInternetConnectionActivity.this,"Internet Connection",45????????????????????????????"You have internet connection",?true);46????????????????}?else?{47????????????????????// Internet connection is not present48????????????????????// Ask user to connect to Internet49????????????????????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 Dialog60?????* @param context - application context61?????* @param title - alert dialog title62?????* @param message - alert message63?????* @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 Title69????????alertDialog.setTitle(title);70??71????????// Setting Dialog Message72????????alertDialog.setMessage(message);73??74????????// Setting alert dialog icon75????????alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);76??77????????// Setting OK Button78????????alertDialog.setButton("OK",?new?DialogInterface.OnClickListener() {79????????????public?void?onClick(DialogInterface dialog,?int?which) {80????????????}81????????});82??83????????// Showing Alert Message84????????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。?