如何检查Android网络连接状态
openkk
12年前
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
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.detectinternetconnection" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <activity android:name=".AndroidDetectInternetConnectionActivity" 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> <!-- Internet Permissions --> <uses-permission android:name="android.permission.INTERNET" /> <!-- Network State Permissions --> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> </manifest>
3.创建一个新的类，名为ConnectionDetector.java，并输入以下代码。
ConnectionDetector.java
package com.example.detectinternetconnection; import android.content.Context; import android.net.ConnectivityManager; import android.net.NetworkInfo; public class ConnectionDetector { private Context _context; public ConnectionDetector(Context context){ this._context = context; } public boolean isConnectingToInternet(){ ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE); if (connectivity != null) { NetworkInfo[] info = connectivity.getAllNetworkInfo(); if (info != null) for (int i = 0; i < info.length; i++) if (info[i].getState() == NetworkInfo.State.CONNECTED) { return true; } } return false; } } 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。
ConnectionDetector cd = new ConnectionDetector(getApplicationContext()); 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
</div> <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Detect Internet Status" /> <Button android:id="@+id/btn_check" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="Check Internet Status" android:layout_centerInParent="true"/> </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。
</div> package com.example.detectinternetconnection; import android.app.Activity; import android.app.AlertDialog; import android.content.Context; import android.content.DialogInterface; import android.os.Bundle; import android.view.View; import android.widget.Button; public class AndroidDetectInternetConnectionActivity extends Activity { // flag for Internet connection status Boolean isInternetPresent = false; // Connection detector class ConnectionDetector cd; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button btnStatus = (Button) findViewById(R.id.btn_check); // creating connection detector class instance cd = new ConnectionDetector(getApplicationContext()); /** * Check Internet status button click event * */ btnStatus.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // get Internet status isInternetPresent = cd.isConnectingToInternet(); // check for Internet status if (isInternetPresent) { // Internet Connection is Present // make HTTP requests showAlertDialog(AndroidDetectInternetConnectionActivity.this, "Internet Connection", "You have internet connection", true); } else { // Internet connection is not present // Ask user to connect to Internet showAlertDialog(AndroidDetectInternetConnectionActivity.this, "No Internet Connection", "You don't have internet connection.", false); } } }); } /** * Function to display simple Alert Dialog * @param context - application context * @param title - alert dialog title * @param message - alert message * @param status - success/failure (used to set icon) * */ public void showAlertDialog(Context context, String title, String message, Boolean status) { AlertDialog alertDialog = new AlertDialog.Builder(context).create(); // Setting Dialog Title alertDialog.setTitle(title); // Setting Dialog Message alertDialog.setMessage(message); // Setting alert dialog icon alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail); // Setting OK Button alertDialog.setButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { } }); // Showing Alert Message alertDialog.show(); } } 运行并测试下你的程序吧！你将会得到类似下面的结果。
