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