怎样检查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
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<?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
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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。
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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
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<?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。
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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。
