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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。
本文创建一个项目演示如何检查网络状况, 界面如下:
检查到有网络连接后:
检查到网络没有连接的情况如下:
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
创建完项目结构如下:
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
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="cn.iigrowing.android.network.check"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="9" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name="cn.iigrowing.android.network.check.InternetConnectionActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
</manifest>
main.xml
<?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_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="Check Internet Status" />
</RelativeLayout>
ConnectionDetector.java
/*
* Copyright (C) 2010 network authors
*
* @author shao
*
* @date 2013.9.21
*
* @blog http://www.iigrowing.cn/
*
* 本程序是android客户端软件演示程序
*
*/
package cn.iigrowing.android.network.check;
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;
}
}
InternetConnectionActivity.java
/*
* Copyright (C) 2010 network authors
*
* @author shao
*
* @date 2013.9.21
*
* @blog http://www.iigrowing.cn/
*
* 本程序是android客户端软件演示程序
*
*/
package cn.iigrowing.android.network.check;
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 InternetConnectionActivity 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(InternetConnectionActivity.this,
"Internet Connection",
"You have internet connection",
true);
} else {
// Internet connection is not present
// Ask user to connect to Internet
showAlertDialog(InternetConnectionActivity.this,
"No Internet Connection",
"You don’t have internet connection.",
false);
}
}
});
}
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();
}
}
