Android 利用广播监视网络是否连接

package com.haitun.msr;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.webkit.WebView.FindListener;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

/**
* 监听网络变化
*/
public class NetworkReceiver extends BroadcastReceiver {

//接受广播
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager connManager = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);
// 获取代表联网状态的NetWorkInfo对象
NetworkInfo networkInfo = connManager.getActiveNetworkInfo();
// 获取当前的网络连接是否可用
//boolean avail = networkInfo.isAvailable();
if (networkInfo != null) {
Log.i("net", "Yes");
} else {
Toast toast=Toast.makeText(context, null, Toast.LENGTH_LONG);
LayoutInflater inflater=(LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v=inflater.inflate(R.layout.toast,new LinearLayout(context),false);
TextView text=(TextView) v.findViewById(R.id.toast_text);
text.setText("当前网络不可用，请检查");
toast.setView(v);
toast.setGravity(Gravity.CENTER, 0, 0);
toast.show();
}

}

}

package com.haitun.msr;

import com.haitun.msr.R;

import android.app.Activity;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

public class LoginActivity extends Activity {

private NetworkReceiver network=new NetworkReceiver();
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
//注册广播
IntentFilter filter=new IntentFilter();
filter.addAction(android.net.ConnectivityManager.CONNECTIVITY_ACTION);
registerReceiver(network, filter);
}
@Override
protected void onDestroy() {
//解除广播
unregisterReceiver(network);
super.onDestroy();
}
}

<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<!-- 广播 -->
<receiver
android:name=".NetworkReceiver"
android:label="networkreceiver">
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
</intent-filter>
</receiver>