Android 检測网络是否连接

权限：

 <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
 <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

代码例如以下：

package com.example.nettest;

import android.net.ConnectivityManager;
import android.net.NetworkInfo.State;
import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.ComponentName;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.view.Menu;
import android.widget.TextView;
import android.widget.Toast;


public class MainActivity extends Activity {


private ConnectivityManager manager;
private TextView tv;
StringBuffer sb = new StringBuffer(256);


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);


tv = (TextView) findViewById(R.id.textView1);
checkNetworkState();
}


/**
* 检測网络是否连接
* 
* @return
*/
private boolean checkNetworkState() {
boolean flag = false;
// 得到网络连接信息
manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
// 去进行推断网络是否连接
if (manager.getActiveNetworkInfo() != null) {
flag = manager.getActiveNetworkInfo().isAvailable();
}
if (!flag) {
setNetwork();
} else {
isNetworkAvailable();
}
tv.setText(sb.toString());
return flag;
}


/**
* 网络未连接时。调用设置方法
*/
private void setNetwork() {
Toast.makeText(this, "wifi is closed!", Toast.LENGTH_SHORT).show();
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setIcon(R.drawable.ic_launcher);
builder.setTitle("网络提示信息");
builder.setMessage("网络不可用。假设继续，请先设置网络！

");
builder.setPositiveButton("设置", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent intent = null;
/**
* 推断手机系统的版本号！

假设API大于10 就是3.0+ 由于3.0以上的版本号的设置和3.0下面的设置不一样。调用的方法不同
*/
if (android.os.Build.VERSION.SDK_INT > 10) {
intent = new Intent(
android.provider.Settings.ACTION_SETTINGS);
} else {
intent = new Intent();
ComponentName component = new ComponentName(
"com.android.settings",
"com.android.settings.WirelessSettings");
intent.setComponent(component);
intent.setAction("android.intent.action.VIEW");
}
startActivity(intent);
}
});


builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
builder.create();
builder.show();
}


/**
* 网络已经连接，然后去推断是wifi连接还是GPRS连接 设置一些自己的逻辑调用
*/
private void isNetworkAvailable() {


State gprs = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE)
.getState();
State wifi = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI)
.getState();
if (gprs == State.CONNECTED || gprs == State.CONNECTING) {
Toast.makeText(this, "gprs is open! ", Toast.LENGTH_SHORT).show();
sb.append(" gprs is open! ");
} else {
sb.append(" gprs is closed! ");
}


// 推断为wifi状态下才载入广告，假设是GPRS手机网络则不载入。
if (wifi == State.CONNECTED || wifi == State.CONNECTING) {
Toast.makeText(this, "wifi is open! ", Toast.LENGTH_SHORT).show();
loadAdmob();
sb.append(" wifi is open! ");
} else {
sb.append(" wifi is closed! ");
}


}


/**
* 在wifi状态下 载入admob广告
*/
private void loadAdmob() {
Toast.makeText(getApplicationContext(), "ad is loding..", 1).show();
sb.append(" ad is loding...");
}
}