Android network status 3G/WIFI

package Android.HelloAndroid; 
import android.app.Activity; 
import android.app.AlertDialog; 
import android.content.Context; 
import android.os.Bundle; 
import android.widget.TextView; 
import android.net.ConnectivityManager; 
import android.net.NetworkInfo; 
import android.net.NetworkInfo.State; 
public class Hello extends Activity { 
/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
TextView tv = new TextView(this); 
tv.setText("检测网络状态"); 
setContentView(tv); 
checkNetworkInfo(); 
goodNet(); 
} 
public boolean goodNet() 
{ 
ConnectivityManager manager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE); 
NetworkInfo networkinfo = manager.getActiveNetworkInfo(); 
if (networkinfo == null || !networkinfo.isAvailable()) { 
new AlertDialog.Builder(this).setMessage("没有可以使用的网络").setPositiveButton("Ok", null).show(); 
return false; 
} 
new AlertDialog.Builder(this).setMessage("网络正常可以使用").setPositiveButton("Ok", null).show(); 
return true; 
} 
private void checkNetworkInfo() 
{ 
ConnectivityManager conMan = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); //mobile 3G Data Network 
State mobile = conMan.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState(); 
new AlertDialog.Builder(this).setMessage(mobile.toString()).setPositiveButton("3G", null).show();//显示3G网络连接状态 
State wifi = conMan.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState(); 
new AlertDialog.Builder(this).setMessage(wifi.toString()).setPositiveButton("WIFI", null).show();//显示wifi网络连接状态 
} 
} 

需要注意:

根据Android的安全机制，在使用ConnectivityManager时，必须在AndroidManifest.xml中添加<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 否则无法获得系统的许可。