android 登录前检察网络状态

package com.dx;import android.app.Activity;import android.app.AlertDialog;import android.content.Context;import android.net.ConnectivityManager;import android.net.NetworkInfo;import android.net.NetworkInfo.State;import android.os.Bundle;import android.widget.TextView;public class Main extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);//        setContentView(R.layout.main);        TextView textView = new TextView(this);        textView.setText("网络检测");        setContentView(textView);                if(checkNetWorkInfo()){        	goToNetWork();        };    }	private boolean goToNetWork() {		// TODO Auto-generated method stub		ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);		NetworkInfo info = connectivityManager.getActiveNetworkInfo();		if(info == null || !info.isAvailable()){			new AlertDialog.Builder(this).setMessage("没有可以使用的网络").setPositiveButton("Ok", null).show();    			return false;		}		else{			new AlertDialog.Builder(this).setMessage("网络正常可以使用").setPositiveButton("Ok", null).show();    		    return true;		}					}	private boolean checkNetWorkInfo() {		// TODO Auto-generated method stub		ConnectivityManager manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);		State wifi  = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).getState();		if(wifi != null){			new AlertDialog.Builder(this).setMessage(wifi.toString()).setPositiveButton("wifi", null).show();//显示wifi网络连接状态    			return true;					}else{			State mobile  = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).getState();			if(mobile != null){				new AlertDialog.Builder(this).setMessage(mobile.toString()).setPositiveButton("3G", null).show();//显示3G网络连接状态    				return true;			}		}		return false;			}}

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