简单网络判断

package com.bawei.myapplication;import android.app.Activity;import android.content.Context;import android.net.ConnectivityManager;import android.net.NetworkInfo;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.widget.Toast;public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        boolean b = gainNet(MainActivity.this);        if(b==false){            Toast.makeText(MainActivity.this,"无网络",Toast.LENGTH_SHORT).show();        }else {            Toast.makeText(MainActivity.this,"有网络",Toast.LENGTH_SHORT).show();        }    }    private boolean gainNet(Context activity) {//获得ConnectivityManage网络管理类        ConnectivityManager manager= (ConnectivityManager) activity.getSystemService(Context.CONNECTIVITY_SERVICE);//获得可用网络信息        NetworkInfo nets = manager.getActiveNetworkInfo();//判断是否为空        if(nets!=null&&nets.isAvailable())        {            return true;        }        return false;    }   //boolean b=gainNet(MainActivity.this);}