检查网络是否连接的工具类

 必须先加下面这两个权限,网络访问权限和差来看网络状态权限<uses-permission android:name="android.permission.INTERNET"/><uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            listview = (ListView) findViewById(R.id.listview);        if (isConnection(this)) {    下面这个方法是自定义的网络请求数据方法,就不上传了            getDataByWeb();        } else {            AlertDialog.Builder builder = new AlertDialog.Builder(this);            builder.setMessage("网络链接中断,是否设置链接网络");            builder.setNegativeButton("取消", null);            builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {                @Override                public void onClick(DialogInterface dialog, int which) {                 
                                 Intent intent = new Intent();                                 intent.setAction("android.net.wifi.PICK_WIFI_NETWORK");                                 startActivity(intent);
                }            });            builder.create().show();        }    }    public boolean isConnection(Context context) {        ConnectivityManager manager = (ConnectivityManager)         context.getSystemService(Context.CONNECTIVITY_SERVICE);        NetworkInfo info = manager.getActiveNetworkInfo();        return (info != null && info.isAvailable());    }