网络是否可用判断以及Fragment

package com.bwie.yuekao01;

import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.provider.Settings;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;

import com.bwie.yuekao01.fragment.GnFragment;
import com.bwie.yuekao01.fragment.JsFragment;
import com.bwie.yuekao01.fragment.KjFragment;
import com.bwie.yuekao01.fragment.TtFragment;

public class MainActivity extends FragmentActivity implements View.OnClickListener {

private FrameLayout frame;
private Button btngn;
private Button btntt;
private Button btnjs;
private Button btnkj;
private TtFragment ttFragment;
private GnFragment gnFragment;
private JsFragment jsFragment;
private KjFragment kjFragment;

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

boolean netWorkInfo = getNetWorkInfo(getApplicationContext());
if (!netWorkInfo) {
final Intent intent = new Intent();
intent.setAction("com.bwie.yuekao01");
intent.putExtra("info", "当前没有可用网络");
sendBroadcast(intent);

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("是否前去设置网络");
builder.setPositiveButton("设置", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {

Intent intent1 = new Intent(Settings.ACTION_WIRELESS_SETTINGS);
startActivity(intent1);

}
});
builder.setNegativeButton("不了",null);
builder.create().show();

}
frame = (FrameLayout) findViewById(R.id.frame);
btngn = (Button) findViewById(R.id.btngn);
btntt = (Button) findViewById(R.id.btntt);
btnjs = (Button) findViewById(R.id.btnjs);
btnkj = (Button) findViewById(R.id.btnkj);

btnkj.setOnClickListener(this);
btntt.setOnClickListener(this);
btngn.setOnClickListener(this);
btnjs.setOnClickListener(this);

ttFragment = new TtFragment();
gnFragment = new GnFragment();
jsFragment = new JsFragment();
kjFragment = new KjFragment();

FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.add(R.id.frame, ttFragment);
transaction.add(R.id.frame, gnFragment);
transaction.add(R.id.frame, jsFragment);
transaction.add(R.id.frame, kjFragment);
transaction.hide(gnFragment);
transaction.hide(jsFragment);
transaction.hide(kjFragment);
transaction.commit();

}

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btntt:
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();
transaction.hide(gnFragment);
transaction.hide(jsFragment);
transaction.hide(kjFragment);
transaction.show(ttFragment);
transaction.commit();
break;
case R.id.btngn:
FragmentManager manager2 = getSupportFragmentManager();
FragmentTransaction transaction2 = manager2.beginTransaction();
transaction2.hide(ttFragment);
transaction2.hide(jsFragment);
transaction2.hide(kjFragment);
transaction2.show(gnFragment);
transaction2.commit();
break;
case R.id.btnkj:
FragmentManager manager3 = getSupportFragmentManager();
FragmentTransaction transaction3 = manager3.beginTransaction();
transaction3.hide(ttFragment);
transaction3.hide(jsFragment);
transaction3.hide(gnFragment);
transaction3.show(kjFragment);
transaction3.commit();
break;
case R.id.btnjs:
FragmentManager manager4 = getSupportFragmentManager();
FragmentTransaction transaction4 = manager4.beginTransaction();
transaction4.hide(ttFragment);
transaction4.hide(kjFragment);
transaction4.hide(gnFragment);
transaction4.show(jsFragment);
transaction4.commit();
break;
}
}
public boolean getNetWorkInfo(Context context) {

ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manager.getActiveNetworkInfo();
return networkInfo != null && networkInfo.isConnected();
}
}