Java 当我调用next fragment form current时，单击按钮时选项卡选择不会改变

我正在尝试开发一个android应用程序，其中我将包含带有片段的标签。请查找以下活动代码：

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;

import java.util.ArrayList;
import java.util.List;
public class EnterActivity extends AppCompatActivity {

private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_enter);
    viewPager = (ViewPager) findViewById(R.id.viewpager);
    setupViewPager(viewPager);
    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);
    tabLayout.getTabAt(3).select();
}


private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new EnterCodeFragment(), "ENTER CODE");
    adapter.addFragment(new HistoryFragment(), "HISTORY");
    adapter.addFragment(new HelpFragment(), "HELP");
    adapter.addFragment(new LogoutFragment(), "LOGOUT");
    viewPager.setAdapter(adapter);
}


class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }
}
}

---

当我点击按钮时，它将移动到下一个片段，但选项卡选择不会改变我认为它正在创建一个新片段。任何帮助都将不胜感激。

我认为您没有像上面的代码那样正确地初始化片段更新

 Button loginButton = (Button)v.findViewById(R.id.button);
        loginButton.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view) {

            EnterCodeFragment fragment = new EnterCodeFragment(); // check this 

            FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.replace(R.id.activity_main,fragment);
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
             //   ViewPagerAdapter.get
            }
        });

---

为什么要在onCreate“tabLayout.getTabAt（3）.select（）；”@Omi中添加此行？实际上，启动活动时，我需要设置默认选项卡。所以我加了这句话。

 Button loginButton = (Button)v.findViewById(R.id.button);
        loginButton.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view) {

            EnterCodeFragment fragment = new EnterCodeFragment(); // check this 

            FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.replace(R.id.activity_main,fragment);
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
             //   ViewPagerAdapter.get
            }
        });