需要帮助才能在使用ViewPager创建的两个选项卡上正常使用Android浮动操作按钮吗

正如标题所说，我的应用程序中有多个选项卡，它们都是用ViewPager创建的。我有一个Android浮动操作按钮，我只想在两个选项卡上显示。我已经让这个[大部分]起作用了

启动应用程序时，会显示选项卡1。当我单击选项卡1上的晶圆厂时，什么也没发生。如果我滑动到Tab#2并单击它的FAB，那么效果会很好。但是，如果我滑回Tab#1，那么FAB也可以正常工作。只有在切换到新选项卡，然后返回到选项卡1后，选项卡1的FAB才会工作

那么，当晶圆厂第一次启动时，如何将其固定在默认选项卡（选项卡1）上

谢谢

以下是我所拥有的：

MainActivity.java

public class MainActivity extends AppCompatActivity {

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

        final FloatingActionButton fab = (FloatingActionButton)findViewById(R.id.fab);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
        tabLayout.addTab(tabLayout.newTab().setText(Constants.TAB_01));
        tabLayout.addTab(tabLayout.newTab().setText(Constants.TAB_02));
        tabLayout.addTab(tabLayout.newTab().setText(Constants.TAB_03));
        tabLayout.addTab(tabLayout.newTab().setText(Constants.TAB_04));
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

        viewPager = (ViewPager) findViewById(R.id.pager);
        pagerAdapter = new PagerAdapter (getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(pagerAdapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                if (tab.getPosition() == Constants.TAB_INDEX_TAB_01) {
                    if (fab != null) {
                        fab.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                Intent activity01Intent = new Intent(getApplicationContext(), Activity01.class);
                                if (activity01Intent != null) {
                                    try {
                                        startActivity(activity01Intent);
                                    } catch (ActivityNotFoundException anfe) {
                                        Toast.makeText(getApplicationContext(), "ERROR ...", Toast.LENGTH_SHORT).show();
                                    }
                                }
                            }
                        });
                    }
                    fab.show();
                } else if(tab.getPosition() == Constants.TAB_INDEX_TAB_02){
                    if(fab != null) {
                        fab.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                Intent activity02Intent = new Intent(getApplicationContext(), Activity02.class);
                                if (activity02Intent != null) {
                                    try {
                                        startActivity(activity02Intent);
                                    } catch (ActivityNotFoundException anfe) {
                                        Toast.makeText(getApplicationContext(), "ERROR ...", Toast.LENGTH_SHORT).show();
                                    }
                                }
                            }
                        });
                    }
                    fab.show();
                } else {
                    fab.hide();
                }
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) { }

            @Override
            public void onTabReselected(TabLayout.Tab tab) { }
        });

    }
}

活动\u main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <include layout="@layout/content_main" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:backgroundTint="@color/DIMGRAY"
        android:src="@android:drawable/ic_input_add" />

</android.support.design.widget.CoordinatorLayout>

---

只需在Oncreate中定义它，也希望它能工作

if (fab != null) {
                            fab.setOnClickListener(new View.OnClickListener() {
                                @Override
                                public void onClick(View v) {
                                    Intent activity01Intent = new Intent(getApplicationContext(), Activity01.class);
                                    if (activity01Intent != null) {
                                        try {
                                            startActivity(activity01Intent);
                                        } catch (ActivityNotFoundException anfe) {
                                            Toast.makeText(getApplicationContext(), "ERROR ...", Toast.LENGTH_SHORT).show();
                                        }
                                    }
                                }
                            });
                        }
                        fab.show();

---

我不知道你在说什么。这正是我在我的职位。