Android Studio“尚未附加片段”

Question

Process: beermap, PID: 9969
java.lang.RuntimeException: Unable to start activity ComponentInfo{beermap/beermap.Main2Activity}: java.lang.IllegalStateException: Fragment tabOne{e379756 (ba34244e-5562-4ef1-86c6-2cfa9113fc92)} has not been attached yet.
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6119)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
 Caused by: java.lang.IllegalStateException: Fragment tabOne{e379756 (ba34244e-5562-4ef1-86c6-2cfa9113fc92)} has not been attached yet.

所以这是 logcat...

在此错误之前，我收到“java.lang.RuntimeException: Unable to start activity ComponentInfo{beermap/beermap.Main2Activity}: java.lang.IllegalArgumentException: No view found for id 0x7f08006e (beermap:id/frameLayout1) ”

以下是类

Main2Activity

public class Main2Activity extends AppCompatActivity{

private String BeerName;
private String BeerDescription;
private TabLayout tabLayout;
private ViewPager viewpager;
private TabItem tabOne, tabTwo;
public PageAdapter pagerAdapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BeerName = getIntent().getStringExtra("Title");
    BeerDescription = getIntent().getStringExtra("Description");
    setTitle(BeerName);

    setContentView(R.layout.activity_main2);
    tabLayout = findViewById(R.id.tabLayout);
    tabOne = findViewById(R.id.tab_Description);
    tabTwo = findViewById(R.id.tab_Interesting);
    viewpager = findViewById(R.id.viewPager);
    pagerAdapter = new PageAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
    viewpager.setAdapter(pagerAdapter);

    tabOne tabone = new tabOne();
    FragmentManager manager = tabone.getChildFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();

    Bundle bundle = new Bundle();
    bundle.putString("Description", BeerDescription);
    tabone.setArguments(bundle);

    transaction.add(R.id.frameLayout1, tabone);
    transaction.commit();

    tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener(){
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewpager.setCurrentItem(tab.getPosition());
            if(tab.getPosition() == 0){
                pagerAdapter.notifyDataSetChanged();
            }
            else if(tab.getPosition() == 1){
                pagerAdapter.notifyDataSetChanged();
            }
        }
        @Override
        public void onTabUnselected(TabLayout.Tab tab) {
        }
        @Override
        public void onTabReselected(TabLayout.Tab tab) {
        }
    });
    viewpager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
}
public String getBeerDescription(){
    return this.BeerDescription;
}

页面适配器

public class PageAdapter extends FragmentPagerAdapter {

private int numberOfTabs;

public PageAdapter(@NonNull FragmentManager fm, int numberoftabs) {
    super(fm);
    this.numberOfTabs = numberoftabs;
}

@NonNull
@Override
public Fragment getItem(int position) {
    switch (position){
        case 0:
            return new tabOne();
        default:
            return new tabTwo();
    }
}

@Override
public int getCount() {
    return numberOfTabs;
}

@Override
public int getItemPosition(@NonNull Object object) {
    return POSITION_NONE;
}

tabOne（片段）

public class tabOne extends Fragment {
TextView tv_FragmentDescription;
String beerDesc;

public tabOne() {
    // Required empty public constructor
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_tab_one, container, false);
    tv_FragmentDescription = view.findViewById(R.id.tv_tabOne_Description);
    Bundle bundle = getArguments();
    beerDesc = bundle.getString("Description");
    tv_FragmentDescription.setText(beerDesc);

    return view;
}

tabTwo（片段）

public class tabTwo extends Fragment {

public tabTwo() {
    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_tab_two, container, false);
}

布局/activity_main2.xml：

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".Main2Activity">

<com.google.android.material.tabs.TabLayout
    android:id="@+id/tabLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <com.google.android.material.tabs.TabItem
        android:id="@+id/tab_Description"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Description" />

    <com.google.android.material.tabs.TabItem
        android:id="@+id/tab_Interesting"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Interesting" />

</com.google.android.material.tabs.TabLayout>

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </androidx.viewpager.widget.ViewPager>

有谁知道问题出在哪里？

Answer 1

如果你删除这六行后你的应用运行没有问题：

tabOne tabone = new tabOne();
FragmentManager manager = tabone.getChildFragmentManager();
FragmentTransaction transaction = manager.beginTransaction();

Bundle bundle = new Bundle();
bundle.putString("Description", BeerDescription);
tabone.setArguments(bundle);

而您只想传递参数字符串"Description"，最好不要来自Main2Activity，而是来自PageAdapter。

修改PageAdapter的getItem（并从Main2Activity中删除以上六行）：

public Fragment getItem(int position) {
    switch (position){
        case 0:
            tabOne tabone = new tabOne();
            Bundle bundle = new Bundle();
            bundle.putString("Description", BeerDescription);
            tabone.setArguments(bundle);
            return tabone;
        default:
            return new tabTwo();
    }
}

除此之外，您必须将字符串BeerDescription 从 Main2Activity 传递给 PageAdapter。为此，您可以修改 PageAdapter 的构造函数并添加成员变量BeerDescription：

private int numberOfTabs;
private String BeerDescription;

public PageAdapter(@NonNull FragmentManager fm, int numberoftabs, String BeerDescription) {
    super(fm);
    this.numberOfTabs = numberoftabs;
    this.BeerDescription = BeerDescription;
}

然后，最后你可以在 Main2Activity 中将 BeerDescripion 作为 PageAdapter 的构造函数参数传递：

@Override
protected void onCreate(Bundle savedInstanceState) {
    (...)
    pagerAdapter = new PageAdapter(getSupportFragmentManager(), tabLayout.getTabCount(), BeerDescription);
    (...)
}