安卓工作室 "碎片尚未被附加"

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...

在这个错误之前，我得到了"java.lang.RuntimeException: 无法启动活动 ComponentInfo{beermapbeermap.Main2Activity}: java.lang.IllegalArgumentException: 没有为id 0x7f08006e (beermap:idframeLayout1)找到视图。"

以下是班级

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 (Fragment)

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);
}

layoutactivity_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，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);

而你只想传递参数String "Description"，最好不要从 Main2Activity 但从 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，你还必须传入 String BeerDescription 到Main2Activity的PageAdapter。要做到这一点，你可以修改PageAdapter的构造函数并添加一个成员变量 BeerDescription还有

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，你终于可以通过 BeerDescripion 作为Main2Activity中PageAdapter的构造函数参数。

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