Question

使用FAB按钮，应用程序在两个片段之间交替显示。我正在尝试使当前片段在旋转屏幕时保持不变，但每次屏幕旋转时应用程序崩溃。我尝试了很多解决方案，但都没有。为什么会崩溃？我正在使用NetBeans，所以我不确定谁发布logcat。

       public class agendaFalante extends AppCompatActivity
{
    /** Called when the activity is first created. */
    private Toolbar toolbar;
    private FloatingActionButton fab ;
    private listViewFrag lvfrag;
    private newEventFrag nef;
    private FragmentManager fragmentManager;
    private FragmentTransaction fragmentTransaction;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        toolbar = (Toolbar) findViewById (R.id.toolbar);
        setSupportActionBar(toolbar);
        fragmentManager = getSupportFragmentManager();
        fragmentTransaction = fragmentManager.beginTransaction();
        if (savedInstanceState == null) {
            lvfrag = new listViewFrag();
            fragmentTransaction.replace(R.id.ll, lvfrag, "lvfrag");
            fragmentTransaction.commit();
        }else{
            if(lvfrag!=null && lvfrag.isVisible()){
                fragmentTransaction.replace(R.id.ll, lvfrag);
                fragmentTransaction.commit();
            }else if(nef!=null && nef.isVisible()){
                fragmentTransaction.replace(R.id.ll, nef);
                fragmentTransaction.commit();
            }
        }
        fab = (FloatingActionButton)  findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            fragmentTransaction = fragmentManager.beginTransaction();
            if(nef!=null && nef.isVisible()){
                lvfrag = (listViewFrag) getSupportFragmentManager().findFragmentByTag("lvfrag");
                fragmentTransaction.replace(R.id.ll,lvfrag);
            }else{
                if(lvfrag.isVisible()){
                    nef = (newEventFrag) getSupportFragmentManager().findFragmentByTag("nef");
                    if(nef==null){
                        nef = new newEventFrag();
                        fragmentTransaction.replace(R.id.ll,nef,"nef");
                    }else{
                        fragmentTransaction.replace(R.id.ll,nef);
                    }                    
                }
            }
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
        }
    });
    }
    public boolean OnCreateOptionsMenu(Menu menu){
        getMenuInflater().inflate(R.menu.menu_layout,menu);
        return true;
    }

}

main xml

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/root"
    tools:context=".agendaFalante">
<LinearLayout android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:id="@+id/ll"
              android:orientation="vertical">
    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:background="?attr/colorPrimary"
        android:elevation="6dp"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
    />

</LinearLayout>
<android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:clickable="true"
        android:src="@drawable/ic_done"
         app:layout_anchor="@id/ll"
          app:backgroundTint="#CE93D8"
        app:layout_anchorGravity="bottom|right|end"/>

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

片段1 xml

public class listViewFrag extends Fragment{

    private ListView atividadesView;
    private ArrayList<String> alist;
    private ArrayAdapter<String> aDapter;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.listviewfrag, container, false);
        atividadesView = (ListView) view.findViewById(R.id.listView);
        alist = new ArrayList<String>();
        alist.add("oi");
        aDapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1,alist);
        atividadesView.setAdapter(aDapter);
        return view;
    }
    public void addText(String text){
        alist.add(text);
        aDapter.notifyDataSetChanged();
    }
}

片段xml：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
>

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

</LinearLayout>

片段2：

public class newEventFrag extends Fragment{

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.neweventfrag, container, false);
        return view;
    }

}

片段xml

<TableLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true"
    >
    <TableRow
        android:layout_height="0dp"
        android:layout_weight="1">
        <EditText
                android:text="Insira o título"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="0.8"
            >
        </EditText>
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="0.2"
            android:id="@+id/record"
            android:src="@drawable/ic_mic"
        >
        </Button>
    </TableRow>
    <TableRow
        android:layout_height="0dp"
        android:layout_weight="1">
        <DatePicker
            android:id="@+id/dpResult"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:datePickerMode="spinner"
            android:calendarViewShown="false"
        />
    </TableRow>
</TableLayout>

Answer 1

在屏幕旋转时，碎片不会被破坏。但是，字段lvfrag将不是您在旋转之前创建的片段，直到找到片段并将其分配给字段。所以你应该首先找到＆＃34; savedInstanceState时的片段不为null。 ---

if (savedInstanceState == null) {
        lvfrag = new listViewFrag();
        fragmentTransaction.replace(R.id.ll, lvfrag, "lvfrag");
        fragmentTransaction.commit();
    }else{
        lvfrag = (listViewFrag)this.getSupportFragmentManager().findFragmentByTag("lvfrag");  
        if(lvfrag!=null)

....你需要重置任何片段的字段，然后在这里替换并提交 }

我在这里仅显示lvfrag，但您也可以将代码包含在nef中。您的mainActivity需要知道活动被销毁时哪个片段可见。您应该覆盖onSaveInstanceState方法，以便在旋转时销毁活动时发回包中可见的碎片，然后在替换碎片时捕获该碎片。

Answer 2

当屏幕旋转时，savedInstanceState中的onCreate()参数将包含Bundle，您可以将Activity恢复为其所处的状态。但您仍然需要将其视为一个全新的Activity并再次加载所有控件：

if (savedInstanceState == null) {
            lvfrag = new listViewFrag();
            fragmentTransaction.replace(R.id.ll, lvfrag, "lvfrag");
            fragmentTransaction.commit();
        } else {
           // even though savedInstanceState is not null
           // lvfrag still needs to be created
            if(lvfrag.isVisible()){

我已经展示了上面代码的一部分 - 在其中，如果lvfrag不为空，则假设已经创建了savedInstanceState - 这是错误的。

每次旋转屏幕时，Android都会从new重新创建您的Activity - 您必须重新创建任何片段（以及任何其他控件）并重新初始化Activity中的所有字段。您的应用崩溃的最可能原因是，当lvfrag.isVisible()尚未初始化时，您尝试拨打lvfrag（因此，为空）。

Answer 3

在以下行中添加以下行：android:configChanges="orientation|screenSize|keyboardHidden" AndroidManifest.xml。

<activity
    android:name=".MainActivity"
    android:label="@string/title_activity_main"
    android:configChanges="orientation|screenSize|keyboardHidden">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
</activity>

碎片在屏幕旋转时崩溃

3 个答案: