如何根據從一個片段發送到另一個片段的數據，使用片段來正確顯示我的Android佈局？

Question

我正在使用一個應用程序，其中我使用了選項卡/片段。我基於我在互聯網上找到的一個示例基於我的應用程序here。

我所擁有的是在Home標籤中的ListView，它顯示了一個類的列表。我想要發生的事情是當我點擊列表中的一個類時，它會發送一個ID到Class選項卡，在那裏我想根據傳入的類ID填充該類中的學生的另一個ListView。我有問題讓這個工作正常。

目前，它主要工作。

這是我在課堂上標籤的佈局（即接收標籤）：

class.xml

<LinearLayout android:id="@+id/class_information_layout"> 
    <TextView android:id="@+id/class_id_display" /> 
    <LinearLayout> 
     <TextView android:id="@+id/column1_row_header" /> 
     <TextView android:id="@+id/column2_row_header" /> 
     <TextView android:id="@+id/column3_row_header" /> 
     <TextView android:id="@+id/column4_row_header" /> 
     <TextView android:id="@+id/column5_row_header" /> 
    </LinearLayout> 

    <android.support.v4.widget.SwipeRefreshLayout 
     android:id="@+swipe_container" /> 
     <ListView android:id="@+student_row"></ListView> 
    </android.support.v4.widget.SwipeRefreshLayout> 
</LinearLayout> 

這裏是填充該佈局類：

ClassInformation.java

package myPackage; 

public class ClassInformation extends Fragment { 

    private View rootView; 
    private ListView myListView; 
    private SwipeRefreshLayout mySwipeRefresh; 
    private DatabaseHelper myDBHelper; 
    private Cursor informationCursor; 
    private SimpleCursorAdapter mySimpleCursorAdapter; 
    private static String classID = "select a class first"; 

    private TextView classIDDisplay; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){ 
     rootView = inflater.inflate(R.layout.class, container, false); 
     classIDDisplay = (TextView) rootView.findViewById(R.id.class_id_display); 
     myListView = (ListView) rootView.findViewById(R.id.student_row); 
     mySwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipe_container); 

     return rootView; 
    } 

    @Override 
    public void onViewCreated(View rootView, Bundle savedInstanceState){ 
     super.onViewCreated(rootView, savedInstanceState); 

     if(getArguments() != null){ 
      classID = getArguments().getString("classID"); 
     } 
     System.out.println("Class ID: " + classID); 

     drawTheView(); 

     mySwipeRefresh.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener(){ 
      @Override 
      public void onRefresh(){ 
       mySwipeRefrehs.setRefreshing(false); 
       drawTheView(); 
      } 
     }); 
    } 

    private void drawTheView(){ 

     myDBHelper = new DatabaseHelper(getActivity()); 

     informationCursor = myDBHelper.getInformationCursor(classID); 
     String[] fromColumns = {"studentID", "firstname", "lastname", "homephone", "homeaddress"}; 
     int[] toViews = {R.id.studentID_textview, R.id.firstname_textview, R.id.lastname_textview, R.id.homephone_textview, R.id.homeaddress_textview}; 
     mySimpleCursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.student_information, informationCursor, fromColumns, toViews, 0); 

     classIDDisplay.setText("Class ID: " + classID); 

     myListView.setAdapter(mySimpleCursorAdapter); 

     myDBHelper.close(); 
    } 
} 

這是student_information佈局逐漸加入適配器：

student_information.xml

<LinearLayout> 
     <TextView android:id="@+id/column1_data" /> 
     <TextView android:id="@+id/column2_data" /> 
     <TextView android:id="@+id/column3_data" /> 
     <TextView android:id="@+id/column4_data" /> 
     <TextView android:id="@+id/column5_data" /> 
</LinearLayout> 

這裏是將信息發送到類選項卡顯示在主頁選項卡類：

Home.java

package myPackage; 

public class Home extends Fragment { 

    private View rootView; 
    private DatabaseHelper myDBHelper; 
    private Cursor classCursor; 
    private SimpleCursorAdapter mySimpleCursorAdapter; 
    private Activity myActivity; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){ 
     rootView = inflater.inflate(R.layout.home, container, false); 

     ViewPager myViewPager = (ViewPager) getActivity.findViewById(R.id.pager); 

     myDBHelper = new DatabaseHelper(getActivity()); 

     classCursor = myDBHelper.getClassCursor(); 
     String[] fromColumns = {"classID"}; 
     int[] toViews = {R.id.class_id_textview}; 
     mySimpleCursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.class_layout, classCursor, fromColumns, toViews, 0); 

     ListView myListView = (ListView) rootView.findViewById(R.id.class_row); 

     myListView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
       Cursor subCursor = (Cursor) mySimpleCursorAdapter.getItem(position); 
       String classID = subCursor.getString(subCursor.getColumnIndex("classID")); 

       ClassInformation classInformation = new ClassInformation(); 
       Bundle myBundle = new Bundle(); 
       myBundle.putString("classID", classID); 
       classInformation.setArguments(myBundle); 
       getFragmentManager().beginTransaction().replace(R.id.class_information_layout, classInformation).commit(); 
       myViewPager.setCurrentItem(1); 
      } 
     }); 

     myListView.setAdapter(mySimpleCursorAdapter); 

     myDBHelper.close(); 

     return rootView; 
    } 
} 

當前，當我第一次啓動應用程序並單擊主頁選項卡中的一個班級時，班級選項卡沒有從主頁選項卡中獲得「ID」，所以學生列表不會填充。然而，這是一個奇怪的部分，如果我（1）將我的Class選項卡關閉到另一個不是Home選項卡的選項卡並返回Class選項卡，或者（2）使用SwipeRefreshLayout向下滑動，學生將被正確繪製。

然後，如果我回到主頁選項卡並選擇不同的類，我的類選項卡仍顯示我選擇的第一個類。再次，如果我（1）單擊我的班級選項卡到另一個不是主頁選項卡並返回到班級選項卡，或（2）使用SwipeRefreshLayout向下滑動，學生列表將正確繪製與新班級的數據。

我沒有收到任何錯誤，只是直到我點擊標籤或刷卡刷新纔會正確顯示。

我在ClassInformation.java文件中有一個System.out.println。這是點擊左右我的應用程序的結果：

Start the app 
    System.out.println = "select a class first" 
Click on a class in the Home tab 
    - System.out.println = "Class ID = <number>" 
    - nothing in the list 
Click off of the Class tab, then back to the class tab -or- use the swipe refresh 
    - System.out.println = "Class ID = <number>" 
    - the list is populated correctly 
Click a different class in the Home tab 
    - System.out.println = "<first class ID>" 
    - the list is not populated correctly 
Click off of the Class tab, then back to the class tab -or- use the swipe refresh 
    - System.out.println = "Class ID = <new class number>" 
    - the list is populated correctly 

- 或 -

Start the app 
    - System.out.println = "select a class first" 
Click on a class in the Home tab 
    - System.out.println = "Class ID = <number>" 
    - nothing in the list 
Swipe Refresh 
    - System.out.println = "Class ID = <number>" 
    - the list is populated correctly 
Click a different class in the Home tab 
    - System.out.println = "<first class ID>" 
    - the list is not populated correctly 
Swipe Refresh 
    - System.out.println = "Class ID = <new class number>" 
    - the list is populated correctly 

我覺得這應該是一個簡單的修復，但我似乎保持俯瞰答案。

Answer 1

我希望發生的是，當我點擊列表中的一類，它會 發送ID到類選項卡，在這裏我想基礎上，通過了班級內填充學生的另一個ListView的 -in類ID

此刻的你正在做一個交易，以增加新的ClassInformation片段，但你已經在ViewPager片段所以不是你可以（也應該）訪問並設置新的ID（一起刷新視圖）。如果您使用的是FragmentPagerAdapter與ViewPager您可以通過使用特殊的標記（具體以FragmentPagerAdapter）這樣的訪問片段：

ClassInformation f = (ClassInformation) getSupportFragmentManager().findFragmentByTag("android:switcher:"+R.id.pager+":" + the_position_of_classinformation_in_viewpager); 
f.setClassId(classID); 

的方法setClassId（）看起來是這樣的：

public void setClassId(String id) { 
    classID = id; 
    if (getView() != null) {// just in case we call it when the view is not built yet 
     drawTheView(); 
    } 
}