片段onSaveInstanceState崩潰屏幕旋轉的應用程序

Question

我有一個應用程序的片段。其中一個片段要求用戶在2個文本字段中輸入隊名。我想將名字保存在onSaveInstanceState中。然而，當我移動到另一個片段並旋轉屏幕時，這種方式可行，我在下面的錯誤點出現在我試圖保存的edittext字段中。有沒有人知道我在這裏做錯了什麼。我得到一個NullPointerException但我不知道爲什麼。謝謝！

顯示java.lang.NullPointerException：嘗試上的空對象引用調用虛擬方法android.view.View android.view.View.findViewById（int）的'

錯誤點，

的EditText teamAname =（EditText）mView.findViewById（R.id.teamAname）;

//Save data 
@Override 
public void onSaveInstanceState(Bundle savedInstanceState) { 
    setUserVisibleHint(false); 

    savedInstanceState.putInt("TeamATry", TeamATry); 
    savedInstanceState.putInt("TeamBTry", TeamBTry); 
    EditText teamAname = (EditText) mView.findViewById(R.id.teamAname); 
    teamAname.setInputType(InputType.TYPE_CLASS_TEXT); 
    String teamAnametext = teamAname.getText().toString(); 
    EditText teamBname = (EditText) mView.findViewById(R.id.teamBname); 
    teamBname.setInputType(InputType.TYPE_CLASS_TEXT); 
    String teamBnametext = teamBname.getText().toString(); 
    savedInstanceState.putInt("TeamAConvert", TeamAConvert); 
    savedInstanceState.putInt("TeamBConvert", TeamBConvert); 
    savedInstanceState.putInt("TeamAPenalty", TeamAPenalty); 
    savedInstanceState.putInt("TeamBPenalty", TeamBPenalty); 
    savedInstanceState.putInt("TeamAScore", TeamAscore); 
    savedInstanceState.putInt("TeamBScore", TeamBscore); 
    savedInstanceState.putString("TeamAname", teamAnametext); 
    savedInstanceState.putString("TeamBname", teamBnametext); 
    super.onSaveInstanceState(savedInstanceState); 
    Log.i("4", teamAnametext + "Saved"); 
    Log.i("4", "Match Frag Scores saved"); 
    super.onSaveInstanceState(savedInstanceState); 
} 

OnCreateView代碼

@Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     super.onCreateView(inflater, container, savedInstanceState); 
     //Inflate rugby layout 
     View rootview = inflater.inflate(R.layout.rugbycounter, container, false); 
     this.mView = rootview; 
     //This will show the menu 
     setHasOptionsMenu(true); 

     //Load saved state 
     if(savedInstanceState!=null) 
     { 
      teamAnametext = savedInstanceState.getString("TeamAname"); 
      teamBnametext = savedInstanceState.getString("TeamBname"); 
      TeamATry = savedInstanceState.getInt("TeamATry"); 
      TeamBTry = savedInstanceState.getInt("TeamBTry"); 
      TeamAConvert = savedInstanceState.getInt("TeamAConvert"); 
      TeamBConvert = savedInstanceState.getInt("TeamBConvert"); 
      TeamAPenalty = savedInstanceState.getInt("TeamAPenalty"); 
      TeamBPenalty = savedInstanceState.getInt("TeamBPenalty"); 
      TeamAscore = savedInstanceState.getInt("TeamAScore"); 
      TeamBscore = savedInstanceState.getInt("TeamBScore"); 
      Log.i("Assign4", "Score values restored"); 
     } 
     return rootview; 
    } 

Rugbycounter.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 

    xmlns:android="http://schemas.android.com/apk/res/android"> 
    <!--Scrollview to handle horizontal orientation--> 
    <ScrollView 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent"> 
     <!--Linear Layout for top section of buttons--> 
     <LinearLayout 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:orientation="vertical" 
      > 
      <!--Table layout with two columns--> 
      <TableLayout 
       android:id="@+id/tableLayout1" 
       android:layout_width="fill_parent" 
       android:layout_height="fill_parent" 
       android:stretchColumns="0,1" 
       android:layout_marginTop="10dp" 
       android:divider="@color/actionbar_background" 
       android:showDividers="middle" 
       android:dividerPadding="5dp"> 

       <TableRow 
        android:id="@+id/tableRow1" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:layout_marginTop="10dp" 
        android:layout_marginBottom="10dp"> 

        <EditText 
         android:layout_width="fill_parent" 
         android:layout_height="wrap_content" 
         android:id="@+id/teamAname" 
         android:text="@+id/teamAname" 
         android:hint="@string/hintEnterTeamA" 
         android:layout_column="0" 
         android:gravity="center" 
         android:freezesText="true" > 
        </EditText> 

        <EditText 
         android:layout_width="fill_parent" 
         android:layout_height="wrap_content" 
         android:id="@+id/teamBname" 
         android:text="@+id/teamBname" 
         android:hint="@string/hintEnterTeamB" 
         android:layout_column="1" 
         android:gravity="center" 
         android:freezesText="true" 
         android:layout_marginStart="1dp"> 
        </EditText> 

       </TableRow> 

       <TableRow 
        android:id="@+id/tableRow2" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:layout_marginTop="10dp" 
        android:layout_marginBottom="10dp"> 

        <TextView 
         android:textAppearance="?android:attr/textAppearanceLarge" 
         android:text="@+id/teamAscore" 
         android:id="@+id/teamAscore" 
         android:layout_column="0" 
         android:gravity="center" 
         android:textSize="50sp" 
         android:textStyle="bold" 
         android:singleLine="true" 
         android:freezesText="true" > 
        </TextView> 

        <TextView 
         android:textAppearance="?android:attr/textAppearanceLarge" 
         android:text="@+id/teamBscore" 
         android:id="@+id/teamBscore" 
         android:layout_column="1" 
         android:gravity="center" 
         android:textStyle="bold" 
         android:textSize="50sp" 
         android:freezesText="true" > 
        </TextView> 

       </TableRow> 

       <TableRow 
        android:id="@+id/tableRow3" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:layout_marginTop="10dp" 
        android:layout_marginBottom="10dp"> 

        <Button 
         style="?android:attr/buttonStyleSmall" 
         android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="@string/penalty3" 
         android:id="@+id/aPenalty" 
         android:layout_marginLeft="10dp" 
         android:layout_marginRight="10dp" 
         android:layout_column="0" /> 

        <Button 
         style="?android:attr/buttonStyleSmall" 
         android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="@string/penalty3" 
         android:id="@+id/bPenalty" 
         android:layout_marginLeft="10dp" 
         android:layout_marginRight="10dp" 
         android:layout_column="1" /> 

       </TableRow> 

       <TableRow 
        android:id="@+id/tableRow4" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:layout_marginTop="10dp" 
        android:layout_marginBottom="10dp"> 

        <Button 
         style="?android:attr/buttonStyleSmall" 
         android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="@string/conversion2" 
         android:id="@+id/aConversion" 
         android:layout_marginLeft="10dp" 
         android:layout_marginRight="10dp" 
         android:layout_column="0" /> 

        <Button 
         style="?android:attr/buttonStyleSmall" 
         android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="@string/conversion2" 
         android:id="@+id/bConversion" 
         android:layout_marginLeft="10dp" 
         android:layout_marginRight="10dp" 
         android:layout_column="1" /> 

       </TableRow> 

       <TableRow 
        android:id="@+id/tableRow5" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:layout_marginTop="10dp" 
        android:layout_marginBottom="10dp"> 

        <Button 
         style="?android:attr/buttonStyleSmall" 
         android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="@string/try5" 
         android:id="@+id/aTry" 
         android:layout_marginLeft="10dp" 
         android:layout_marginRight="10dp" 
         android:layout_column="0" /> 

        <Button 
         style="?android:attr/buttonStyleSmall" 
         android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="@string/try5" 
         android:id="@+id/bTry" 
         android:layout_marginLeft="10dp" 
         android:layout_marginRight="10dp" 
         android:layout_column="1" /> 

       </TableRow> 

      </TableLayout> 
      <!--Linear layout to create separation between top and bottom layout--> 
      <LinearLayout 
       android:layout_width="fill_parent" 
       android:layout_height="50dp"> 

      </LinearLayout> 
      <!--Linear Layout for bottom 3 buttons--> 
      <LinearLayout 
       android:orientation="horizontal" 
       android:layout_width="match_parent" 
       android:layout_height="0dp" 
       android:layout_weight="2" 
       android:paddingStart="10dp" 
       android:paddingEnd="10dp" 
       android:gravity="center_horizontal"> 

       <Button 
        style="?android:attr/buttonStyleSmall" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="@string/reset" 
        android:id="@+id/resetButton" 
        android:height="50dp" 
        android:layout_marginBottom="10dp" 
        android:layout_marginStart="5dp" 
        android:paddingLeft="10dp" 
        android:paddingRight="10dp"/> 

       <Button 
        style="?android:attr/buttonStyleSmall" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="@string/SUMMARY" 
        android:id="@+id/summaryButton" 
        android:layout_gravity="end" 
        android:height="50dp" 
        android:layout_marginEnd="5dp" 
        android:layout_marginStart="40dp" 
        android:paddingLeft="10dp" 
        android:paddingRight="10dp"/> 

      </LinearLayout> 
     </LinearLayout> 
    </ScrollView> 
</LinearLayout> 

Answer 1

移動所有的findViewById()您onCreateView()方法調用，並使用成員變量，以保持您的EditText字段的引用。您不應該在onSaveInstanceState()方法中調用findViewById()。

在您的片段類定義，定義的EditText字段作爲類的成員變量：（）

public class MyFragment extends Fragment { 
    EditText teamAname; 
    EditText teamBname; 
    //....... 

然後在onCreateView初始化它們：

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    super.onCreateView(inflater, container, savedInstanceState); 
    //Inflate rugby layout 
    View rootview = inflater.inflate(R.layout.rugbycounter, container, false); 

    //Not needed, don't do this: 
    //this.mView = rootview; 

    //This will show the menu 
    setHasOptionsMenu(true); 

    //Add this: 
    teamAname = (EditText) rootview.findViewById(R.id.teamAname); 
    teamBname = (EditText) rootview.findViewById(R.id.teamBname); 
    teamAname.setInputType(InputType.TYPE_CLASS_TEXT); 
    teamBname.setInputType(InputType.TYPE_CLASS_TEXT); 

    //Null check: 
    if (teamAname == null) { 
      Toast.makeText(this, "teamAname null", Toast.LENGTH_LONG).show(); 
    } 

    if (teamBname == null) { 
      Toast.makeText(this, "teamBname null", Toast.LENGTH_LONG).show(); 
    } 

    //Load saved state 
    if(savedInstanceState!=null) 
    { 
     teamAnametext = savedInstanceState.getString("TeamAname"); 
     teamBnametext = savedInstanceState.getString("TeamBname"); 
     TeamATry = savedInstanceState.getInt("TeamATry"); 
     TeamBTry = savedInstanceState.getInt("TeamBTry"); 
     TeamAConvert = savedInstanceState.getInt("TeamAConvert"); 
     TeamBConvert = savedInstanceState.getInt("TeamBConvert"); 
     TeamAPenalty = savedInstanceState.getInt("TeamAPenalty"); 
     TeamBPenalty = savedInstanceState.getInt("TeamBPenalty"); 
     TeamAscore = savedInstanceState.getInt("TeamAScore"); 
     TeamBscore = savedInstanceState.getInt("TeamBScore"); 
     Log.i("Assign4", "Score values restored"); 
    } 
    return rootview; 
} 

然後，EditText上田準備在onSaveInstanceState（）中使用，因此您可以刪除調用findViewById（）：

@Override 
public void onSaveInstanceState(Bundle savedInstanceState) { 
    setUserVisibleHint(false); 

    savedInstanceState.putInt("TeamATry", TeamATry); 
    savedInstanceState.putInt("TeamBTry", TeamBTry); 
    //EditText teamAname = (EditText) mView.findViewById(R.id.teamAname); 
    //teamAname.setInputType(InputType.TYPE_CLASS_TEXT); 
    String teamAnametext = teamAname.getText().toString(); 
    //EditText teamBname = (EditText) mView.findViewById(R.id.teamBname); 
    //teamBname.setInputType(InputType.TYPE_CLASS_TEXT); 
    String teamBnametext = teamBname.getText().toString(); 
    savedInstanceState.putInt("TeamAConvert", TeamAConvert); 
    savedInstanceState.putInt("TeamBConvert", TeamBConvert); 
    savedInstanceState.putInt("TeamAPenalty", TeamAPenalty); 
    savedInstanceState.putInt("TeamBPenalty", TeamBPenalty); 
    savedInstanceState.putInt("TeamAScore", TeamAscore); 
    savedInstanceState.putInt("TeamBScore", TeamBscore); 
    savedInstanceState.putString("TeamAname", teamAnametext); 
    savedInstanceState.putString("TeamBname", teamBnametext); 
    super.onSaveInstanceState(savedInstanceState); 
    Log.i("4", teamAnametext + "Saved"); 
    Log.i("4", "Match Frag Scores saved"); 
    super.onSaveInstanceState(savedInstanceState); 
}