Android游标越界异常

Question

错误是游标索引越界异常，游标为空，无法接收任何内容。

这里是logcat的：

FATAL EXCEPTION: main: com.example.root.notebook, PID: 
    .database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0 
    at android.database.AbstractCursor.checkPosition(AbstractCursor.java:460) 
    at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136) 
    at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50) 
    at com.example.root.notebook.NotebookDbAdapter.cursorToNote(NotebookDbAdapter.java:101) 
    at com.example.root.notebook.NotebookDbAdapter.createNote(NotebookDbAdapter.java:67) 
    at com.example.root.notebook.NoteEditFragment$4.onClick(NoteEditFragment.java:160) 
    at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:163) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:5417) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

NotebookDbAdapter.java

package com.example.root.notebook; 

    import android.content.ContentValues; 
    import android.content.Context; 
    import android.database.Cursor; 
    import android.database.sqlite.SQLiteDatabase; 
    import android.database.sqlite.SQLiteOpenHelper; 
    import android.util.Log; 

    import java.util.ArrayList; 
    import java.util.Calendar; 

    /** 
    * Created by root on 28/04/2016. 
    */ 
    public class NotebookDbAdapter { 

     private static final String DATABASE_NAME="notebook.db"; 
     private static final int DATABASE_VERSION=1; 
     public static final String NOTE_TABLE="note"; 
     public static final String COLUMN_ID="_id"; 
     public static final String COLUMN_TITLE="title"; 
     public static final String COLUMN_MESSAGE="message"; 
     public static final String COLUMN_CATEGORY="category"; 
     public static final String COLUMN_DATE="date"; 

     public String[] allColumns={COLUMN_ID, COLUMN_TITLE, COLUMN_MESSAGE, COLUMN_CATEGORY, COLUMN_DATE}; 

     public static final String CREATE_TABLE_NOTE= " create table " + NOTE_TABLE + " (" 
       + COLUMN_ID +" integer primary key autoincrement, " 
       +COLUMN_TITLE +" text not null, " 
       +COLUMN_MESSAGE+ " text not null, " 
       +COLUMN_CATEGORY+" integer not null, " 
       +COLUMN_DATE+"); "; 
     private SQLiteDatabase sqlDB; 
     private NotebookDbHelper notebookDbHelper; 
     private Context context; 
     public NotebookDbAdapter (Context ctx){ 
      context=ctx; 
     } 

     public NotebookDbAdapter open() throws android.database.SQLException{ 

      notebookDbHelper=new NotebookDbHelper(context); 
      sqlDB=notebookDbHelper.getWritableDatabase(); 

      return this; 

     } 
     public void close(){ 

      notebookDbHelper.close(); 
     } 

     public Note createNote(String title,String message,Note.Category category){ 

      ContentValues values=new ContentValues(); 
      values.put(COLUMN_TITLE,title); 
      values.put(COLUMN_MESSAGE,message); 
      values.put(COLUMN_CATEGORY,category.name()); 
      values.put(COLUMN_DATE, Calendar.getInstance().getTimeInMillis() + ""); 

      long insertId=sqlDB.insert(NOTE_TABLE,null,values); 

      Cursor cursor=sqlDB.query(NOTE_TABLE,allColumns, COLUMN_ID + " = " + insertId , null, null, null, null); 
      cursor.moveToFirst(); 
      Note newNote=cursorToNote(cursor); 
      cursor.close(); 
      return newNote; 

     } 


     public long deleteNote(long idToDelete){ 
      return sqlDB.delete(NOTE_TABLE,COLUMN_ID +" = "+idToDelete ,null); 
     } 
     public long updateNote(long idToUpdate,String newTitle,String newMessage,Note.Category newCategory){ 
      ContentValues values=new ContentValues(); 
      values.put(COLUMN_TITLE,newTitle); 
      values.put(COLUMN_MESSAGE,newMessage); 
      values.put(COLUMN_CATEGORY,newCategory.name()); 
      values.put(COLUMN_DATE, Calendar.getInstance().getTimeInMillis() + ""); 

      return sqlDB.update(NOTE_TABLE, values ,COLUMN_ID + " = " + idToUpdate, null); 

     } 


     public ArrayList<Note> getAllnotes(){ 
      ArrayList<Note> notes=new ArrayList<Note>(); 
      Cursor cursor=sqlDB.query(NOTE_TABLE,allColumns, null ,null ,null ,null ,null); 
      for (cursor.moveToLast(); !cursor.isBeforeFirst(); cursor.moveToPrevious()){ 
       Note note=cursorToNote(cursor); 
       notes.add(note); 
      } 
      cursor.close(); 
      return notes; 

     } 
     private Note cursorToNote(Cursor cursor){ 
      Note newNote=new Note(cursor.getString(1),cursor.getString(2), Note.Category.valueOf(cursor.getString(3)), 
        cursor.getLong(0),cursor.getLong(4)); 
      return newNote; 

     } 
    private static class NotebookDbHelper extends SQLiteOpenHelper{ 


     NotebookDbHelper(Context ctx){ 
      super(ctx,DATABASE_NAME,null,DATABASE_VERSION); 
     } 
     @Override 
     public void onCreate(SQLiteDatabase db) 
     { 
      db.execSQL(CREATE_TABLE_NOTE); 
     } 
     @Override 
     public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){ 

      Log.w(NotebookDbHelper.class.getName(),"upgrading database from version "+ newVersion+"to"+oldVersion+",which will destroy all old data"); 
      db.execSQL("Drop table if exist "+ NOTE_TABLE); 
      onCreate(db); 

     } 
    } 

    } 

Answer 1

替换您如下代码

 cursor.moveToFirst(); 
     Note newNote=cursorToNote(cursor); 
     cursor.close(); 
     return newNote; 

随着

if (cursor != null && cursor.moveToFirst()) { 
      Note newNote=cursorToNote(cursor); 
      cursor.close(); 
      return newNote; 
    } 
    else { 
     return null; 
    } 

Answer 2

试试这个：

public ArrayList<Note> getAllnotes(){ 
     ArrayList<Note> notes=new ArrayList<Note>(); 
     Cursor cursor = sqlDB.rawQuery("SELECT * FROM " + NOTE_TABLE, null); 
     if(cursor.getCount() > 0) { 
      if (cursor.moveToFirst()) { 
       do { 
        Note note=new Note(cursor.getString(1),cursor.getString(2), Note.Category.valueOf(cursor.getString(3)), cursor.getLong(0),cursor.getLong(4)); 
        notes.add(note); 
       } while (cursor.moveToNext()); 
      } 
     } 

     cursor.close(); 
     return notes; 
    }