错误是游标索引越界异常，游标为空，什么也没有收到。
这是logcat：
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);
}
}
}
答案 0 :(得分：2)
替换以下代码
cursor.moveToFirst();
Note newNote=cursorToNote(cursor);
cursor.close();
return newNote;
使用
if (cursor != null && cursor.moveToFirst()) {
Note newNote=cursorToNote(cursor);
cursor.close();
return newNote;
}
else {
return null;
}
答案 1 :(得分：0)
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;
}