android sqlite游标

Question

运行应用程序时出现这些错误

Unable to start activity ComponentInfo{com.rika/com.rika.LatihanActivity}:

android.database.StaleDataException: Access closed cursor

ERROR/AndroidRuntime(299): Caused by: android.database.StaleDataException: Access closed cursor

是游标代码导致的错误吗？

是 Activity 类

public class LatihanActivity extends Activity{
/** Called when the activity is first created. */
private RadioButton radioButton;
private TextView quizQuestion;  

private int rowIndex = 1;
private int questNo=0;
private boolean checked=false;
private boolean flag=true;

private RadioGroup radioGroup;

String[] corrAns = new String[5];

final DatabaseHelper db = new DatabaseHelper(this);

Cursor c1;
Cursor c2;
Cursor c3;

int counter=1;
String label;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    String options[] = new String[19];
 
    
    // get reference to radio group in layout
    final RadioGroup radiogroup = (RadioGroup) findViewById(R.id.rdbGp1);

     // layout params to use when adding each radio button
     LinearLayout.LayoutParams layoutParams = new RadioGroup.LayoutParams(
                RadioGroup.LayoutParams.WRAP_CONTENT,
                RadioGroup.LayoutParams.WRAP_CONTENT);

    try {
            db.createDataBase();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    
    c3 = db.getCorrAns();
    
    
    for(c3.moveToFirst();!c3.isAfterLast(); c3.moveToNext())
    {
        for (int i=0;i<=4;i++)
          {
             //... get data from DB
        corrAns[i]=c3.getString(0);}
    }
    //then you can close it
    c3.close();

    
    ///////////////////////////////////////
    
    radioGroup = (RadioGroup) findViewById(R.id.rdbGp1);
     
    radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // TODO Auto-generated method stub
            for(int i=0; i<radiogroup.getChildCount() ; i++) {
                      RadioButton btn = (RadioButton) radioGroup.getChildAt(i);                   
                       String text;
                          
                 if (btn.isPressed() && btn.isChecked() && questNo < 5)
                  {
                   
                      Log.e("corrAns[questNo]",corrAns[questNo]);
                  
                     if (corrAns[questNo].equals(btn.getText()) && flag==true)
                     {
                     flag=false;
                     checked = true; 
                     }
                     else if(checked==true)
                     {
                     flag=true;
                     checked = false;
                     }

                  }
            }   
        }
    });     
        
   


    quizQuestion = (TextView) findViewById(R.id.TextView01);
         
    displayQuestion();
         


    /*Saves the selected values in the database on the save button*/
    Button btnSave = (Button) findViewById(R.id.btnSave);
    btnSave.setOnClickListener(btnSave_Listener);
    
}
      
    
    


/*Called when save button is clicked*/
private View.OnClickListener btnSave_Listener= new View.OnClickListener() {

    @Override
    public void onClick(View v) {


}
};


private void displayQuestion()  {
    //Fetching data quiz data and incrementing on each click
    
    c1=db.getQuiz_Content(rowIndex);
    
    c2 =db.getAns(rowIndex++);
        
    quizQuestion.setText(c1.getString(0));
        
    radioGroup.removeAllViews();
    
    
    //***
    if (c2.moveToFirst())
    {                       
        for (int i=0;i<=3;i++)
        {
            //Generating and adding 4 radio buttons dynamically 
            radioButton = new RadioButton(this);
            radioButton.setText(c2.getString(0));
            radioButton.setId(i);
            c2.moveToNext();
            radioGroup.addView(radioButton);
        }           
    }

    
}}

它是数据库助手类

public class DatabaseHelper extends SQLiteOpenHelper{

private static String DB_PATH = "/data/data/com.rika/databases/";
private static String DB_NAME = "test.sqlite";
private static String Table_name="Quiz";
private SQLiteDatabase myDataBase;
private SQLiteDatabase myData;
private final Context myContext;



public DatabaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}


public void createDataBase() throws IOException{
    boolean dbExist = checkDataBase();
    if(dbExist){
    //do nothing - database already exist
    }else{
    CopyFiles();
    }
}

private boolean checkDataBase() {
    // TODO Auto-generated method stub
    return false;
}

@SuppressWarnings("null")
private void CopyFiles() throws IOException
{
    FileOutputStream myOutput = null;
    try
    {
        InputStream is = myContext.getAssets().open(DB_NAME);
        File outfile = new File(DB_PATH,DB_NAME);
        outfile.getParentFile().mkdirs();
        outfile.createNewFile();

            if (is == null)
                throw new RuntimeException("stream is null");
            
            else
            {
                FileOutputStream out = new FileOutputStream(outfile);
                // BufferedOutputStream out = new BufferedOutputStream( new FileOutputStream(outfile));
                byte buf[] = new byte[128];
                do {
                int numread = is.read(buf);
                if (numread <= 0) break; out.write(buf, 0, numread); } while (true); is.close(); out.close(); } //AssetFileDescriptor af = am.openFd("world_treasure_hunter_deluxe.apk"); } catch (IOException e) { throw new RuntimeException(e); } } /** * Check if the database already exist to avoid re-copying the file each time you open the application. * @return true if it exists, false if it doesn't */ private boolean checkDataBase(){ SQLiteDatabase checkDB = null; try{ String myPath = DB_PATH + DB_NAME; checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); }catch(SQLiteException e){ } if(checkDB != null){ checkDB.close(); } return checkDB != null ? true : false; } /** * Copies your database from your local assets-folder to the just created empty database in the * system folder, from where it can be accessed and handled. * This is done by transfering bytestream. * */ private void copyDataBase() throws IOException{ //Open your local db as the input stream InputStream myInput = myContext.getAssets().open(DB_NAME); // Path to the just created empty db String outFileName = DB_PATH + DB_NAME; //Open the empty db as the output stream OutputStream myOutput = new FileOutputStream(outFileName); //transfer bytes from the inputfile to the outputfile byte[] buffer = new byte[1024]; int length; while ((length = myInput.read(buffer))>0){
                byte[] buffer = null;
                int length = 0;
                myOutput.write(buffer, 0, length);
            } finally{}

        //Close the streams
        myOutput.flush();
        myOutput.close();
        FileOutputStream myInput = null;
        myInput.close();

}


public void openDataBase() throws SQLException{


String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

}

@Override
public synchronized void close() {

    if(myDataBase != null)
    myDataBase.close();

    super.close();
}

@Override
public void onCreate(SQLiteDatabase db) {
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}


public Cursor getQuiz_Content(int bookId)
{
    String myPath = DB_PATH + DB_NAME;
    myData = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    Cursor cur;
    cur=myData.rawQuery("select Quiz_text from Quiz where Quiz_id='"+bookId+"'",null);
    cur.moveToFirst();
    cur.moveToNext(); 
    return cur;
};


public Cursor getQuiz_List()
{
    String myPath = DB_PATH + DB_NAME;
    myData = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    int i;

    Cursor cur;
    cur=myData.rawQuery("select Quiz_id,Quiz_text,Correct_Answer from Quiz",null);
    cur.moveToFirst();
    i = cur.getCount();
    myData.close();

    return cur; 
};



public Cursor getAns(int quizid)
{
String myPath = DB_PATH + DB_NAME;
myData = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);


Cursor cur;
cur = myData.rawQuery("select Answer from Answers where Quiz_id='"+quizid+"'", null);
cur.moveToFirst();
myData.close();

return cur;
}


public Cursor getAnsList()
{
String myPath = DB_PATH + DB_NAME;
myData = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);


Cursor cur;
cur = myData.rawQuery("select Answer from Answers", null);
cur.moveToFirst();
cur.moveToNext(); 
myData.close();


return cur;
}




public Cursor getCorrAns()
{
String myPath = DB_PATH + DB_NAME;
myData = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);


Cursor cur;
cur = myData.rawQuery("select Correct_Answer from Quiz", null);
cur.moveToFirst();
cur.moveToNext(); 
myData.close();



return cur;
}}

Answer 1

可能在处理任何您尝试做的事情之前，您正在关闭光标。

Cursor cursor = getBaseContext().managedQuery(uri, null, null, null, null);


    for(cursor.moveToFirst();!cursor.isAfterLast(); cursor.moveToNext())
    {
             //... get data from DB
    }
    //then you can close it
    cursor.close();