Question

我在游标查询中遇到问题。当我单击listview编辑/删除数据时，错误显示。

LogCat错误显示如下：

12-07 02:40:37.721: E/AndroidRuntime(1482): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myrecordapps/com.example.myrecordapps.EditCourse}: java.lang.IllegalStateException: Couldn't read row 0, col 3 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

我的编码如下所示。

Subject.java

    super.onCreate(savedInstanceState);
    setContentView(R.layout.subject);
    nameList = (ListView) findViewById(R.id.list);
    registerBtn = (Button) findViewById(R.id.addsubject);
    adapter_ob = new DBHandlerCourse(this);

    String[] from = { DBHelperCourse.KEY_COURSE_NAME, DBHelperCourse.KEY_COURSE_CODE, DBHelperCourse.KEY_START_TIME};
    int[] to = { R.id.coursename, R.id.coursecode, R.id.starttime };
    cursor = adapter_ob.queryName();
    @SuppressWarnings("deprecation")
    SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(this,R.layout.row, cursor, from, to);
    nameList.setAdapter(cursorAdapter);
    nameList.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                 long arg3) {
            // TODO Auto-generated method stub
             Bundle passdata = new Bundle();
            Cursor listCursor = (Cursor) arg0.getItemAtPosition(arg2);
            int nameId = listCursor.getInt(listCursor.getColumnIndex(DBHelperCourse.KEY_ID));
            Toast.makeText(getApplicationContext(),Integer.toString(nameId), 500).show();
            passdata.putInt("keyid", nameId);
            Intent passIntent = new Intent(Subject.this,EditCourse.class);
            passIntent.putExtras(passdata);
            startActivity(passIntent);
        }
    });

    registerBtn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            Intent registerIntent = new Intent(Subject.this,
                AddCourse.class);
            startActivity(registerIntent);
        }
    });
}

@SuppressWarnings("deprecation")
@Override
public void onResume() {
    super.onResume();
    cursor.requery();
}

DBHandlerCourse.java

public DBHandlerCourse(Context c) {
    context = c;
}

public DBHandlerCourse opnToRead() {
    openHelper_ob = new DBHelperCourse(context,
    DBHelperCourse.DATABASE_NAME, null, DBHelperCourse.VERSION);
    database_ob = openHelper_ob.getReadableDatabase();
    return this;
}

public DBHandlerCourse opnToWrite() {
    openHelper_ob = new DBHelperCourse(context,
    DBHelperCourse.DATABASE_NAME, null, DBHelperCourse.VERSION);
    database_ob = openHelper_ob.getWritableDatabase();
    return this;
}

public void Close() {
    database_ob.close();
}

public long insertDetails(String courseName, String courseCode, String lecturer, String creditHour, String startTime) {
    ContentValues contentValues = new ContentValues();
    contentValues.put(DBHelperCourse.KEY_COURSE_NAME, courseName);
    contentValues.put(DBHelperCourse.KEY_COURSE_CODE, courseCode);
    contentValues.put(DBHelperCourse.KEY_LECTURER, lecturer);
    contentValues.put(DBHelperCourse.KEY_CREDIT_HOUR, creditHour);
    contentValues.put(DBHelperCourse.KEY_START_TIME, startTime);
    opnToWrite();
    long val = database_ob.insert(DBHelperCourse.TABLE_NAME, null,
    contentValues);
    Close();
    return val;
}

public Cursor queryName() {
    String[] cols = { DBHelperCourse.KEY_ID, DBHelperCourse.KEY_COURSE_NAME,
                      DBHelperCourse.KEY_COURSE_CODE, DBHelperCourse.KEY_START_TIME};
    opnToWrite();
    Cursor c = database_ob.query(DBHelperCourse.TABLE_NAME, cols, null,
    null, null, null, null);

    return c;
}

public Cursor queryAll(int nameId) {
    String[] cols = { DBHelperCourse.KEY_COURSE_NAME, DBHelperCourse.KEY_COURSE_CODE,  DBHelperCourse.KEY_START_TIME };
    opnToWrite();
    Cursor c = database_ob.query(DBHelperCourse.TABLE_NAME, cols,
    DBHelperCourse.KEY_ID + "=" + nameId, null, null, null, null);

    return c;
}

public long updateldetail(int rowId, String courseName, String courseCode, String lecturer, String creditHour, String startTime) {
    ContentValues contentValues = new ContentValues();
    contentValues.put(DBHelperCourse.KEY_COURSE_NAME, courseName);
    contentValues.put(DBHelperCourse.KEY_COURSE_CODE, courseCode);
    contentValues.put(DBHelperCourse.KEY_LECTURER, lecturer);
    contentValues.put(DBHelperCourse.KEY_CREDIT_HOUR, creditHour);
    contentValues.put(DBHelperCourse.KEY_START_TIME, startTime);
    opnToWrite();
    long val = database_ob.update(DBHelperCourse.TABLE_NAME, contentValues,
    DBHelperCourse.KEY_ID + "=" + rowId, null);
    Close();
    return val;
}

public int deletOneRecord(int rowId) {
    // TODO Auto-generated method stub
    opnToWrite();
    int val = database_ob.delete(DBHelperCourse.TABLE_NAME,
    DBHelperCourse.KEY_ID + "=" + rowId, null);
    Close();
    return val;
}

EditCourse.java

DBHandlerCourse regadapter;
DBHelperCourse openHelper;
int rowId;
Cursor c;
String courseNameValue, courseCodeValue, lecturerValue, creditHourValue, startTimeValue;
EditText courseName, courseCode, lecturer, creditHour, startTime;
Button editSubmit, btnDelete;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fragment_edit_course);
    courseName = (EditText) findViewById(R.id.et_course_name);
    courseCode = (EditText) findViewById(R.id.et_course_code);
    lecturer = (EditText) findViewById(R.id.et_lecturer);
    creditHour = (EditText) findViewById(R.id.et_credit_hour);
    startTime = (EditText) findViewById(R.id.et_start_time);
    editSubmit = (Button) findViewById(R.id.btn_update);
    btnDelete = (Button) findViewById(R.id.btn_delete);

    Bundle showData = getIntent().getExtras();
    rowId = showData.getInt("keyid");
    // Toast.makeText(getApplicationContext(), Integer.toString(rowId),
    // 500).show();
    regadapter = new DBHandlerCourse(this);

    c = regadapter.queryAll(rowId);

    if (c.moveToFirst()) {
        do {
            courseName.setText(c.getString(1));
            courseCode.setText(c.getString(2));
            lecturer.setText(c.getString(3));
            creditHour.setText(c.getString(4));
            startTime.setText(c.getString(5));
        } while (c.moveToNext());
    }

    editSubmit.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            regadapter.updateldetail(
                rowId, courseName.getText().toString(),
                courseCode.getText().toString(),
                lecturer.getText().toString(),
                creditHour.getText().toString(),
                startTime.getText().toString());
            finish();
        }
    });
    btnDelete.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            regadapter.deletOneRecord(rowId);
            finish();
        }
    });
}

Answer 1

问题在于：

 if (c.moveToFirst()) {
   do {
       courseName.setText(c.getString(1));
       courseCode.setText(c.getString(2));
       lecturer.setText(c.getString(3));
       creditHour.setText(c.getString(4));
       startTime.setText(c.getString(5));

   } while (c.moveToNext());

您的查询只包含三列：

public Cursor queryAll(int nameId) {
    String[] cols = { DBHelperCourse.KEY_COURSE_NAME, DBHelperCourse.KEY_COURSE_CODE,  DBHelperCourse.KEY_START_TIME };
    opnToWrite();
    Cursor c = database_ob.query(DBHelperCourse.TABLE_NAME, cols,
    DBHelperCourse.KEY_ID + "=" + nameId, null, null, null, null);

    return c;
}

但是你使用的不仅仅是导致IllegalStateException的因素。另请注意，游标索引以0开头。

如何在Android中单击ListView编辑数据库？

Subject.java

DBHandlerCourse.java

EditCourse.java

1 个答案: