Question

我目前正在尝试通过查询提供适配器的SQLite数据库来填充ListView，我可以通过添加条目来更新。但是，除非我重新启动应用程序，否则ListView不会更新。

这是我的数据源代码：

public class DataSource {

    // Database fields
    private SQLiteDatabase database;
    private SQLHelper dbHelper;
    private String[] allColumns = null;

    public DataSource(Context context) {
        dbHelper = new SQLHelper(context);
    }

    public void open() throws SQLException {
        database = dbHelper.getWritableDatabase();
    }

    public void close() {
        dbHelper.close();
    }

    public Person addPerson(String firstname, String lastname) {    
        ContentValues values = new ContentValues();
        values.put(SQLHelper.COLUMN_FIRSTNAME, firstname);
        values.put(SQLHelper.COLUMN_LASTNAME, lastname);

        long insertId = database.insert(SQLHelper.TABLE_PEOPLE, null, values);
        Cursor cursor = database.query(SQLHelper.TABLE_PEOPLE, allColumns, SQLHelper.COLUMN_ID + " = " + insertId, null, null, null, null);
        cursor.moveToFirst();
        Person newPerson = cursorToPerson(cursor);
        cursor.close();
        return newPerson;
    }

    public List<Person> getAllPeople() {
        List<Person> people = new ArrayList<Person>();

        Cursor cursor = database.query(SQLHelper.TABLE_PEOPLE, allColumns, null, null, null, null, null);

        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            Person person = cursorToPerson(cursor);
            people.add(person);
            cursor.moveToNext();
        }
        cursor.close();
        return people;
    }

    private Person cursorToPerson(Cursor cursor) {
        if(cursor.getCount() > 0) {
            Person person = new Person();
            person.setId(cursor.getLong(0));
            person.setFirstname(cursor.getString(1));
            person.setLastname(cursor.getString(1));
            return person;
       }
       return null;
    }
}

这是SQLHelper：

public class SQLHelper extends SQLiteOpenHelper {

    // Database
    private static final String DATABASE_NAME = "people.db";
    private static final int DATABASE_VERSION = 1;

    // Table
    public static final String TABLE_PEOPLE = "people";

    // Columns
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_FIRSTNAME = "first_name";
    public static final String COLUMN_LASTNAME = "last_name";

    // Database creation sql statement
    private static final String DATABASE_CREATE = "create table " + TABLE_PEOPLE + "(" + COLUMN_ID + " integer primary key autoincrement, " + COLUMN_FIRSTNAME + " text not null, " + COLUMN_LASTNAME + " text not null);";

    public SQLHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase database) {
        database.execSQL(DATABASE_CREATE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(SQLHelper.class.getName(), "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); 
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_PEOPLE);
        onCreate(db);
    }
}

要填充我的ListView适配器，我调用getAllPeople()方法。要添加到我的数据库，我调用addPerson()方法。 ListView位于对话框中。

为什么我必须重新启动我的应用程序才能让新人更新ListView，这是否有任何特殊原因？

Answer 1

您必须通知适配器有关更改的数据。根据适配器的类型，您需要拨打for (x <- xs; y <- x * x) yield y或swapCursor()

Answer 2

每次添加Person时都调用notifyDataSetChanged吗？

Android - 添加到SQLite数据库后，ListView没有更新，除非重新启动应用程序

2 个答案: