java - 如何在 SQLite 中插入和检索数据？

Question

我编写了一个应用程序，我必须将其数据插入 sqlite 数据库并在一个 Activity 中显示它。但我的代码显示“未找到记录”，即使我已插入它。

我尝试使用不同的选项，例如首先将光标移动到第一条记录，然后使用循环迭代该记录。

将数据插入数据库

private void saveToDB() {
        SQLiteDatabase database = new ChildMonitoringAppDBHelper(this).getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(ChildMonitoringAppDBHelper.CHILD_NAME, name.getText().toString());
        values.put(ChildMonitoringAppDBHelper.CHILD_AGE, age.getText().toString());
        values.put(ChildMonitoringAppDBHelper.CHILD_DOB, dob.getText().toString());
        values.put(ChildMonitoringAppDBHelper.CHILD_HEIGHT, height.getText().toString());
        values.put(ChildMonitoringAppDBHelper.CHILD_WEIGHT, weight.getText().toString());
        database.insert(ChildMonitoringAppDBHelper.CHILD_TABLE_NAME, null, values);
        database.close();   
    }

从数据库中检索数据

public ArrayList<Child> readFromDB()
    {
        ArrayList<Child> List = new ArrayList<>();
        SQLiteDatabase database = new ChildMonitoringAppDBHelper(this).getReadableDatabase();
        Cursor cursor = database.rawQuery("select * from " + ChildMonitoringAppDBHelper.CHILD_TABLE_NAME, null);
        cursor.moveToFirst();
        while(!cursor.isAfterLast())
        {
            Child child = new Child(cursor.getString(cursor.getColumnIndex("CHILD_NAME")), cursor.getString(cursor.getColumnIndex("CHILD_AGE")), cursor.getString(cursor.getColumnIndex("CHILD_DOB")), cursor.getString(cursor.getColumnIndex("CHILD_HEIGHT")), cursor.getString(cursor.getColumnIndex("CHILD_WEIGHT")));
            List.add(child);
            cursor.moveToNext();
        }
        cursor.close();
        return List;
    }

它应该显示输入的记录，但它使 toast“未找到记录”。

Answer 1

    Cursor cursor = database.rawQuery("select * from " + ChildMonitoringAppDBHelper.CHILD_TABLE_NAME, null);
    if (cursor.moveToFirst())
    {
        do {
            Child child = new Child(cursor.getString(cursor.getColumnIndex("CHILD_NAME")), cursor.getString(cursor.getColumnIndex("CHILD_AGE")), cursor.getString(cursor.getColumnIndex("CHILD_DOB")), cursor.getString(cursor.getColumnIndex("CHILD_HEIGHT")), cursor.getString(cursor.getColumnIndex("CHILD_WEIGHT")));
            List.add(child);
        } while (cursor.moveToNext());
    }
    cursor.close();
    return List;

您可以尝试一下这段代码并看看它是否适合您吗？