创建一个 android sqlite 包含一个只有单行的表

Question

我想创建一个只有一行的 android sqlite 表，用于插入或更新和读取，我该怎么做，因为我只知道如何创建多行

该表仅包含 1 行，用于用户插入数据和存储，读取时数据会出来，最后更新意味着它将覆盖该行中的数据。

这是我的 DBHelperNote.java

 public static final String TABLE_GOAL = "goal";
    public static final String GOAL_ID= "goal_id";
    public static final String GENDER = "gender";
    public static final String AGE = "age";
    public static final String HEIGHT = "height";
    public static final String WEIGHT = "weight";
    public static final String GOAL = "goal";

        private static final String CREATE_TABLE_GOAL = "CREATE TABLE " + TABLE_GOAL + " (" +
                    GOAL_ID + " INTEGER PRIMARY KEY, " +
                    GENDER + " text not null, " +
                    AGE + " text not null, "+
                    HEIGHT + " text not null, "+
                    WEIGHT + " text not null, "+
                    GOAL + " text not null "+
                    " );";

这是 SQLControlerWeight.java

public void insertGoal(String gd,String age,String hg,String wg,,String gl) {
        ContentValues cv = new ContentValues();
        cv.put(DBHelperNote.GENDER, gd);
        cv.put(DBHelperNote.AGE, age);
        cv.put(DBHelperNote.HEIGHT, hg);
        cv.put(DBHelperNote.WEIGHT, wg);
        cv.put(DBHelperNote.GOAL, gl);
        database.insert(DBHelperNote.TABLE_GOAL, null, cv);
    }

    public Cursor readGoal() {
        String[] allColummn = new String[] {
                DBHelperNote.GOAL_ID,
                DBHelperNote.GENDER,
                DBHelperNote.AGE,
                DBHelperNote.HEIGHT,
                DBHelperNote.WEIGHT,
                DBHelperNote.GOAL,
        };
        Cursor c = database.query(DBHelperNote.TABLE_GOAL, allColummn, null,
                null, null, null, null);
        if (c != null) {
            c.moveToFirst();
        }
        return c;
    }

这实际上是读取数据的方法，但它来自数组意味着多行，但我不知道如何将其更改为仅调用一行

dbconnection = new SQLControlerWeight(this);
        dbconnection.openDatabase();

        Cursor cursor = dbconnection.readGoal();

        String[] from = new String[]{
                DBHelperNote.GOAL_ID,
                DBHelperNote.GENDER,
                DBHelperNote.AGE,
                DBHelperNote.HEIGHT,
                DBHelperNote.WEIGHT,
                DBHelperNote.GOAL,
        };
        int[] to = new int[]{
                R.id.goal_id,
                R.id.field_gender,
                R.id.field_age,
                R.id.field_height,
                R.id.field_weight,
                R.id.field_goal,

        };

Answer 1

由于您将插入 GOAL_ID，您可以将插入函数修改为

public void insertGoal(String goal_id, String gd,String age,String hg,String wg,,String gl) {
        ContentValues cv = new ContentValues();
        if (goal_id != null){
            cv.put(DBHelperNote.GOAL_ID, goal_id);
        }
        cv.put(DBHelperNote.GENDER, gd);
        cv.put(DBHelperNote.AGE, age);
        cv.put(DBHelperNote.HEIGHT, hg);
        cv.put(DBHelperNote.WEIGHT, wg);
        cv.put(DBHelperNote.GOAL, gl);
        database.replace(DBHelperNote.TABLE_GOAL, null, cv);
    }

所做的修改是将插入更改为替换，这将确保如果提供了主键值并且行存在具有该 id 的行，那么它将替换现有行而不创建新行。最重要的是用于检查goal_id 是否为null 的if 条件，如果为null 则不要在contentvalue 中提供。

正确修改 if 条件以正确比较 Goal_id，因为我刚刚使用了我可以从您的问题内容中看到的那个。

Answer 2

使用 RawQuery 方法更容易一些。

c1 = db.rawQuery("select * from Table_Name", null); c1.moveToFirst();

做{

 str = c1.getString(c1.getColumnIndex("FieldName"));
 ab.add(str);
} while (c1.moveToNext());