我开始编写饮食计划程序项目，这是我的数据库表。我使用外部数据库并在其中定义表外键，然后将其复制到资产文件夹中，然后将其连接到我的项目。
standardUnit，Foods和standardFoodUnit是3个具有静态数据的表，我之前已填充它们，但是EatenFood表在计算后被动态填充。
我使用模型类并尝试使用androidhive database tutorial指令编写databaseAdapter。但是因为我最近启动了android，所以我对此没有任何见识。
尝试阅读书籍或在线教程，但他们让我更加困惑。现在这是我的问题，我想为EatenFood表外键知道如何放置food-id值？我之前在数据库中定义了food_id INTEGER REFERENCES Foods ( _id )，但是在databaseAdapter类中用于插入或更新或获取功能，我不知道该怎么办使用此外键行事。
这是EatenFood桌子的模型课
public class EatenFood {
int eatenfoodid;
boolean breakfast;
boolean lunch;
boolean snack;
boolean appetizers;
boolean dinner;
Data day;
String equivalent;
boolean dairy;
boolean vegetables;
boolean fruit;
boolean meat_bean_egg;
boolean bread_cereals;
boolean fat;
boolean suger;
double unitsum;
int food_id;
public boolean isAppetizers() {
return appetizers;
}
public void setAppetizers(boolean appetizers) {
this.appetizers = appetizers;
}
public Data getDay() {
return day;
}
public void setDay(Data day) {
this.day = day;
}
public double getUnitsum() {
return unitsum;
}
public void setUnitsum(double unitsum) {
this.unitsum = unitsum;
}
public int getFood_id() {
return food_id;
}
public void setFood_id(int food_id) {
this.food_id = food_id;
}
//all remaining getter and setter .........}
餐桌模型类
public class Foods {
int foodid;
String foodname;
boolean breakfast;
boolean lunch;
boolean snack;
boolean appetizers;
boolean dinner;
boolean mainfood;
boolean secondary;
public boolean isAppetizers() {
return appetizers;
}
public void setAppetizers(boolean appetizers) {
this.appetizers = appetizers;
}
public int getFoodid() {
return foodid;
}
public void setFoodid(int foodid) {
this.foodid = foodid;
}
//all remaining getter and setter .........}
DatabaseAdapter函数
public class DatabaseAdapter {
private final String TAG = "DatabaseAdapter";
private DatabaseOpenHelper openHelper;
public Long insertEatenFood(EatenFood eatenfood) {
SQLiteDatabase myDataBase = null;
Long id = -1L;
try {
ContentValues values = new ContentValues();
values.put(TABLE_EATENFOOD_BREAKFAST, eatenfood.isBreakfast());
values.put(TABLE_EATENFOOD_LUNCH, eatenfood.isLunch());
values.put(TABLE_EATENFOOD_SNACK, eatenfood.isSnack());
values.put(TABLE_EATENFOOD_APPETIZERS, eatenfood.isAppetizers());
values.put(TABLE_EATENFOOD_DINNER, eatenfood.isDinner());
// values.put(TABLE_EATENFOOD_DATA, eatenfood.getDay().getClass());
values.put(TABLE_EATENFOOD_EQUIVALENT, eatenfood.getEquivalent());
values.put(TABLE_EATENFOOD_DAIRY, eatenfood.isDairy());
values.put(TABLE_EATENFOOD_VEGETABLES, eatenfood.isVegetables());
values.put(TABLE_EATENFOOD_FRUIT, eatenfood.isFruit());
values.put(TABLE_EATENFOOD_MEAT_BEAN_EGG,
eatenfood.isMeat_bean_egg());
values.put(TABLE_EATENFOOD_BREAD_CEREALS,
eatenfood.isBread_cereals());
values.put(TABLE_EATENFOOD_FAT, eatenfood.isFat());
values.put(TABLE_EATENFOOD_SUGER, eatenfood.isSuger());
values.put(TABLE_EATENFOOD_UNITSUM, eatenfood.getUnitsum());
myDataBase = openHelper.getWritableDatabase();
id = myDataBase.insert(TABLE_EATENFOOD, null, values);
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.getMessage());
} finally {
if (myDataBase != null && myDataBase.isOpen())
myDataBase.close();
}
return id;
}
// update EateanFood table =====================================================
public int updateEatenFood(EatenFood eatenfood) {
SQLiteDatabase myDataBase = null;
int count = -1;
try {
myDataBase = openHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(TABLE_EATENFOOD_BREAKFAST, eatenfood.isBreakfast());
values.put(TABLE_EATENFOOD_LUNCH, eatenfood.isLunch());
values.put(TABLE_EATENFOOD_SNACK, eatenfood.isSnack());
values.put(TABLE_EATENFOOD_APPETIZERS, eatenfood.isAppetizers());
values.put(TABLE_EATENFOOD_DINNER, eatenfood.isDinner());
// values.put(TABLE_EATENFOOD_DATA, eatenfood.getDay().getClass());
values.put(TABLE_EATENFOOD_EQUIVALENT, eatenfood.getEquivalent());
values.put(TABLE_EATENFOOD_DAIRY, eatenfood.isDairy());
values.put(TABLE_EATENFOOD_VEGETABLES, eatenfood.isVegetables());
values.put(TABLE_EATENFOOD_FRUIT, eatenfood.isFruit());
values.put(TABLE_EATENFOOD_MEAT_BEAN_EGG,
eatenfood.isMeat_bean_egg());
values.put(TABLE_EATENFOOD_BREAD_CEREALS,
eatenfood.isBread_cereals());
values.put(TABLE_EATENFOOD_FAT, eatenfood.isFat());
values.put(TABLE_EATENFOOD_SUGER, eatenfood.isSuger());
values.put(TABLE_EATENFOOD_UNITSUM, eatenfood.getUnitsum());
count = myDataBase
.update(TABLE_EATENFOOD, values, TABLE_EATENFOOD_ID + "=?",
new String[] { String.valueOf(eatenfood
.getEatenfoodid()) });
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.getMessage());
} finally {
myDataBase.close();
}
return count;
}
// Getting All EatenFood ================================================
public ArrayList<EatenFood> getEatenfoods() {
ArrayList<EatenFood> result = null;
SQLiteDatabase myDataBase = null;
Cursor cursor = null;
try {
myDataBase = openHelper.getWritableDatabase();
cursor = myDataBase.query(TABLE_EATENFOOD, new String[] { "*" }, null, null,
null, null, null);
if (cursor.moveToFirst()) {
result = new ArrayList<EatenFood>();
do {
result.add(extractEatenFood(cursor));
} while (cursor.moveToNext());
}
} catch (Exception e) {
Log.e(TAG, "Exception: " + e.getMessage());
}
finally {
if (cursor != null) {
cursor.close();
}
myDataBase.close();
}
return result;
}
// extractEatenFood=============================================================
private EatenFood extractEatenFood(Cursor cursor){
EatenFood eatenfood = new EatenFood();
eatenfood.setEatenfoodid(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_ID)));
eatenfood.setBreakfast(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_BREAKFAST)) != 0);
eatenfood.setLunch(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_LUNCH))!=0);
eatenfood.setSnack(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_SNACK))!=0);
eatenfood.setAppetizers(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_APPETIZERS))!=0);
eatenfood.setDinner(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_DINNER))!=0);
// ???????????????????????? baraye day k sabt beshe
eatenfood.setEquivalent(cursor.getString(cursor.getColumnIndex(TABLE_EATENFOOD_EQUIVALENT)));
eatenfood.setDairy(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_DAIRY))!=0);
eatenfood.setVegetables(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_VEGETABLES))!=0);
eatenfood.setFruit(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_FRUIT))!=0);
eatenfood.setBread_cereals(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_BREAD_CEREALS))!=0);
eatenfood.setFat(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_FAT))!=0);
eatenfood.setSuger(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_SUGER))!=0);
eatenfood.setFood_id(cursor.getInt(cursor.getColumnIndex(TABLE_EATENFOOD_F_FOODID)));
return eatenfood ;
}
最佳答案
每当您要将食物添加到eatenfood表中时。您必须在特定食物对象上调用getFoodid函数并获取food_id，然后在insertEatenFood类中使用DatabaseAdapter函数将其插入数据库。
最好是提及自己是问题的完整例子，这样可以更轻松地为您提供帮助。
也许您有一个关于如何找到要插入到eatenfood表中的food_id的问题。最好写出自己是算法的算法，然后找出不同用户所需的food_id。
关于java - 动态表中已初始化的外键，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/26448300/