How to make primary key as autoincrement for Room Persistence lib
AndroidKotlinAndroid RoomAndroid Problem Overview
I am creating an Entity (Room Persistence Library) class Food, where I want to make foodId
as autoincrement.
@Entity
class Food(var foodName: String, var foodDesc: String, var protein: Double, var carbs: Double, var fat: Double)
{
@PrimaryKey
var foodId: Int = 0
var calories: Double = 0.toDouble()
}
How can I set foodId
an autoincrement field?
Android Solutions
Solution 1 - Android
You need to use the autoGenerate
property
Your primary key annotation should be like this:
@PrimaryKey(autoGenerate = true)
Reference for PrimaryKey.
Solution 2 - Android
You can add @PrimaryKey(autoGenerate = true)
like this:
@Entity
data class Food(
var foodName: String,
var foodDesc: String,
var protein: Double,
var carbs: Double,
var fat: Double
){
@PrimaryKey(autoGenerate = true)
var foodId: Int = 0 // or foodId: Int? = null
var calories: Double = 0.toDouble()
}
Solution 3 - Android
add @PrimaryKey(autoGenerate = true)
@Entity
public class User {
@PrimaryKey(autoGenerate = true)
private int id;
@ColumnInfo(name = "full_name")
private String name;
@ColumnInfo(name = "phone")
private String phone;
public User(){
}
//type-1
public User(String name, String phone) {
this.name = name;
this.phone = phone;
}
//type-2
public User(int id, String name, String phone) {
this.id = id;
this.name = name;
this.phone = phone;
}
}
while storing data
//type-1
db.userDao().InsertAll(new User(sName,sPhone));
//type-2
db.userDao().InsertAll(new User(0,sName,sPhone));
>type-1
> If you are not passing value for primary key, by default it will 0 or > null.
type-2
Put null or zero for the id while creating object (my case user object)
If the field type is long or int (or its TypeConverter converts it to a long or int), Insert methods treat 0 as not-set while inserting the item.
If the field's type is Integer or Long (Object) (or its TypeConverter converts it to an Integer or a Long), Insert methods treat null as not-set while inserting the item.
Solution 4 - Android
Its unbelievable after so many answers, but I did it little differently in the end. I don't like primary key to be nullable, I want to have it as first argument and also want to insert without defining it and also it should not be var.
@Entity(tableName = "employments")
data class Employment(
@PrimaryKey(autoGenerate = true) val id: Long,
@ColumnInfo(name = "code") val code: String,
@ColumnInfo(name = "title") val name: String
){
constructor(code: String, name: String) : this(0, code, name)
}
Solution 5 - Android
This works for me:
@Entity(tableName = "note_table")
data class Note(
@ColumnInfo(name="title") var title: String,
@ColumnInfo(name="description") var description: String = "",
@ColumnInfo(name="priority") var priority: Int,
@PrimaryKey(autoGenerate = true) var id: Int = 0//last so that we don't have to pass an ID value or named arguments
)
Note that the id is last to avoid having to use named arguments when creating the entity, before inserting it into Room. Once it's been added to room, use the id when updating the entity.
Solution 6 - Android
For example, if you have a users
entity you want to store, with fields (firstname, lastname , email)
and you want autogenerated id, you do this.
@Entity(tableName = "users")
data class Users(
@PrimaryKey(autoGenerate = true)
val id: Long,
val firstname: String,
val lastname: String,
val email: String
)
Room will then autogenerate and auto-increment the id
field.
Solution 7 - Android
@Entity(tableName = "user")
data class User(
@PrimaryKey(autoGenerate = true) var id: Int?,
var name: String,
var dob: String,
var address: String,
var gender: String
)
{
constructor():this(null,
"","","","")
}
Solution 8 - Android
Annotate your Entity class with the code below.
In Java:
@PrimaryKey(autoGenerate = true)
private int id;
In Kotlin:
@PrimaryKey(autoGenerate = true)
var id: Int
Room will then auto-generate and auto-increment the id field.
Solution 9 - Android
In the example below when you create a new user pass the parameters as is in the constructor. Room will autogenerate the id. All user object ids are already set to the int default in the id setter so don't call setId
@Entity
public class User {
@PrimaryKey(autoGenerate = true)
private int id;
@ColumnInfo(name = "full_name")
private String name;
@ColumnInfo(name = "phone")
private String phone;
public User(String name, String phone) {
this.name = name;
this.phone = phone;
}
public void setId(int id){
this.id = id;
}
}