Could not deserialize object. Class does not define a no-argument constructor.If you are using ProGuard, make sure these constructors are not stripped

Question

https://github.com/neuberfran/JThings/blob/main/app/src/main/java/neuberfran/com/jfran/model/FireFran.kt

I have this POJO above with the error mentioned in the topic. I know it is a mistake already mentioned here, but I have tried several classes (besides this one) and I have not been successful, since my model/POJO class (and Code implementation) is different from several that I saw:(Every help is welcome)

Could not deserialize object. Class does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped (found in field 'value')

Change made to the garagem document, exchanged value for valorb, etc...

Answer 1

The error is very clear, your class "FireFran" doesn't have a no-argument constructor. When you try to deserialize an object from Cloud Firestore, the Android SDKs require that the class must have a default no-arg constructor and also setters that map to each database property.

In Kotlin, the data classes don't provide a default no-arg constructor. So you need somehow ensure the compiler that all the properties have an initial value. You can provide to all of the properties an initial value of null or any other value you find more appropriate.

So your "FireFran" might look like this:

class FireFran(
    var alarmstate: Boolean  = false,
    var garagestate: Boolean = false,
    var id: String? = null,
    var userId: String? = null,
    var value: FireFranValue? = null //Newly added
) {
    //var value: FireFranValue = FireFranValue(false, 0)
    companion object Factory {
        fun create() :FireViewModel = FireViewModel()
        var COLLECTION = "device-configs"
        var DOCUMENT = "alarme"
        var FIELD_userId = "userId"
    }
}

Now adding the properties in the constructor, Kotlin will automatically generate a default no-arg constructor. In this way, the Firebase Android SDK will be able to use. It will also generate setters for each property. Please see that each property is var and not a val, and provides a default null value in case of "id" and "userId".

If don't make this change, you won't be able to use automatic deserialization. You'll have to read the value for each property out of the DocumentSnapshot object and pass them all to Kotlin's constructor.

Edit:

1. In your screenshot, the "value" property is on an object of type "FireFranValue", which has only two properties, "brightness" and "on". To be able to read the data under "value", your "FireFran" class should contain a new property of type "FireFranValue". Please check above the class.

2. If you don't want to use automatic deserialization, you can get the value of each property individually. For example, you can get the value of the "userId" property using DocumentSnapshot's getString(String field) method:

    val userId = snapshot.getString("userId")
   

Edit2:

Your three classes should look like this:

class FireFran(
    var alarmstate: Boolean  = false,
    var garagestate: Boolean = false,
    var id: String? = null,
    var userId: String? = null,
    var owner: String? = null,
    var value: FireFranValue = FireFranValue(false),
    var valorb: FireFranValueB = FireFranValueB(openPercent = 0)
)
data class FireFranValue(
    var on: Boolean // = false
)

data class FireFranValueB(
    var openPercent: Number // = 0
)

Edit3:

class FireFran(
    var alarmstate: Boolean  = false,
    var garagestate: Boolean = false,
    var id: String? = null,
    var userId: String? = null,
    var owner: String? = null,
    var value: FireFranValue? = null,
    var valorb: FireFranValueB? = null
)
data class FireFranValue(
    var on: Boolean? = null
)

data class FireFranValueB(
    var openPercent: Number? = null
)

Now, "on" and "openPercent" will get the values from the database.

Please check the following class declaration:

Answer 2

You can define a no-arg constructor in kotlin like this:

data class SampleClass(
    val field1: String,
    val field2: String
) {
    constructor(): this("", "")
}

Answer 3

First thing: It was not necessary to create the field (map type) called valorb. It was resolved with value.openPercent

As I have two documents (alarme and garagem) I created two POJO classes (FireFran and FireFranB)

https://github.com/neuberfran/JThingsFinal/blob/main/app/src/main/java/neuberfran/com/jfran/model/FireFranB.kt

The secret was to treat the value.on and value.openPercent fields as maps (as facts are):