DEV Community: Abdalla Elnaggar

I love Compound View

Abdalla Elnaggar — Sun, 05 Jun 2022 20:45:04 +0000

I love separating a piece of the UI to a compound view;
first here how to do it.
create the view in xml as normal,

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="40dp"
    tools:parentTag="androidx.constraintlayout.widget.ConstraintLayout"
    android:layout_height="76dp"
    >
    <TextView
        tools:text="سبت"
        android:fontFamily="@font/neo_sans_arabic"
        android:textStyle="bold"
        android:textColor="#FE000000"
        android:id="@+id/dayNameTextView"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
</merge>

as you see the parent tag is it will take where you gonna inflate it at as its parent.
we create new class that extends ConstraintLayout and infalte it using viewBinding:

class PlanDayView(context: Context, attributeSet: AttributeSet?=null) :
    ConstraintLayout(context, attributeSet) {
    var binding: FoodPlansDayBinding

    init {
        inflate(context, R.layout.food_plans_day, this)
        binding = FoodPlansDayBinding.bind(this)
    }


    fun render(uiDayView: UiDayView) {
           TODO("")
    }

}

then you make a model represent this Compound View:

data class UiDayView(
    val name: String,
    val number: String,
    val progress: Int,
    val isPassedOrToday: Boolean,
    val isFree: Boolean = false,
    val isSelected: Boolean = false,
    val onClick: (UiDayView)-> Unit,
)

Now you can use this in xml like any normal view
or in code by

val view = PlanDayView(context)

here you made a compound and made UiModel for it and separate a piece of the ui.
here is a question how you use this in viewHolder?.

Digging down for isSuccess() in bad API response

Abdalla Elnaggar — Thu, 02 Jun 2022 17:13:40 +0000

Nothing frustrating than a bad design api, what if you have such api

{
status : "Success",
message : "",
x : {},
y:10
}

as the sample above x can be changed from api to another and some time there is other key along side.
what I want to say every response has status and message but we don't know what it has alongside with it, that task here is to know that if the response came with success or failed,
you can deserialize each response to its object and then check

xResponse.success = "Success"

for each type, that bad and I dont want to do that each time,
I want

xResposne.isSuccess()

there is two solution:
first one is base class and make every response class extend it

open class BaseResponse {
    @SerializedName("Status")
    val status: String = "Failures"
    @SerializedName("Message")
    val message: String = ""
}
fun BaseResponse.isSuccessful(): Boolean {
    if (status == "Success") {
        return true
    }
    return false
}

and then

data class ArticlesResponse(
    @SerializedName("news")
    val news: ArrayList<New>,
    @SerializedName("pageCount")
    val pageCount: Int,
):BaseResponse()

I don't like this solution because every new response class has to extend this base response, this extra for every response.
solution number two is reflection, because we know that every response class has a status property we can use that knowledge to create method that do reflection.
don't forget to add the reflection library
implementation "org.jetbrains.kotlin:kotlin-reflect:1.6.21"
then the actual work

fun Any.isSuccess(): Boolean {
    val clazz = this.javaClass.kotlin
    clazz.memberProperties.forEach {
        if (it.name == "status") {
            val status = it.get(this)
            return status == "Success"
        }
    }
    return false
}

and that is it, the problem with this solution is you get isSuccess() extension method on every class

ViewModel runtime dependencies or not?

Abdalla Elnaggar — Thu, 17 Mar 2022 07:04:04 +0000

We all know ViewModel is build to hold ui state and survive configuration change, so by this given it should retrieve the data needed to create ui state as soon as possible, most of the time that mean when you initialize it, what if you need to pass an id to that ViewModel like postId or articleId, when you use hilt the dependencies of the Viewmodel must be known at compile time if you want Hilt to inject them without any effort, what happen if you want to pass runtime dependencies,
the solution:
first: create @AssistedFactory Annotated Interface

@AssistedFactory
interface UserViewModelAssistedFactory {
    fun create(name: String): UserViewModel
}

second: create factory class or object

class Factory(  
        private val assistedFactory: UserViewModelAssistedFactory,  
        private val name: String,  
    ) : ViewModelProvider.Factory {  
        override fun <T : ViewModel?> create(modelClass: Class<T>): T {  
            return assistedFactory.create(name) as T  
        }
    }

third: inject the factory in fragment and use it to create the viewModle

@Inject 
lateinit var assistedFactory: UserViewModelAssistedFactory  
private val userViewModel: UserViewModel by viewModels {  
    UserViewModel.Factory(assistedFactory, navArgs.name)  
}

this is so much right I felt the same.
it turns out that if your dependices is coming from Navigation argument you can use the provided by defualt SavedStateHandle to get that navArgs, it comes with this version,

implementation 'androidx.navigation:navigation-ui-ktx:2.4.1'

you can access navigation arguments through the saved state handle

@HiltViewModel
class RecentChatViewModel @Inject constructor(
    private val getRecentChatUseCase: GetRecentChatUseCase,
    savedStateHandle: SavedStateHandle
) : ViewModel() {
    private val accountId: Int = RecentChatFragmentArgs.
fromSavedStateHandle(savedStateHandle).accountId

be careful you will need to update your compile sdk to 31 if
you are not.
it is simple right why I had to search so much me and my friend Elfiky to reach out this simple solution.
I copied some code from this article because I am lazy

Gson and R8 force final object to be null at runtime

Abdalla Elnaggar — Fri, 30 Apr 2021 04:29:40 +0000

I had this weird issues that a field is null only on release build, even if I checked it's nullity before access it,
it turns out that R8 when it minify code and you use Gson Library the reflection can alter final fields to be null, WHAT, ya that is the case,final values are able to be modified during reflection - which is how Gson updates final values, that is the statement from one of google employees comment on the issue,

ok how we end up fixing this issue is by adding proguard rule

#Prevent R8 from leaving Data object members always null
-keepclassmembers,allowobfuscation class * {
 @com.google.gson.annotations.SerializedName <fields>;
}

you can check this issue on issue tracker
https://issuetracker.google.com/issues/136600124
I had so many hours trying to check null, build release and try ,so here is the issue and here how to fix it.
I hope it helps any who will face this issue.
I read a couple of posts that advocate against Gson and advertise Moshi, I am starting to believe.