How to write the same UI code from two activities in Kotlin?

Issue

I have 2 activities with similar UI layouts, which contain some TextViews in the same place, that receive some text. I want to avoid writing this code twice, so I would like to create a class that will do the writing for both activities. The problem is that I need to pass the ViewBinding pointer to this class and then based on the type write either to Activity1 or Activity2. How can I do this?

Here is a solution that works but I am having to write the same code twice. Assume there are three TextViews.

// Activity1
class MainActivity : AppCompatActivity(), UiCommon {
    private lateinit var uib: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        uib = ActivityMainBinding.inflate(layoutInflater)
        setContentView(uib.root)
        
        // write common part
        val draw = DrawUiCommon(uib)
        draw.draw("a1_text1", "a1_text2", "a1_text3")
    }
}

// Activity2
class MainActivity2 : AppCompatActivity(), UiCommon {
    lateinit var uib: ActivityMain2Binding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        uib = ActivityMain2Binding.inflate(layoutInflater)
        setContentView(uib.root)
        
        // write common part
        val draw = DrawUiCommon(uib)
        draw.draw("a2_text1", "a2_text2","a3_text3")
    }
}

// Common part
class DrawUiCommon(val pt: androidx.viewbinding.ViewBinding){

    fun draw(t1: String, t2: String, t3: String){
        if (pt is ActivityMainBinding){
            pt.textView1.text = t1
            pt.textView2.text = t2
            pt.textView3.text = t3
        }
        else if (pt is ActivityMain2Binding){
            pt.textView1.text = t1
            pt.textView2.text = t2
            pt.textView3.text = t3
        }
    }
}

Solution

You didn't show your layout code, but based on your description, it sounds like you have some views in each activity layout that are the same.

Step 1 - extract those common views into it's own layout that you can resuse.

Step 2 - Reference the included layout:

// Activity2
class MainActivity2 : AppCompatActivity(), UiCommon {
    lateinit var uib: ActivityMain2Binding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        uib = ActivityMain2Binding.inflate(layoutInflater)
        setContentView(uib.root)
        
        // write common part
        val draw = DrawUiCommon(uib.includedLayout) // <-- Use included layout that has the comment views
        draw.draw("a2_text1", "a2_text2","a3_text3")
    }
}

// Common part
class DrawUiCommon(val pt: IncludedLayoutViewBinding ){ // <---Now we know the type

    fun draw(t1: String, t2: String, t3: String){
        //if (pt is ActivityMainBinding){ // <-- No if check needed
            pt.textView1.text = t1
            pt.textView2.text = t2
            pt.textView3.text = t3
        //}
        //else if (pt is ActivityMain2Binding){ // <-- No branch needed
        //    pt.textView1.text = t1
        //    pt.textView2.text = t2
        //    pt.textView3.text = t3
        //}
    }
}

---

OPTIONAL BONUS:

Create a Custom View that encapsulates this common layout and behavior.

Sample activity layout:

<LinearLayour>
    <MyCustomView>
    // OTHER THINGS
</LinearLayour>

Sample Activity:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    uib = ActivityMain2Binding.inflate(layoutInflater)
    setContentView(uib.root)
    
    // write common part
    uib.myCustomView.setValues("a2_text1", "a2_text2","a3_text3")
}

Sample Custom View:

class MyCustomView(...) {
    // Important init stuff up here ...


    fun setValues(t1: String, t2: String, t3: String) {
        // Custom View creates and has its own binding
        binding.textView1.text = t1
        binding.textView2.text = t2
        binding.textView3.text = t3
    }
}

Answered By - dominicoder