Android Slide Up/Down in Kotlin

Animating views to slide up or down can create a dynamic user experience in Android apps. Let's see how to create a slide-up and slide-down animation in Kotlin for Android.

1. Create Animation Resources

Firstly, you need to define the slide-up and slide-down animations in XML:

res/anim/slide_up.xml:

<?xml version="1.0" encoding="utf-8"?>
<translate
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:fromYDelta="100%p"
    android:toYDelta="0%p"
    android:duration="500" />

res/anim/slide_down.xml:

<?xml version="1.0" encoding="utf-8"?>
<translate
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:fromYDelta="0%p"
    android:toYDelta="100%p"
    android:duration="500" />

2. Apply the Animations in Kotlin:

In your Kotlin code (perhaps in an Activity or Fragment), you can load and start the animations as follows:

import android.os.Bundle
import android.view.animation.AnimationUtils
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Load animations
        val slideUp = AnimationUtils.loadAnimation(this, R.anim.slide_up)
        val slideDown = AnimationUtils.loadAnimation(this, R.anim.slide_down)

        // Assuming you have a button or some other view named 'myButton'
        // that you want to animate:

        myButton.setOnClickListener {
            if (viewIsVisible) {
                myView.startAnimation(slideDown)
                myView.visibility = View.GONE
            } else {
                myView.startAnimation(slideUp)
                myView.visibility = View.VISIBLE
            }
            viewIsVisible = !viewIsVisible // Toggle view state
        }
    }

    private var viewIsVisible = true
}

Note: Make sure you have the myView view defined in your XML layout which you want to slide up or down. The viewIsVisible variable is just a simple flag to track the visibility state of the myView.

3. Kotlin Extension (Optional):

To make the code more idiomatic to Kotlin, you can define extension functions:

fun View.slideUp() {
    val slideUp = AnimationUtils.loadAnimation(context, R.anim.slide_up)
    startAnimation(slideUp)
    visibility = View.VISIBLE
}

fun View.slideDown() {
    val slideDown = AnimationUtils.loadAnimation(context, R.anim.slide_down)
    startAnimation(slideDown)
    visibility = View.GONE
}

// Usage:
myView.slideUp()   // to slide up
myView.slideDown() // to slide down

This approach allows you to easily use slideUp() or slideDown() on any view.

Slide up and slide down view animation in Android Kotlin:
Use TranslateAnimation for sliding views:
```
val slideUp = TranslateAnimation(0f, 0f, 0f, -view.height.toFloat())
slideUp.duration = 500
view.startAnimation(slideUp)
```
For sliding down, adjust the TranslateAnimation parameters.

Sliding view pager animation in Android using Kotlin:

Apply a slide animation to ViewPager fragments:

viewPager.setPageTransformer { page, position ->
    val translationX = page.width * -position
    page.translationX = translationX
}

Animate fragment slide in Android with Kotlin:

Use FragmentTransaction for fragment transitions with slide animations:

val transaction = supportFragmentManager.beginTransaction()
transaction.setCustomAnimations(R.anim.slide_in, R.anim.slide_out)
transaction.replace(R.id.container, newFragment)
transaction.addToBackStack(null)
transaction.commit()

Slide transition animation between activities in Android Kotlin:
Utilize overridePendingTransition for slide animations between activities:
```
startActivity(intent)
overridePendingTransition(R.anim.slide_in, R.anim.slide_out)
```