How can I set the focus (and display the keyboard) on my EditText programmatically

Question

I have a layout which contains some views like this:

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Answer 1

I recommend using a LifecycleObserver which is part of the Handling Lifecycles with Lifecycle-Aware Components of Android Jetpack.

I want to open and close the Keyboard when the Fragment/Activity appears. Firstly, define two extension functions for the EditText. You can put them anywhere in your project:

fun EditText.showKeyboard() {
    requestFocus()
    val imm = context.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
    imm.showSoftInput(this, InputMethodManager.SHOW_IMPLICIT)
}

fun EditText.hideKeyboard() {
    val imm = context.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
    imm.hideSoftInputFromWindow(this.windowToken, 0)
}

Then define a LifecycleObserver which opens and closes the keyboard when the Activity/Fragment reaches onResume() or onPause:

class EditTextKeyboardLifecycleObserver(private val editText: WeakReference) :
    LifecycleObserver {

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    fun openKeyboard() {
        editText.get()?.postDelayed({ editText.get()?.showKeyboard() }, 100)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    fun closeKeyboard() {
        editText.get()?.hideKeyboard()
    }
}

Then add the following line to any of your Fragments/Activities, you can reuse the LifecycleObserver any times. E.g. for a Fragment:

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

    // inflate the Fragment layout

    lifecycle.addObserver(EditTextKeyboardLifecycleObserver(WeakReference(myEditText)))

    // do other stuff and return the view

}