Even when I’ve just realised that action bar back button is not completely necessary in my app (because access to all screens are already present in footer menu), I need to understand why it is making my app unresponsive.

To start with necessary information, I’ll first say that my main activity is “TestTypeMenuActivity” and that all activities inherit from a base activity called “BaseActivity”.

Let’s take one of my activities as an example to work with, CollegeSearchActivity:

In my AndroidManifest I define it and set its parent to main activity as follows:

<activity
    android:name=".ui.activities.main.collegesearch.CollegeSearchActivity">
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value=".ui.activities.test.testtypemenu.TestTypeMenuActivity" />
</activity>

In CollegeSearchActivity:

override fun createActionBar() {
    val activityTitle = TMLocale.getStringResourceByResId(R.string.activitycommunity_textview_findcolleges).uppercase()
    super.createActionBar(activityTitle, showBackButton = true, capitalizeTitle = true)
}

In BaseActivity:

fun createActionBar(title: String, showBackButton: Boolean, capitalizeTitle: Boolean){
    if(useToolBar){
        val toolbar = this.createToolbar(title, capitalizeTitle)
        if (toolbar!=null) setSupportActionBar(toolbar)
        supportActionBar?.setDisplayHomeAsUpEnabled(showBackButton)
        val toolbarColor = getActivityTextColor()
        toolbar?.setNavigationIconColor(Color.parseColor(toolbarColor))
    }
}

Extension Methods class:

fun Activity.createToolbar(actionbarTitle: String, capitalizeTitle: Boolean = true): Toolbar? {
    val toolbar = findViewById<Toolbar>(R.id.toolbar)
    if (toolbar != null) {
        this.setActionBarBackground(toolbar)
        val capitalizedTitle = if (capitalizeTitle)
            WordUtils.capitalizeFully(actionbarTitle) else actionbarTitle
        val tvActionBarTitle = toolbar.findViewById<TextView>(R.id.tvActionBarTitle)

        val textColor = BaseActivity.getAppTextColor(context)
        tvActionBarTitle.setTextColor(Color.parseColor(textColor))

        if (tvActionBarTitle != null) tvActionBarTitle.text = capitalizedTitle
    }

    return toolbar
}

Everything was working fine until now, when suddenly back button in action bar started making my app unresponsive, and I cannot figure out why.

The weird thing is that if I insert the next lines -taken from another SO related question- into my BaseActivity the problem just disappear:

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    if (item.itemId == android.R.id.home) {
        super.onBackPressed()
        return true
    }
    return super.onOptionsItemSelected(item)
}

Instead of being “lazy” and just forget about the issue when it is solved just putting that lines below, I need to understand why the problem started happening and why that lines solves it.

Any help?