正如@mayurgajra让我意识到的，其他一些代码干扰了textview中的更改。我用一个布尔值解决了这个问题。我在imagebutton事件中将其设置为true，现在我只在布尔值为false时修改其他代码中的textview可见性。

private var deleted: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
        ...
        findViewById<ImageButton>(R.id.delete_btn).setOnClickListener {
            pieChart.visibility = View.GONE
            totalUsage.visibility = View.GONE
            deleted = true
            appsViewModel.removeAll()
            Toast.makeText(this, "Successfully deleted all", Toast.LENGTH_SHORT).show()
        }
}

private fun otherMethod(){
           ...
           if (!deleted) {
                  totalUsage.text = "Total usage today: $hour"
                  totalUsage.visibility = View.VISIBLE
           }
}