Change singleapp to fragment, put toolbar in activity, add search bar

app/src/main/java/com/illusionware/npsbrowser/activities/MainActivity.kt

@@ -2,18 +2,26 @@ package com.illusionware.npsbrowser.activities
 
 import android.os.Bundle
 import android.view.MenuItem
+import androidx.fragment.app.FragmentManager
 import com.illusionware.npsbrowser.R
 import com.illusionware.npsbrowser.fragments.mainactivity.MainActivityFragment
 
-class MainActivity : BaseActivity() {
+class MainActivity : BaseActivity(), FragmentManager.OnBackStackChangedListener  {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setTheme(R.style.NPSTheme)
         setContentView(R.layout.activity_main)
+        setSupportActionBar(findViewById(R.id.toolbar))
+        supportFragmentManager.addOnBackStackChangedListener(this);
+
+        if (supportFragmentManager.backStackEntryCount > 0) {
+            showUpButton()
+        }
+
         if (savedInstanceState == null) {
             supportFragmentManager.beginTransaction()
-                .replace(R.id.container, MainActivityFragment.newInstance())
+                .replace(R.id.container, MainActivityFragment())
                 .commitNow()
         }
     }
@@ -28,12 +36,20 @@ class MainActivity : BaseActivity() {
         return super.onOptionsItemSelected(item)
     }
 
-    fun showUpButton() {
+    override fun onBackStackChanged() {
+        // enable Up button only  if there are entries on the backstack
+        if (supportFragmentManager.backStackEntryCount < 1) {
+            hideUpButton()
+        } else {
+            showUpButton()
+        }
+    }
+
+    private fun showUpButton() {
         supportActionBar!!.setDisplayHomeAsUpEnabled(true)
     }
 
-    fun hideUpButton() {
+    private fun hideUpButton() {
         supportActionBar!!.setDisplayHomeAsUpEnabled(false)
     }
-
 }