Android_Review_3

Navigation

1. create new project, select default layout called Navigation Drawer Layout stype choices from on of them.

    // activity_main.xml
    
       package com.example.android.katesapp
       
       [default modules]
       import androidx.appcompat.app.AppCompatActivity
       import android.os.Bundle
       
       [databinding modules]
       import androidx.databinding.DataBindingUtil
       import com.example.andorid.katesapp.databinding.ActivityMainBinding
       
       [drawerlayout modules]
       import androidx.drawerlayout.widget.Drawerlayout
       
       [naviagtion modules]
       import androidx.navigation.findNavController //a Public Method to be called
       import androidx.navigation.ui.NavigationUI
       
       class MainActivity: AppCompatActivity(){
       
          private lateinit var drawerLayout: DrawerLayout
       
          override fun onCreate(savedInstanceState: Bundle?){
          
              val binding = DataBinding.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
              
              drawerLayout = binding.drawerLayout
              
              val navController = this.findNavController(R.id.myNavHostFragment)
              
              NavigationUI.setupActionBarWithNavController(this, navController, drawerlayout)
              
              NavigationUI.setupWithNavController(binding.navView, navController)
          
          }
          
       
          /*override fun onSupportNavigateUp(): Boolean {
          
            val navController = findNavController(R.id.myNavHostFragment)
            return navController.navigateUp(appBarConfiguration) || super.onSupportNavigateUp()
           
          }*/
          
          override fun onSupportNavigateUp(): Boolean {
          
             val navController = this.findNavController(R.id.myNavHostFragment)
             return NaviagtionUI.navigateUp(navController, drawerLayout)
          
          }
       
       }
   

2. UI Layout. The NavController instance is binding with the fragment id tagged as myNavHostFragment.

    // activity_main.xml 
    
    <?xml encoding="utf-8"?>
    
    <layout>
    
         <androidx.drawerlayout.widget.DrawerLayout
            android:id="@+id/drawerlayout"
         >
         
             <LinearLayout
                  android:orientation="vertical"
             >
             
                  <fragment
                      android:id="@+id/myNavHostFragment"
                      android:name="androidx.navigation.fragment.NavHostFragment"
                  />
             
             </LinearLayout>
         
         </androidx.drawerlayout.widget.DrawerLayout>
    
    </layout>
   

   ---

3. today's tip (this)

   https://www.kotlincn.net/docs/reference/this-expressions.html

4. today's UI setup sample ( common properties of constraintlayout and ImageView)

   https://github.com/google-developer-training/android-kotlin-fundamentals-apps/blob/master/AndroidTriviaNavigation/app/src/main/res/layout/nav_header.xml