Android_Review_6

Logcat & Lifecycle

1. Lifecycle in Android System.

   onCreate(savedInstanceState: Bundle?){
      super.onCreate(saveInstanceSate)
   }
   
   onStart()
   
   onResume()
   
   onPause()
   
   onStop()
   
   onDestroy()
   
   onRestart()
   
   // called when the user navigates away from the app but might come back 
   onSaveInstanceSate(outSate: Bundle){
       super.onSaveInstanceStae(outState)
   }
   

2. design layout with UI element. And add on Guideline to make a space between ImageView & ImageButton.

   //activity_main.xml
   
   <?xml encoding="utf-8"?>
   
   <layout>
   
       <data>
       </data>
       
       <androidx.constraintlayout.widget.ConstraintLayout
          tools:context=".MainActivity"
       >
       
       <ImageView
         android:id="img"
         android:scaleType="centerCrop"
         android:srcCompat="@drawable/aaa"
       />
       
       <androidx.constraintlayout.widget.Guideline
          android:id="@+id/ggg"
          android:orientation=""
          app:layout_constaintGuide_end="@dimen/default_spacing"
       />
       
       <ImageButton
          android:id="imgB"
          android:scaleType="centerCrop"
          tools:src="@drawable/bbb"
       />
       
       </androidx.constraintlayout.widget.ConstraintLayout>
   
   </layout>
   

3. define dimens.

      // go to app/src/main/res/values/dimens.xml
      
      <?xml encoding="utf-8"?>
      
      <resources>
          <dimen name="default_spacing"> 16dp </dimen>
      </resources>
   

4. define customed color.

       // go to app/src/main/res/values/colors.xml
       
       <?xml encoding="utf-8"?>
       
       <resources>
       
          <color name="white">#ffffff</color>
          <color name="green">#6ab343</color>
          <color name="grey">#99000000</color>
          
       </resources>
   

5. define resorces in app/src/main/res/drawable.

6. design menu resource.

   // go to app/src/main/res/menu
   // main_menu.xml
   
   <?xml encoding="utf-8">
   <menu>
      <item
          android:id="@+id/shareMenuButton"
          android:icon="?android:attr/actionModeShareDrawable"
          android:visible="true"
          andrdoid:enable="true"
          android:showAsAction="ifRoom"
      />
   </menu>
   

7. source line of code.

   package com.example.android.katesapp
   
   [default module]
   import android.os.bundle
   import androidx.appcompat.app.AppCompatActivity
   
   [databind module]
   import androidx.databinding.DataBindingUtil
   import com.example.android.katesapp.databinding.ActivityMainBinding
   
   [system error handler module]
   import android.content.ActivityNotFoundException
   
   [log module]
   import timber.log.Timber
   import android.util.Log
   
   [menu module]
   // TODO
   
   [Toast module]
   // TODO
   
   class MainActivity: AppCompatActivity(){
   
        private lateinit var binding: ActivityMainBinding
   
        override fun onCreate(savedInstanceState: Bundle?){
        
             super.onCreate(savedInstanceState)
             Timber.i("onCreate Phase now!")
             
             // see Anroid_Review_7 to code data class to replace this passing class instance
             kClassInstance = KClass(param)
             
             binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
             
             // to add param as imageID
             binding.imgB.setImageResource()
             
             binding.imgB.setOnClickListener {
                 clickHandler()
             }
             
        }
        
        private fun clickHandler(){
             
             // TODO
             // to update the Image Resource
             binding.img = // TODO
             
        }
   
   }
   

8. android's tip (LifeCycle)

   https://developer.android.com/topic/libraries/architecture/lifecycle