Android_Review_5

Linear Layout & Click Handler

1. create a project in android studio, and design a layout using constraintLayout style, and add 5 TextViews + 2 Buttons.

   // activity_main.kt
   
   <?xml encoding="utf-8"?>
   
   <androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android=""
    xmlns:app=""
    xmlns:tools=""
    tools:context=".MainActivity"
    android:id=""
   >
   
   <TextView
      android:id="@+id/text_one"
   />
   
   <TextView
       android:id="@+id/text_two"
   />
   
   <TextView
      android:id="@+id/text_three"
   />
   
   <TextView
        android:id="@+id/label_text"
   />
   
   <TextView
        android:id="@+id/info_text"
   />
   
   <Button
        android:id="@+id/button_red"
   />
   
   <Button/
        android:id="@+id/button_blue"
   >
   
   </androidx.constraintlayout.widget.ConstraintLayout>
   

2. to setup properties of TextView and Button.

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

3. source lines of code.

   // MainActivity.kt
   package com.android.example.katesapp
   
   [default modules]
   import androidx.appcompat.app.AppCompatActivity
   import android.os.Bundle
   
   [UI element]
   import android.widget.Button
   import android.widget.TextView
   
   [view]
   import android.view.View
   
   [kotlin]
   import kotlinx.android.synthetic.main.activity_main.*
   
   class MainActivity: AppCompatActivity(){
   
          override fun onCreate(savedInstanceState: Bundle?){
          
                 super.onCreate(savedInstanceState)
                 setContentView(R.layout.activity_main)
                 
                 functionCalled()
          
          
          }
          
          private fun functionCalled(){
          
          
          
          
          }
          
          private fun wrappedFun(){
          
          
          
          }
   
   
   }
   

4. databinding without databind modules and add onClickListner to TexTView & Button.

        // MainActivity.kt
         package com.android.example.katesapp
   
         [default modules]
         import androidx.appcompat.app.AppCompatActivity
         import android.os.Bundle
   
         [UI element]
         import android.widget.Button
         import android.widget.TextView
   
         [view]
         import android.view.View
   
         [kotlin]
         import kotlinx.android.synthetic.main.activity_main.*
   
         class MainActivity: AppCompatActivity(){
   
                override fun onCreate(savedInstanceState: Bundle?){
   
                       super.onCreate(savedInstanceState)
                       setContentView(R.layout.activity_main)
   
                       functionCalled()
   
   
                }
   
                private fun functionCalled(){
                
                       
                     val boxOneText = findViewById<TextView>(R.id.text_one)
                     val boxTwoText = findViewById<TextView>(R.id.text_two)
                     val boxThreeText = findViewById<TextView>(R.id.text_three)
   
                     val rootLayout = findViewById<View>(R.id.constraint_layout)
   
                     val redButton = findViewById<Button>(R.id.button_red)
                     val greenButton = findViewById<Button>(R.id.button_blue)
                     
                     // 將畫面中元件組成一個集合型別 List<> 的實例
                     // 這些集合中的成員皆為 View 型別
                     // val seperateView: List<View> 為宣告
                     // val seperateView: List<View> = ListOf (a, b, c) 為定義
                     
                     val seperateView: List<View> = ListOf (
                  
                       boxOneText, boxTwoText, boxThreeText, 
                       rootLayout, redButton, greenButton
                     
                     )
                     
                     // for-in loop
                     // setOnClickListner  不只可在 Button 也可以在 TextView 上添加
                     for (i in eperateView){
                        i.setOnClickListner{ wrappedFun(it) }
                     }
   
   
   
                }
   
                private fun wrappedFun(view: View){
                
                       when(view.id) {
                       
                           // lambda
                           // {param -> body}
                           // (param) -> {body}
                           
                           // use color class
                           R.id.text_one -> view.setBackgroundColor(Color.BLUE)
                           R.id.text_two -> view.setBackgroundColor(Color.PURPLE)
                           R.id.text_three -> view.setBackgroundColor(Color.GREEN)
                           
                           // use customed color 
                           R.id.button_red -> text_two.setBackgroundResource(R.color.my_pink)
                           R.id.button_blue -> text_one.setBackgroundResource(R.color.my_pink) 
                           
                           else -> view.setBackgroundColor(Color.GREEN)
                       
                       
                       }
   
                }
   
         }