Menu, Toast, Exception Handler
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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> <variable name="price" type="Integer" /> <variable name="volume" type="Integer" /> </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" /> <TextView android:id="@+id/price" /> <TextView android:id="@+id/volume" /> <ImageButton android:id="imgB" android:scaleType="centerCrop" tools:src="@drawable/bbb" /> </androidx.constraintlayout.widget.ConstraintLayout> </layout> -
define dimens.
// go to app/src/main/res/values/dimens.xml <?xml encoding="utf-8"?> <resources> <dimen name="default_spacing"> 16dp </dimen> </resources> -
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> -
define resorces in app/src/main/res/drawable.
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design menu resource.
// go to app/src/main/res/menu // main_menu.xml <?xml encoding="utf-8"> <menu> <item android:id="@+id/showMenuTouch" android:icon="?android:attr/actionModeShareDrawable" android:visible="true" andrdoid:enable="true" android:showAsAction="ifRoom" /> </menu> -
to create a R.string which is located in file called string.xml under dir res/values/.
<resources> <string name="app_name">Dessert Clicker</string> <string name="dollar_sign">$</string> <string name="zero">0</string> <string name="dessert_sold">Desserts Sold</string> <string name="share_text">I\'ve clicked %1$d Desserts for a total of %2$d$ #AndroidDessertClicker</string> <string name="share">Share</string> <string name="sharing_not_available">Sharing Not Available</string> </resources> -
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 [menu module] import android.view.Menu import android.view.MenuItem [Toast module] import android.widget.Toast class MainActivity: AppCompatActivity(){ // 類別中的共用變數 private var price = 0 private var volume = 0 private lateinit var binding: ActivityMainBinding // 製作資料型別 // create a Data Type // Data Class // it includes the resource id. data class garmin3C(val imgId: Int, val price: Int, val volumn: Int) // 建立集合裝載資料型別的成員 // create a List // 拆解集合為成員 private val allGarmin3C = listOf( garmin3C(R.drawable.watchA, 6990, 5), garmin3C(R.drawable.watchB, 7990, 15), garmin3C(R.drawable.watchC, 19900, 20) ) // 提取集合中的成員，成員有 id、價格、數量等屬性 private var currentWatch = allGarmin3C[0] override fun onCreate(savedInstanceState: Bundle?){ super.onCreate(savedInstanceState) // 綁定 UI 元件 binding = DataBindingUtil.setContentView(this, R.layout.activity_main) // 顯示 UI 元件 binding.imgB.setOnClickListner { clickBuyHandler() } binding.img.setImageResource(currentWatch.imgId) binding.imgB.setImageResource(R.drawable.gotobuy) binding.price = price binding.volumn = volumn } private fun clickBuyHandler() { // update value of volumn when user click on the button to demonstrate he/she wanna buy it volumnAfterBuy-- binding.volumn = volumnAfterBuy showOtherWatch() } private fun showOtherWatch() { // use the data class called allGraminWatch var newWatch = allGarmin3C[0] for (watch in allGarmin3C){ // TODO: an inspection flow if(){ newWatch = watch } } // update image // inspection control flow if(currentWatch != newWatch){ currentWatch = newWatch biding.img.setImageResource(newWatch.imageId) } } // Menu to be inflated override fun onCreateOptionsMenu(menu: Menu): Boolean { menuInflater.inflate(R.menu.main_menu, menu) return super.onCreateOptionsMenu(menu) } // Items to be selected override fun onOptionsItemSelected(item: MenuItem): Boolean { // lambda // (itemId) -> {body} // {itemId -> body} when(item.itemId){ R,id.showMenuTouch -> showGarmin() } return super.onOptionsItemSelected(item) } // Exception Handler private fun showGarmin() { // wait to define // see Android_Review_8 // to import core module to call the Intent Builder constructor val showIntent = try { // to start an Avtivity to show the intent to render plain text // see Android_Review_8 } catch(ex: ActivityNotFoundException) { // R.string path see app/src/main/res/values/strings.xml Toast.makeText(this, getString(R.string.sharing_not_available), Toast.LENGTH_LONG).show() } } } -
today's tip (lateinit and lazy)
https://medium.com/@carterchen247/kotlin使用心得-十一-lateinit-vs-lazy-1ef96bc5b3b3
https://medium.com/@yongjhih/lateinit-與-lazy-使用時機-kotlin-53daf0affee4