gradle 配置

Moudle:app gradle

android {

compileSdkVersion 29

buildToolsVersion "29.0.2"

defaultConfig {

applicationId "top.zcwfeng.kotlin"

minSdkVersion 19

targetSdkVersion 29

versionCode 1

versionName "1.0"

testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

//需要自己添加,对应布局文件件

vectorDrawables.useSupportLibrary = true

}

buildTypes {

release {

minifyEnabled false

proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'

}

}

// 需要自己添加dataBinding

dataBinding {

enabled = true

}

}

vectorDrawables.useSupportLibrary = true

对应

app:srcCompat="@drawable/empty_dice"

dataBinding 打开之后就可以不用findViewById

有点像黄油刀ButterKnife的用法

布局文件xml

xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

xmlns:app="http://schemas.android.com/apk/res-auto">

type="top.zcwfeng.kotlin.bean.MyName"/>

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

android:gravity="center_vertical"

tools:context=".MainActivity">

android:id="@+id/dice_image"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_gravity="center_horizontal"

app:srcCompat="@drawable/empty_dice"

tools:src="@drawable/dice_1"/>

android:layout_gravity="center_horizontal"

android:id="@+id/btn_kotlin"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Hello Kotlin"/>

最外层包裹layout

注意MainActivity 的一些写法

。。。

import androidx.databinding.DataBindingUtil

import top.zcwfeng.kotlin.databinding.ActivityMainBinding

。。。

class MainActivity : AppCompatActivity() {

lateinit var databinding:ActivityMainBinding//Kotlin laterinit

var myName:MyName = MyName("Alice")// Class MyName

override fun onCreate(savedInstanceState: Bundle?) {

super.onCreate(savedInstanceState)

//setContentView(R.layout.activity_main)

databinding = DataBindingUtil.setContentView(this,R.layout.activity_main)

databinding.btnKotlin.setOnClickListener {

rollDice(it)

}

}

private fun rollDice(view: View) {

var RandomInt = Random().nextInt(6) + 1

//Kotlin-> java switch

var drawableResource = when(RandomInt){

1-> R.drawable.dice_1

2-> R.drawable.dice_2

3-> R.drawable.dice_3

4-> R.drawable.dice_4

5-> R.drawable.dice_5

else -> R.drawable.dice_6

}

// 不需要去findViewById

databinding.apply {

databinding.textName.setText("Finshy")

databinding.diceImage.setImageResource(drawableResource)

invalidateAll()

}

}

}

MyName Class:

data class MyName( var name:String="",var nickName:String="")

小结：

使用了lateinit

lateinit var A:String 不需要 var A:String? = null

使用了dataBinding:binding View bindingData

配置gradle 开关，布局加入layout包裹

使用了Kotlin 的when

定义Kotlin Class