Android 入门程序 Kotlin版（1）

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myui">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyUI">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id ="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <Button
        android:id ="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text ="@string/click_me" />

    <EditText
        android:id ="@+id/editText1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint ="@string/input_something"
        android:inputType="text"
        android:autofillHints="text" />

    <ImageView
        android:id ="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src ="@drawable/cats"/>

</LinearLayout>

package com.example.myui

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        imageView.setTag(R.drawable.cats)

        button1.setOnClickListener{
            val inputText = editText1.text.toString()
            Toast.makeText(this,inputText, Toast.LENGTH_SHORT).show()
            when(imageView.getTag()){
                R.drawable.cats->{
                    imageView.setImageResource(R.drawable.xq)
                    imageView.setTag(R.drawable.xq)
                }
                R.drawable.xq->{
                    imageView.setImageResource(R.drawable.cats)
                    imageView.setTag(R.drawable.cats)
                }
            }

        }
    }
}

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
}
android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"
    defaultConfig {
        applicationId "com.example.myui"
        minSdkVersion 29
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}
dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.2'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}