​

Jetpack Composes 是什么 ？

Jetpack Compose 是用于构建原生界面的最新的 Android 工具包，采用声明式 UI 的设计，拥有更简单的自定义和实时的交互预览功能，由 Android 官方团队全新打造的 UI 框架

1.选择创建 Empty Compose Activity

2. 保持版本更新

尝试使用最新的 Compose 版本和 Compose 要求的 Kotlin 版本 (1.5.31)

Gradle 版本​: 7.2

可手动在 ​​gradle-wrapper.properties​​ 中更新

gradle-wrapper.properties

#Thu May 26 08:35:05 CST 2022
distributionBase=GRADLE_USER_HOME
distributionUrl=https://services.gradle.org/distributions/gradle-7.2-bin.zip
distributionPath=wrapper/dists
zipStorePath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME

build.gradle.kts (Project)

buildscript {

    val compose_version by extra("1.1.1") // Compose 版本

    repositories {
        google()
        mavenCentral()
    }
    dependencies {

        classpath("com.android.tools.build:gradle:7.1.3")

        // Kotlin 版本，注意：Compose 版本有时候需要要求 Kotlin 到达一定的版本，请同步更新
        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.10")

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle.kts files
    }
}

build.gradle (Project)

buildscript {
    ext {
        compose_version = '1.1.1'
    }
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:7.1.3"'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.6.10"

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

3. 配置 Gradle（可忽略）

您需要将应用的最低 API 级别设置为 21 或更高级别，并在应用的 build.gradle 文件中启用 Jetpack Compose，如下所示。另外还要设置 Kotlin 编译器插件的版本。

build.gradle

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
}

android {
    compileSdk 32

    defaultConfig {
        applicationId "com.example.composestudy"
        minSdk 25
        targetSdk 32
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        vectorDrawables {
            useSupportLibrary true
        }
    }

    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'
    }
    buildFeatures {
        compose true
    }
    composeOptions {
        kotlinCompilerExtensionVersion compose_version
    }
    packagingOptions {
        resources {
            excludes += '/META-INF/{AL2.0,LGPL2.1}'
        }
    }
}

dependencies {

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation "androidx.compose.ui:ui:$compose_version"
    implementation "androidx.compose.material:material:$compose_version"
    implementation "androidx.compose.ui:ui-tooling-preview:$compose_version"
    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
    implementation 'androidx.activity:activity-compose:1.3.1'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
    androidTestImplementation "androidx.compose.ui:ui-test-junit4:$compose_version"
    debugImplementation "androidx.compose.ui:ui-tooling:$compose_version"
}

4. 编写第一个 Compose 程序

现在，如果一切都正常，我们可以看到，MainActivity.kt 上显示以下代码

MainActivity.kt

package com.example.composestudy

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Surface
import androidx.compose.material.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.tooling.preview.Preview
import com.example.composestudy.ui.theme.ComposestudyTheme

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            ComposestudyTheme {
              //这里根据你创建的项目有所不同
                // A surface container using the 'background' color from the theme
                Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background) {
                    Greeting("Android")
                }
            }
        }
    }
}

@Composable
fun Greeting(name: String) {
    Text(text = "Hello $name!")
}

@Preview(showBackground = true)
@Composable
fun DefaultPreview() {
    ComposestudyTheme {
        Greeting("Android")
    }
}

现在，我们将 MainActivity.kt 修改成以下：

MainActivity.kt

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            
        }
    }
}

在明天的中，你将会通过添加不同的元素来构建一个简单的 app