Android MVVM架构Demo（kotlin+databinding+livedata+lifecycle+协程+retrofit）

MVVM优势

主要解决的问题：

• 解耦
• 解决了生命周期问题导致的内存泄漏
• 解决了mvp中的大量接口

MVVM的分层

• View层就是展示数据的，以及接收到用户的操作传递给viewModel层，通过dataBinding实现数据与view的单向绑定或双向绑定
• Model层最重要的作用就是获取数据。（由于使用了协程所以不需要通过接口回调数据）
• ViewModel 层通过调用model层获取数据，以及业务逻辑的处理。
• MVVM中 viewModel 和MVP中的presenter 的作用类似 ，只不过是通过 databinding 将数据与ui进行了绑定。livedata用来通知数据的更新。

V层（activity+xml布局，主要负责UI的显示和交互）

class Main3Activity : AppCompatActivity() {

    companion object {
        @JvmStatic
        fun start(context: Context) {
            val starter = Intent(context, Main3Activity::class.java)
            context.startActivity(starter)
        }
    }

    private lateinit var viewModel: Main3ViewModel
    private lateinit var binding: ActivityMain3Binding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel = ViewModelProvider(this, ViewModelProvider.AndroidViewModelFactory(application)).get(Main3ViewModel::class.java)
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main3)
        binding.lifecycleOwner = this
        binding.viewModel = viewModel

        lifecycleScope.launch {
            viewModel.searchArticle2()
        }
    }

    fun onClick(view: View) {
        when (view) {
            binding.tvTest -> {
                lifecycleScope.launch { viewModel.searchArticle2() }
            }
        }
    }
    
}

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

    <data>

        <variable
            name="viewModel"
            type="com.zhangyu.myjetpack.vm.Main3ViewModel" />
    </data>

    <TextView
        android:id="@+id/tv_test"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:onClick="onClick"
        android:text="@{viewModel.liveData.results.get(0).url}" />

</layout>

VM层（从M层获取数据，处理业务逻辑）

import android.util.Log
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import com.zhangyu.myjetpack.bean.Article
import com.zhangyu.myjetpack.data.ArticleRepository
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response

private const val TAG = "Main3ViewModel"

class Main3ViewModel : ViewModel() {

    private val repository = ArticleRepository()

    var liveData: MutableLiveData<Article> = MutableLiveData()

    //协程，同步方式
    suspend fun searchArticle2() {
        liveData.value = repository.searchRandomData2()
        Log.d(TAG, "searchArticle2: " + liveData.value?.results)
    }

    //线程，异步方式，通过接口回调数据
    fun searchArticle3() {
        repository.searchRandomData3().enqueue(object : Callback<Article> {
            override fun onFailure(call: Call<Article>, t: Throwable) {
                Log.e(TAG, "onFailure: " + t.message)
            }

            override fun onResponse(call: Call<Article>, response: Response<Article>) {
                liveData.value = response.body()
            }
        })
    }
}

M层（获取数据）

private const val TAG = "ArticleRepository"

class ArticleRepository {

    //协程+Retrofit，同步方式
    suspend fun searchRandomData2(): Article {
        return try {
            RetrofitUtil.provide(ArticleService::class.java).getRandomArticle2("福利", "10")
        } catch (e: Exception) {
            Log.e(TAG, "searchRandomData2: " + e.message)
            Article(true, null)//databinding自带空检查所以可以null
        }
    }

    //线程+Retrofit，异步
    fun searchRandomData3(): Call<Article> {
        return RetrofitUtil.provide(ArticleService::class.java).getRandomArticle3("福利", "10")
    }
}

interface ArticleService {
    /**
     * 数据类型：福利 | Android | iOS | 休息视频 | 拓展资源 | 前端
     * 个数： 数字，大于0
     */

    //协程+Retrofit，同步方式
    @GET("api/random/data/{type}/{size}")
    suspend fun getRandomArticle2(@Path("type") type: String?, @Path("size") size: String?): Article

    //线程+Retrofit，异步
    @GET("api/random/data/{type}/{size}")
    fun getRandomArticle3(@Path("type") type: String?, @Path("size") size: String?): Call<Article>
}

package com.zhangyu.myjetpack.bean

data class Article(
        val error: Boolean,
        val results: List<Result>?
)

data class Result(
    val _id: String,
    val createdAt: String,
    val desc: String,
    val publishedAt: String,
    val source: String,
    val type: String,
    val url: String,
    val used: Boolean,
    val who: String
)

网络库的封装

import android.util.ArrayMap
import okhttp3.OkHttpClient
import okhttp3.logging.HttpLoggingInterceptor
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory

object RetrofitUtil {

    const val BASE_URL = "https://gank.io/"

    private fun getRetrofit(): Retrofit {
        val logger = HttpLoggingInterceptor().apply { level = HttpLoggingInterceptor.Level.BASIC }

        val client = OkHttpClient.Builder()
                .addInterceptor(logger)
                .build()

        return Retrofit.Builder()
                .client(client)
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build()
    }

    private val mApis = ArrayMap<String, Any>()

    @Suppress("UNCHECKED_CAST")
    fun <T> provide(apiInterfaceClass: Class<T>): T {
        val api = mApis[apiInterfaceClass.name] as T ?: getRetrofit().create(apiInterfaceClass)
        mApis[apiInterfaceClass.name] = api
        return api
    }

}

Gradle

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'


android {
    compileSdkVersion 30
    buildToolsVersion "30.0.2"

    buildFeatures {
        dataBinding = true
        // for view binding :
        viewBinding = true
    }

	...
	
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        // work-runtime-ktx 2.1.0 and above now requires Java 8
        jvmTarget = "1.8"

        // Enable Coroutines and Flow APIs
        freeCompilerArgs += "-Xopt-in=kotlinx.coroutines.ExperimentalCoroutinesApi"
        freeCompilerArgs += "-Xopt-in=kotlinx.coroutines.FlowPreview"
    }

}

dependencies {
	...
	
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
    implementation 'com.squareup.okhttp3:logging-interceptor:4.7.2'
    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.2.0'
}

本文地址：https://blog.csdn.net/yu540135101/article/details/110628935