Android MVVM+Retrofit+协程实践

本文用到的组件：

ViewModel
LiveData
Retrofit
Coroutine

废话不多说，直接上代码，写个简易框架。

添加依赖

        //ViewModel+LiveData+lifecycle && 协程扩展库
        def lifecycle_version = "2.2.0"
        // ViewModel
        api "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
        // LiveData
        api "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
        // Lifecycles only (without ViewModel or LiveData)
        api "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version"

BaseViewModel

abstract class BaseViewModel : ViewModel() {
    /**
     * 协程状态管理
     *
     * 开始 CoroutineState.START
     * 刷新 CoroutineState.REFRESH
     * 结束 CoroutineState.FINISH
     * 异常 CoroutineState.ERROR
     */
    val statusLiveData: MutableLiveData<CoroutineState> by lazy {
        MutableLiveData<CoroutineState>()
    }

    fun launch(refresh: Boolean = true, block: Block) {
        viewModelScope.launch {
            try {
                if (refresh) {
                    statusLiveData.value = CoroutineState.REFRESH
                } else {
                    statusLiveData.value = CoroutineState.START
                }
                block()
                statusLiveData.value = CoroutineState.FINISH
            } catch (e: Exception) {
                statusLiveData.value = CoroutineState.ERROR
                //处理协程异常
            }
        }
    }
}

Alias.kt

internal typealias Block = suspend CoroutineScope.() -> Unit

CoroutineState

/**
 * 协程状态
 */
enum class CoroutineState {
    START,
    REFRESH,
    FINISH,
    ERROR
}

BaseActivity

abstract class BaseActivity<T : BaseViewModel> : BaseSimpleActivity() {
    protected lateinit var viewModel: T

    override fun initViewModel() {
        super.initViewModel()
        viewModel = createViewModel()
        initViewModelActions()
    }

    private fun initViewModelActions() {
        viewModel.statusLiveData.observe(this, Observer { status ->
            status?.run {
                when (this) {
                    CoroutineState.START -> {//协程开始
                        Log.d("coroutine", "开始")
                    }
                    CoroutineState.REFRESH -> {//协程开始&&进度菊花圈
                        Log.d("coroutine", "刷新")
                        DialogHelper.getInstance().showProgress(this@BaseActivity)
                    }
                    CoroutineState.FINISH -> {//协程结束
                        Log.d("coroutine", "结束")
                        DialogHelper.getInstance().dismissProgress()
                    }
                    CoroutineState.ERROR -> {//协程异常
                        Log.d("coroutine", "异常")
                        DialogHelper.getInstance().dismissProgress()
                    }
                }
            }
        })
    }

    abstract fun createViewModel(): T

    fun launch(block: Block) {
        lifecycleScope.launch {
            try {
                block()
            } catch (e: Exception) {
                //异常处理
            }
        }

    }
}

BaseSimpleActivity

abstract class BaseSimpleActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(getContentView())
        initViewModel()
        initImmersionBar()
        initView(savedInstanceState)
        initData(savedInstanceState)
    }

    private fun initImmersionBar() {
        immersionBar {
            barColor(R.color.colorPrimary)
        }
    }

    open fun initViewModel(){

    }

    abstract fun getContentView(): Int

    abstract fun initData(savedInstanceState: Bundle?)

    abstract fun initView(savedInstanceState: Bundle?)
}

对于ViewmModel和LiveData还不太了解的同学可以移步ViewmModel、LiveData

下面写个示例，请求wanandroid接口。

LoginViewModel

class LoginViewModel : BaseViewModel() {
    val contentLiveData: MutableLiveData<String> by lazy {
        MutableLiveData<String>()
    }

    fun getChapters() {
        launch {
            val service = ApiServiceUtil.getApiService<LoginApiService>()
            val chapters = withContext(Dispatchers.IO) {
                service.getChapters()
            }
            val json = Gson().toJson(chapters)
            contentLiveData.value = json
        }
    }
}

Retrofit 2.6.0版本之后支持suspend函数无缝对接协程

interface LoginApiService : BaseService {
    @GET("/wxarticle/chapters/json")
    suspend fun getChapters(): Chapters
}

实体类 Chapters

data class Chapters(
    val `data`: List<Data>,
    val errorCode: Int,
    val errorMsg: String
)

data class Data(
    val children: List<Any>,
    val courseId: Int,
    val id: Int,
    val name: String,
    val order: Int,
    val parentChapterId: Int,
    val userControlSetTop: Boolean,
    val visible: Int
)

ApiServiceUtil

object ApiServiceUtil {
    private val map = mutableMapOf<Class<*>, Any?>()

    inline fun <reified T> getApiService() =
        getService(T::class.java)

    @Suppress("UNCHECKED_CAST")
    fun <T> getService(type: Class<T>): T {
        return if (map.containsKey(type)) {
            map[type] as T
        } else {
            val temp = Api.getInstance().retrofit.create(type)
            map[type] = temp
            temp
        }
    }
}

LoginActivity

class LoginActivity : BaseActivity<LoginViewModel>() {
    override fun createViewModel() = ViewModelProvider(this)[LoginViewModel::class.java]

    override fun getContentView() = R.layout.activity_login

    override fun initData(savedInstanceState: Bundle?) {
    }

    override fun initView(savedInstanceState: Bundle?) {
        viewModel.contentLiveData.observe(this, Observer<String> { content ->
            tvLogin.text = content
        })

        tvLogin.setSingleClick {
            viewModel.getChapters()
        }
    }
}

activity_login.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.LoginActivity">

    <TextView
        android:id="@+id/tvLogin"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ellipsize="end"
        android:maxLines="5"
        android:text="HTTP"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

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