RLQ

Jet_Demo

2020/06/22

Jetpack Demo

1. Demo GitHub

  1. 运用Jetpack技术点：ViewModel, ViewModelProvider.Factory, AbstractSavedStateViewModelFactory, Room, LiveData, MVVM, bindAdapter, lifecycleOwner, Navigate, WorkManager等
  2. demo下载

2. Demo流程

1. DataBase：Dao + Entity + Repository——对plant的增删改查

  1. AppDataBase

    @Database(entities = [GardenPlanting::class, Plant::class], version = 1, exportSchema = false)
@TypeConverters(Converters::class)
abstract class AppDatabase : RoomDatabase() {
		abstract fun gardenPlantingDao(): GardenPlantingDao
    abstract fun plantDao(): PlantDao
       
    private fun buildDatabase(context: Context): AppDatabase {
    return Room.databaseBuilder(context, AppDatabase::class.java, DATABASE_NAME)
                .addCallback(object: RoomDatabase.Callback(){
                    override fun onCreate(db: SupportSQLiteDatabase) {
                        super.onCreate(db)
                    }
                })
                .build()
    }
}

  2. @Entity(tableName = "plants")

  3. @Dao interface PlantDao SQL语句拼接增删改查接口

  4. data class 数据类，连接VM与DB

  5. 对外接口数据操作类

// 这是一个对GardenPlanting 表的操作类
class GardenPlantingRepository private constructor(
    // 私有构造函数
    private val gardenPlantingDao: GardenPlantingDao
) {

    suspend fun createGardenPlanting(plantId: String) {
        val gardenPlanting = GardenPlanting(plantId)
        gardenPlantingDao.insertGardenPlanting(gardenPlanting)
    }

    suspend fun removeGardenPlanting(gardenPlanting: GardenPlanting) {
        gardenPlantingDao.deleteGardenPlanting(gardenPlanting)
    }

    fun isPlanted(plantId: String) = gardenPlantingDao.isPlanted(plantId)

    fun getPlantedGardens() = gardenPlantingDao.getPlantedGardens()

}

2. WorkManager

  1. 将数据内置到assets/plant.json文件中

  2. 创建一个CoroutineWorker，在子线程中执行文件读取和DB操作

    class SeedDatabaseWorker(
    context: Context,
    workerParams: WorkerParameters
): CoroutineWorker(context, workerParams) {
    // 实现doWork
    override suspend fun doWork(): Result = coroutineScope {
        try {
            // 这里就是子线程读取文件，然后插入DB
            applicationContext.assets.open(PLANT_DATA_FILENAME).use { inputStream ->
                // JsonReader 是com.google.gson.stream.JsonReader
                JsonReader(inputStream.reader()).use { jsonReader ->
                    val plantType = object : TypeToken<List<Plant>>() {}.type
                    val plantList: List<Plant> = Gson().fromJson(jsonReader, plantType)
                    val database = AppDatabase.getInstance(applicationContext)
                    database.plantDao().insertAll(plantList)
                    Log.e(TAG, "jsonReader :" + plantList.toString())
                    Result.success()
                }
            }
        } catch (ex: Exception) {
            // 有个异常，没加PLANT_DATA_FILENAME json文件
            Log.e(TAG, "jsonReader222 :", ex)
            Result.failure()
        }
    }
   
    companion object {
        private const val TAG = "SeedDatabaseWorker"
    }
}

  3. 生成DB时，执行后台任务

     private fun buildDatabase(context: Context): AppDatabase {
            return Room.databaseBuilder(context, AppDatabase::class.java, DATABASE_NAME)
                .addCallback(object: RoomDatabase.Callback(){
                    override fun onCreate(db: SupportSQLiteDatabase) {
                        super.onCreate(db)
                        // 子线程操作DB
                        val request = OneTimeWorkRequestBuilder<SeedDatabaseWorker>().build()
                        WorkManager.getInstance(context).enqueue(request)
                    }
                })
                .build()
        }

3. ViewModel 和 Factory

  1. VM 结合

    class GardenPlantingListViewModel internal constructor(
    gardenPlantingRepository: GardenPlantingRepository
) : ViewModel() {
    val plantAndGardenPlantings: LiveData<List<PlantAndGardenPlantings>> =
        gardenPlantingRepository.getPlantedGardens()
}

  2. Factory

    class GardenPlantingListViewModelFactory(
    private val repository: GardenPlantingRepository
) : ViewModelProvider.Factory {
    @Suppress("UNCHECKED_CAST")
    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
        return GardenPlantingListViewModel(repository) as T
    }
}

  3. 在Manager类中奖VM与Factory进行整合

    // 获取我的花园 种植的植物 工厂
    fun provideGardenPlantingListVieModelFactory(context: Context): GardenPlantingListViewModelFactory {
        val repository = getGardenPlantingRepository(context)
        return GardenPlantingListViewModelFactory(
            repository
        )
    }
   
    // 获取种植的花园植物 Dao
    private fun getGardenPlantingRepository(context: Context): GardenPlantingRepository {
        return GardenPlantingRepository.getInstance(
            AppDatabase.getInstance(context.applicationContext).gardenPlantingDao()
        )
    }

4. Layout

  1. 在build.gradle中添加

    android {
		dataBinding {
        enabled =true //允许使用dataBinding
    }
 }

  2. xml布局中添加 , 使用变量 app:isGone="@{viewModel.isPlanted}"

    <layout 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">
   
    <data>
        <variable
                name="hasPlantings"
                type="boolean" />
    </data>
   
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:orientation="vertical"
        app:isGone="@{hasPlantings}">
   
        <TextView
            android:id="@+id/empty_garden"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/garden_empty"
            android:textAppearance="?attr/textAppearanceHeadline5" />
      </LinearLayout>
</layout>

5. Fragment + Adapter

  1. Adapter中新增绑定layout中事件

    @BindingAdapter("isGone")
fun bindIsGone(view: View, isGone: Boolean) {
    view.visibility = if (isGone) {
        View.GONE
    } else {
        View.VISIBLE
    }
}

  2. Fragment中使用binding和Adapter

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentGardenBinding.inflate(inflater, container, false)
        val adapter = GardenPlantingAdapter()
        binding.gardenList.adapter = adapter
        binding.addPlant.setOnClickListener {
            navigateToPlantListPage()
        }
        subscribeUI(adapter, binding)
        return binding.root
    }

  3. 加载VM中的数据

    // 加载数据
    private val viewModel: GardenPlantingListViewModel by viewModels {
        GardenPlantManager.provideGardenPlantingListVieModelFactory(
            requireContext()
        )
    }

6. Navigation

  1. Home页Layout

    <?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
   
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
   
        <fragment
            android:id="@+id/nav_host"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="true"
            app:navGraph="@navigation/nav_garden"/>
   
    </FrameLayout>
   
</layout>

  2. Home页加载UI

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView<ActivityMainBinding>(this, R.layout.activity_main)
    }

  3. 在res/navigation/nav_garden.xml中添加跳转逻辑

    <navigation 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"
    app:startDestination="@id/view_pager_fragment">
   
    <fragment
        android:id="@+id/view_pager_fragment"
        android:name="com.lq.he.sum.home.HomeViewPagerFragment"
        >
   
        <action
                android:id="@+id/action_view_pager_fragment_to_plant_detail_fragment"
                app:destination="@id/plant_detail_fragment"
                app:enterAnim="@anim/slide_in_right"
                app:exitAnim="@anim/slide_out_left"
                app:popEnterAnim="@anim/slide_in_left"
                app:popExitAnim="@anim/slide_out_right" />
   
    </fragment>
   
    <fragment
        android:id="@+id/plant_detail_fragment"
        android:name="com.lq.he.sum.pdetail.PlantDetailFragment"
        tools:layout="@layout/fragment_plant_detail"
        android:label="@string/plant_details_title">
        <argument
            android:name="plantId"
            app:argType="string" />
    </fragment>
   
</navigation>
   
会自动生成
class HomeViewPagerFragmentDirections private constructor() {
  private data class ActionViewPagerFragmentToPlantDetailFragment(
    val plantId: String
  ) : NavDirections {
    override fun getActionId(): Int = R.id.action_view_pager_fragment_to_plant_detail_fragment
   
    override fun getArguments(): Bundle {
      val result = Bundle()
      result.putString("plantId", this.plantId)
      return result
    }
  }
   
  companion object {
    fun actionViewPagerFragmentToPlantDetailFragment(plantId: String): NavDirections =
        ActionViewPagerFragmentToPlantDetailFragment(plantId)
  }
}

  4. 点击跳转

    private fun navigateToPlant(plantId: String, view: View) {
            val direction = HomeViewPagerFragmentDirections.actionViewPagerFragmentToPlantDetailFragment(plantId)
            // 找到的Navigation控制器，然后导航到相应页面，但direction其实就是一个fragment
            view.findNavController().navigate(direction)
        }

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