Kotlin Android Util

本库主要包括：

• 日常使用中使用到的Kotlin函数

  示例：

  未添加。

• Retrofit2配合LiveData需要的LiveDataCallAdapterFactory

• 可以与Kotlin协程库配合的CoroutineViewModel

• 基于Kotlin扩展方法的LiveData响应式流操作符（拥有Java静态方法版本），包括但不限于map,mapIndex,merge,flatMap,filter,distinct,throttleFirst,collect,reduce,count,cast,groupBy,timestamp,take,takeWhile,skip,skipUntil,at

  示例1：

  private var isAdd = false
  fun tasks(): MediatorLiveData<List<MutableLiveData<DownloadTask>>> {
      if (!isAdd) {
          val paused = downloadTaskService.getPausedTasks().map { list ->
              list.map {
                  MutableLiveData(it)
              }
          }
          val finished = downloadTaskService.getFinishedTasks().map { list ->
              list.map {
                  MutableLiveData(it)
              }
          }
          val combine = listOf(downloadService.tasks(), paused, finished).mergeList()
          tasks.addSource(combine) {
              tasks.value = it.sortedByDescending { item ->
                  item.value?.createTime?.toDate() ?: Date()
              }
          }
      }
      return tasks
  }

  示例2：

  class WallpaperModel(application: Application) : CoroutineViewModel(application) {
  
      data class Extra(var skip: Int = 0, var isFirstAdd: Boolean = true)
  
      private val wallpaperCache = HashMap<String, Any>()
      private val extraCache = HashMap<String, Any>()
      private val wallpaperRepo = Wallpaper2Repository
      val categoryIndexs = SparseIntArray(4)
  
      var channelIndex = AppSetting.initChannel
  
      fun getAllChannel() = wallpaperRepo.getAllChannel()
  
      fun getCategory(channel: Int, isFilter: Boolean = true): LiveData<List<Category>> {
          val result = wallpaperRepo.getCategory(channel)
          return if (!isFilter) result
          else {
              val set = AppSetting.ignores
              result.map { list ->
                  list.filter { !set.contains(it.key) }
              }
          }
      }
  
      fun getAllCategory(isFilter: Boolean = false): LiveData<List<Category>> {
          return if (!isFilter) wallpaperRepo.getAllCategory()
          else {
              val set = AppSetting.ignores
              wallpaperRepo.getAllCategory().map { list ->
                  list.filter {
                      !set.contains(it.key).apply {
                          wallpaperCache.remove(it.key)
                      }
                  }
              }
          }
      }
  
      fun getWallpaper(category: Category, skip: Int = 0): LiveData<List<Wallpaper>> {
          val key = category.key
          val extra = getCache(extraCache, key) { Extra() }
          extra.skip = skip
          val mediatorLiveData = getCache(wallpaperCache, key) { MediatorLiveData<List<Wallpaper>>() }
          if (extra.isFirstAdd || skip != 0) {
              extra.isFirstAdd = false
              val data = wallpaperRepo.getWallpaper(category, skip)
              mediatorLiveData.addSource(data) { list ->
                  val newList = mutableListOf<Wallpaper>()
                  newList.addAll(mediatorLiveData.value ?: emptyList())
                  newList.addAll(list)
                  mediatorLiveData.value = newList
                  mediatorLiveData.removeSource(data)
              }
          }
          return mediatorLiveData
      }
  
  
      fun skip(category: Category, skip: Int = (getCache(extraCache, category.key) { Extra() }).skip + 20)     {
          getWallpaper(category, skip)
      }
  
  }

• 一个适用于Glide Transition的ColorMatrixTransition

  示例：

  val transitionOptions = ColorMatrixTransitionOptions.withSaturationFade()
  
  fun onBindViewHolder(holder: ViewHolder, item: Wallpaper) {
      super.onBindViewHolder(holder, item)
      holder.load(
          R.id.itemImageView, item.showImage,
          translation = transitionOptions,
          notAnimate = true
      )
  }
  
  fun ImageView.load(
      obj: Any?,
      option: RequestOptions? = null,
      listener: RequestListener<Drawable>? = null,
      translation: TransitionOptions<*, in Drawable>? = null,
      thumbnail: RequestBuilder<Drawable>? = null,
      override: Pair<Int, Int>? = null,
      notAnimate: Boolean = false
  ) {
      val builder = GlideApp.with(this).load(obj)
      if (option != null)
          builder.apply(option)
      if (listener != null)
          builder.listener(listener)
      if (translation != null)
          builder.transition(translation)
      if (thumbnail != null)
          builder.thumbnail(thumbnail)
      if (override != null)
          builder.override(override.first, override.second)
      if (notAnimate)
          builder.dontAnimate()
  
      builder
          .skipMemoryCache(false)
          .into(this)
  }
  
  fun ImageView.clear() {
      GlideApp.with(this).clear(this)
  }
  
  fun ViewHolder.load(
      @IdRes id: Int, obj: Any?,
      option: RequestOptions? = null,
      listener: RequestListener<Drawable>? = null,
      translation: TransitionOptions<*, in Drawable>? = null,
      thumbnail: RequestBuilder<Drawable>? = null,
      override: Pair<Int, Int>? = null,
      notAnimate: Boolean = false
  ) {
      view<ImageView>(id).apply {
          clear()
          load(obj, option, listener, translation, thumbnail, override, notAnimate)
      }
  }

• 利用Kotlin lambda参数简化Android权限申请的PermissionFragment

  示例：

  requestPermissions(Manifest.permission.WRITE_EXTERNAL_STORAGE) { result ->
      if (result) {
          viewModel.save(wallpaper.largeImageURL, "${wallpaper.id}.jpg", listener = downloadListener)
          toast2(getString(R.string.notice_add_download_task))
      } else {
          toast2(getString(R.string.notice_require_permission))
      }
  }

• 利用Kotlin lambda参数简化Android Activity返回值的ResultFragment

  示例：

  startActivityForResult(Intent(context, IgnoreLabelsActivity::class.java)) { resultCode: Int, data:  Intent? ->
      activity?.takeIf { resultCode == Activity.RESULT_OK }?.let {
          //todo fix refresh
          val FIXED_REFRESH = false
          if (FIXED_REFRESH)
              ActivityCompat.recreate(it)
          else {
              it.finish()
              startActivity(Intent(activity, MainActivity2::class.java))
          }
      }
  }

• 一个参照自Kotlin官方的Preference代理类

  示例：

  object Setting {
      var blurPixels: Int by Preference(200)
      var isCustom: Boolean by Preference(false)
      var imagePath: String by Preference("")
      var downloadTask: Long by Preference(0L)
      var darkTheme: Boolean by Preference(false)
  }

• Preference代理类的扩展类PreferenceX

  示例：

  object Setting {
      var enableAnim: Boolean by PreferenceX(true, null, { _: Any?, _: KProperty<*>, value: Boolean ->
          animLiveData.value = value
      })
      val animLiveData: MutableLiveData<Boolean> = MutableLiveData(enableAnim)
  }

• 一个尚未发布的RecyclerView Adapter类：MultiTypeAdapter。利用Kotlin lambda参数简化Adapter的编写，避免为每一个RecyclerView都要生成一个Adapter Class的麻烦，最大程度复用代码，同时提供多类型支持，预加载支持。

  示例1：

          recyclerView.apply {
              val spanCount = if (isPortrait) 2 else 3
              layoutManager = StaggeredGridLayoutManager(spanCount, StaggeredGridLayoutManager.VERTICAL)
              addItemDecoration(SpaceItemDecoration(resources.getDimensionPixelSize(R.dimen.split_small),     spanCount))
              adapter = adapterOf<Favorite> { holder, item ->
                  val position = holder.layoutPosition
                  val height = heightCache.get(position, resources.getDimensionPixelSize  (R.dimen.image_height_normal))
                  holder.load(
                      R.id.itemImageView, item.previewURL,
                      listener = Listener(position, heightCache),
                      override = widthCache to height,
                      notAnimate = true
                  )
                  holder.transitionName(R.id.itemImageView, item.showImage)
                  /*
                    * like bind
                    * */
                  holder.imageResource(R.id.likeButton, R.drawable.ic_favorite_border_white_24dp)
                  viewModel.isLiked(item.showImage).observe(this@FavoriteFragment, Observer { liked ->
                      if (liked) holder.imageResource(R.id.likeButton,    R.drawable.ic_favorite_red_400_24dp)
                      else holder.imageResource(R.id.likeButton, R.drawable.ic_favorite_border_white_24dp)
                  })
                  lateinit var observer: Observer<Boolean>
                  observer = Observer { liked ->
                      if (liked) {
                          Snackbar.make(view, "确定要取消收藏吗", Snackbar.LENGTH_LONG)
                              .also {
                                  it.view.setBackgroundColor(Color.WHITE)
                                  it.view.findViewById<TextView>  (com.google.android.material.R.id.snackbar_text)
                                      .setTextColor(Color.BLACK)
                              }
                              .setAction("确定") {
                                  viewModel.unlike(item.showImage)
                              }
                              .show()
                      } else
                          viewModel.like(item)
                      viewModel.isLiked(item.showImage).removeObserver(observer)
                  }
                  holder.onClick(R.id.likeButton) {
                      viewModel.isLiked(item.showImage).observe(this@FavoriteFragment, observer)
                  }
                  holder.onClick(R.id.downloadButton) {
                      requestPermissions(Manifest.permission.WRITE_EXTERNAL_STORAGE) { result ->
                          if (result) {
                              downloadActionModel.save(item.largeImageURL, "${item.id}.jpg", listener =   downloadListener)
                              toast2(getString(R.string.notice_add_download_task))
                          } else {
                              toast2(getString(R.string.notice_require_permission))
                          }
                      }
                  }
              }.apply {
                  onItemClick = { view, position ->
                      val transitionView = view.findViewById<View>(R.id.itemImageView)!!
                      val bindRecyclerView = view.parent as? RecyclerView
                      bindRecyclerView?.let { recyclerView ->
                          AppSetting.sharedElementEnterPosition = position
                          AppSetting.sharedElementExitPosition = position
                          AppSetting.sharedElementMinPosition = recyclerView.getFirstItemPosition()
                          AppSetting.sharedElementMaxPosition = recyclerView.getLastItemPosition()
                          (recyclerView.adapter as? MultiTypeAdapter)?.data?.let { data ->
                              activity?.let {
                                  val mapData = ArrayList<Wallpaper>(data.map {
                                      val favorite = it.first as Favorite
                                      Wallpaper(
                                          id = favorite.id, category = favorite.category, channel =   favorite.channel,
                                          previewURL = favorite.previewURL, middleImageURL =  favorite.middleImageURL,
                                          largeImageURL = favorite.largeImageURL
                                      )
                                  })
                                  ImagePreviewActivity.navigate(it, mapData, position, transitionView,    transitionView.transitionName ?: "")
                              }
                          }
                      }
                  }
              }
          }

  示例2：

      private fun getAdapter(liveData: LiveData<List<Wallpaper>>): MultiTypeAdapter {
          if (this.adapter != null) return this.adapter!!
          val adapter = adapterOf(mutableListOf(), this::onBindViewHolder).apply {
              onItemClick = { view: View, itemPosition: Int ->
                  val transitionView = view.findViewById<View>(R.id.itemImageView)!!
                  val bindRecyclerView = view.parent as? RecyclerView
                  bindRecyclerView?.let { recyclerView ->
                      AppSetting.sharedElementEnterPosition = itemPosition
                      AppSetting.sharedElementExitPosition = itemPosition
                      AppSetting.sharedElementMinPosition = recyclerView.getFirstItemPosition()
                      AppSetting.sharedElementMaxPosition = recyclerView.getLastItemPosition()
                      (recyclerView.adapter as? MultiTypeAdapter)?.data?.let { data ->
                          activity?.let {
                              val mapData = ArrayList<Wallpaper>(data.map { it.first as Wallpaper })
                              ImagePreviewActivity.navigate(it, mapData, itemPosition, transitionView,    transitionView.transitionName ?: "")
                          }
                      }
                  }
              }
              onPreload = {
                  category?.let { viewModel.skip(it) }
              }
          }
          liveData.observe(this, Observer { newData ->
              adapter.replaceAll(newData.map { it to itemLayoutId })
              loadingPage.removeInParent()
          })
          this.adapter = adapter
          return adapter
      }