Android EditText 协程去抖动运算符，如 RxJava

Question

我需要使 EditText 具有自动建议功能，并且我需要听取其输入。以编程方式设置时，我还需要忽略 EditText 更改。

想知道是否有解决方案可以在这种情况下使用 Coroutines 使 EditText 去抖动而不使用延迟。

Answer 1

将文本更改事件转为 Flow

使用 kotlinx.coroutines 1.5.0

@ExperimentalCoroutinesApi
@CheckResult
fun EditText.textChanges(): Flow<CharSequence?> {
  return callbackFlow<CharSequence?> {
    val listener = object : TextWatcher {
      override fun afterTextChanged(s: Editable?) = Unit
      override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) = Unit
      override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
        trySend(s)
      }
    }
    addTextChangedListener(listener)
    awaitClose { removeTextChangedListener(listener) }
  }.onStart { emit(text) }
}

并使用：

editText.textChanges().debounce(300)
    .onEach { ... }
    .launchIn(lifecycleScope)

和这样的事情：

fun executeSearch(term: String): Flow<SearchResult> { ... }

editText.textChanges()
    .distinctUntilChanged()
    .filterNot { it.isNullOrBlank() } 
    .debounce(300)
    .flatMapLatest { executeSearch(it) }
    .onEach { updateUI(it) }
    .launchIn(lifecycleScope)

源代码：https : //github.com/Kotlin-Android-Open-Source/MVI-Coroutines-Flow/blob/master/core/src/main/java/com/hoc/flowmvi/core/FlowBinding.kt#L116

Answer 2

在对协程和 Flow 进行了一些研究之后，我提出了创建自定义 EditText 的解决方案，该解决方案在其中保存去抖逻辑，并使我能够附加去抖 TextWatcher 并在需要时将其删除。这是我的解决方案的代码

class DebounceEditText @JvmOverloads constructor(
    context: Context,
    attributeSet: AttributeSet? = null,
    defStyleAttr: Int = 0
) : AppCompatEditText(context, attributeSet, defStyleAttr) {

    private val debouncePeriod = 600L
    private var searchJob: Job? = null

    @FlowPreview
    @ExperimentalCoroutinesApi
    fun setOnDebounceTextWatcher(lifecycle: Lifecycle, onDebounceAction: (String) -> Unit) {
        searchJob?.cancel()
        searchJob = onDebounceTextChanged()
            .debounce(debouncePeriod)
            .onEach { onDebounceAction(it) }
            .launchIn(lifecycle.coroutineScope)
    }

    fun removeOnDebounceTextWatcher() {
        searchJob?.cancel()
    }

    @ExperimentalCoroutinesApi
    private fun onDebounceTextChanged(): Flow<String> = channelFlow {
        val textWatcher = object : TextWatcher {
            override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}

            override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}

            override fun afterTextChanged(p0: Editable?) {
                offer(p0.toString())
            }
        }

        addTextChangedListener(textWatcher)

        awaitClose {
            removeTextChangedListener(textWatcher)
        }
    }
}

当我想激活 Debounce TextWatcher 时，我只需调用

// lifecycle is passed from Activity/Fragment lifecycle, because we want to relate Coroutine lifecycle with the one DebounceEditText belongs   
debounceEditText.setOnDebounceTextWatcher(lifecycle) { input ->
    Log.d("DebounceEditText", input)
}

我在 xml 中实现 DebounceEditText 时遇到了焦点问题，因此我必须将 clickable、selectable 和 focusableInTouchMode 设置为 true。

    android:focusable="true"
    android:focusableInTouchMode="true"
    android:clickable="true"

如果我想在 DebounceEditText 中设置输入而不触发，只需通过调用删除 TextWatcher

debounceEditText.removeOnDebounceTextWatcher()