像RxJava这样的Android EditText Coroutine反跳运算符

编程问答 2022-08-16

问题描述

我需要使EditText具有自动建议功能，并且需要听其输入。以编程方式设置EditText时，我还需要忽略它。

想知道是否有解决方案可以在不使用延迟的情况下使用协同程序对EditText进行去抖动。

解决方法

将文本更改事件转换为Flow 

@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?,before: Int,count: Int) {
        offer(s)
      }
    }
    addTextChangedListener(listener)
    awaitClose { removeTextChangedListener(listener) }
  }.onStart { emit(text) }
}

并使用：

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

是这样的：

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

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

在对协程和流程进行了一些研究之后，我想到了创建自定义EditText的解决方案，该自定义EditText在其中包含了防反跳逻辑，并使我能够附加防反跳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?,p3: Int) {}

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

        addTextChangedListener(textWatcher)

        awaitClose {
            removeTextChangedListener(textWatcher)
        }
    }
}

当我想激活Debounce TextWatcher时，我只是打电话

// 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)
}

在xml中实现DebounceEditText时，焦点出现问题，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中设置输入而无需触发，只需通过调用删除TextWatcher 

debounceEditText.removeOnDebounceTextWatcher()
androidandroidcoroutinecoroutinekotlinkotlinkotlin-coroutines