在 SearchView 中限制 onQueryTextChange

Question

“节流” onQueryTextChange的最佳方法是什么，以便我的performSearch()方法每秒只调用一次，而不是每次用户键入时调用？

public boolean onQueryTextChange(final String newText) {
    if (newText.length() > 3) {
        // throttle to call performSearch once every second
        performSearch(nextText);
    }
    return false;
}

Answer 1

如果您使用 Kotlin 和协程，您可以执行以下操作：

var queryTextChangedJob: Job? = null

...

fun onQueryTextChange(query: String) {

    queryTextChangedJob?.cancel()
    
    queryTextChangedJob = launch(Dispatchers.Main) {
        delay(500)
        performSearch(query)
    }
}

Answer 2

基于 aherrick 的代码，我有一个更好的解决方案。 每次更改查询文本时，声明一个可运行变量并清除处理程序上的回调队列，而不是使用布尔值“canRun”。 这是我最终使用的代码：

@Override
public boolean onQueryTextChange(final String newText) {
    searchText = newText;

    // Remove all previous callbacks.
    handler.removeCallbacks(runnable);

    runnable = new Runnable() {
        @Override
        public void run() {
            // Your code here.
        }
    };
    handler.postDelayed(runnable, 500);

    return false;
}

Answer 3

我想出了一个使用RxJava的解决方案，特别是它的debounce运算符。

使用 Jake Wharton 方便的RxBinding ，我们将拥有：

RxSearchView.queryTextChanges(searchView)
        .debounce(1, TimeUnit.SECONDS) // stream will go down after 1 second inactivity of user
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(new Consumer<CharSequence>() {
            @Override
            public void accept(@NonNull CharSequence charSequence) throws Exception {
                // perform necessary operation with `charSequence`
            }
        });

Answer 4

1. 创建抽象类：

    public abstract class DelayedOnQueryTextListener implements SearchView.OnQueryTextListener { private Handler handler = new Handler(); private Runnable runnable; @Override public boolean onQueryTextSubmit(String s) { return false; } @Override public boolean onQueryTextChange(String s) { handler.removeCallbacks(runnable); runnable = () -> onDelayerQueryTextChange(s); handler.postDelayed(runnable, 400); return true; } public abstract void onDelayedQueryTextChange(String query);

   }

2. 像这样设置它：

    searchView.setOnQueryTextListener(new DelayedOnQueryTextListener() { @Override public void onDelayedQueryTextChange(String query) { // Handle query } });

Answer 5

对于科林

在coroutineScope.launch(Dispatchers.Main) {}的情况下，您可能会遇到问题Suspend function '...' should be called only from a coroutine or another suspend function 。

我找到了以下方法

private var queryTextChangedJob: Job? = null
private lateinit var searchText: String

接下来不要忘记使用implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.3.0-alpha05"

override fun onQueryTextChange(newText: String?): Boolean {

    val text = newText ?: return false
    searchText = text

    queryTextChangedJob?.cancel()
    queryTextChangedJob = lifecycleScope.launch(Dispatchers.Main) {
        println("async work started...")
        delay(2000)
        doSearch()
        println("async work done!")
    }

    return false
}

如果您想在 ViewModel 中使用launch ，请使用implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.3.0-alpha05"

queryTextChangedJob = viewModelScope.launch(Dispatchers.Main) {
        //...
}

Answer 6

您可以使用RxJava轻松实现它。 此外，您将需要RxAndroid和RxBinding （但如果您使用 RxJava，您的项目中可能已经拥有它们）。

RxTextView.textChangeEvents(yourEditText)
          .debounce(1, TimeUnit.SECONDS)
          .observeOn(AndroidSchedulers.mainThread())
          .subscribe(performSearch());

这是 Kaushik Gopal 的完整示例。

Answer 7

使用协程和流程：

private fun SearchView.onQueryTextChanged(): ReceiveChannel<String> =
    Channel<String>(capacity = Channel.UNLIMITED).also { channel ->
        setOnQueryTextListener(object : SearchView.OnQueryTextListener{
            override fun onQueryTextSubmit(query: String?): Boolean {
                return false
            }

            override fun onQueryTextChange(newText: String?): Boolean {
                newText.orEmpty().let(channel::offer)
                return true
            }
        })
    }

@ExperimentalCoroutinesApi
fun <T> ReceiveChannel<T>.debounce(time: Long, unit: TimeUnit = TimeUnit.MILLISECONDS, scope: CoroutineScope): ReceiveChannel<T> =
    Channel<T>(capacity = Channel.CONFLATED).also { channel ->
        scope.launch {
            var value = receive()
            whileSelect {
                onTimeout(time) {
                    channel.offer(value)
                    value = receive()
                    true
                }
                onReceive {
                    value = it
                    true
                }
            }
        }
    }

并像这样添加到您的搜索视图中：

lifecycleScope.launch {
   searchView.onQueryTextChanged().debounce(time = 500, scope = lifecycleScope).consumeEach { newText ->
          //Use debounced query
   }
}

Answer 8

我没有找到使我能够使用诸如distinctUntilChanged之类的流运算符的解决方案，我尝试了这种方法，也许有人需要它：

首先从SearchView创建一个扩展函数

private fun SearchView.getQueryTextChangeStateFlow(): StateFlow<String> {
    val query = MutableStateFlow("")
    
    setOnQueryTextListener(object : SearchView.OnQueryTextListener {
        override fun onQueryTextSubmit(query: String?): Boolean {
            return true
        }
        override fun onQueryTextChange(newText: String): Boolean {
            query.value = newText
            return true
        }
    })

    return query
}

然后

 private fun setUpSearchStateFlow(searchView: SearchView) {
    lifecycleScope.launch {
        searchView.getQueryTextChangeStateFlow()
            .debounce(300)
            .distinctUntilChanged()
            .map { query ->
                startSearchRequestHere(query)
            }
            .flowOn(Dispatchers.Default)
            .collect {}
    }
}

参考

Answer 9

我最终得到了类似于下面的解决方案。 这样它应该每半秒触发一次。

        public boolean onQueryTextChange(final String newText) {

            if (newText.length() > 3) {

                if (canRun) {
                    canRun = false;
                    handler.postDelayed(new Runnable() {
                        @Override
                        public void run() {

                            canRun = true;
                            handleLocationSearch(newText);
                        }
                    }, 500);
                }
            }

            return false;
        }