Question

我在监视某个文件的java中有这样的代码：

private Handler mHandler = new Handler();
private final Runnable monitor = new Runnable() {

    public void run() {
        // Do my stuff
        mHandler.postDelayed(monitor, 1000); // 1 second
    }
};

这是我的kotlin代码：

private val mHandler = Handler()
val monitor: Runnable = Runnable {
    // do my stuff
    mHandler.postDelayed(whatToDoHere, 1000) // 1 second
}

我不明白我应该将Runnable传递给mHandler.postDelayed。什么是正确的解决方案？另一个有趣的事情是，当我提供这段代码时，kotlin到java转换器会冻结。

Answer 1

Lambda表达式没有this，但是对象表达式（匿名类）没有。

object : Runnable {
    override fun run() {
        handler.postDelayed(this, 1000)
    }
}

Answer 2

稍微不同的方法可能更具可读性

val timer = Timer()
val monitor = object : TimerTask() {
    override fun run() {
        // whatever you need to do every second
    }
}

timer.schedule(monitor, 1000, 1000)

来自：Repeat an action every 2 seconds in java

Answer 3

Lambda表达式没有 this ，但是对象表达式（匿名类）具有。那么正确的代码将是：

const GRID_SIZE = 50;
for(let i = 0; i < GRID_SIZE * GRID_SIZE; i++){
    const container = document.getElementById('container');
    let div = document.createElement('div');
    div.classList.add('box');
    container.appendChild(div);
}

function fillBox(evt){
    evt.preventDefault(); // tell the browser we handle that event
    this.classList.add('filled');
}

function clearGrid(){
    const boxes = document.querySelectorAll('.box');
    boxes.forEach(box => box.classList.remove('filled'));
}

function startDrawing(evt){
    evt.preventDefault(); // tell the browser we handle that event
    // console.log("start drawing");
    const boxes = document.querySelectorAll('.box');
    boxes.forEach(box => box.addEventListener('mouseover', fillBox));
}

function stopDrawing(evt){
    evt.preventDefault(); // tell the browser we handle that event
    // console.log("stop drawing");
    const boxes = document.querySelectorAll('.box');
    boxes.forEach(box => box.removeEventListener('mouseover', fillBox));
}

const container = document.querySelector('#container');
container.addEventListener('mousedown', startDrawing);
container.addEventListener('mouseup', stopDrawing);

const button = document.querySelector('#clear-grid-btn');
button.onclick = clearGrid;

Answer 4

runnable 显示 Toast Message "Hello World 每 4 秒

//在一个类的主要活动中

    val handler: Handler = Handler()
    val run = object : Runnable {
       override fun run() {
           val message: String = "Hello World" // your message
           handler.postDelayed(this, 4000)// 4 seconds
           Toast.makeText(this@MainActivity,message,Toast.LENGTH_SHORT).show() // toast method
       }

   }
    handler.post(run)
}

无限期地将Runnable从java转换为kotlin

4 个答案: