Question

我希望public class ScreenActivity extends AppCompatActivity { ImageView img; int width,height; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_screen); img=(ImageView)findViewById(R.id.imageView); Display display = getWindowManager().getDefaultDisplay(); width = display.getWidth(); height = display.getHeight(); // while (true) for (int i=0;i<100;i++) new GetImg().execute(); } Bitmap imgscr; public class GetImg extends AsyncTask<Object,Void,Bitmap> { @Override protected Bitmap doInBackground(Object[] params) { Socket client= null; try { client = new Socket("192.168.1.5",6767); InputStream in=client.getInputStream(); imgscr=Bitmap.createScaledBitmap(BitmapFactory.decodeStream(in), width, height, false); } catch (Exception e) { e.printStackTrace(); } return imgscr; } @Override protected void onPostExecute(Bitmap bm) { img.setImageBitmap(bm); } } }和函数修改变量close，使填充更大，直到它等于变量gate。我不知道为什么它不起作用，请帮忙。

open

Answer 1

JS中的超时没有阻塞 - 它们在一个单独的线程中运行。关于他们如何在线工作的资源很多，所以我不会深入研究。

要修复代码，您可以重构是进行递归调用：

var closed = 1;
var opened = 19;
var gate = opened;
var gateEl = document.getElementById('gate');

function close() {
    if (gate !== closed) {
        gate -= 1;
        gateEl.style.paddingTop = gate + '%'; // open stays the same
        setTimeout(close, 100);
    }
}

对close函数
定义一个将填充更改的元素
使用gate代替open来实际更改填充

这是一个实例：

var closed = 1;
var opened = 19;
var gate = opened;
var gateDiv = document.getElementById('gate');

function close() {
  console.log(gate);
  if (gate > closed) {
    gate -= 1;
    gateDiv.style.paddingTop = gate + '%';
    setTimeout(close, 100);
  }
}

close();

#gate {
  height: 50px;
  width: 50px;
  background: green;
}

<div id="gate"></div>

Answer 2

更好的实施方式如下：

＆＃13;

// gate element
var gate = document.getElementById("gate");
// the space between the gate and the ground
var gap = 100;
// how many pixels/percentage you want it to move at each iteration
var increment = -2;

function close() {
  // gap = 0 means it's closed
  // as long as it's not closed run this
  if (gap > 0) {
    // decrease the gap
    gap = gap + increment;
    gate.style.top = (gap * -1) + "%";
  } else {
    // gate is closed, so we clear the interval
    clearInterval(closing);
  }
}

// a reference to interval
var closing = setInterval(close, 100);

＆＃13;

#container {
  width: 300px;
  height: 100px;
  border: 1px solid rgba(0, 0, 0, .2);
  position: relative;
  overflow: hidden;
}
#gate {
  width: 100%;
  height: 100%;
  background: brown;
  position: absolute;
  top: -100%;
}

＆＃13;

<div id="container">
  <div id="gate"></div>
</div>

＆＃13;

Answer 3

这是一个非常高级的话题！我强烈建议您阅读Promise和async/await。拥有异步编程和JavaScript的经验也很有帮助。

将来你可以使用async/await来写这个和你一样：

function wait() {
    return new Promise(function(resolve) {
        setTimeout(resolve, 100)
    });
}

async function close() {
    var closed = 1;
    var opened = 19;
    var gate = opened;

    while (gate !== closed) {
        gate -= 1;
        gateEl.style.paddingTop = open + '%';
        await wait();
    }
}

这有几个不同的部分，所以我会仔细阅读..

首先，我修复了您的代码的几个常见问题：

gate.style.paddingTop = open'%';
// changed to:
gateEl.style.paddingTop = open + '%';
// First, we need to join the open variable and the '%' string, so
// I add a + for that; second, gate is a number, not a DOM element,
// so I assumed there is a new variable called "gateEl" that means
// the actual element. Supply that in the actual code.

然后我在代码中实现了async / await。这涉及一些变化。我重新定义了函数wait：

function wait() {
    return new Promise(function(resolve) {
        setTimeout(resolve, 100)
    });
}

看起来有点令人困惑，但基本上我给出了一个函数参数的新Promise对象。 Promise使async / await成功。在我的wait函数中，当调用await wait()时，在100毫秒后调用resolve。 resolve表示await wait()之后的代码可以运行。

接下来，我在async之前添加了function close() {...} - 这使await在其中工作。

最后，我将wait()替换为await wait()。这会将您的浏览器从“调用wait函数”改为“调用wait函数”，然后等到promise ^{_{实际上是可用对象} < / sup>它回归解决。“而且我们知道，在wait被调用之后，承诺会解决100ms - 因为我们将其定义为这样做。}

关于await fn()的好处是循环和其他控制结构能够很好地工作。

Java脚本函数错误

3 个答案: