Swipe up to change the head of uniapp

In mobile development, if you need to change the header content (such as title or background color) when the page scrolls, you can use some techniques to achieve it. In this article, we will introduce how to use event listening and dynamic style changes to achieve this functionality in Uniapp.

Uniapp is a framework for developing applications based on Vue.js, which can build multi-platform applications by writing once. It adopts a hierarchical structure and provides support for multi-level page structures for applications. Uniapp also provides a wealth of components and plug-ins for applications, allowing developers to easily implement complex functions.

In Uniapp, we can use event listening and dynamic style changes to achieve head changes when sliding.

Step one: Use the scroll-view component

To change the content of the head when sliding, we need to use the scroll view scroll-view component. This component provides related events when the screen slides.

Add a scroll-view element to the page, which needs to set the height and scroll height so that events can be triggered when the content scrolls. For example, now we create a page with a scroll-view element, the height is set to 500px, and the scroll height is 1000px:

<template>
  <div>
    <scroll-view :scroll-y="true" style="height:500px;overflow:hidden;">
      <div style="height:1000px;"></div>
    </scroll-view>
  </div>
</template>

In this example, we use the scroll-y attribute to set vertical scrolling , the overflow:hidden attribute in the style is used to hide the scroll bar. Specific scroll event handling will be introduced in the next step.

Step 2: Listen to the scroll event

We need to listen to the scroll event of the scroll-view component. In Uniapp, we can use @scroll to set a listener for scroll events. We can specify a method as a handler for the @scroll event, which will be called whenever the scroll view scrolls.

<template>
  <div>
    <scroll-view :scroll-y="true" style="height:500px;overflow:hidden;" @scroll="scrollHandler">
      <div style="height:1000px;"></div>
    </scroll-view>
  </div>
</template>

<script>
export default {
  methods: {
    scrollHandler: function(e) {
      console.log(e)
    }
  }
}
</script>

In this example, we define a method scrollHandler to handle scroll events. The e parameter provides information about the scroll position as well as the scroll event itself. You can write the logic for your header changes in this method and apply it to the header element.

Step Three: Change the Header Style

Now we have the scroll information needed to handle the scroll event and the handler method to call. Next, we need to change the header style when a scroll event occurs.

Here, we can use Vue's dynamic style to set the style of the head. We can style the header as a set of objects and bind it to the header element. Whenever a scroll event occurs, we can change the properties of these objects as needed.

<template>
  <div>
    <div :style="headerStyle">HEADER</div>
    <scroll-view :scroll-y="true" style="height:500px;overflow:hidden;" @scroll="scrollHandler">
      <div style="height:1000px;"></div>
    </scroll-view>
  </div>
</template>

<script>
export default {
  data: function() {
    return {
      headerStyle: {
        backgroundColor: '#fff',
        color: '#000'
      }
    }
  },
  methods: {
    scrollHandler: function(e) {
      if (e.detail.scrollTop >= 100) {
        this.headerStyle.backgroundColor = '#000'
        this.headerStyle.color = '#fff'
      } else {
        this.headerStyle.backgroundColor = '#fff'
        this.headerStyle.color = '#000'
      }
    }
  }
}
</script>

In this example, we define a style object headerStyle, which contains a backgroundColor property and a color property. We dynamically change the values ​​of these properties based on the details of the scroll event. When scrolling up changes the background color to black and text color to white and when scrolling down changes it back.

Finally, we need to bind this style object to the head element. We can do this using v-bind in Vue or the shorthand syntax colon (:).

Summary:

In Uniapp, we can use the scroll-view component and scroll event to listen for screen scrolling events. Using dynamic styles to change our header element allows us to change the header effect as we scroll on the page. In this way we can make the interface of the application more dynamic and interesting.

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