Implementation method of waterfall flow layout developed in PHP in WeChat mini program

With the popularity of WeChat mini programs, more and more developers are beginning to get involved. As a widely used layout method, waterfall flow layout is also widely used in small programs. This article will introduce how to use PHP development to implement waterfall flow layout in WeChat applet.

The implementation principle of waterfall flow layout

Waterfall flow layout is a flow layout method. Its characteristic is that the height of each column is not necessarily the same, and the elements are arranged in sequence like a waterfall. In web pages, this layout method is usually implemented through JavaScript.

In the WeChat applet, we can use PHP to write server-side scripts, read data from the database and perform waterfall flow layout. The specific implementation principle is as follows:

1. The client sends a request to the server

When the user opens the mini program page, the client sends a request to the server to request the data source. At this time, the server has not returned any data.

2. The server reads the data source and analyzes it

When the server receives the request, it will read the data source from the database and analyze it according to the request parameters. . At this time, the server will calculate the height of each column and the position information of each element, and return this information to the client.

3. The client receives data and renders the page

When the client receives the data returned by the server, it will use the rendering engine to render the page.

Implementation steps

Below, we will introduce the specific implementation steps.

1. Prepare the data source

First, you need to prepare the data source, that is, the image or other elements to be displayed on the page.

2. Writing server-side script

You need to write a server-side script to read the data source from the database and calculate the element position information according to the requirements of the waterfall flow layout. Server-side scripts can be written in PHP, or for simple small programs, other languages ​​such as Node.js.

The following is a simple PHP code example for reading the data source from the database and calculating the position information of the element:

<?php
header('Content-type: application/json');

// 从数据库中读取数据源
$items = [
    ['img' => '1.jpg', 'width' => 300, 'height' => 200],
    ['img' => '2.jpg', 'width' => 200, 'height' => 300],
    ['img' => '3.jpg', 'width' => 250, 'height' => 150],
    ['img' => '4.jpg', 'width' => 350, 'height' => 400],
    ['img' => '5.jpg', 'width' => 180, 'height' => 250],
];

// 计算每列的高度
$columnHeight = [0, 0, 0];
foreach ($items as $item) {
    $minHeight = min($columnHeight);
    $minIndex = array_search($minHeight, $columnHeight);
    $item['left'] = 10 + $minIndex * (300 + 10);
    $item['top'] = $columnHeight[$minIndex] + 10;
    $columnHeight[$minIndex] += $item['height'] + 10;
}

// 输出结果
echo json_encode($items);
?>

In the above code, we first read from the database The data source contains the image link, width and height information, and then calculates the height of each column, the left and top values ​​​​of each element, and outputs the results into JSON format data.

3. Use a network request in the mini program client to obtain the data source returned by the server

The mini program client needs to send the request to the server through a network request and receive it The data source returned by the server. You can use the wx.request method provided by the applet to achieve this function. In the success callback function of the wx.request method, we can save the data source returned by the server to the page data and render it.

4. Component implementation

In waterfall flow layout, the position and size of each element are dynamically calculated. Therefore, to facilitate implementation, we can encapsulate each element into a component. In this way, in the server-side script we only need to calculate the position and size of each element, and on the client side, we can automatically implement the waterfall flow layout through this component.

The following is an example of componentized dynamic waterfall flow implementation:

<view class="waterfall">
  <waterfall-item wx:for="{{items}}" bindtap="onTap" width="{{item.width}}" height="{{item.height}}" x="{{item.left}}" y="{{item.top}}" index="{{index}}"></waterfall-item>
</view>

In the above code, we define a waterfall-item component, which receives an x, y coordinate and width, Height information, used to draw pictures. The code of the component is as follows:

<template name="waterfall-item">
  <block>
    <view style="position: absolute;left: {{x}}rpx;top: {{y}}rpx;width: {{width}}rpx;height: {{height}}rpx;">
      <image src="{{img}}" mode="aspectFill" style="width: 100%;height: 100%;"></image>
    </view>
  </block>
</template>

In the above code, we use an absolutely positioned view to draw the picture, and apply the x, y coordinates, width, and height information to the view through the style attribute.

Summary

In this article, we introduced how to use PHP to write server-side scripts, read data sources from the database and perform waterfall layout. Through componentization, we can encapsulate each element into a component to achieve a dynamic waterfall flow effect. I hope this article will be helpful to developers who want to implement waterfall flow layout in WeChat mini programs.

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