CSS按钮无法居中求助：已尝试Flex等方法均无效

问题概述 #

尝试在CSS中实现按钮水平居中，但始终无法成功。已尝试display: flex; align-items: center; justify-content: center;等Flex布局方案，参考多篇文章仍无效，推测存在样式冲突导致按钮无法居中。当前效果为按钮左对齐，未与上方输入框保持居中对齐。

相关代码 #

CSS代码 #

* {
    margin:0;
    padding: 0;

}

body {
    font-family: "Roboto", sans-serif;
    background: #bef2ff;
}


.nav {  
    background: #4f7097; 
    
    color: white;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 2rem;
    padding: 1rem;;

}

.nav a{
    color: inherit;
    text-decoration: none;
}

.nav ul{
    padding: 0;
    margin: 0;
    list-style: none;
    display: flex;
    gap: 1rem;
}

.site-title {
    font-size: 2rem;
}

section{
    margin: 2rem 0 1rem 0;
}

.controls{
    display: flex;
    align-items: center;
    flex-direction: column;
}

input{
    text-align: center;
    padding: 0.5rem;
    margin-bottom: 1rem;
}


button{
    padding: 0.5rem 1rem;
    background: #1bf5af;
    color: rgb(0, 0, 0);
    border: none;
    font-family: "Arial", sans-serif;
    font-size: 1rem;
    cursor: pointer;
    transition: 0.4s;
    border-radius: 10px;
}


button:hover {
    transform: scale(1.05);
    background-color: rgb(4, 205, 205);
}

.getplan{
    display: flex;
    align-items: center;
    flex-direction: column;
}


main{
    display: flex;
    flex-direction: column;
    align-items: center;
}

h1{
    text-align: center;
    margin-bottom: 2rem;
}

.nutrients ul{
    display: flex;
    width: 35rem;
    justify-content: space-evenly;
}

ul{
    list-style: none;
}

.meals{
    display: flex;
}

img{
    width: 100%;
    margin-bottom: 1rem;
}

article{
    display: flex;
    flex-direction: column;
    padding: 2rem;
    margin: 0 1rem;
    max-width: 18rem;
    box-shadow: 0 4px 8 px 2px rgb(79, 76, 76, 0.15) 
}

.instrucitons{
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

a{
    text-decoration: none;
    color: rgb(0, 0, 0);
    width: fit-content;
    padding: 0.5rem 1rem;
    cursor: pointer;
    transition: 0.4s;
   
}

a:hover {
    transform: scale(1.05);
    background-color: rgb(4, 205, 205);
}

@media only screen and (max-width: 550px){
    .meals{
        align-items: center;
    }

    .nutrients ul{
        display: flex;
        flex-direction: column;
        align-items: center;
        width: 100%;
    }
    
}

a.class1 {
    padding: 0.5rem 1rem;
    background: #1bf5af;
    color: rgb(0, 0, 0);
    border: none;
    font-family: "Arial", sans-serif;
    font-size: 1rem;
    cursor: pointer;
    transition: 0.4s;
    border-radius: 10px;
}

React组件代码 #

<section className='controls'>
  <input 
  type="number"
  placeholder='Number of Calories'
  onChange={handleChange}/>
</section>
<button onClick={getMealData}>Get daily meal plan</button>
{mealData && <MealList mealData={mealData}/> }
</div>
);
}

export default App;

解决方法 #

以下三种方案任选其一即可解决问题：

1. 利用已有.controls容器的居中样式
   将按钮移入controlssection内部，直接复用该容器的flex-direction: column; align-items: center;样式实现居中：

<section className='controls'>
  <input 
  type="number"
  placeholder='Number of Calories'
  onChange={handleChange}/>
  <button onClick={getMealData}>Get daily meal plan</button>
</section>
{mealData && <MealList mealData={mealData}/> }

2. 使用已定义的.getplan类
   给按钮包裹一个容器，并应用你已定义好的.getplan类（该类已包含居中所需的Flex属性）：

<section className='controls'>
  <input 
  type="number"
  placeholder='Number of Calories'
  onChange={handleChange}/>
</section>
<div className='getplan'>
  <button onClick={getMealData}>Get daily meal plan</button>
</div>
{mealData && <MealList mealData={mealData}/> }

3. 直接给按钮添加居中样式
   修改CSS中的button选择器，添加块级显示和左右自动margin，实现水平居中：

button{
    padding: 0.5rem 1rem;
    background: #1bf5af;
    color: rgb(0, 0, 0);
    border: none;
    font-family: "Arial", sans-serif;
    font-size: 1rem;
    cursor: pointer;
    transition: 0.4s;
    border-radius: 10px;
    /* 添加以下两行 */
    display: block;
    margin: 0 auto;
}

内容的提问来源于stack exchange，提问作者Oscar _OOO