Styling FAQ

This document addresses common styling-related questions and issues in uni-app development.

Basic Styling Issues

Q: How to set global styles?

A: You can set global styles in App.vue:

<style>
/* Global styles */
page {
  background-color: #f5f5f5;
  font-size: 14px;
}

.container {
  padding: 20px;
}

/* Global class styles */
.text-center {
  text-align: center;
}

.flex-row {
  display: flex;
  flex-direction: row;
}
</style>

Q: How to use CSS variables?

A: uni-app supports CSS custom properties (CSS variables):

<template>
  <view class="container">
    <text class="title">Title</text>
    <text class="content">Content</text>
  </view>
</template>

<style>
:root {
  --primary-color: #007aff;
  --text-color: #333;
  --border-radius: 8px;
}

.container {
  color: var(--text-color);
}

.title {
  color: var(--primary-color);
  border-radius: var(--border-radius);
}
</style>

Q: How to import external CSS files?

A: You can import CSS files using @import:

<style>
@import url('./common.css');
@import './styles/base.css';

.custom-class {
  /* Custom styles */
}
</style>

Layout Issues

Q: How to implement responsive layout?

A: Use media queries and flexible units:

<template>
  <view class="responsive-container">
    <view class="item">Item 1</view>
    <view class="item">Item 2</view>
    <view class="item">Item 3</view>
  </view>
</template>

<style>
.responsive-container {
  display: flex;
  flex-wrap: wrap;
  padding: 20rpx;
}

.item {
  width: 100%;
  margin-bottom: 20rpx;
}

/* Tablet */
@media screen and (min-width: 768px) {
  .item {
    width: 48%;
    margin-right: 2%;
  }
}

/* Desktop */
@media screen and (min-width: 1024px) {
  .item {
    width: 31%;
    margin-right: 2%;
  }
}
</style>

Q: How to center elements vertically and horizontally?

A: Use flexbox for centering:

<template>
  <view class="center-container">
    <view class="centered-content">Centered Content</view>
  </view>
</template>

<style>
.center-container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.centered-content {
  padding: 20rpx;
  background-color: #f0f0f0;
  border-radius: 10rpx;
}
</style>

Q: How to implement sticky positioning?

A: Use position: sticky:

<template>
  <view class="container">
    <view class="sticky-header">Sticky Header</view>
    <view class="content">
      <!-- Long content -->
    </view>
  </view>
</template>

<style>
.sticky-header {
  position: sticky;
  top: 0;
  background-color: #fff;
  padding: 20rpx;
  border-bottom: 1px solid #eee;
  z-index: 100;
}

.content {
  height: 2000rpx; /* Long content for scrolling */
  padding: 20rpx;
}
</style>

Font and Icon Issues

Q: How to use custom fonts?

A: Import and use custom fonts:

<style>
@font-face {
  font-family: 'CustomFont';
  src: url('./fonts/custom-font.ttf') format('truetype');
}

.custom-text {
  font-family: 'CustomFont', sans-serif;
  font-size: 16px;
}
</style>

Q: How to use icon fonts?

A: Import icon font files and use them:

<template>
  <text class="iconfont icon-home"></text>
  <text class="iconfont icon-user"></text>
</template>

<style>
@font-face {
  font-family: 'iconfont';
  src: url('./fonts/iconfont.ttf') format('truetype');
}

.iconfont {
  font-family: 'iconfont' !important;
  font-style: normal;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.icon-home:before {
  content: "\e600";
}

.icon-user:before {
  content: "\e601";
}
</style>

Q: How to adjust font size for different platforms?

A: Use conditional compilation:

<style>
.text {
  /* #ifdef APP-PLUS */
  font-size: 16px;
  /* #endif */
  
  /* #ifdef H5 */
  font-size: 14px;
  /* #endif */
  
  /* #ifdef MP-WEIXIN */
  font-size: 30rpx;
  /* #endif */
}
</style>

Animation and Transition Effects

Q: How to implement CSS animations?

A: Use CSS animations and transitions:

<template>
  <view class="animated-box" @click="toggleAnimation">
    Click me
  </view>
</template>

<script>
export default {
  data() {
    return {
      isAnimating: false
    }
  },
  methods: {
    toggleAnimation() {
      this.isAnimating = !this.isAnimating;
    }
  }
}
</script>

<style>
.animated-box {
  width: 100px;
  height: 100px;
  background-color: #007aff;
  transition: all 0.3s ease;
  cursor: pointer;
}

.animated-box:hover {
  transform: scale(1.1);
  background-color: #0056cc;
}

/* Keyframe animation */
@keyframes bounce {
  0%, 20%, 50%, 80%, 100% {
    transform: translateY(0);
  }
  40% {
    transform: translateY(-30px);
  }
  60% {
    transform: translateY(-15px);
  }
}

.bounce {
  animation: bounce 1s infinite;
}
</style>

Q: How to implement page transition animations?

A: Use uni-app's page transition API:

// In pages.json
{
  "pages": [
    {
      "path": "pages/index/index",
      "style": {
        "animationType": "slide-in-right",
        "animationDuration": 300
      }
    }
  ]
}

<!-- In page component -->
<template>
  <view class="page-container">
    <!-- Page content -->
  </view>
</template>

<style>
.page-container {
  opacity: 0;
  transform: translateX(100%);
  animation: slideIn 0.3s ease-out forwards;
}

@keyframes slideIn {
  to {
    opacity: 1;
    transform: translateX(0);
  }
}
</style>

Style Compatibility Issues

Q: How to handle style differences across platforms?

A: Use conditional compilation and platform-specific styles:

<style>
.button {
  padding: 10px 20px;
  border-radius: 5px;
  
  /* #ifdef APP-PLUS */
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
  /* #endif */
  
  /* #ifdef H5 */
  cursor: pointer;
  user-select: none;
  /* #endif */
  
  /* #ifdef MP-WEIXIN */
  border: 1px solid #ddd;
  /* #endif */
}
</style>

Q: How to handle rpx unit compatibility?

A: Use rpx for responsive design, px for fixed sizes:

<style>
.container {
  width: 750rpx; /* Full width on all devices */
  padding: 20rpx; /* Responsive padding */
}

.fixed-element {
  width: 1px; /* Fixed 1px border */
  height: 44px; /* Fixed navigation height */
}
</style>

Q: How to handle safe area adaptation?

A: Use CSS environment variables:

<style>
.safe-area-container {
  padding-top: constant(safe-area-inset-top);
  padding-top: env(safe-area-inset-top);
  padding-bottom: constant(safe-area-inset-bottom);
  padding-bottom: env(safe-area-inset-bottom);
}

.bottom-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: 50px;
  padding-bottom: constant(safe-area-inset-bottom);
  padding-bottom: env(safe-area-inset-bottom);
}
</style>

Common Style Implementations

Q: How to implement a card layout?

A: Create reusable card components:

<template>
  <view class="card">
    <view class="card-header">
      <text class="card-title">Card Title</text>
    </view>
    <view class="card-body">
      <text class="card-content">Card content goes here...</text>
    </view>
    <view class="card-footer">
      <button class="card-button">Action</button>
    </view>
  </view>
</template>

<style>
.card {
  background-color: #fff;
  border-radius: 8rpx;
  box-shadow: 0 2rpx 8rpx rgba(0,0,0,0.1);
  margin: 20rpx;
  overflow: hidden;
}

.card-header {
  padding: 30rpx;
  border-bottom: 1rpx solid #f0f0f0;
}

.card-title {
  font-size: 32rpx;
  font-weight: bold;
  color: #333;
}

.card-body {
  padding: 30rpx;
}

.card-content {
  font-size: 28rpx;
  color: #666;
  line-height: 1.5;
}

.card-footer {
  padding: 20rpx 30rpx;
  background-color: #f9f9f9;
  text-align: right;
}

.card-button {
  background-color: #007aff;
  color: #fff;
  border: none;
  padding: 10rpx 20rpx;
  border-radius: 4rpx;
  font-size: 26rpx;
}
</style>

Q: How to implement a grid layout?

A: Use CSS Grid or Flexbox:

<template>
  <view class="grid-container">
    <view class="grid-item" v-for="item in items" :key="item.id">
      {{ item.title }}
    </view>
  </view>
</template>

<style>
/* CSS Grid approach */
.grid-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200rpx, 1fr));
  gap: 20rpx;
  padding: 20rpx;
}

.grid-item {
  background-color: #f0f0f0;
  padding: 30rpx;
  border-radius: 8rpx;
  text-align: center;
}

/* Flexbox approach */
.flex-grid {
  display: flex;
  flex-wrap: wrap;
  margin: -10rpx;
}

.flex-item {
  flex: 0 0 calc(50% - 20rpx);
  margin: 10rpx;
  background-color: #f0f0f0;
  padding: 30rpx;
  border-radius: 8rpx;
}
</style>

Q: How to implement a loading spinner?

A: Create CSS-based loading animations:

<template>
  <view class="loading-container" v-if="loading">
    <view class="spinner"></view>
    <text class="loading-text">Loading...</text>
  </view>
</template>

<style>
.loading-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40rpx;
}

.spinner {
  width: 40rpx;
  height: 40rpx;
  border: 4rpx solid #f3f3f3;
  border-top: 4rpx solid #007aff;
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.loading-text {
  margin-top: 20rpx;
  font-size: 28rpx;
  color: #666;
}
</style>

Best Practices

1. Use Semantic Class Names

/* Good */
.product-card { }
.user-avatar { }
.navigation-menu { }

/* Avoid */
.red-box { }
.big-text { }
.left-item { }

2. Organize Styles Hierarchically

<style>
/* Base styles */
.container { }

/* Component styles */
.header { }
.header-title { }
.header-nav { }

/* State styles */
.is-active { }
.is-disabled { }
.is-loading { }

/* Modifier styles */
.button--primary { }
.button--secondary { }
.button--large { }
</style>

3. Use CSS Custom Properties for Theming

<style>
:root {
  --color-primary: #007aff;
  --color-secondary: #34c759;
  --color-danger: #ff3b30;
  --spacing-small: 10rpx;
  --spacing-medium: 20rpx;
  --spacing-large: 40rpx;
}

.theme-dark {
  --color-primary: #0a84ff;
  --color-background: #1c1c1e;
  --color-text: #ffffff;
}
</style>

4. Optimize for Performance

<style>
/* Use transform for animations */
.slide-enter-active {
  transform: translateX(100%);
  transition: transform 0.3s ease;
}

.slide-enter-to {
  transform: translateX(0);
}

/* Avoid expensive properties in animations */
/* Bad */
.expensive-animation {
  animation: badAnimation 1s ease;
}

@keyframes badAnimation {
  from { width: 0; height: 0; }
  to { width: 100px; height: 100px; }
}

/* Good */
.efficient-animation {
  animation: goodAnimation 1s ease;
}

@keyframes goodAnimation {
  from { transform: scale(0); }
  to { transform: scale(1); }
}
</style>

Troubleshooting

Common Issues and Solutions

1. Styles not applying: Check selector specificity and CSS syntax
2. Layout breaking on different devices: Use responsive units (rpx, %, vw/vh)
3. Animations not smooth: Use transform and opacity properties
4. Font not loading: Verify font file path and format support
5. Z-index issues: Establish proper stacking context

Debugging Tips

1. Use browser developer tools for H5 platform
2. Check uni-app console for style warnings
3. Test on multiple devices and platforms
4. Validate CSS syntax and properties
5. Use conditional compilation for platform-specific fixes

For more styling guidance, refer to the Components Documentation and Best Practices Guide.