loading-states（加载状态）

Loading & Empty States

Maintain user confidence when content isn't immediately available.

Loading State Types

Choose by Duration

Skeleton Screens

When to Use

• Page or section content loading
• Lists, cards, tables
• Better than spinners for known layouts

Basic Skeleton

.skeleton {
  background: #e5e7eb;
  border-radius: 4px;
}

/* Animated shimmer */
.skeleton-animated {
  background: linear-gradient(
    90deg,
    #f3f4f6 25%,
    #e5e7eb 50%,
    #f3f4f6 75%
  );
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
}

@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

Skeleton Components

<!-- Text skeleton -->
<div class="skeleton skeleton-text" style="width: 80%"></div>
<div class="skeleton skeleton-text" style="width: 60%"></div>

<!-- Avatar skeleton -->
<div class="skeleton skeleton-avatar"></div>

<!-- Image skeleton -->
<div class="skeleton skeleton-image"></div>

.skeleton-text {
  height: 16px;
  margin-bottom: 8px;
}

.skeleton-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
}

.skeleton-image {
  width: 100%;
  aspect-ratio: 16/9;
}

Card Skeleton Example

<article class="card card-skeleton">
  <div class="skeleton skeleton-image"></div>
  <div class="card-content">
    <div class="skeleton skeleton-text" style="width: 70%"></div>
    <div class="skeleton skeleton-text" style="width: 90%"></div>
    <div class="skeleton skeleton-text" style="width: 50%"></div>
  </div>
</article>

What NOT to Skeleton

• Modals (should be instant or loading indicator inside)
• Toasts/notifications
• Dropdown menus
• The skeleton itself shouldn't have a skeleton

Spinners

When to Use

• Unknown content structure
• Short operations (1-3 seconds)
• Small areas (buttons, inputs)

Simple Spinner

.spinner {
  width: 24px;
  height: 24px;
  border: 3px solid #e5e7eb;
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

Button Loading State

.button-loading {
  position: relative;
  color: transparent; /* Hide text */
  pointer-events: none;
}

.button-loading::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 20px;
  height: 20px;
  border: 2px solid currentColor;
  border-top-color: transparent;
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

Inline Loading Text

<span class="loading-text">
  Loading
  <span class="loading-dots">
    <span>.</span><span>.</span><span>.</span>
  </span>
</span>

Progress Bars

When to Use

• Operations > 10 seconds
• File uploads/downloads
• Multi-step processes

Basic Progress Bar

<div class="progress">
  <div
    class="progress-bar"
    role="progressbar"
    style="width: 65%"
    aria-valuenow="65"
    aria-valuemin="0"
    aria-valuemax="100"
  >
    65%
  </div>
</div>

.progress {
  height: 8px;
  background: #e5e7eb;
  border-radius: 4px;
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: var(--primary);
  transition: width 0.3s ease-out;
}

Indeterminate Progress

.progress-indeterminate .progress-bar {
  width: 30%;
  animation: indeterminate 1.5s infinite ease-in-out;
}

@keyframes indeterminate {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(400%); }
}

Empty States

Types of Empty States

1. First Use: User hasn't added data yet
2. No Results: Search/filter returned nothing
3. Error State: Something went wrong
4. Success Empty: Completed all tasks (inbox zero)

First Use Empty State

<div class="empty-state">
  <img src="illustration.svg" alt="" class="empty-illustration">
  <h3 class="empty-title">No projects yet</h3>
  <p class="empty-description">
    Create your first project to get started
  </p>
  <button class="button-primary">
    Create Project
  </button>
</div>

No Results Empty State

<div class="empty-state">
  <span class="empty-icon">🔍</span>
  <h3 class="empty-title">No results found</h3>
  <p class="empty-description">
    Try adjusting your search or filters
  </p>
  <button class="button-secondary">
    Clear Filters
  </button>
</div>

Empty State Styles

.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 48px 24px;
  text-align: center;
}

.empty-illustration {
  width: 200px;
  max-width: 100%;
  margin-bottom: 24px;
}

.empty-icon {
  font-size: 48px;
  margin-bottom: 16px;
}

.empty-title {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.empty-description {
  font-size: 14px;
  color: var(--text-secondary);
  max-width: 300px;
  margin-bottom: 24px;
}

Error States

<div class="empty-state error-state">
  <span class="empty-icon">⚠️</span>
  <h3 class="empty-title">Something went wrong</h3>
  <p class="empty-description">
    We couldn't load your data. Please try again.
  </p>
  <button class="button-primary">
    Retry
  </button>
</div>

Best Practices

Do

• Match skeleton layout to actual content
• Show loading state immediately (don't wait)
• Use animations to indicate activity
• Provide progress info when possible
• Include helpful actions in empty states
• Keep messaging friendly and helpful

Don't

• Show spinners for everything
• Use loading states for instant operations
• Leave users without feedback
• Make empty states feel like dead ends
• Animate aggressively (respect motion preferences)

Accessibility

/* Announce loading to screen readers */
.loading-region[aria-busy="true"]::before {
  content: "Loading...";
  position: absolute;
  clip: rect(0, 0, 0, 0);
}

/* Respect reduced motion */
@media (prefers-reduced-motion: reduce) {
  .skeleton-animated {
    animation: none;
  }

  .spinner {
    animation-duration: 1.5s;
  }
}

Checklist

• Loading appears within 100ms of action
• Skeleton matches content structure
• Progress shown for long operations (>10s)
• Empty states have helpful actions
• Error states include retry option
• Animations respect prefers-reduced-motion
• Screen readers announce loading state
• Loading doesn't block entire page unnecessarily