feat: 一些bug修复

miniprogram/englishPages/letterTracing/letterTracing.ts

@@ -52,6 +52,24 @@ function getDailyGroupIndex(letters?: string[]): number {
     return idx >= 0 ? idx : 0;
 }
 
+function pickRandomIndexExcept(total: number, current: number): number {
+    if (total <= 1) return 0;
+    let next = Math.floor(Math.random() * total);
+    while (next === current) {
+        next = Math.floor(Math.random() * total);
+    }
+    return next;
+}
+
+function pickRandomLetterExcept(current: string): string {
+    if (LETTERS_UPPER.length <= 1) return LETTERS_UPPER[0] ?? 'A';
+    let next = LETTERS_UPPER[Math.floor(Math.random() * LETTERS_UPPER.length)];
+    while (next === current) {
+        next = LETTERS_UPPER[Math.floor(Math.random() * LETTERS_UPPER.length)];
+    }
+    return next;
+}
+
 const pageInfoLookup = getModeInfo;
 
 type PageData = CanvasDataState & {
@@ -279,6 +297,51 @@ createPage(
             this.drawCanvas();
         },
 
+        /** 预览区刷新：按当前模式随机换字母 / 分组后重绘 */
+        onPreviewRefresh() {
+            const mode = this.data.traceMode;
+            const updates: Partial<PageData> = {};
+
+            switch (mode) {
+                case 'letter-tracing-single': {
+                    const next = pickRandomLetterExcept(
+                        this.data.selectedLetter,
+                    );
+                    updates.selectedLetter = next;
+                    updates.selectedLetterPair = `${next}${next.toLowerCase()}`;
+                    break;
+                }
+                case 'letter-tracing-case-pairing':
+                case 'letter-tracing-half':
+                    updates.letterCaseLower = !this.data.letterCaseLower;
+                    break;
+                case 'letter-tracing-three':
+                    updates.selectedTripleGroupIdx = pickRandomIndexExcept(
+                        TRIPLE_GROUPS.length,
+                        this.data.selectedTripleGroupIdx,
+                    );
+                    break;
+                case 'letter-tracing-daily-checkin':
+                    updates.selectedDailyGroupIdx = pickRandomIndexExcept(
+                        DAILY_GROUPS.length,
+                        this.data.selectedDailyGroupIdx,
+                    );
+                    break;
+                default:
+                    break;
+            }
+
+            if (Object.keys(updates).length > 0) {
+                this.setData(
+                    updates as Partial<PageData> & WechatMiniprogram.IAnyObject,
+                    () => this.drawCanvas(),
+                );
+                return;
+            }
+
+            this.drawCanvas();
+        },
+
         async onPreviewFavorite() {
             const next = !this.data.isPreviewFavorite;
             this.setData({ isPreviewFavorite: next });

miniprogram/englishPages/letterTracing/letterTracing.wxml

@@ -4,10 +4,11 @@
     <view class="lt-main">
         <preview-card
             id="previewCard"
-            showRefresh="{{false}}"
+            showRefresh="{{true}}"
             showFavorite="{{true}}"
             favorited="{{isPreviewFavorite}}"
             bind:canvas-ready="onCanvasReady"
+            bind:refresh="onPreviewRefresh"
             bind:favorite="onPreviewFavorite" />
 
         <!-- 选择字母（默认字帖模式） -->