fix: address Copilot review comments for code quality

- Extract magic number 0.01f to SCALING_THRESHOLD constant in SettingFragment
- Extract scaling ratios to named constants in FontSizeUtil for better maintainability
- Fix potential duplicate scroll listeners by checking if already set
- Simplify instanceof check in MainActivity (remove unnecessary null check)
- Add field to track scroll listener to prevent duplicates

Addresses all code quality feedback from Copilot in PR #131

Author: graycreate

app/src/main/java/me/ghui/v2er/module/home/MainActivity.java

@@ -316,8 +316,8 @@ private void applyFontSizeToNavigationMenu() {
 
     private void applyFontScalingToMenuItems() {
         // Apply scaling only once to avoid repeated scaling
-        ViewGroup menuView = (ViewGroup) mNavigationView.getChildAt(0);
-        if (menuView != null && menuView instanceof RecyclerView) {
+        View menuView = mNavigationView.getChildAt(0);
+        if (menuView instanceof RecyclerView) {
             RecyclerView recyclerView = (RecyclerView) menuView;
             // Apply to currently visible items
             for (int i = 0; i < recyclerView.getChildCount(); i++) {

app/src/main/java/me/ghui/v2er/module/settings/SettingFragment.java

@@ -39,7 +39,9 @@
  */
 
 public class SettingFragment extends PreferenceFragment implements Preference.OnPreferenceClickListener {
+    private static final float SCALING_THRESHOLD = 0.01f;
     private ListView mListView;
+    private android.widget.AbsListView.OnScrollListener mScrollListener;
     private Preference cachePref;
     private Preference loginPreference;
 
@@ -116,7 +118,7 @@ private void applyFontScalingToPreferences(ListView listView) {
         // Apply font scaling after a short delay to ensure views are created
         listView.postDelayed(() -> {
             float scalingRatio = FontSizeUtil.getScalingRatio();
-            if (Math.abs(scalingRatio - 1.0f) < 0.01f) {
+            if (Math.abs(scalingRatio - 1.0f) < SCALING_THRESHOLD) {
                 // No scaling needed for default size
                 return;
             }
@@ -127,8 +129,9 @@ private void applyFontScalingToPreferences(ListView listView) {
                 applyFontScalingToView(child);
             }
 
-            // Add scroll listener to apply scaling to new items
-            listView.setOnScrollListener(new android.widget.AbsListView.OnScrollListener() {
+            // Add scroll listener to apply scaling to new items (only if not already set)
+            if (mScrollListener == null) {
+                mScrollListener = new android.widget.AbsListView.OnScrollListener() {
                 @Override
                 public void onScrollStateChanged(android.widget.AbsListView view, int scrollState) {
                     // Not needed
@@ -146,7 +149,9 @@ public void onScroll(android.widget.AbsListView view, int firstVisibleItem,
                         }
                     }
                 }
-            });
+                };
+                listView.setOnScrollListener(mScrollListener);
+            }
         }, 100);
     }
 

app/src/main/java/me/ghui/v2er/util/FontSizeUtil.java

@@ -5,6 +5,11 @@
 import me.ghui.v2er.general.Pref;
 
 public class FontSizeUtil {
+    // Scaling ratio constants
+    private static final float SMALL_SCALE = 0.875f;   // 87.5% of default
+    private static final float MEDIUM_SCALE = 1.0f;    // 100% default
+    private static final float LARGE_SCALE = 1.25f;    // 125% of default
+    private static final float EXTRA_LARGE_SCALE = 1.5f; // 150% of default
 
     /**
      * Common helper method to get font dimension based on size preference
@@ -75,14 +80,14 @@ public static float getScalingRatio() {
         String size = Pref.read(R.string.pref_key_fontsize);
         switch (size) {
             case "小":
-                return 0.875f;  // 87.5% of default
+                return SMALL_SCALE;
             case "大":
-                return 1.25f;   // 125% of default
+                return LARGE_SCALE;
             case "特大":
-                return 1.5f;    // 150% of default
+                return EXTRA_LARGE_SCALE;
             case "中":
             default:
-                return 1.0f;    // 100% default
+                return MEDIUM_SCALE;
         }
     }