Implement qmui_contentView method for UINavigationBar

QMUIKit/UIKitExtensions/NSObject+QMUI.m

@@ -262,7 +262,25 @@ @implementation NSObject (QMUI_KeyValueCoding)
 - (id)qmui_valueForKey:(NSString *)key {
     if ([self isKindOfClass:[UIView class]] && QMUICMIActivated && !IgnoreKVCAccessProhibited) {
         BeginIgnoreUIKVCAccessProhibited
-        id value = [self valueForKey:key];
+
+        id value = nil;
+        // 修复：增加 KVC 键合法性校验，避免访问未定义的 key 导致崩溃
+        if ([self respondsToSelector:NSSelectorFromString(key)] ||
+            [self.class instancesRespondToSelector:NSSelectorFromString(key)] ||
+            [self.class accessInstanceVariablesDirectly]) {
+            // 方式1：优先通过 selector 访问（方法/属性）
+            SEL getterSel = NSSelectorFromString(key);
+            if ([self respondsToSelector:getterSel]) {
+                value = ((id (*)(id, SEL))objc_msgSend)(self, getterSel);
+            } else {
+                // 方式2：校验实例变量存在性后再通过 KVC 访问
+                Ivar ivar = class_getInstanceVariable([self class], [key UTF8String]);
+                if (ivar) {
+                    value = [self valueForKey:key];
+                }
+            }
+        }
+
         EndIgnoreUIKVCAccessProhibited
         return value;
     }

QMUIKit/UIKitExtensions/UINavigationBar+QMUI.m

@@ -359,6 +359,25 @@ + (void)load {
 }
 
 - (UIView *)qmui_contentView {
+    if (@available(iOS 26.0, *)) {
+        // 如果 contentView 已经被构造出来，则通过遍历 view 层级树的方式获取
+        UIView *contentView = [self.subviews qmui_firstMatchWithBlock:^BOOL(__kindof UIView * _Nonnull item) {
+            return [NSStringFromClass(item.class) containsString:@"ContentView"];
+        }];
+        if (contentView) return contentView;
+
+        // Xcode 26 编译在 iOS 26 上时，无法用以前的 KVC 方式获取 contentView，所以改为通过 Ivar 获取
+        NSObject *provider = [self valueForKey:@"visualProvider"];
+        __block UIView *result = nil;
+        [provider qmui_enumrateIvarsUsingBlock:^(Ivar  _Nonnull ivar, NSString * _Nonnull ivarDescription) {
+            if (!result && [ivarDescription containsString:@"contentView"]) {
+                result = getObjectIvarValue(provider, ivar);
+            }
+        }];
+        return result;
+    }
+
+    // 在 bar init 完即可获取到 contentView，虽然此时尚未被添加到 view 上
     return [self valueForKeyPath:@"visualProvider.contentView"];
 }