最近公司做一个项目，会用自定预览界面，首先想到的就是QLPreviewController，因为这是Apple自带的框架，效率上也比WebView好些。但是QLPreviewController的自定义特性比较差，我们的界面不需要QLPreviewController 的 NavigationBar 右上角的 分享按钮，纠结了很久一直没有找到比较好的解决方法，后来还是万能的github给出了一个较为理想的答案。
老外给的建议是用runtime改写原来的方法，用的是UINavigationItem的类别。如果是QLPreviewController类那么就自定义的setRightBarButtonItem或者setRightBarButtonItems方法，其他的类就按照原来的方法执行。乍一看其实挺完美的一个方案，但是还是有隐患的，因为是类别方法，而且load的时候就加载了，那么后续如果其他人不知道有这种情况，想用系统的分享按钮也用不着了，因为所有的QLPreviewController都会用到这个类别。
方案一
+ (void)load
{
MethodSwizzle(self, @selector(setRightBarButtonItem:animated:), @selector(override_setRightBarButtonItem:animated:));
MethodSwizzle(self, @selector(setRightBarButtonItems:animated:), @selector(override_setRightBarButtonItems:animated:));
}
void MethodSwizzle(Class class, SEL originalSEL, SEL overrideSEL)
{
Method originalMethod = class_getInstanceMethod(class, originalSEL);
Method overrideMethod = class_getInstanceMethod(class, overrideSEL);
if (class_addMethod(class, originalSEL, method_getImplementation(overrideMethod), method_getTypeEncoding(overrideMethod))) {
class_replaceMethod(class, overrideSEL, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, overrideMethod);
}
}
- (void)override_setRightBarButtonItem:(UIBarButtonItem *)item animated:(BOOL)animated
{
if (item && [item.target isKindOfClass:[QLPreviewController class]] && item.action == @selector(actionButtonTapped:)){
QLPreviewController *previewController = (QLPreviewController *)item.target;
[self override_setRightBarButtonItem:previewController.navigationItem.rightBarButtonItem animated:animated];
} else {
[self override_setRightBarButtonItem:item animated:animated];
}
}
- (void)override_setRightBarButtonItems:(NSArray *)items animated:(BOOL)animated
{
if ([items count] == 0) {
return;
} else {
UIBarButtonItem *firstItem = [items objectAtIndex:0];
BOOL override = NO;
if (firstItem && [firstItem.target isKindOfClass:[QLPreviewController class]] && firstItem.action == @selector(actionButtonTapped:)) {
override = YES;
}
if (override) {
QLPreviewController *previewController = (QLPreviewController *)firstItem.target;
[self override_setRightBarButtonItems:previewController.navigationItem.rightBarButtonItems animated:animated];
} else {
[self override_setRightBarButtonItems:items animated:animated];
}
}
}
1.因为load方法是UIBarButtonItem类加载的时候就会调用的，所以保证了有效性
2.然后交换原来的方法，用我们自己的方法实现
3.这里作者用了个技巧，因为已经交换了方法，所以再调用一次override_*方法相当于调用了原来的方法
方案二
既然这样我做一下小改动，自定义一个QLPreviewController的子类，再界面显示前我替换掉原来的方法，界面显示完以后我就把原来的方法再交换回来，那么其他的类包括QLPreviewController本身因该是不会收到影响的。
+ (void)exchangeMethod
{
MethodSwizzle(self, @selector(setRightBarButtonItem:animated:), @selector(override_setRightBarButtonItem:animated:));
MethodSwizzle(self, @selector(setRightBarButtonItems:animated:), @selector(override_setRightBarButtonItems:animated:));
}
+ (void)noExchangeMethod
{
MethodSwizzle(self, @selector(override_setRightBarButtonItem:animated:), @selector(setRightBarButtonItem:animated:));
MethodSwizzle(self, @selector(override_setRightBarButtonItems:animated:), @selector(setRightBarButtonItems:animated:));
}
方案三
那还有没有其他方案？这里我稍加修改了下，我不用类别，直接使用runtime行不行？因为只是隐藏rightBarButtonItem或是rightBarButtonItems那么我简单的执行一个空方法就可以了，末了我在把原来的方法还原回去。
首先定义两个函数指针变量存储原来的实现方法
@implementation CSPreviewController
{
IMP origImpOne;
IMP origImpTwo;
}
这里是两个空方法，注意格式
static void override_setRightBarButtonItem(id _self, SEL __cmd, UIBarButtonItem *item, BOOL animated)
{
//
}
static void override_setRightBarButtonItems(id _self, SEL __cmd, NSArray *items, BOOL animated)
{
//
}
runtime实现
- (void)overrideMethod
{
SEL selectorOneToOverride = @selector(setRightBarButtonItem:animated:);
Method methodOne = class_getInstanceMethod([UINavigationItem class], selectorOneToOverride);
origImpOne = class_getMethodImplementation([UINavigationItem class], selectorOneToOverride);
method_setImplementation(methodOne, (IMP)override_setRightBarButtonItem);
SEL selectorTwoToOverride = @selector(setRightBarButtonItems:animated:);
Method methodTwo = class_getInstanceMethod([UINavigationItem class], selectorTwoToOverride);
origImpTwo = class_getMethodImplementation([UINavigationItem class], selectorTwoToOverride);
method_setImplementation(methodTwo, (IMP)override_setRightBarButtonItems);
}
- (void)noOverrideMethod
{
SEL selectorOneToOverride = @selector(setRightBarButtonItem:animated:);
Method methodOne = class_getInstanceMethod([UINavigationItem class], selectorOneToOverride);
method_setImplementation(methodOne, origImpOne);
SEL selectorTwoToOverride = @selector(setRightBarButtonItems:animated:);
Method methodTwo = class_getInstanceMethod([UINavigationItem class], selectorTwoToOverride);
method_setImplementation(methodTwo, origImpTwo);
}
放在super方法之前调用，因为super调用的时候已经开始调用set方法了，再改就来不及了。
- (void)viewWillAppear:(BOOL)animated
{
[self overrideMethod];
[super viewWillAppear:animated];
}
- (void)viewWillDisappear:(BOOL)animated
{
[self noOverrideMethod];
[super viewWillDisappear:animated];
}
如果需要更详细的自定义，那么修改以上方案即可。
PS:Demo源码