UIControl——event-target-action

最新推荐文章于 2022-01-11 15:25:19 发布

原创最新推荐文章于 2022-01-11 15:25:19 发布 · 672 阅读

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#UIControl #UIControlEvents #event #target #action

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概述

UIView支持手势添加，UIControl继承自UIControl，添加了一些常见手势，这些常见手势会触发一些预定义的UIControlEvent

UIControlEvents

typedef NS_OPTIONS(NSUInteger, UIControlEvents) {
    UIControlEventTouchDown                                         = 1 <<  0,      // on all touch downs
    UIControlEventTouchDownRepeat                                   = 1 <<  1,      // on multiple touchdowns (tap count > 1)
    UIControlEventTouchDragInside                                   = 1 <<  2,
    UIControlEventTouchDragOutside                                  = 1 <<  3,
    UIControlEventTouchDragEnter                                    = 1 <<  4,
    UIControlEventTouchDragExit                                     = 1 <<  5,
    UIControlEventTouchUpInside                                     = 1 <<  6,
    UIControlEventTouchUpOutside                                    = 1 <<  7,
    UIControlEventTouchCancel                                       = 1 <<  8,

    UIControlEventValueChanged                                      = 1 << 12,     // sliders, etc.
    UIControlEventPrimaryActionTriggered NS_ENUM_AVAILABLE_IOS(9_0) = 1 << 13,     // semantic action: for buttons, etc.

    UIControlEventEditingDidBegin                                   = 1 << 16,     // UITextField
    UIControlEventEditingChanged                                    = 1 << 17,
    UIControlEventEditingDidEnd                                     = 1 << 18,
    UIControlEventEditingDidEndOnExit                               = 1 << 19,     // 'return key' ending editing

    UIControlEventAllTouchEvents                                    = 0x00000FFF,  // for touch events
    UIControlEventAllEditingEvents                                  = 0x000F0000,  // for UITextField
    UIControlEventApplicationReserved                               = 0x0F000000,  // range available for application use
    UIControlEventSystemReserved                                    = 0xF0000000,  // range reserved for internal framework use
    UIControlEventAllEvents                                         = 0xFFFFFFFF
};

UIControlEvents bitmask形式保存UIControlEvent，可以同时保存多个UIControlEvent

手势触发的UIControlEvent

UIControlEventTouchDown                                         = 1 <<  0,      // on all touch downs
UIControlEventTouchDownRepeat                                   = 1 <<  1,      // on multiple touchdowns (tap count > 1)
UIControlEventTouchDragInside                                   = 1 <<  2,
UIControlEventTouchDragOutside                                  = 1 <<  3,
UIControlEventTouchDragEnter                                    = 1 <<  4,
UIControlEventTouchDragExit                                     = 1 <<  5,
UIControlEventTouchUpInside                                     = 1 <<  6,
UIControlEventTouchUpOutside                                    = 1 <<  7,
UIControlEventTouchCancel                                       = 1 <<  8,

解释

UIControlEventTouchDown：bounds内点击，highlighted = 1
UIControlEventTouchDownRepeat：bounds内短时间内连击(大于1次)，在触发TouchDownRepeat之前先触发TouchDown，然后触发DownRepeat，然后触发TouchUpInside，因此如果连击3次，依次触发的事件为TouchDown->TouchUpInside->TouchDown->TouchDownRepeat->TouchUpInside->TouchDown->TouchDownRepeat->TouchUpInside
UIControlEventTouchDragInside：bounds内拖动，持续触发，highlighted = 1
UIControlEventTouchDragOutside：bounds内拖动出bounds，在bounds外拖动，持续触发，highlighted = 0
UIControlEventTouchDragEnter：bounds内拖动出bounds，然后再拖动回bounds内临界，不持续触发
UIControlEventTouchDragExit：bounds内拖动出bounds临界，不持续触发
UIControlEventTouchUpInside：bounds内释放，highlighted = 0
UIControlEventTouchUpOutside：bounds内拖动出bounds，在bounds外释放，highlighted = 0
UIControlEventTouchCancel：取消touch Event

概述

UIView支持手势添加，UIControl继承自UIView，自然支持手势添加，但UIControl在UIView基础上预定义了一些常见手势，这些常见手势定义在UIControlEvents中

UIControlEvents

typedef NS_OPTIONS(NSUInteger, UIControlEvents) {
    UIControlEventTouchDown                                         = 1 <<  0,      // on all touch downs
    UIControlEventTouchDownRepeat                                   = 1 <<  1,      // on multiple touchdowns (tap count > 1)
    UIControlEventTouchDragInside                                   = 1 <<  2,
    UIControlEventTouchDragOutside                                  = 1 <<  3,
    UIControlEventTouchDragEnter                                    = 1 <<  4,
    UIControlEventTouchDragExit                                     = 1 <<  5,
    UIControlEventTouchUpInside                                     = 1 <<  6,
    UIControlEventTouchUpOutside                                    = 1 <<  7,
    UIControlEventTouchCancel                                       = 1 <<  8,

    UIControlEventValueChanged                                      = 1 << 12,     // sliders, etc.
    UIControlEventPrimaryActionTriggered NS_ENUM_AVAILABLE_IOS(9_0) = 1 << 13,     // semantic action: for buttons, etc.

    UIControlEventEditingDidBegin                                   = 1 << 16,     // UITextField
    UIControlEventEditingChanged                                    = 1 << 17,
    UIControlEventEditingDidEnd                                     = 1 << 18,
    UIControlEventEditingDidEndOnExit                               = 1 << 19,     // 'return key' ending editing

    UIControlEventAllTouchEvents                                    = 0x00000FFF,  // for touch events
    UIControlEventAllEditingEvents                                  = 0x000F0000,  // for UITextField
    UIControlEventApplicationReserved                               = 0x0F000000,  // range available for application use
    UIControlEventSystemReserved                                    = 0xF0000000,  // range reserved for internal framework use
    UIControlEventAllEvents                                         = 0xFFFFFFFF
};

预定义手势：

UIControlEventTouchDown                                         = 1 <<  0,      // on all touch downs
UIControlEventTouchDownRepeat                                   = 1 <<  1,      // on multiple touchdowns (tap count > 1)
UIControlEventTouchDragInside                                   = 1 <<  2,
UIControlEventTouchDragOutside                                  = 1 <<  3,
UIControlEventTouchDragEnter                                    = 1 <<  4,
UIControlEventTouchDragExit                                     = 1 <<  5,
UIControlEventTouchUpInside                                     = 1 <<  6,
UIControlEventTouchUpOutside                                    = 1 <<  7,
UIControlEventTouchCancel                                       = 1 <<  8,

event-target-action

// add target/action for particular event. you can call this multiple times and you can specify multiple target/actions for a particular event.
// passing in nil as the target goes up the responder chain. The action may optionally include the sender and the event in that order
// the action cannot be NULL. Note that the target is not retained.
- (void)addTarget:(nullable id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents;
// remove the target/action for a set of events. pass in NULL for the action to remove all actions for that target
- (void)removeTarget:(nullable id)target action:(nullable SEL)action forControlEvents:(UIControlEvents)controlEvents;
- (nullable NSArray<nsstring> *)actionsForTarget:(nullable id)target forControlEvent:(UIControlEvents)controlEvent;    // single event. returns NSArray of NSString selector names. returns nil if none
- (UIControlEvents)allControlEvents;                                                       // list of all events that have at least one action
// get info about target & actions. this makes it possible to enumerate all target/actions by checking for each event kind
- (NSSet *)allTargets;                                                                     // set may include NSNull to indicate at least one nil target

- (void)displayIvarList:(Class)aClass
{
    unsigned int varCnt = 0;
    Ivar *classIvars = class_copyIvarList(aClass, &varCnt);
    for(int i = 0; i < varCnt; i++)
    {
        Ivar thisIvar = classIvars[i];
        NSString *varName = [NSString stringWithUTF8String:ivar_getName(thisIvar)];
        NSString *varType = [NSString stringWithUTF8String:ivar_getTypeEncoding(thisIvar)];
        NSLog(@"varName = %@, varType = %@", varName, varType);
    }
    free(classIvars);
}

[self displayIvarList:[UIControl class]];

output：

varName = _targetActions, varType = @"NSMutableArray"
varName = _previousPoint, varType = {CGPoint="x"d"y"d}
varName = _downTime, varType = d
varName = _controlFlags, varType = {?="disabled"b1"tracking"b1"touchInside"b1"touchDragged"b1"requiresDisplayOnTracking"b1"highlighted"b1"dontHighlightOnTouchDown"b1"delayActions"b1"allowActionsToQueue"b1"pendingUnhighlight"b1"selected"b1"verticalAlignment"b2"horizontalAlignment"b2"wasLastHighlightSuccessful"b1"touchHasHighlighted"b1}

分析：

UIControl内含一个NSMutableArray结构，对象类型为event-target-action，event-target-action不能重复，当event触发时，从头依序遍历NSMutableArray，依序调用与event相等的event-target-action中的target-action

注意：

addTarget:action:forControlEvents: ——target可以为nil，controlEvents是UIControlEvents组合，当event触发时，target不为nil时，依序调用与event相等的event-action-action中的target-action，如果找不到target-action，crash；target为nil时，以responder chain顺序寻找action，找到调用，找不到do nothing，不会crash
removeTarget:action:forControlEvents:——target可以为nil，action被ignored，controlEvents是UIControlEvents组合，target不为nil时，删除event-target相等的所有event-target-action，target为nil时，删除event相等的所有event-target-action
actionForTarget:target:forCOntrolEvent:——target为nil，返回也nil，无意义，controlEvent是单一UIControlEvents，不能是UIControlEvents组合，否则方法意义不大，返回event-target相等的action(SEL) NSArray
allControlEvents——返回NSMutableArray中的所有event
allTargets——返回NSMutableArray中的所有target，包括NSNull，如果addTarget:action:forControlEvents: 时target传了nil

注：target参数是弱引用