Cocoa處理mouse事件

Apple的《Handling Mouse Events》文檔中有幾個列子記錄一下

 

Listing 4-2  Simple handling of mouse click—sending an action message

- (void)mouseDown:(NSEvent *)theEvent {

[self setFrameColor:[NSColor redColor]];

[self setNeedsDisplay:YES];

}

- (void)mouseUp:(NSEvent *)theEvent {

[self setFrameColor:[NSColor greenColor]];

[self setNeedsDisplay:YES];

[NSApp sendAction:[self action] to:[self target] from:self];

}

- (SEL)action {return action; }

- (void)setAction:(SEL)newAction {

action = newAction;

}

- (id)target { return target; }

- (void)setTarget:(id)newTarget {

target = newTarget;

}

 

處理鼠標拖拽操做：

Application Kit通常有兩種方法處理鼠標拖動事件：

第一種方法重載NSResponder中mouseDown:, mouseDragged:,  mouseUp:（用鼠標左鍵操做）。每一個拖拽動做下，首先Application Kit發送一個MouseDown消息給NSResponder對象，接着發送一個或者多個mouseDragged消息，最後發送一個mouseUp：消息。

第二種方法將鼠標拖動系列事件看成一個單一的事件處理，NSResponder一般必須建立事件循環機制獲取鼠標事件， NSApplication和NSWindow 都有nextEventMatchingMask:untilDate:inMode:dequeue: 方法獲取事件。

這兩種方法都有本身的優勢和缺點。在應用程序拖動操做期間接管鼠標跟蹤循環處理事件。然而，應用程序的主線程沒法處理其餘事件和NSTimer也不會觸發。鼠標跟蹤方法更有效，由於它一般須要更少的代碼，容許全部拖動變量是局部。然而，全部拖動代碼在子類中繼承更困難。

而重載mouseDown:, mouseDragged:,  mouseUp:方法相比前一種方法，更邏輯更清晰，範圍也明確，子類也容易繼承處理鼠標拖動事件。

 

下面是重載mouseDown:, mouseDragged:,  mouseUp:

- (void)mouseDown:(NSEvent *)theEvent {

// mouseInCloseBox and trackingCloseBoxHit are instance variables

if (mouseInCloseBox = NSPointInRect([self convertPoint:[theEvent locationInWindow] fromView:nil], closeBox)) {

trackingCloseBoxHit = YES;

[self setNeedsDisplayInRect:closeBox];

}

else if ([theEvent clickCount] > 1) {

[[self window] miniaturize:self];

return;

}

}

- (void)mouseDragged:(NSEvent *)theEvent {

NSPoint windowOrigin;

NSWindow *window = [self window];

if (trackingCloseBoxHit) {

mouseInCloseBox = NSPointInRect([self convertPoint:[theEvent locationInWindow] fromView:nil], closeBox);

[self setNeedsDisplayInRect:closeBox];

return;

}

windowOrigin = [window frame].origin;

[window setFrameOrigin:NSMakePoint(windowOrigin.x + [theEvent deltaX], windowOrigin.y - [theEvent deltaY])];

}

- (void)mouseUp:(NSEvent *)theEvent {

if (NSPointInRect([self convertPoint:[theEvent locationInWindow] fromView:nil], closeBox)) {

[self tryToCloseWindow];

return;

}

trackingCloseBoxHit = NO;

[self setNeedsDisplayInRect:closeBox];

}

 

下面跟蹤鼠標循環方式，處理拖拽事件：（簡單例子）

- (void)mouseDown:(NSEvent *)theEvent {

BOOL keepOn = YES;

BOOL isInside = YES;

NSPoint mouseLoc;

while (keepOn) {

theEvent = [[self window] nextEventMatchingMask: NSLeftMouseUpMask |

NSLeftMouseDraggedMask];

mouseLoc = [self convertPoint:[theEvent locationInWindow] fromView:nil];

isInside = [self mouse:mouseLoc inRect:[self bounds]];

switch ([theEvent type]) {

case NSLeftMouseDragged:

[self highlight:isInside];

break;

case NSLeftMouseUp:

if (isInside) [self doSomethingSignificant];

[self highlight:NO];

keepOn = NO;

break;

default:

/* Ignore any other kind of event. */

break;

}

};

return;

}

 

 

下面跟蹤鼠標循環方式，處理拖拽事件：（複雜例子）

- (void)mouseDown:(NSEvent *)theEvent

{

if ([theEvent modifierFlags] & NSAlternateKeyMask) {

BOOL dragActive = YES;

NSPoint location = [renderView convertPoint:[theEvent locationInWindow] fromView:nil];

NSAutoreleasePool *myPool = nil;

NSEvent* event = NULL;

NSWindow *targetWindow = [renderView window];

myPool = [[NSAutoreleasePool alloc] init];

while (dragActive) {

event = [targetWindow nextEventMatchingMask:(NSLeftMouseDraggedMask | NSLeftMouseUpMask)

untilDate:[NSDate distantFuture]

inMode:NSEventTrackingRunLoopMode

dequeue:YES];

if(!event)

continue;

location = [renderView convertPoint:[event locationInWindow] fromView:nil];

switch ([event type]) {

case NSLeftMouseDragged:

annotationPeel = (location.x * 2.0 / [renderView bounds].size.width);

[imageLayer showLens:(annotationPeel <= 0.0)];

[peelOffFilter setValue:[NSNumber numberWithFloat:annotationPeel] forKey:@"inputTime"];

[self refresh];

break;

case NSLeftMouseUp:

dragActive = NO;

break;

default:

break;

}

}

[myPool release];

} else {

// other tasks handled here......

}

}

 

 

下面跟蹤鼠標循環方式，處理拖拽事件：（經典例子）

- (void)mouseDown:(NSEvent *)theEvent {

NSPoint pos;

while ((theEvent = [[self window] nextEventMatchingMask:

NSLeftMouseUpMask | NSLeftMouseDraggedMask])) {

NSPoint pos = [self convertPoint:[theEvent locationInWindow]

fromView:nil];

if ([theEvent type] == NSLeftMouseUp)

break;

// Do some other processing...

}

}