Question

我正在开发一款简单的游戏，其中“粒子”被用户触摸所吸引。

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    NSArray *touch = [touches allObjects];
    for (numberOfTouches = 0; numberOfTouches < [touch count]; numberOfTouches++) {
        lastTouches[numberOfTouches] = [((UITouch *)[touch objectAtIndex:numberOfTouches]) locationInView:self];
    }
    isTouching = YES;
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    NSArray *touch = [touches allObjects];
    for (numberOfTouches = 0; numberOfTouches < [touch count]; numberOfTouches++) {
        lastTouches[numberOfTouches] = [((UITouch *)[touch objectAtIndex:numberOfTouches]) locationInView:self];
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    NSArray *touch = [touches allObjects];
    for (numberOfTouches = 0; numberOfTouches < [touch count]; numberOfTouches++) {
        lastTouches[numberOfTouches] = [((UITouch *)[touch objectAtIndex:numberOfTouches]) locationInView:self];
    }
    if (!stickyFingers) {
        isTouching = NO;
    }
}

lastTouches是CGPoint的数组，程序的另一部分用于移动粒子。

我遇到的问题是我现在设置它的方式，无论何时调用3个函数中的任何一个，它们都会覆盖CGPoints数组和numberOfTouches。我不认为这会是一个问题，但事实证明，TouchesMoved只能获得已经改变的触摸并且没有得到保持不变的触摸。因此，如果您移动一根手指而不是另一只手指，则程序会忘记手指没有移动，所有粒子都朝向移动的手指。如果你移动两个手指，粒子就会在两个手指之间移动。

我需要在保持更新已经移动的触摸时保持尚未移动的触摸。

任何建议？

Answer 1

Set theory救援！

//Instance variables
NSMutableSet *allTheTouches;
NSMutableSet *touchesThatHaveNotMoved;
NSMutableSet *touchesThatHaveNeverMoved;

//In touchesBegan:withEvent:
if (!allTheTouches) {
    allTheTouches = [[NSMutableSet alloc] init];
    touchesThatHaveNotMoved = [[NSMutableSet alloc] init];
    touchesThatHaveNeverMoved = [[NSMutableSet alloc] init];
}
[allTheTouches unionSet:touches];
[touchesThatHaveNotMoved unionSet:touches];
[touchesThatHaveNeverMoved unionSet:touches];

//In touchesMoved:withEvent:
[touchesThatHaveNeverMoved minusSet:touches];
[touchesThatHaveNotMoved setSet:allTheTouches];
[touchesThatHaveNotMoved minusSet:touches];

//In touchesEnded:withEvent:
[allTheTouches minusSet:touches];
if ([allTheTouches count] == 0) {
    [allTheTouches release]; //Omit if using ARC
    allTheTouches = nil;
    [touchesThatHaveNotMoved release]; //Omit if using ARC
    touchesThatHaveNotMoved = nil;
}
[touchesThatHaveNotMoved minusSet:touches];
[touchesThatHaveNeverMoved minusSet:touches];

在上文中，touchesThatHaveNotMoved将保留在最后touchesMoved:内没有移动的触摸，而touchesThatHaveNeverMoved将保留自开始以来一直没有移动过的触摸。您可以省略一个或两个变量，以及您不关心的所有涉及它们的语句。

TouchesMoved仅返回已更改的触摸，忽略未更改的触摸

1 个答案: