我查看了 Apple 的示例触摸应用程序，但它并没有解决我的问题。在他们的示例应用程序中，当触摸事件发生时，它会尝试将视图保持在发生触摸事件的位置。这使得逻辑很简单。他们只是寻找其框架包含触摸位置的视图。
这在我的场景中不起作用。这是我的场景。
有一个包含一堆子视图的视图。这个想法是允许用户在他们手势的方向上投掷其中一个子视图。我希望touchesBegan事件找到其中心最接近触摸的视图。
然后，我希望touchesEnded事件以由开始和结束事件确定的速度移动同一视图。速度不一定与手指速度相同，因此我不能像 Apple 在示例应用程序中所做的那样简单地将视图“附加”到触摸位置。
我想过用触摸对象标记标识的视图touchesBegan，并使用它与事件中的触摸对象进行比较touchesEnded，但这不起作用。touchesBegan和touchesEnded事件的触摸对象不同。
那么我错过了什么？如何保存要移动的视图和触摸之间的关系？
TouchObject 将不相似。对象会随着触摸的视图、位置等发生变化。请查看UITouch 类以获取详细信息。
建议一：
我通过子类化 UIView并在子类中添加触摸代理在我的项目中实现了同样的事情。我创建了这个子类的实例而不是普通的 UIView。
@interface myView : UIView
@end
@implementation myView
//over ride the following methods
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
}
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event
{
}
@end
建议二
使用UIPanGesture做同样的事情。这将是一种更简单的方法。
UIPanGestureRecognizer *panGesture = [[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panGestureMoveAround:)] autorelease];
[panGesture setMaximumNumberOfTouches:2];
[panGesture setDelegate:self];
[yourSubView addGestureRecognizer:panGesture];
-(void)panGestureMoveAround:(UIPanGestureRecognizer *)gesture;
{
UIView *piece = [gesture view];
[self adjustAnchorPointForGestureRecognizer:gesture];
if ([gesture state] == UIGestureRecognizerStateBegan || [gesture state] == UIGestureRecognizerStateChanged) {
CGPoint translation = [gesture translationInView:[piece superview]];
[piece setCenter:CGPointMake([piece center].x + translation.x, [piece center].y+translation.y*0.1)];
[gesture setTranslation:CGPointZero inView:[piece superview]];
}
}
一个例子是here
这是我的解决方案。在此解决方案中，scaledView是箭头视图移动的视图。它们属于类spriteView，它是 的子类UIView。
-(spriteView *)findArrowContainingTouch:(UITouch *)touch inView:(UIView *)scaledView atPoint:(CGPoint) touchPoint
//There could be multiple subviews whose rectangles include the point. Find the one whose center is closest.
{
spriteView * touchedView = nil;
float bestDistance2 = 9999999999.9;
float testDistance2 = 0;
for (spriteView *arrow in scaledView.subviews) {
if (arrow.tag == ARROWTAG) {
if (CGRectContainsPoint(arrow.frame, touchPoint)) {
testDistance2 = [self distance2Between:touchPoint and:arrow.center];
if (testDistance2<bestDistance2) {
bestDistance2 = testDistance2;
touchedView = arrow;
}
}
}
}
return touchedView;
}
该方法distance2Between计算两点之间距离的平方。
-(spriteView *)findArrowTouchedAtLocation:(CGPoint)p inView:(UIView *)scaledView
{
spriteView * arrow = nil;
for (spriteView *testArrow in scaledView.subviews) {
if (testArrow.tag == ARROWTAG) {
if ((p.x == testArrow.touch.x) && (p.y == testArrow.touch.y)) {
arrow = testArrow;
}
}
}
return arrow;
}
中有不是箭头的子视图scaledView，所以我使用常量 ARROWTAG 来标识箭头。
#pragma mark - Touches
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UIView *scaledView = [self getScaledView];
for (UITouch *touch in touches) {
CGPoint touchLocation = [touch locationInView:scaledView];
spriteView * arrow = [self findArrowContainingTouch:touch inView:scaledView atPoint:touchLocation];
if (!(arrow==nil)) {
//Record the original location of the touch event in a property, originalTouchLocation, of the arrow instance. Additionally, store the same point on the property touch.
//Both properties are necessary. The originalTouchLocation will be used in `touchesEnded` and is not available in the `touch` object. So the information is stored separately.
//The `touch` property, a CGPoint, is stored in order to identify the view. This property is updated by every touch event. The new value will be used by the upcoming event to find the appropriate view.
arrow.touch = CGPointMake(touchLocation.x, touchLocation.y);
arrow.originalTouchLocation = CGPointMake(touchLocation.x, touchLocation.y);
arrow.debugFlag = YES;
arrow.timeTouchBegan = touch.timestamp;
}
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UIView *scaledView = [self getScaledView];
for (UITouch *touch in touches) {
CGPoint touchLocation = [touch locationInView:scaledView];
CGPoint previousLocation = [touch previousLocationInView:scaledView];
//previousLocation is used to find the right view. This must be in the coordinate system of the same view used in `touchesBegan`.
spriteView * arrow = [self findArrowTouchedAtLocation:previousLocation inView:scaledView];
if (!(arrow==nil)) {
arrow.touch = CGPointMake(touchLocation.x, touchLocation.y);
}
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
UIView *scaledView = [self getScaledView];
for (UITouch *touch in touches) {
CGPoint touchLocation = [touch locationInView:scaledView];
CGPoint previousLocation = [touch previousLocationInView:scaledView];
spriteView * arrow = [self findArrowTouchedAtLocation:previousLocation inView:scaledView];
if (!(arrow==nil)) {
arrow.touch = CGPointMake(touchLocation.x, touchLocation.y);
float strokeAngle = [self findAngleFrom:arrow.originalTouchLocation to:touchLocation];
float strokeDistance2 = sqrt([self distance2Between:arrow.originalTouchLocation and:touchLocation]);
NSTimeInterval timeElapsed = touch.timestamp - arrow.timeTouchBegan;
float newArrowSpeed = strokeDistance2 / timeElapsed / 100; //might want to use a different conversion factor, but this one works quite well
arrow.transform = CGAffineTransformMakeRotation(strokeAngle);
arrow.currentSpeed = newArrowSpeed;
}
}
}
-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
UIView *scaledView = [self getScaledView];
for (UITouch *touch in touches) {
CGPoint previousLocation = [touch previousLocationInView:scaledView];
spriteView * arrow = [self findArrowTouchedAtLocation:previousLocation inView:scaledView];
if (!(arrow==nil)) {
arrow.originalTouchLocation = CGPointMake(99999.0, 99999.0);
NSLog(@"Arrow original location erased");
}
}
}
实际上，触摸对象在touchesBegan和中是相同的touchesEnded。事实证明，这是跟踪触摸的方式。