iphone - 如何实现连续拖拽菜单效果？

Question

我正在尝试实现拖放菜单效果。我不确定该怎么做，也许有人对这种确切效果有经验。

很简单，当用户触摸菜单项时，我希望在他们的触摸位置出现一个图形。他们的触摸现在将控制图形的平移。释放触摸后，图形将位于其位置并呈现完整的 alpha。

我已经熟悉创建平移手势和实例化图形。到目前为止，我可以创建触摸菜单项的图形。最大的问题是我如何“跳过”触摸手势，使其成为一个连续的 Action 。

另外，菜单项应该是 UIButton 还是 UIImageView？

感谢任何帮助。谢谢

Answer 1

我玩这个很开心。以下代码将在触摸时从按钮抓取图像，将图像拖动到 alpha=0.5，然后将其放在触摸结束的 alpha=1.0 处。此后它将继续可拖动。

导入QuartzCore后，新建一个文件。 .h 应为:

#import <Foundation/Foundation.h>
#import <QuartzCore/CAGradientLayer.h>
#import <QuartzCore/CALayer.h>

@interface DraggableImage : CAGradientLayer

- (void)draw:(UIImage *)image;

- (void)moveToFront;

- (void)appearDraggable;

- (void)appearNormal;

@end

.m 应该是:

#import "DraggableImage.h"

@implementation DraggableImage

- (void)draw:(UIImage *)image{
    CGRect buttonFrame = self.bounds;
    int buttonWidth = buttonFrame.size.width;
    int buttonHeight = buttonFrame.size.height;
    UIGraphicsBeginImageContext( CGSizeMake(buttonWidth, buttonHeight) );
    [image drawInRect:self.bounds];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    [newImage drawInRect:self.bounds];
}

- (void)moveToFront {
    CALayer *superlayer = self.superlayer;
    [self removeFromSuperlayer];
    [superlayer addSublayer:self];
}

- (void)appearDraggable {
    self.opacity = 0.5;
}


- (void)appearNormal {
    self.opacity = 1.0;
}

@end

现在在你的主视图 Controller 中，添加:

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
#import "DraggableImage.h"

@interface YourViewController : UIViewController{
    DraggableImage *heldImage;
    DraggableImage *imageForFrame[5]; // or however many
    UIButton *buttonPressed;
    int imageCount;
}
@property (weak, nonatomic) IBOutlet UIButton *imageButton;
-(IBAction)buildImageLayerForButton:(UIButton *)sender;
- (void)moveHeldImageToPoint:(CGPoint)location;
- (CALayer *)layerForTouch:(UITouch *)touch;

本例中的 imageButton 将是您的 apple Button。现在在您的 .m 文件中，添加以下内容:

@synthesize imageButton;

#pragma - mark Touches

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    CALayer *hitLayer = [self layerForTouch:[touches anyObject]];
    if ([hitLayer isKindOfClass:[DraggableImage class]]) {
        DraggableImage *image = (DraggableImage *)hitLayer;

        heldImage = image;
        [heldImage moveToFront];
    }
    hitLayer = nil;
    [super touchesBegan:touches withEvent:event];
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{

        if (heldImage) 
        {
            UITouch *touch = [touches anyObject];
            UIView *view = self.view;
            CGPoint location = [touch locationInView:view];
            [self moveHeldImageToPoint:location];
        }

}

- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
    if (heldImage) {
        [heldImage appearNormal];
        heldImage = nil;
    }
}

- (void)dragBegan:(UIControl *)c withEvent:ev {
}
- (void)dragMoving:(UIControl *)c withEvent:ev {
    UITouch *touch = [[ev allTouches] anyObject];
    CGPoint touchPoint = [touch locationInView:self.view];
    [self moveHeldImageToPoint:touchPoint];
}

- (void)dragEnded:(UIControl *)c withEvent:ev {
    UITouch *touch = [[ev allTouches] anyObject];
    CGPoint touchPoint = [touch locationInView:self.view];
    [self moveHeldImageToPoint:touchPoint];
    [heldImage appearNormal];
    heldImage = nil;
}



-(IBAction)buildImageLayerForButton:(UIButton *)sender{


        DraggableImage *image = [[DraggableImage alloc] init];
        buttonPressed = sender;
        CGRect buttonFrame = sender.bounds;
        int buttonWidth = buttonFrame.size.width;
        int buttonHeight = buttonFrame.size.height;

        image.frame = CGRectMake(120, 24, buttonWidth*3, buttonHeight*3);
        image.backgroundColor = [UIColor lightGrayColor].CGColor;
        image.delegate = self;
        imageForFrame[imageCount] = image;
        [self.view.layer addSublayer:image];
        [image setNeedsDisplay];
        [image moveToFront];
        [image appearDraggable];
        heldImage = image;
        [self moveHeldImageToPoint:sender.center];

        imageCount++;

}
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
    UIGraphicsPushContext(ctx);

    DraggableImage *image = (DraggableImage *)layer;
    [image draw:[buttonPressed imageForState:UIControlStateNormal]];

    UIGraphicsPopContext();
}

- (void)moveHeldImageToPoint:(CGPoint)location 
{
    float dx = location.x;
    float dy = location.y;
    CGPoint newPosition = CGPointMake(dx, dy);

    [CATransaction begin];
    [CATransaction setDisableActions:TRUE];
    heldImage.position = newPosition;
    [CATransaction commit];
}

- (CALayer *)layerForTouch:(UITouch *)touch 
{
    UIView *view = self.view;

    CGPoint location = [touch locationInView:view];
    location = [view convertPoint:location toView:nil];

    CALayer *hitPresentationLayer = [view.layer.presentationLayer hitTest:location];
    if (hitPresentationLayer) 
    {
        return hitPresentationLayer.modelLayer;
    }

    return nil;
}

-(void)viewDidLoad{
    [imageButton addTarget:self action:@selector(dragBegan:withEvent:) forControlEvents: UIControlEventTouchDown];
    [imageButton addTarget:self action:@selector(dragMoving:withEvent:) forControlEvents: UIControlEventTouchDragInside | UIControlEventTouchDragOutside];
    [imageButton addTarget:self action:@selector(dragEnded:withEvent:) forControlEvents: UIControlEventTouchUpInside | UIControlEventTouchUpOutside];
    [super viewDidLoad];
}

- (void)viewDidUnload {
    [self setImageButton:nil];
    [super viewDidUnload];
}

等等!连接你的按钮，设置它的图像，然后将副本扔到整个屏幕上。 :)

注意:我没有发表太多评论，但很乐意回答任何问题。

干杯!

编辑:修复了 -(void)draw:(UIImage *)image{} 以便正确调整图像大小。