我玩这个很开心。以下代码将在触摸时从按钮中抓取图像,将该图像拖动到 alpha=0.5,然后将其拖放到您触摸结束时 alpha=1.0 的任何位置。此后它将继续可拖动。
导入 QuartzCore 后,创建一个新文件。 .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
现在在您的主视图控制器中,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;
在这种情况下,imageButton 将是您的苹果按钮。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];
}
瞧!连接你的按钮,设置它的图像,然后把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{}
,以便它可以正确调整图像大小。