将图像从工具栏拖放到视图画布

Question

我想创建一个应用程序，我需要一个工具栏。工具栏将具有各种数量的对象（图像）。这些对象应该是可拖动的，并放置在它正上方的视图中。

这是一种绘图应用程序，用户可以在画布上选择任何形状和位置。谁能告诉我最好的方法呢？

提前致谢。

Answer 1

艰难的一个。

我要做的是让工具栏上的每个项目都是UIView并覆盖touchesBegan，touchesEnded和touchesMoved。让你的画布另一个UIView。当用户单击要拖动的项目时，请在某处注册该项目，例如正方形。然后当他们放在画布上时，在那个位置画出那个方块。为了使它看起来漂亮，可能会使用类似.4的alpha的UIImageView随着用户的触摸移动，这样他们就知道它们在拖动什么，以及它将落在哪里。

这是代码。 UIViewController.h

@class ToolBox;

@interface ViewController : UIViewController {

    IBOutlet UIView *canvas;

    IBOutlet ToolBox *toolBox;
}

@property (nonatomic, retain) UIView *canvas;
@property (nonatomic, retain) ToolBox *toolBox;

@end

UIViewController.m

#import "ViewController.h"
#import "ToolBox.h"
#import "Tool.h"

@implementation ViewController
@synthesize canvas, toolBox;

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    [[self toolBox] setCanvas:[self canvas]];

    Tool *tool = [[[Tool alloc] initWithFrame:CGRectMake(0,0,64,64)] autorelease];
    [tool setImageView:[[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"1.png"]] autorelease]];
    [tool setImage:[UIImage imageNamed:@"1.png"]];
    [tool addSubview:[tool imageView]];
    [tool setToolBox:[self toolBox]];

    [[self toolBox] addObject:tool];
}

@end

ToolBox.h

@class Tool;
@interface ToolBox : UIView {
    NSMutableArray *tools;

    UIView *canvas;

    UIImage *currentTool;
}

@property (nonatomic, retain) UIImage *currentTool;
@property (nonatomic, retain) NSMutableArray *tools;
@property (nonatomic, retain) UIView *canvas;

-(void)addObject:(Tool *)newTool;
-(void)updatePositions;

@end

ToolBox.m

@implementation ToolBox
@synthesize tools, canvas, currentTool;

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];

    if (self) {

    }

    return self;
}

-(void) dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];

    [super dealloc];
}

-(NSMutableArray *)tools {
    if(tools == nil) {
        [self setTools:[NSMutableArray array]];
    }

    return tools;
}

-(void)addObject:(Tool *)newTool {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(draggingTool:) name:@"Dragging New Tool" object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(draggedTool:) name:@"Dragged Tool To" object:nil];
    [[self tools] addObject:newTool];

    [self updatePositions];
}

-(void)updatePositions {
    int x = 0;
    int y = 0;
    int width = 64;
    int height = 64;

    for(Tool *button in [self tools]) {
        [button setFrame:CGRectMake(x, y, width, height)];
        x += width;
        [self addSubview:button];
    }
}

-(void)draggingTool:(NSNotification *)notif {
    NSDictionary *dict = [notif userInfo];  

    UIImage *image = [dict valueForKey:@"Image"];

    [self setCurrentTool:image];
}

-(void)draggedTool:(NSNotification *)notif {
    UITouch *touch = [[notif userInfo] valueForKey:@"Touch"];   

    CGPoint point = [touch locationInView:canvas];

    UIImageView *imageView = [[[UIImageView alloc] initWithImage:currentTool] autorelease];
    [imageView setCenter:point];
    [canvas addSubview:imageView];
}

@end

Tool.h

@class ToolBox;

@interface Tool : UIView {
    UIImageView *imageView;
    UIImage *image;

    UIImageView *ghostImageView;

    ToolBox *toolBox;
}

@property (nonatomic, retain) UIImageView *imageView;
@property (nonatomic, retain) UIImage *image;
@property (nonatomic, retain) UIImageView *ghostImageView;
@property (nonatomic, retain) ToolBox *toolBox;

@end

Tool.m

#import "Tool.h"
#import "ToolBox.h"

@implementation Tool
@synthesize imageView, image, ghostImageView, toolBox;

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    NSLog(@"tool touches began");
    NSDictionary *dict = [NSDictionary dictionaryWithObject:[self image] forKey:@"Image"];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"Dragging New Tool" object:nil userInfo:dict];

    UITouch *touch = [touches anyObject];
    CGPoint center = [touch locationInView:[[self toolBox] canvas]];

    [self setGhostImageView:[[[UIImageView alloc] initWithImage:[self image]] autorelease]];
    [[self ghostImageView] setCenter:center];
    [[[self toolBox] canvas] addSubview:[self ghostImageView]];

    [[self ghostImageView] setAlpha:.4];
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    NSLog(@"tool touches ended");
    NSDictionary *dict = [NSDictionary dictionaryWithObject:[touches anyObject] forKey:@"Touch"];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"Dragged Tool To" object:nil userInfo:dict];

    [self setGhostImageView:nil];
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    NSLog(@"tool touch moved");
    if([self ghostImageView] != nil) {
        UITouch *touch = [touches anyObject];
        CGPoint center = [touch locationInView:[[self toolBox] canvas]];
        NSLog(@"Ghost : %2f, %2f", center.x, center.y);
        [[self ghostImageView] setCenter:center];
    }
}

@end

我的计划就是这样 -

初始屏幕：工具已准备好拖放到画布上

将工具放在画布上

这是转型的幽灵

Answer 2

我不确定如何在目标c中实现它，但我几乎完全按照你在java中描述的内容完成了。基本上，当您开始在工具栏中拖动对象时，它将识别该操作并将该项的新实例存储在我称为传输容器的内容中，该传输容器基本上是一个全局静态变量。这样当拖动动作竞争时（即掉落），您可以从容器中抓取该对象并将其添加到丢弃的任何位置。