目标-c：在按钮单击时将视图添加到窗口

Question

我是 Objective-c 的新手，所以请耐心等待。这看起来很简单，但我一定做错了什么。在 IB 中，我创建了一个对象，将其命名为 AppController，然后添加了一个名为 makeView 的操作和两个 IBOutlets，btnMakeView 和 mainWin，然后正确连接所有内容并从中编写类文件。

在 AppController.h 我有这个代码：

#import <Cocoa/Cocoa.h>
@interface AppController : NSObject {
    IBOutlet NSWindow * mainWin;
    IBOutlet id btnMakeView;
}
- (IBAction)makeView:(id)sender;
@end

在 AppController.m 中这段代码：

#import "AppController.h"
#import "ViewController.h"
@implementation AppController
- (IBAction)makeView:(id)sender {

    //declare a new instance of viewcontroller, which inherits fromNSView, were going to allocate it with 
    //a frame and set the bounds of that frame using NSMakeRect and the floats we plug in.
    ViewController* testbox = [[ViewController alloc]initWithFrame:NSMakeRect(10.0, 10.0, 100.0, 20.0)];

    //this tells the window to add our subview testbox to it's contentview
    [[mainWin contentView]addSubview:testbox];
}
-(BOOL)isFlipped {
    return YES;
}
@end

在 ViewController.h 我有这个代码：

#import <Cocoa/Cocoa.h>
@interface ViewController : NSView {
}
@end

最后在 ViewController.m 我有这个代码：

#import "ViewController.h"

@implementation ViewController    
- (id)initWithFrame:(NSRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code here.
    }
    return self;
}

- (void)drawRect:(NSRect)rect {
    // Drawing code here.

    //sets the background color of the view object
    [[NSColor redColor]set];

    //fills the bounds of the view object with the background color
    NSRectFill([self bounds]);
}

@end

它编译得很好，没有错误但没有得到一个对象，我假设它是一个矩形，从 x,y 10/10 开始，为 100x20。我做错了什么？

Answer 1

mainWin 指的是一个有效的窗口吗？除此之外，您的代码可以工作，尽管它可能需要一些改进。例如，

• ViewController 是视图，而不是控制器，因此不应将其命名为控制器。
• 您遇到了内存泄漏。你永远不会释放你创建的ViewController。 memory management rules are very simple;阅读它们。

尝试以下更改。首先，将ViewController 重命名为RedView（或SolidColorView 或类似名称）。您可以通过 refactoring 非常简单地做到这一点：right-click @interface 或 @implementation 声明中的类名并选择“重构...”。

在 RedView.m 中：

- (id)initWithFrame:(NSRect)frame {
    // the idiom is to call super's init method and test self all in the
    // same line. Note the extra parentheses around the expression. This is a 
    // hint that we really want the assignment and not an equality comparison.
    if ((self = [super initWithFrame:frame])) {
        // Initialization code here.
    }
    return self;
}

在 AppController.m 中：

- (IBAction)makeView:(id)sender {
    //declare a new instance of viewcontroller, which inherits fromNSView, were going to allocate it with 
    //a frame and set the bounds of that frame using NSMakeRect and the floats we plug in.
    RedView* testbox = [[RedView alloc] initWithFrame:NSMakeRect(10.0, 10.0, 100.0, 20.0)];

    //this tells the window to add our subview testbox to it's contentview
    // You don't need to keep a reference to the main window. The application already
    // does this. You might forget to hook up mainWin, but the following won't fail
    // as long as the app has a main window.
    [[[[NSApplication sharedApplication] mainWindow] contentView] addSubview:testbox];
    // We're done with testbox, so release it.
    [testbox release];
}