Question

平，

刚刚开始进入C4，到目前为止，我的经历非常棒。我正在复制用相机示例拍摄照片，出于某种原因，当我按照教程（http://www.c4ios.com/tutorials/takingSnapshots）中所述完成所有操作时，我得到以下错误： “'TakePhoto'没有可见的@interface声明选择器'listenFor：from Object：'”（Take Photo是我正在处理的文件）我想我必须在类定义中声明“imageWasCaptured”，但我不知道是什么？有什么建议吗？

更新：这是代码 https://github.com/susemiessner/Urban-Alphabets/tree/master/urbanAlphabets 或者只是简单复制的 TakePhoto.h

#import "C4CanvasController.h"

@interface TakePhoto : C4CanvasController

@end

TakePhoto.m

    #import "TakePhoto.h"
    #define NavBarHeight 42
    #define TopBarFromTop 20

    @interface TakePhoto ()

    @end

    @implementation TakePhoto {
        //common variables
        UIColor *navBarColor;
        UIColor *buttonColor;
        UIColor *typeColor;

        //top toolbar
        C4Shape *topNavBar;
        C4Font *fatFont;
        C4Label *takePhoto;



        //camera
        C4Camera *cam;

        //bottom Toolbar
        C4Shape *bottomNavBar;
        C4Button *takePhotoButton;
    }
    -(void) setup{
        navBarColor=[UIColor colorWithRed:0.96875 green:0.96875 blue:0.96875 alpha:1];
        buttonColor= [UIColor colorWithRed:0.8984275 green:0.8984275 blue:0.8984275 alpha:1];
        typeColor=[UIColor colorWithRed:0.19921875 green:0.19921875 blue:0.19921875 alpha:1];

        [self topBarSetup];
        [self bottomBarSetup];
        [self cameraSetup];

    }
    -(void)topBarSetup{
        topNavBar=[C4Shape rect:CGRectMake(0, TopBarFromTop, self.canvas.width, NavBarHeight)];
        topNavBar.fillColor=navBarColor;
        topNavBar.lineWidth=0;
        [self.canvas addShape:topNavBar];


        fatFont=[C4Font fontWithName:@"HelveticaNeue-Bold" size:17];
        takePhoto = [C4Label labelWithText:@"Take Photo" font:fatFont];
        takePhoto.center=topNavBar.center;
        [self.canvas addLabel:takePhoto];}

    -(void)cameraSetup{
        cam = [C4Camera cameraWithFrame:CGRectMake(0,TopBarFromTop+NavBarHeight, self.canvas.width, self.canvas.height-(2*NavBarHeight+TopBarFromTop))];
        [self.canvas addCamera:cam];
        [cam initCapture];
        //tapping to take image
        [self addGesture:TAP name:@"capture" action:@"capturedImage"];
        [self numberOfTouchesRequired:1 forGesture:@"capture"];
//the following line is where I get the error
        [self listenFor:@"imageWasCaptured" fromObject:@"putCapturedImageOnCanvas"];
    }
    -(void) bottomBarSetup{
        bottomNavBar=[C4Shape rect:CGRectMake(0, self.canvas.height-(NavBarHeight), self.canvas.width, NavBarHeight)];
        bottomNavBar.fillColor= navBarColor;
        bottomNavBar.lineWidth=0;
        [self.canvas addShape:bottomNavBar];

        takePhotoButton=[UIButton buttonWithType: ROUNDEDRECT];
        [takePhotoButton setTitle:@"TakePhoto" forState:UIControlStateNormal];
        takePhotoButton.frame=CGRectMake(self.canvas.width/2-50, self.canvas.height-(NavBarHeight), 100, NavBarHeight);
        takePhotoButton.backgroundColor=buttonColor;
        takePhotoButton.tintColor=typeColor;
        [self.canvas addSubview:takePhotoButton];

    }

    -(void) takingPhoto{
        [cam captureImage];
    }
    -(void) captureImage{
        [cam captureImage];
    }
    -(void)putCapturedImageOnCanvas{
        C4Image *img = cam.capturedImage;
        img.width=240;
        img.center=CGPointMake(self.canvas.width*2/3, self.canvas.center.y);

    }


    @end

Answer 1

为了让你的概念发挥作用，你的方法中有一些漏洞会阻止你看到实际发生的任何事情。你的问题肯定是其中之一。

回答你的问题：

listenFor:fromObject:无法识别，因为它实际上并不存在。

listenFor方法的目的是使您的应用程序或特定对象能够对应用程序中其他位置发生的通知或操作做出反应。所以你想要做的是在事情发生时运行一个方法。

你的方法应该是：

[self listenFor:@"imageWasCaptured" fromObject:cam andRunMethod:@"methodName"];

您希望在摄像头完成捕获时收听，然后对其进行操作......

我注意到的其他事情......

如果您想使用C4Button，请执行以下操作：

takePhotoButton=[UIButton buttonWithType: ROUNDEDRECT];
[takePhotoButton setTitle:@"TakePhoto" forState:UIControlStateNormal];

应该是：

takePhotoButton = [C4Button buttonWithType:ROUNDEDRECT];
[takePhotoButton setTitle:@"TakePhoto" forState:NORMAL];

此外，您还要继承C4CanvasController。要将TakePhoto对象的视图放到主画布上，您需要正确创建它。

要在主画布中执行此操作，我在工作区中编写了以下内容：

#import "C4Workspace.h"
#import "TakePhoto.h"

@implementation C4WorkSpace {
    TakePhoto *tp;
}

-(void)setup {
    tp = [TakePhoto new];
    tp.canvas.frame = CGRectMake(30,
                                 30,
                                 self.canvas.width - 60,
                                 self.canvas.height - 60);
    tp.canvas.shadowOffset = CGSizeMake(10,10);
    tp.canvas.shadowOpacity = 1.0f;
    tp.canvas.userInteractionEnabled = YES;
    [tp setup];
    tp.mainCanvas = self.canvas;
    [self.canvas addSubview:tp.canvas];
}
@end

最后，为了将相机的图像放到主画布上，我已经做了一点桥接。我在TakePhoto中创建了一个属性，允许我在新控制器中设置主画布。您会在上面的代码中注意到tp.mainCanvas = self.canvas ...

的行

TakePhoto标题现在看起来像：

#import "C4CanvasController.h"

@interface TakePhoto : C4CanvasController
@property (readwrite, strong) C4Window *mainCanvas;
@end

putImageOnCanvas方法现在看起来像：

-(void)putCapturedImageOnCanvas{
    C4Image *img = cam.capturedImage;
    img.width=240;
//    img.center=CGPointMake(self.canvas.width*2/3, self.canvas.center.y);
    img.center = CGPointMake([C4Math randomInt:self.mainCanvas.width], [C4Math randomInt:self.mainCanvas.height]);
    [self.mainCanvas addImage:img];
    [self.mainCanvas bringSubviewToFront:self.canvas];
}

最后两行将图像放在画布上，然后确保将TakePhoto画布（即带有相机的画布）带到前台，以便新添加的图像不会遮挡它

因为您正在使用C4CanvasController的子类，您的应用结构如下所示：

C4WorkSpace.canvas > TakePhoto.canvas > Camera

C4捕捉相机图像示例

1 个答案: