在Objective-C中繪圖

Question

我知道您可以使用CoreGraphics在視圖中繪制。 但這僅限於drawRect函數。

我想知道您是否可以使用一個具有兩個按鈕（上，下，左，右）的應用程序。 而且，當用戶選擇按鈕時，它會從原始點沿剛剛選擇了20像素的按鈕方向繪制一條線。

例如 ：

假設用戶點擊了右鍵：

              Start
                +----------+

然后他們按下按鈕：

              Start
                +----------+
                           |
                           |
                           |
                           |
                           +

然后他們按左鍵

                +----------+
                           |
                           |
                           |
                           |
                +----------+

等等，

可以使用石英完成此操作，還是需要學習OpenGL之類的知識？

Answer 1

使用UIBezierPath這非常簡單：

這是一個快速，基本的示例，如何繪制它

1. UIView子類讓我們說MoveView ，與公共方法-moveToDirection:
2. 查看陣列中的商店方向
3. 每次添加新方向時，我們都調用-setNeedsDisplay繪制新線

注意：這只是基本示例，請確保您需要對其進行修改並實施一些限制

MoveView.h

#import <UIKit/UIKit.h>

typedef NS_ENUM(NSInteger, MovieViewDirection) {
    MoveViewDirectionRight,
    MoveViewDirectionLeft,
    MoveViewDirectionUp,
    MoveViewDirectionDown
};

@interface MoveView : UIView

- (void)moveInDirection:(MovieViewDirection)direction;

@end

MoveView.m

#import "MoveView.h"

static const CGFloat kMoveViewStepDistance = 20.0f;

@interface MoveView ()

@property (nonatomic, strong) NSArray *movingDirections;

@end

@implementation MoveView

#pragma mark - Services

- (void)drawRect:(CGRect)rect {

    UIBezierPath* bezierPath = UIBezierPath.bezierPath;        

    CGPoint currentPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMidY(rect));        
//    Start point by default it is a center
    [bezierPath moveToPoint: currentPoint];

    for (NSNumber *direction in self.movingDirections) {
        CGPoint moveToPoint;
        switch (direction.integerValue) {
            case MoveViewDirectionLeft:
                moveToPoint = CGPointMake(currentPoint.x - kMoveViewStepDistance, currentPoint.y);
                break;
            case MoveViewDirectionRight:
                moveToPoint = CGPointMake(currentPoint.x + kMoveViewStepDistance, currentPoint.y);
                break;
            case MoveViewDirectionUp:
                moveToPoint = CGPointMake(currentPoint.x, currentPoint.y - kMoveViewStepDistance);
                break;
            case MoveViewDirectionDown:
                moveToPoint = CGPointMake(currentPoint.x, currentPoint.y + kMoveViewStepDistance);
                break;                
            default:
                break;
        }
        currentPoint = moveToPoint;
        [bezierPath addLineToPoint: moveToPoint];
    }

    [UIColor.redColor setStroke];
    bezierPath.lineWidth = 1;
    [bezierPath stroke];

}

#pragma mark - Public
- (void)moveInDirection:(MovieViewDirection)direction {
    [self addMoveStepInDirection:direction];
    [self setNeedsDisplay];
}

#pragma mark - Private

- (void)addMoveStepInDirection:(MovieViewDirection)direction {
    NSMutableArray *steps = [NSMutableArray arrayWithArray:self.movingDirections];
    [steps addObject:[NSNumber numberWithInteger:direction]];
    self.movingDirections = steps;
}

@end

這就是我得到的：