iOS应用开发教程：新建UIView的子类

From: http://mobile.51cto.com/iphone-271839.htm

 

 

大致步骤

1) 新建一个UIView的子类(@interface HypnosisView : UIView)

2) 自定义绘图函数：(void) drawRect:(CGRect)rect

◆确定绘图范围：CGRect bounds=[self bounds]

◆获得CGContext, CGContextRef context=UIGraphicsGetCurrentContext();

◆进行绘图操作

3) 将新视图绑定到主窗口

◆在HypnosisterAppDelegate中添加一个成员变量HypnosisView *view;

◆确定绘图范围

◆在didFinishLaunchingWithOptions中增加子视图:[_window addSubview:view];

◆进行显示 [_window makeKeyAndVisible];

待确定事项：

1) CGContextStrokePath的功能

2) makeKeyAndVisible消息的功能

关键代码如下：

Java代码

1) 绑定处理：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

NSLog(@"didFinishLaunchingWithOptions.");

CGRect drawingArea=[_window bounds];

view = [[HypnosisView alloc] initWithFrame:drawingArea];

[view setBackgroundColor:[UIColor yellowColor]];

[_window addSubview:view];

// Override point for customization after application launch.

[_window makeKeyAndVisible];

return YES;

}

2) 绘图处理：

- (void) drawRect:(CGRect)rect

{

NSLog(@"Entering the drawing function of HyponsisView.");

//Get the drawing rectangle

CGRect bounds=[self bounds];

//Calculate the references

CGPoint center;

center.x=bounds.origin.x+bounds.size.width/2.0;

center.y=bounds.origin.y+bounds.size.height/2.0;

float radius=hypot(bounds.size.width, bounds.size.height)/2.0;

//Prepare Drawing

CGContextRef context=UIGraphicsGetCurrentContext();

CGContextSetLineWidth(context,10);

[[UIColor greenColor] setStroke];

//Drawing the circles

for( float r=radius; r>0; rr=r-25)

{

CGContextAddArc(context, center.x, center.y, r, 0.0, M_PI*2.0,YES);

CGContextStrokePath(context);

}

}

运行效果：