iOS开发之自定义View

iOS sdk中的view是UIView,我们可以很方便的自定义一个View。

创建一个 Window-based Application程序,在其中添加一个Hypnosister的类,这个类选择继承UIObject。修改这个类,使他继承:UIView

@interface HypnosisView : UIView

自定义View的关键是定义drawRect: 方法,因为主要是通过重载这个方法,来改变view的外观。例如,可以使用下面代码绘制一个很多环中环的效果的view。

View Code
- (void)drawRect:(CGRect)rect 
{
// What rectangle am I filling?
CGRect bounds = [self bounds];
// Where is its center?
CGPoint center;
center.x
= bounds.origin.x + bounds.size.width / 2.0;
center.y
= bounds.origin.y + bounds.size.height / 2.0;
// From the center how far out to a corner?
float maxRadius = hypot(bounds.size.width, bounds.size.height) / 2.0;
// Get the context being drawn upon
CGContextRef context = UIGraphicsGetCurrentContext();
// All lines will be drawn 10 points wide
CGContextSetLineWidth(context, 10);
// Set the stroke color to light gray
[[UIColor lightGrayColor] setStroke];
// Draw concentric circles from the outside in
for (float currentRadius = maxRadius; currentRadius > 0; currentRadius -= 20)
{
CGContextAddArc(context, center.x, center.y,
currentRadius,
0.0, M_PI * 2.0, YES);
CGContextStrokePath(context);
}
}

这样view的效果如下图:

iOS开发之自定义View_第1张图片

我们可以继续绘制一些东西,比如绘制文字,将下面代码添加带这个方法后面。

   // Create a string
NSString *text = @"我是朱祁林,不是朱麒麟";
// Get a font to draw it in
UIFont *font = [UIFont boldSystemFontOfSize:28];
// Where am I going to draw it?
CGRect textRect;
textRect.size
= [text sizeWithFont:font];
textRect.origin.x
= center.x - textRect.size.width / 2.0;
textRect.origin.y
= center.y - textRect.size.height / 2.0;
// Set the fill color of the current context to black
[[UIColor blackColor] setFill];
// Set the shadow to be offset 4 points right, 3 points down,
// dark gray and with a blur radius of 2 points
CGSize offset = CGSizeMake(4, 3);
CGColorRef color
= [[UIColor darkGrayColor] CGColor];
CGContextSetShadowWithColor(context, offset,
2.0, color);
// Draw the string
[text drawInRect:textRect
withFont:font];

效果:

iOS开发之自定义View_第2张图片

如果view过大,我们可以把它放置到一个UIScrollView中间,这样就可以进行拖动了。UIScrollView与View的关系如下图:

iOS开发之自定义View_第3张图片

使用下面代码创建一个比iPhone屏幕大4倍的View,然后通过UIScrollView来展示,代码如下:

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


//创建一个窗体大小的CGRect
CGRect wholeWindow = [[self window] bounds];

// 创建一个窗体大小的HypnosisView实例
view = [[HypnosisView alloc] initWithFrame:wholeWindow];

UIScrollView
*scrollView = [[UIScrollView alloc] initWithFrame:wholeWindow];
[[self window] addSubview:scrollView];
// Make your view twice as large as the window
CGRect reallyBigRect;
reallyBigRect.origin
= CGPointZero;
reallyBigRect.size.width
= wholeWindow.size.width * 2.0;
reallyBigRect.size.height
= wholeWindow.size.height * 2.0;
[scrollView setContentSize:reallyBigRect.size];
CGPoint offset;
offset.x
= wholeWindow.size.width * 0.5;
offset.y
= wholeWindow.size.height * 0.5;
[scrollView setContentOffset:offset];

// Create the view
view = [[HypnosisView alloc] initWithFrame:reallyBigRect];
[view setBackgroundColor:[UIColor clearColor]];
[scrollView addSubview:view];
[scrollView release];
[[UIApplication sharedApplication] setStatusBarHidden:YES
withAnimation:UIStatusBarAnimationFade];
[[self window] makeKeyAndVisible];
return YES;


}

这样我们就可以拖动来展示看不到的view了,如下图:

iOS开发之自定义View_第4张图片

通过UIScrollView我们还可以设置view的缩放功能,将下面代码添加到中。这样我们就可以使用两根手指缩放view了。

    // Enable zooming
[scrollView setMinimumZoomScale:0.5];
[scrollView setMaximumZoomScale:
5];
[scrollView setDelegate:self];

总结:文本简单的总结了一下自定义view的使用。

代码:Hypnosister.zip

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