ios app: view: 怎样创建自己的view

我是个不喜欢普通的人，Cocao 的common view 设计的很好。也许是审美疲劳，从开始准备写App时我就准备自己写view，让一切看起来与众不同。我也不想分享什么，也不是想帮助任何人。我只是纪录下我学的帮助自己理解，理清自己的思路。

什么解释都不如代码来的快：

init一个view的时候通常需要创建一个frame给它，它以后的范围就是这个frame了。这里是个很典型的view 的init方法。

- (id)init {
// Retrieve the image for the view and determine its size
UIImage *image = [UIImage imageNamed:@"Placard.png"];
CGRect frame = CGRectMake(0, 0, image.size.width, image.size.height);

// Set self's frame to encompass the image，根据image的size来建立frame并初始化自己。
self = [self initWithFrame:frame];
if (self) {

self.opaque = NO;
placardImage = image;

// Load the display strings
NSString *path = [[NSBundle mainBundle] pathForResource:@"DisplayStrings" ofType:@"txt"];
NSString *string = [NSString stringWithContentsOfFile:path encoding:NSUTF16BigEndianStringEncoding error:NULL];
self.displayStrings = [string componentsSeparatedByString:@"\n"];
displayStringsIndex = 0;
[self setupNextDisplayString];
}
return self;
}

dealloc 是需要的，release 你创建的东西，每人想要memory leak。

- (void)dealloc {
[placardImage release];
[currentDisplayString release];
[displayStrings release];
[super dealloc];
}

最重要的是-(view)drawRect: (CGRect) rect {...}, 重写这个方法实现自己view的look

- (void)drawRect:(CGRect)rect {

// Draw the placard at 0, 0
[placardImage drawAtPoint:(CGPointMake(0.0f, 0.0f))];

/*
Draw the current display string.
Typically you would use a UILabel, but this example serves to illustrate the UIKit extensions to NSString.
The text is drawn center of the view twice - first slightly offset in black, then in white -- to give an embossed appearance.
The size of the font and text are calculated in setupNextDisplayString.
*/

// Find point at which to draw the string so it will be in the center of the view
CGFloat x = self.bounds.size.width/2 - textSize.width/2;
CGFloat y = self.bounds.size.height/2 - textSize.height/2;
CGPoint point;

// Get the font of the appropriate size
UIFont *font = [UIFont systemFontOfSize:fontSize];

[[UIColor blackColor] set];
point = CGPointMake(x, y + 0.5f);
[currentDisplayString drawAtPoint:point forWidth:(self.bounds.size.width-STRING_INDENT) withFont:font fontSize:fontSize lineBreakMode:UILineBreakModeMiddleTruncation baselineAdjustment:UIBaselineAdjustmentAlignBaselines];

[[UIColor whiteColor] set];
point = CGPointMake(x, y);
[currentDisplayString drawAtPoint:point forWidth:(self.bounds.size.width-STRING_INDENT) withFont:font fontSize:fontSize lineBreakMode:UILineBreakModeMiddleTruncation baselineAdjustment:UIBaselineAdjustmentAlignBaselines];
}

4. 提供方法改变你的view的look当和用户交换的时候

- (void)setupNextDisplayString {

// Get the string at the current index, then increment the index
self.currentDisplayString = [displayStrings objectAtIndex:displayStringsIndex];
//self.currentDisplayString = @"Mac KLV";
displayStringsIndex++;
if (displayStringsIndex >= [displayStrings count]) {
displayStringsIndex = 0;
}

UIFont *font = [UIFont systemFontOfSize:24];
// Precalculate size of text and size of font so that text fits inside placard
textSize = [currentDisplayString sizeWithFont:font minFontSize:9.0f actualFontSize:&fontSize forWidth:(self.bounds.size.width-STRING_INDENT) lineBreakMode:UILineBreakModeMiddleTruncation];

[self setNeedsDisplay];
}

Go there：好吧解释一下我的理解：

第一步时我们给自己的view在init建立一个frame就框起来我们view的大小。在drawRect方法里面我们开始画我们的view，当然范围就是我们第一步实现的frame范围里面。然后，我们不希望自己的view时不会动的，所以要提供一个改变的方法给其他人调用，这就是第四步时创建的setupNextDispalyString方法。记住改变了后不会立即成效显现出来。最后要调用一个“［self setNeedsDisplay］”.当绘图周期到的时候，图像就被改变了，很快，快的几乎不让你感觉到。