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：

1. 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 sizeUIImage *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 stringsNSString *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;}

2. 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];}

3. 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 viewCGFloat 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 sizeUIFont *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 indexself.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 placardtextSize = [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。