系统优化的我一愣一愣的，原来是下面的优化规则

TodoViewController *contentViewController = [[TodoViewController alloc] init];

UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:contentViewController];

navigationController.contentSizeForViewInPopover = CGSizeMake(100, 100); //内容大小

    UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:navigationController];

popover.popoverContentSize = CGSizeMake(300, 300); //弹出窗口大小，如果屏幕画不下，会挤小的。这个值默认是320×1100

CGRect popoverRect = CGRectMake(200, 700, 10, 10);

[popover presentPopoverFromRect:popoverRect  //popoverRect的中心点是用来画箭头的，如果中心点如果出了屏幕，系统会优化到窗口边缘

 inView:self.view //上面的矩形坐标是以这个view为参考的

   permittedArrowDirections:UIPopoverArrowDirectionDown  //箭头方向

   animated:YES];

[contentViewController release];

[navigationController release];

//最佳实践，使用哪个view做参考，就以哪个view的bounds送进去就好了，箭头自动指向这个view的中心

UINavigationBar自定义导航栏背景和按钮，完美支持横屏竖屏旋转，视图控制器可以分别使用自己的导航栏

此方法可以通过Apple审核，导航上的按钮背景需要做，否则看起来不那么和之又谐

//CustomNavigationBar.h
@interface UINavigationBar (UINavigationBarCategory)
UIImageView *backgroundView;
- (void)setBackgroundImage:(UIImage*)image;
- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index;
@end

//CustomNavigationBar.m
@implementation UINavigationBar (UINavigationBarCategory)
-(void)setBackgroundImage:(UIImage*)image
{
	if(image == nil)
	{
		[backgroundView removeFromSuperview];
	}
	else
	{
		backgroundView = [[UIImageView alloc] initWithImage:image];
		backgroundView.tag = 1;
		backgroundView.frame = CGRectMake(0.f, 0.f, self.frame.size.width, self.frame.size.height);
		backgroundView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
		[self addSubview:backgroundView];
		[self sendSubviewToBack:backgroundView];
		[backgroundView release];
	}
}

//for other views
- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index
{
	[super insertSubview:view atIndex:index];
	[self sendSubviewToBack:backgroundView];
}
@end

//YourViewController.m
- (void)viewWillAppear:(BOOL)animated
{
	[super viewWillAppear:animated];
	[self.navigationController.navigationBar
		setBackgroundImage:[UIImage imageNamed:@"navigation_bar_bg.png"]];
}

创建按钮

	UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
	button.frame = CGRectMake(10.0, 10.0, 100.0, 40.0);
	[button setTitle:@"Normal" forState:UIControlStateNormal];
	UIImage *image = [UIImage imageNamed:@"normal.png"];
	UIImage *newImage = [image stretchableImageWithLeftCapWidth:12.0 topCapHeight:0.0];
	[button setBackgroundImage:newImage forState:UIControlStateNormal];
	button.adjustsImageWhenHighlighted = NO;
	[button addTarget:self action:@selector(buttonSwitch:) forControlEvents:UIControlEventTouchDown];
	[self.view addSubview:button];

事件处理

-(void)buttonSwitch:(id)sender
{
	static BOOL isHighlighted = NO;
	
	UIButton *button = (UIButton*)sender;
	UIImage *image = nil;
	NSString *title = nil;
	if (isHighlighted)
	{
		title = @"Normal";
		image = [UIImage imageNamed:@"normal.png"];
	}
	else
	{
		title = @"Hightlight";
		image = [UIImage imageNamed:@"highlight.png"];
	}
	
	[button setTitle:title forState:UIControlStateNormal];
	UIImage *newImage = [image stretchableImageWithLeftCapWidth:12.0 topCapHeight:0.0];
	[button setBackgroundImage:newImage forState:UIControlStateNormal];
	isHighlighted = !isHighlighted;
}

Xcode代码提示生成源代码程序块默认格式如下，注意左花括号的位置：

if ( condition ) {
    do ...
}

因为以前的使用习惯，我想让自动生成的左右花括号都单独成行，变成下面的样子：

if ( condition )
{
    do ...
}

在Terminal里面，运行下面命令，然后重启Xcode：

defaults write com.apple.Xcode XCCodeSenseFormattingOptions -dict BlockSeparator "\n"

这个命令修改了~/Library/Preferences/com.apple.Xcode.plist，这是Xcode的配置文件

比如地图导航数据G级别的数据，模拟器调试的时候将是个恶梦

后面要做一个导航类应用程序，所以未雨绸缪先纪录下来

设备调试时，把测试数据尽量最小化吧

模拟器调试时，使用固定路径，指定到程序外路径，模拟器貌似没有沙盒，下面代码在模拟器里是可以读取文件的。设备调试时改为resources

NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:@"/Users/george/Desktop/Test.plist"];