IOS开发之自动计算Label的高度

#import "AppDelegate.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

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

    // Override point for customization after application launch.

    

     _window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];

    

    [_window setBackgroundColor:[UIColor whiteColor]];

    

    

    //自动计算label高度的前提是固定label的宽度

    //固定宽度为200

    NSString *str = @"很垃圾头奥特顾阿焊工我鞥接啊奥尔偶偶拒绝嘎嘎啊就怕呕吐拍就阿訇噶举啊过哈多蛾";

    

    //计算显示当前字符串须要多大的空间(宽和高);

    //参数一:限制显示当前字符串的最大宽度和最大高度;

    //参数二:渲染模式

    //参数三:字符串的属性(设置文字颜色和字体)

    //NSFontAttributeName设置字体的键;

    //NSForegroundColorAttributeName设置文字颜色

    //参数四:上下文;

    CGRect rect =  [str boundingRectWithSize:CGSizeMake(200, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:

     @{NSFontAttributeName:[UIFont systemFontOfSize:14],NSForegroundColorAttributeName:

           [UIColor redColor]} context:nil];

    

    

    //建立label显示文字

    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(50, 50, rect.size.width, rect.size.height)];

    

    //将label添加到界面上

    [_window addSubview:label];

    

    //设置文字

    label.text = str;

    [label setFont:[UIFont systemFontOfSize:14]];//这里必须设置显示的字体与计算字体同样大或者比计算的字体小一些，不然label显示不完

    [label setBackgroundColor:[UIColor redColor]];

    //label.textColor = [UIColor cyanColor];

    

    //设置换行

    label.numberOfLines = 0;

    label.lineBreakMode = NSLineBreakByWordWrapping;

    

    [_window makeKeyAndVisible];

    

    return YES;

}

- (void)applicationWillResignActive:(UIApplication *)application {

    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.

    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.

}

- (void)applicationDidEnterBackground:(UIApplication *)application {

    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.

    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.

}

- (void)applicationWillEnterForeground:(UIApplication *)application {

    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.

}

- (void)applicationDidBecomeActive:(UIApplication *)application {

    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.

}

- (void)applicationWillTerminate:(UIApplication *)application {

    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.

}

@end