iOS: 学习笔记实例, 用代码控制视图创建与切换

1. 创建iOS, Single View Application.
2. 修改YYViewController.m

//
//  YYViewController.m
//  DynamicViewDemo
//
//  Created by yao_yu on 14-5-28.
//  Copyright (c) 2014年 yao_yu. All rights reserved.
//

#import "YYViewController.h"

@interface YYViewController ()

@property(nonatomic, strong) UIView *body;

@property (nonatomic, strong) UIView *currentPage;

@end

const CGFloat HEIGHTEDGE = 40;

@implementation YYViewController

-(void)createBodyView
{
    CGRect statusBarFrame = [[UIApplication sharedApplication] statusBarFrame];
    CGRect parentFrame = self.view.frame;
    CGRect bodyFrame = CGRectMake(parentFrame.origin.x, parentFrame.origin.y + statusBarFrame.size.height + HEIGHTEDGE, parentFrame.size.width, parentFrame.size.height -  statusBarFrame.size.height - HEIGHTEDGE);
    self.body = [[UIView alloc] initWithFrame:bodyFrame];
    [self.body setBackgroundColor:[UIColor blackColor]];
    [self.view addSubview:self.body];
}

-(void)createCommands
{
    CGRect statusBarFrame = [[UIApplication sharedApplication] statusBarFrame];
    CGRect parentFrame = self.view.frame;
    CGRect bodyFrame = CGRectMake(parentFrame.origin.x, parentFrame.origin.y + statusBarFrame.size.height, parentFrame.size.width, HEIGHTEDGE);
    UIView *view = [[UIView alloc] initWithFrame:bodyFrame];
    [view setBackgroundColor:[UIColor redColor]];
    [self.view addSubview:view];

    //添加命令按钮
    const CGFloat COMMANDWIDTH = 50;
    const CGFloat COMMANDHEIGHT = 30;
    CGFloat midx = bodyFrame.size.width/2;
    CGFloat midy = bodyFrame.size.height/2;
    CGRect rect = CGRectMake(midx - COMMANDWIDTH/2, midy - COMMANDHEIGHT/2, COMMANDWIDTH, COMMANDHEIGHT);
    UIButton *btnPage1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [btnPage1 setBackgroundColor:[UIColor clearColor]];
    [btnPage1 setTitle:@"第1页" forState:UIControlStateNormal];
    rect.origin.x -= COMMANDWIDTH + 20;
    btnPage1.frame = rect;
    [btnPage1 addTarget:self action:@selector(onShowPage1:) forControlEvents:UIControlEventTouchUpInside];
    [view addSubview:btnPage1];

    btnPage1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [btnPage1 setTitle:@"第2页" forState:UIControlStateNormal];
    rect.origin.x += COMMANDWIDTH + 20;
    btnPage1.frame = rect;
    [btnPage1 addTarget:self action:@selector(onShowPage2:) forControlEvents:UIControlEventTouchUpInside];
    [view addSubview:btnPage1];

    btnPage1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [btnPage1 setTitle:@"第3页" forState:UIControlStateNormal];
    rect.origin.x += COMMANDWIDTH + 20;
    btnPage1.frame = rect;
    [btnPage1 addTarget:self action:@selector(onShowPage3:) forControlEvents:UIControlEventTouchUpInside];
    [view addSubview:btnPage1];

}

-(void) onShowPage1:(id)sender
{
    [self clearCurrentPage];
    CGRect frame = CGRectMake(0, 0, self.body.frame.size.width, self.body.frame.size.height);
    self.currentPage = [[UIView alloc] initWithFrame: frame];
    [self.currentPage setBackgroundColor:[UIColor blueColor]];
    [self.body addSubview:self.currentPage];
}

-(void) onShowPage2:(id)sender
{
    [self clearCurrentPage];
    CGRect frame = CGRectMake(0, 0, self.body.frame.size.width, self.body.frame.size.height);
    self.currentPage = [[UIView alloc] initWithFrame: frame];
    [self.currentPage setBackgroundColor:[UIColor yellowColor]];
    [self.body addSubview:self.currentPage];
}

-(void) onShowPage3:(id)sender
{
    [self clearCurrentPage];
    CGRect frame = CGRectMake(0, 0, self.body.frame.size.width, self.body.frame.size.height);
    self.currentPage = [[UIView alloc] initWithFrame: frame];
    [self.currentPage setBackgroundColor:[UIColor greenColor]];
    [self.body addSubview:self.currentPage];
}

-(void) clearCurrentPage
{
    if (self.currentPage)
        [self.currentPage removeFromSuperview];
    self.currentPage = nil;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.currentPage = nil;
    [self createBodyView];
    [self createCommands];
	// Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

3.运行