1. iphone/ipad大小
| Device | Screen dimensions(in points) |
| iphone and ipod | 320 X 480 |
| ipad | 768 X 1024 |
2. UIScreen bounds and applicationFrame
[UISCreen mainScreen].bounds, 永远返回portait模式的width/height, 也就是说width:320 height:480 for iPhone
[UISCreen mainScreen].applicationFrame更加复杂一些，它考虑了status bar的高度。
portait模式， x:0, y:20, width:320, height:460
landscape, x:20, y:0, width:300, height:480
关于frame和bounds的区别，请参考UIView中的frame和bounds属性的区别
3. status bar height: 20, tool bar height: 44, tab bar height:44
4. UIScrollView
// Called when the UIKeyboardDidShowNotification is sent.- (void)keyboardWasShown:(NSNotification*)aNotification{ NSDictionary* info = [aNotification userInfo]; CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size; UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0); scrollView.contentInset = contentInsets; scrollView.scrollIndicatorInsets = contentInsets; // If active text field is hidden by keyboard, scroll it so it's visible // Your application might not need or want this behavior. CGRect aRect = self.view.frame; aRect.size.height -= kbSize.height; if (!CGRectContainsPoint(aRect, activeField.frame.origin) ) { //判断该text field是否在可见区域 CGPoint scrollPoint = CGPointMake(0.0, instance); //这里需要计算需要scroll的长度，假设instance是计算出来的结果。 [scrollView setContentOffset:scrollPoint animated:YES]; }}
原文来自这里， 这里介绍几个关键的内容：
1. pagingMode需要设置为YES
2. contentSize是所有页数的width总和， 例如你需要显示100页，那contentSize的宽度就是100*scroll.frame.size.width
3. showsHorizontalScrollIndicator和showsVerticalScrollIndicator设置为NO
然后需要在scroll view的delegate中实现scrollViewDidScroll:方法，这个方法在scroll view的contentOffSet发生变化的时候被调用。翻页模式的核心思想就是scroll view需要显示下一页的时候，创建一个view, 在这个view上准备好数据，然后把这个view加到scroll view当前显示的位置。
代码如下所示，另外还可以改进的一个地方是需要翻页之前，需要把后面一页的内容也显示出来，否则会有一半黑的屏幕显示。
-(void) loadPageView:(NSUInteger)page{ UIView* view = [[UIView alloc] init]; view.backgroundColor = [UIColor whiteColor]; CGRect rc = self.view.frame; rc.origin.y = 0; rc.origin.x = page * self.view.frame.size.width; //创建一个view，调整x直，因为其他直和scroll view都是一样的 view.frame = rc; UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(0, 20, rc.size.width, 40)]; label.text = [NSString stringWithFormat:@"current page is :%d", page]; [view addSubview:label]; [(UIScrollView*)self.view addSubview:view];}- (void)scrollViewDidScroll:(UIScrollView *)scrollView{ if (scrollView.contentOffset.x >= (myCurrentPage+0.5) * self.view.frame.size.width) //需要显示下一页了 { myCurrentPage++; [self loadPageView:myCurrentPage]; }}
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