iphone:保持表单输入的可见性——自动滚动视图

iPhone: Maintain visibility of form inputs - auto-scrolling views

当你开发图标或者任何有输入区域的界面，偶尔输入框再键盘弹出时会被挡住。这样用户体验不好，用户在输入时看不到他们所输入的东西。一个解决方案，是滑动整个view让编辑区域一直是可见的。

我提供的整个解决方案对UIView添加了一些方法（我知道，添加类别到cocoa的类是顽皮的）这将决定基于整个屏幕的输入位置滑动视图的多少，还有和键盘弹起一样的速度滑动视图。在编辑完成时滑动回到原来的位置。

做到这样很简单，这是我如何通过计算来滚动视图：

- (void) maintainVisibityOfControl:(UIControl *)control offset:(float)offset {        static const float deviceHeight = 480;        static const float keyboardHeight = 216;        static const float gap = 5; //gap between the top of keyboard and the control        //Find the controls absolute position in the 320*480 window - it could be nested in other views        CGPoint absolute = [control.superview convertPoint:control.frame.origin toView:nil];        //If it would be hidden behind the keyboard....        if (absolute.y > (keyboardHeight + gap)) {                //Shift the view                float shiftBy = (deviceHeight - absolute.y) - (deviceHeight - keyboardHeight - gap - offset);                [UIView beginAnimations:nil context:nil];                [UIView setAnimationDuration:0.3f]; //this is speed of keyboard                CGAffineTransform slideTransform = CGAffineTransformMakeTranslation(0.0, shiftBy);                self.transform = slideTransform;                [UIView commitAnimations];        }}

..然后我重置了视图通过使用：

- (void) resetViewToIdentityTransform {        [UIView beginAnimations:nil context:nil];        [UIView setAnimationDuration:0.3f]; //this is speed of keyboard        CGAffineTransform slideTransform = CGAffineTransformIdentity;        self.transform = slideTransform;        [UIView commitAnimations];}

你只需要对你的代码做一些小的改动，并在UITextFieldDelegate调用这些方法（或其他控制代理）：

- (void) textFieldDidBeginEditing:(UITextField *)textField {        [self.view maintainVisibityOfControl:textField offset:0.0f];}- (void)textFieldDidEndEditing:(UITextField *)textField {        if (textField == currentControl) {                //If the textfield is still the same one, we can reset the view animated                [self.view resetViewToIdentityTransform];        }else {                //However, if the currentControl has changed - that indicates the user has                //gone into another control - so don't reset view, otherwise animations jump around        }}

这里是工程拷贝(见附件)。