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)。