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iOS8中提示框的使用UIAlertController(UIAlertView和UIActionSheet二合一)
iOS8推出了几个新的“controller”，主要是把类似之前的UIAlertView变成了UIAlertController，这不经意的改变，貌似把我之前理解的“controller”一下子推翻了～但是也无所谓，有新东西不怕，学会使用了就行。接下来会探讨一下这些个新的Controller。
- (void)showOkayCancelAlert { NSString *title = NSLocalizedString(@"A Short Title Is Best", nil); NSString *message = NSLocalizedString(@"A message should be a short, complete sentence.", nil); NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil); NSString *otherButtonTitle = NSLocalizedString(@"OK", nil); UIAlertController *alertController = [UIAlertController alertControllerWithTitle:title message:message preferredStyle:UIAlertControllerStyleAlert]; // Create the actions. UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) { NSLog(@"The \"Okay/Cancel\" alert‘s cancel action occured."); }]; UIAlertAction *otherAction = [UIAlertAction actionWithTitle:otherButtonTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) { NSLog(@"The \"Okay/Cancel\" alert‘s other action occured."); }]; // Add the actions. [alertController addAction:cancelAction]; [alertController addAction:otherAction]; [self presentViewController:alertController animated:YES completion:nil];}这是最普通的一个alertcontroller，一个取消按钮，一个确定按钮。
新的alertcontroller，其初始化方法也不一样了，按钮响应方法绑定使用了block方式，有利有弊。需要注意的是不要因为block导致了引用循环，记得使用__weak，尤其是使用到self。
上面的界面如下：
如果UIAlertAction *otherAction这种otherAction多几个的话，它会自动排列成如下：
另外，很多时候，我们需要在alertcontroller中添加一个输入框，例如输入密码：
这时候可以添加如下代码：
[alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) { // 可以在这里对textfield进行定制，例如改变背景色 textField.backgroundColor = [UIColor orangeColor]; }];而改变背景色会这样：
完整的密码输入：
- (void)showSecureTextEntryAlert { NSString *title = NSLocalizedString(@"A Short Title Is Best", nil); NSString *message = NSLocalizedString(@"A message should be a short, complete sentence.", nil); NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil); NSString *otherButtonTitle = NSLocalizedString(@"OK", nil); UIAlertController *alertController = [UIAlertController alertControllerWithTitle:title message:message preferredStyle:UIAlertControllerStyleAlert]; // Add the text field for the secure text entry. [alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) { // Listen for changes to the text field‘s text so that we can toggle the current // action‘s enabled property based on whether the user has entered a sufficiently // secure entry. [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleTextFieldTextDidChangeNotification:) name:UITextFieldTextDidChangeNotification object:textField]; textField.secureTextEntry = YES; }]; // Create the actions. UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) { NSLog(@"The \"Secure Text Entry\" alert‘s cancel action occured."); // Stop listening for text changed notifications. [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidChangeNotification object:alertController.textFields.firstObject]; }]; UIAlertAction *otherAction = [UIAlertAction actionWithTitle:otherButtonTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) { NSLog(@"The \"Secure Text Entry\" alert‘s other action occured."); // Stop listening for text changed notifications. [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidChangeNotification object:alertController.textFields.firstObject]; }]; // The text field initially has no text in the text field, so we‘ll disable it. otherAction.enabled = NO; // Hold onto the secure text alert action to toggle the enabled/disabled state when the text changed. self.secureTextAlertAction = otherAction; // Add the actions. [alertController addAction:cancelAction]; [alertController addAction:otherAction]; [self presentViewController:alertController animated:YES completion:nil];}注意四点：
1.添加通知，监听textfield内容的改变：
// Add the text field for the secure text entry. [alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) { // Listen for changes to the text field‘s text so that we can toggle the current // action‘s enabled property based on whether the user has entered a sufficiently // secure entry. [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleTextFieldTextDidChangeNotification:) name:UITextFieldTextDidChangeNotification object:textField]; textField.secureTextEntry = YES; }];2.初始化时候，禁用“ok”按钮：
otherAction.enabled = NO;
self.secureTextAlertAction = otherAction;//定义一个全局变量来存储
3.当输入超过5个字符时候，使self.secureTextAlertAction ＝ YES：
- (void)handleTextFieldTextDidChangeNotification:(NSNotification *)notification { UITextField *textField = notification.object; // Enforce a minimum length of >= 5 characters for secure text alerts. self.secureTextAlertAction.enabled = textField.text.length >= 5;}4.在“OK”action中去掉通知：
UIAlertAction *otherAction = [UIAlertAction actionWithTitle:otherButtonTitle style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) { NSLog(@"The \"Secure Text Entry\" alert‘s other action occured."); // Stop listening for text changed notifications. [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidChangeNotification object:alertController.textFields.firstObject]; }];
最后是以前经常是alertview与actionsheet结合使用，这里同样也有：
- (void)showOkayCancelActionSheet { NSString *cancelButtonTitle = NSLocalizedString(@"Cancel", nil); NSString *destructiveButtonTitle = NSLocalizedString(@"OK", nil); UIAlertController *alertController = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet]; // Create the actions. UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:cancelButtonTitle style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) { NSLog(@"The \"Okay/Cancel\" alert action sheet‘s cancel action occured."); }]; UIAlertAction *destructiveAction = [UIAlertAction actionWithTitle:destructiveButtonTitle style:UIAlertActionStyleDestructive handler:^(UIAlertAction *action) { NSLog(@"The \"Okay/Cancel\" alert action sheet‘s destructive action occured."); }]; // Add the actions. [alertController addAction:cancelAction]; [alertController addAction:destructiveAction]; [self presentViewController:alertController animated:YES completion:nil];}在底部显示如下：
iOS8中提示框的使用UIAlertController(UIAlertView和UIActionSheet二合一)
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