ios键盘通知和自定义键盘

最新推荐文章于 2019-07-25 18:42:03 发布

原创最新推荐文章于 2019-07-25 18:42:03 发布 · 827 阅读

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本文详细介绍了iOS系统中当文本视图成为first responder时，键盘显示和隐藏的通知机制。包括UIKeyboardWillShowNotification、UIKeyboardDidShowNotification等四种通知类型及其userInfo字典中各项参数的具体含义。

一.键盘通知

当文本View(如UITextField,UITextView, UIWebView内的输入框)进入编辑模式成为first responder时，系统会自动显示键盘。成为firstresponder可能由用户点击触发，也可向文本View发送becomeFirstResponder消息触发。当文本视图退出first responder时，键盘会消失。文本View退出first responder可能由用户点击键盘上的Done或Return键结束输入触发，也可向文本View发送resignFirstResponder消息触发。

当键盘显示或消失时，系统会发送相关的通知:
UIKeyboardWillShowNotification
UIKeyboardDidShowNotification
UIKeyboardWillHideNotification
UIKeyboardDidHideNotification

通知消息 NSNotification中的 userInfo字典中包含键盘的位置和大小信息，对应的key为

UIKeyboardFrameBeginUserInfoKey
UIKeyboardFrameEndUserInfoKey
UIKeyboardAnimationDurationUserInfoKey
UIKeyboardAnimationCurveUserInfoKey

UIKeyboardFrameBeginUserInfoKey,UIKeyboardFrameEndUserInfoKey对应的Value是个NSValue对象，内部包含CGRect结构，分别为键盘起始时和终止时的位置信息。

UIKeyboardAnimationCurveUserInfoKey对应的Value是NSNumber对象，内部为UIViewAnimationCurve类型的数据，表示键盘显示或消失的动画类型。

UIKeyboardAnimationDurationUserInfoKey对应的Value也是NSNumber对象，内部为double类型的数据，表示键盘h显示或消失时动画的持续时间。

例如，在UIKeyboardWillShowNotification，UIKeyboardDidShowNotification通知中的userInfo内容为

userInfo = {
    UIKeyboardAnimationCurveUserInfoKey = 0;
    UIKeyboardAnimationDurationUserInfoKey = "0.25";
    UIKeyboardBoundsUserInfoKey = "NSRect: {{0, 0}, {320, 216}}";
    UIKeyboardCenterBeginUserInfoKey = "NSPoint: {160, 588}";
    UIKeyboardCenterEndUserInfoKey = "NSPoint: {160, 372}";
    UIKeyboardFrameBeginUserInfoKey = "NSRect: {{0, 480}, {320, 216}}";
    UIKeyboardFrameChangedByUserInteraction = 0;
    UIKeyboardFrameEndUserInfoKey = "NSRect: {{0, 264}, {320, 216}}";
}

在UIKeyboardWillHideNotification,UIKeyboardDidHideNotification通知中的
userInfo内容为:

userInfo = {
    UIKeyboardAnimationCurveUserInfoKey = 0;
    UIKeyboardAnimationDurationUserInfoKey = "0.25";
    UIKeyboardBoundsUserInfoKey = "NSRect: {{0, 0}, {320, 216}}";
    UIKeyboardCenterBeginUserInfoKey = "NSPoint: {160, 372}";
    UIKeyboardCenterEndUserInfoKey = "NSPoint: {160, 588}";
    UIKeyboardFrameBeginUserInfoKey = "NSRect: {{0, 264}, {320, 216}}";
    UIKeyboardFrameChangedByUserInteraction = 0;
    UIKeyboardFrameEndUserInfoKey = "NSRect: {{0, 480}, {320, 216}}";
}

在Text,Web, and Editing Programming Guide for iOS中，有如下描述Note: The rectangle contained in the UIKeyboardFrameBeginUserInfoKey and UIKeyboardFrameEndUserInfoKey properties of the userInfo dictionary should be used only for the size information it contains. Do not use the origin of the rectangle (which is always {0.0, 0.0}) in rectangle-intersection operations. Because the keyboard is animated into position, the actual bounding rectangle of the keyboard changes over time.
但从实际获取的信息来看，矩形的origin并不为{0.0, 0.0},这里应该不准确。