我想获取在Xamarin Forms中 Android 和 iOS 上的 Keyboard 高度。
当屏幕以 Portrait 模式和 Landscape 模式显示时，如何获得键盘高度值？
我已经找到了有关在 iOS 上使用 Swift 的参考文献:
What is the height of iPhone's onscreen keyboard?
How to get height of Keyboard?
但是能否提供在 Xamarin 上的源代码？
如何获取 Android 上键盘的高度呢？
请帮助我！
有两种方法可以实现这个功能！
第一种方法：如果你的应用程序很小，只需为一个UIViewController实现以下步骤即可：
步骤1：添加用于显示和隐藏观察者的字段：
private NSObject _keyboardObserverWillShow;
private NSObject _keyboardObserverWillHide;
步骤2：更新ViewDidLoad和ViewDidUnload覆盖方法，以便在键盘显示或隐藏时添加/删除观察者：
public override void ViewDidLoad() {
base.ViewDidLoad ();
_keyboardObserverWillShow = NSNotificationCenter.DefaultCenter.AddObserver(UIKeyboard.DidShowNotification, KeyboardDidShowNotification);
_keyboardObserverWillHide = NSNotificationCenter.DefaultCenter.AddObserver(UIKeyboard.WillHideNotification, KeyboardWillHideNotification);
}
public override void ViewDidUnload() {
base.ViewDidUnload();
NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardObserverWillShow);
NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardObserverWillHide);
}
步骤三：然后您填充执行每个观察者的函数KeyboardDidShowNotification和KeyboardWillHideNotification。这段代码比较长，需要一些时间来解释每个部分，但您可以在评论区询问我。代码如下：
private void KeyboardWillHideNotification (NSNotification notification)
{
UIView activeView = View.FindFirstResponder();
if (activeView == null)
return;
UIScrollView scrollView = activeView.FindSuperviewOfType (this.View, typeof(UIScrollView)) as UIScrollView;
if (scrollView == null)
return;
// Reset the content inset of the scrollView and animate using the current keyboard animation duration
double animationDuration = UIKeyboard.AnimationDurationFromNotification(notification);
UIEdgeInsets contentInsets = new UIEdgeInsets(0.0f, 0.0f, 0.0f, 0.0f);
UIView.Animate(animationDuration, delegate{
scrollView.ContentInset = contentInsets;
scrollView.ScrollIndicatorInsets = contentInsets;
});
}
private void KeyboardDidShowNotification (NSNotification notification)
{
UIView activeView = View.FindFirstResponder();
if (activeView == null)
return;
((UITextField)activeView).ShowDoneButtonOnKeyboard();
UIScrollView scrollView = activeView.FindSuperviewOfType(this.View, typeof(UIScrollView)) as UIScrollView;
if (scrollView == null)
return;
RectangleF keyboardBounds = UIKeyboard.BoundsFromNotification(notification);
UIEdgeInsets contentInsets = new UIEdgeInsets(0.0f, 0.0f, keyboardBounds.Size.Height, 0.0f);
scrollView.ContentInset = contentInsets;
scrollView.ScrollIndicatorInsets = contentInsets;
// If activeField is hidden by keyboard, scroll it so it's visible
RectangleF viewRectAboveKeyboard = new RectangleF(this.View.Frame.Location, new SizeF(this.View.Frame.Width, this.View.Frame.Size.Height - keyboardBounds.Size.Height));
RectangleF activeFieldAbsoluteFrame = activeView.Superview.ConvertRectToView(activeView.Frame, this.View);
// activeFieldAbsoluteFrame is relative to this.View so does not include any scrollView.ContentOffset
// Check if the activeField will be partially or entirely covered by the keyboard
if (!viewRectAboveKeyboard.Contains(activeFieldAbsoluteFrame)) {
// Scroll to the activeField Y position + activeField.Height + current scrollView.ContentOffset.Y - the keyboard Height
PointF scrollPoint = new PointF(0.0f, activeFieldAbsoluteFrame.Location.Y + activeFieldAbsoluteFrame.Height + scrollView.ContentOffset.Y - viewRectAboveKeyboard.Height);
scrollView.SetContentOffset(scrollPoint, true);
}
}
第二种方式：创建一个键盘处理程序，通过您的BaseViewController可在每个页面上使用。
您可以按照StackOverflow提供的解决方案Xamarin solution here((Activity)Forms.Context).Window.SetSoftInputMode(SoftInput.AdjustPan);进行操作。有时这不起作用，所以您可以使用此方法进行修复。PS：没有复制这些答案，因为重新编写答案没有意义。
namespace YourCoreProject.Services
{
using System.Reactive.Subjects;
/// <summary>
/// A service to interact with the software keyboard.
/// </summary>
public interface IKeyboardInteractionService
{
/// <summary>
/// Gets a <see cref="Subject{T}" /> which notifies about changes of the keyboard height.
/// </summary>
public Subject<float> KeyboardHeightChanged { get; }
}
}
namespace YourProject.iOS.Services
{
using System.Reactive.Subjects;
using UIKit;
/// <inheritdoc cref="IKeyboardInteractionService" />
public class KeyboardInteractionService : IKeyboardInteractionService
{
/// <summary>
/// Initializes a new instance of the <see cref="KeyboardInteractionService" /> class.
/// </summary>
public KeyboardInteractionService()
{
UIKeyboard.Notifications.ObserveWillShow((_, uiKeyboardEventArgs) =>
{
var newKeyboardHeight = (float)uiKeyboardEventArgs.FrameEnd.Height;
this.KeyboardHeightChanged.OnNext(newKeyboardHeight);
});
UIKeyboard.Notifications.ObserveWillHide((_, uiKeyboardEventArgs) =>
{
this.KeyboardHeightChanged.OnNext(0);
});
}
/// <inheritdoc cref="IKeyboardInteractionService.KeyboardHeightChanged" />
public Subject<float> KeyboardHeightChanged { get; } = new Subject<float>();
}
}
Android实现
namespace YourProject.Droid.Services
{
using System;
using System.Reactive.Subjects;
using Android.App;
using Android.Views.InputMethods;
using Xamarin.Essentials;
/// <inheritdoc cref="IKeyboardInteractionService" />
public class KeyboardInteractionService : IKeyboardInteractionService
{
/// <summary>
/// Initializes a new instance of the <see cref="KeyboardInteractionService" /> class.
/// </summary>
public KeyboardInteractionService()
{
var globalLayoutListener = new GlobalLayoutListener();
this.KeyboardHeightChanged = globalLayoutListener.KeyboardHeightChanged;
}
/// <inheritdoc cref="IKeyboardInteractionService.KeyboardHeightChanged" />
public Subject<float> KeyboardHeightChanged { get; }
}
}
namespace YourProject.Droid.Services
{
using System;
using System.Reactive.Subjects;
using Android.App;
using Android.Content.Res;
using Android.Graphics;
using Xamarin.Essentials;
using static Android.Views.ViewTreeObserver;
/// <inheritdoc cref="IOnGlobalLayoutListener"/>
public class GlobalLayoutListener : Java.Lang.Object, IOnGlobalLayoutListener
{
private readonly Activity activity;
/// <summary>
/// Initializes a new instance of the <see cref="GlobalLayoutListener" /> class.
/// </summary>
public GlobalLayoutListener()
{
this.activity = Platform.CurrentActivity;
if (this.activity?.Window?.DecorView?.ViewTreeObserver == null)
{
throw new InvalidOperationException($"{this.GetType().FullName}.Constructor: The {nameof(this.activity)} or a follow up variable is null!");
}
this.activity.Window.DecorView.ViewTreeObserver.AddOnGlobalLayoutListener(this);
}
/// <summary>
/// Gets a <see cref="Subject{T}" /> which notifies about changes of the keyboard height.
/// </summary>
public Subject<float> KeyboardHeightChanged { get; } = new Subject<float>();
/// <inheritdoc cref="IOnGlobalLayoutListener.OnGlobalLayout" />
public void OnGlobalLayout()
{
if (!this.KeyboardHeightChanged.HasObservers)
{
return;
}
var screenSize = new Point();
this.activity.WindowManager?.DefaultDisplay?.GetSize(screenSize);
var screenHeight = screenSize.Y;
var rootView = this.activity.FindViewById(Android.Resource.Id.Content);
if (rootView == null)
{
return;
}
var screenHeightWithoutKeyboard = new Rect();
rootView.GetWindowVisibleDisplayFrame(screenHeightWithoutKeyboard);
int keyboardHeight;
// Android officially supports display cutouts on devices running Android 9 (API level 28) and higher.
if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.P)
{
var displayCutout = rootView.RootWindowInsets?.DisplayCutout;
// Displays with a cutout need to be handled different due to the cutout type:
//
// Default cutout:
// A display has no cutout. The screen height can be used used as usual.
//
// Corner cutout:
// A display has a cutout in a corner on the top of the display. The screen height must add the safe area of the top to get the total screen height.
//
// Double cutout:
// A display has a cutout in the middle on the top and in the middle on the bottom of the display.
// The screen height must add the safe area of the bottom only to get the total screen height.
// Adding the screen height of the top as well, would lead to false results.
//
// Tall cutout:
// A display has a cutout in the middle on the top of the display. The screen height must add the safe area of the top to get the total screen height.
keyboardHeight = displayCutout == null ?
screenHeight - screenHeightWithoutKeyboard.Bottom :
displayCutout.SafeInsetBottom <= 0 ?
screenHeight + displayCutout.SafeInsetTop - screenHeightWithoutKeyboard.Bottom :
screenHeight + displayCutout.SafeInsetBottom - screenHeightWithoutKeyboard.Bottom;
}
else
{
keyboardHeight = screenHeight - screenHeightWithoutKeyboard.Bottom;
}
var keyboardHeightInDip = keyboardHeight / Resources.System?.DisplayMetrics?.Density ?? 1;
if (keyboardHeightInDip < 0.0f)
{
keyboardHeightInDip = 0.0f;
}
this.KeyboardHeightChanged.OnNext(keyboardHeightInDip);
}
}
}
var keyboardHeight = rootView.Height - screenSizeWithoutKeyboard.Bottom + screenSizeWithoutKeyboard.Top; - Niro