调整调整大小在 Xamarin.Forms 上的 AppCompat 的 API 22 中不起作用

Question

我在 Android 上有一个 Xamarin.Forms 项目，我想使用“AdjustResize”作为处理软键盘的默认方法。我通过在OnCreate 中设置它来做到这一点：

[Activity(Label = "TestWhite.Droid", Icon = "@drawable/icon", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
public class MainActivity : FormsAppCompatActivity
{
  protected override void OnCreate(Bundle bundle)
  {
    FormsAppCompatActivity.ToolbarResource = Resource.Layout.toolbar;
    FormsAppCompatActivity.TabLayoutResource = Resource.Layout.tabs;

    base.OnCreate(bundle);

    global::Xamarin.Forms.Forms.Init(this, bundle);

    Window.SetSoftInputMode(SoftInput.AdjustResize);

    LoadApplication(new App());
  }
}

由于我已更新到AppCompat，AdjustResize 不适用于 API 22，但仍适用于 API 19。

使用仅包含一个页面的应用程序可以很容易地测试该问题，该页面包含滚动视图和页面底部的编辑器：

public MainPage()
{
    InitializePage();
}

void InitializePage()
{
    var editor = new Editor
    {
        VerticalOptions = LayoutOptions.FillAndExpand,
        HorizontalOptions = LayoutOptions.FillAndExpand,
        HeightRequest = 200,
    };

    var tallLayout = new StackLayout
    {
        HorizontalOptions = LayoutOptions.FillAndExpand,
        Orientation = StackOrientation.Horizontal,
        HeightRequest = 450, 
        BackgroundColor = Color.Lime,
    };

    var layout = new StackLayout
    {
        Orientation = StackOrientation.Vertical,
        VerticalOptions = LayoutOptions.FillAndExpand,
        HorizontalOptions = LayoutOptions.FillAndExpand,
        Children = { tallLayout, editor },
    };

    var scrollView = new ScrollView
    {                
        VerticalOptions = LayoutOptions.FillAndExpand,
        HorizontalOptions = LayoutOptions.FillAndExpand, 
    };
    scrollView.Content = layout;

    Content = scrollView;
}

使用 API 19，当用户单击 Editor 时，视图会被向上推，以便用户可以看到他正在写的内容。相反，使用 API 22，键盘只出现在视图上，隐藏了 Editor。关于这种行为背后的原因有什么想法吗？

Answer 1

在 MainActivity 的 OnCreate 方法中，您应该将输入模式设置为 AdjustResize。然后，为了处理here 报告的android bug，您可以使用下面的实用程序类（最初由@user1658602 由java 代码转换而来）。快乐编码！

protected override void OnCreate(Bundle bundle)
{
    base.OnCreate(bundle);

    Xamarin.Forms.Forms.Init(this, bundle);

    Window.SetSoftInputMode(SoftInput.AdjustResize);

    AndroidBug5497WorkaroundForXamarinAndroid.assistActivity(this);

    ToolbarResource = Resource.Layout.toolbar;
    TabLayoutResource = Resource.Layout.tabs;

    LoadApplication(new App());

}

public class AndroidBug5497WorkaroundForXamarinAndroid
{

    // For more information, see https://code.google.com/p/android/issues/detail?id=5497
    // To use this class, simply invoke assistActivity() on an Activity that already has its content view set.

    // CREDIT TO Joseph Johnson (http://stackoverflow.com/users/341631/joseph-johnson) for publishing the original Android solution on stackoverflow.com

    public static void assistActivity(Activity activity)
    {
        new AndroidBug5497WorkaroundForXamarinAndroid(activity);
    }

    private Android.Views.View mChildOfContent;
    private int usableHeightPrevious;
    private FrameLayout.LayoutParams frameLayoutParams;

    private AndroidBug5497WorkaroundForXamarinAndroid(Activity activity)
    {
        FrameLayout content = (FrameLayout)activity.FindViewById(Android.Resource.Id.Content);
        mChildOfContent = content.GetChildAt(0);
        ViewTreeObserver vto = mChildOfContent.ViewTreeObserver;
        vto.GlobalLayout += (object sender, EventArgs e) => {
            possiblyResizeChildOfContent();
        };
        frameLayoutParams = (FrameLayout.LayoutParams)mChildOfContent.LayoutParameters;
    }

    private void possiblyResizeChildOfContent()
    {
        int usableHeightNow = computeUsableHeight();
        if (usableHeightNow != usableHeightPrevious)
        {
            int usableHeightSansKeyboard = mChildOfContent.RootView.Height;
            int heightDifference = usableHeightSansKeyboard - usableHeightNow;

            frameLayoutParams.Height = usableHeightSansKeyboard - heightDifference;

            mChildOfContent.RequestLayout();
            usableHeightPrevious = usableHeightNow;
        }
    }

    private int computeUsableHeight()
    {
        Rect r = new Rect();
        mChildOfContent.GetWindowVisibleDisplayFrame(r);
        if (Build.VERSION.SdkInt < BuildVersionCodes.Lollipop)
        {
            return (r.Bottom - r.Top);
        }
        return r.Bottom;
    }
}