对于Xamarin.Android：

public void HideKeyboard()
{
    var imm = activity.GetSystemService(Context.InputMethodService).JavaCast<InputMethodManager>();
    var view = activity.CurrentFocus ?? new View(activity);
    imm.HideSoftInputFromWindow(view.WindowToken, HideSoftInputFlags.None);
}

Kotlin中的Wiki答案：

1-在文件中创建顶级函数（例如，包含所有顶级函数的文件）：

fun Activity.hideKeyboard(){
    val imm = this.getSystemService(Activity.INPUT_METHOD_SERVICE) as InputMethodManager
    var view = currentFocus
    if (view == null) { view = View(this) }
    imm.hideSoftInputFromWindow(view.windowToken, 0)
}

2-然后在你需要的任何活动中调用它：

this.hideKeyboard()

 fun hideKeyboard(appCompatActivity: AppCompatActivity) {
        val view = appCompatActivity.currentFocus
        val imm = appCompatActivity.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
        imm.hideSoftInputFromWindow(view.windowToken, 0)
    }

通过将Generic方法添加到Utility或Helper类。通过调用自己，您可以隐藏和显示键盘

fun AppCompatActivity.hideKeyboard() {
            val view = this.currentFocus
            if (view != null) {
                val imm = getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
                imm.hideSoftInputFromWindow(view.windowToken, 0)
            }
           window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN)

        }


 fun AppCompatActivity.showKeyboard() {
            val view = this.currentFocus
            if (view != null) {
                val imm = getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
                imm.hideSoftInputFromWindow(view.windowToken, 0)
            }                     window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN)

        }

Kotlin版本：

fun showKeyboard(mEtSearch: EditText, context: Context) {
        mEtSearch.requestFocus()
        val imm: InputMethodManager =
            context.getSystemService(Activity.INPUT_METHOD_SERVICE) as InputMethodManager
        imm.showSoftInput(mEtSearch, 0)
}

您可以使用InputMethodManager强制Android隐藏虚拟键盘，调用hideSoftInputFromWindow，传入包含焦点视图的窗口的标记。

// Check if no view has focus:
View view = this.getCurrentFocus();
if (view != null) {  
    InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
    imm.hideSoftInputFromWindow(view.getWindowToken(), 0);
}

这将在所有情况下强制隐藏键盘。在某些情况下，您需要将InputMethodManager.HIDE_IMPLICIT_ONLY作为第二个参数传递，以确保仅在用户未显式强制显示键盘时（通过按住菜单）隐藏键盘。

注意：如果您想在Kotlin中执行此操作，请使用：上下文getSystemService（Context.INPUT_METHOD_SERVICE）作为InputMethodManager

Kotlin语法

// Only runs if there is a view that is currently focused
this.currentFocus?.let { view ->
    val imm = getSystemService(Context.INPUT_METHOD_SERVICE) as? InputMethodManager
    imm?.hideSoftInputFromWindow(view.windowToken, 0)
}