我找到了这个例子http://android-codes-examples.blogspot.com/2011/11/show-or-hide-soft-keyboard-on-opening.html。在alert.show()之前添加以下代码。

InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.toggleSoftInput(InputMethodManager.SHOW_FORCED,0);

让我指出一些额外的信息，解决yuku，因为我发现很难得到这个工作!我如何从我的AlertDialog. builder获得AlertDialog对象?嗯，这是alert.show()执行的结果:

final AlertDialog.Builder alert = new AlertDialog.Builder(getActivity());
final EditText input = new EditText(getActivity());
alert.setView(input);

// do what you need, like setting positive and negative buttons...

final AlertDialog dialog = alert.show();

input.setOnFocusChangeListener(new OnFocusChangeListener() {
   @Override
   public void onFocusChange(View v, boolean hasFocus) {
      if(hasFocus) {
         dialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
      }
   }
});

问题似乎是，因为你输入文本的地方最初是隐藏的(或嵌套或其他)，AlertDialog自动设置标志WindowManager.LayoutParams。FLAG_ALT_FOCUSABLE_IM或WindowManager.LayoutParams。FLAG_NOT_FOCUSABLE，这样就不会触发软输入来显示。

解决这个问题的方法是添加以下内容:

(...)
// Create the dialog and show it
Dialog dialog = builder.create()
dialog.show();

// After show (this is important specially if you have a list, a pager or other view that uses a adapter), clear the flags and set the soft input mode
dialog.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|WindowManager.LayoutParams.FLAG_ALT_FOCUSABLE_IM);
dialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);

你可以在EditText上附加onFocusListener或在AlertDialog上附加onShowListener，并添加以下内容:

val methodManager = activity.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
methodManager.showSoftInput(view, InputMethodManager.SHOW_IMPLICIT)

将这些方法放在Util类中，并在任何地方使用。

科特林

fun hideKeyboard(activity: Activity) {
    val view = activity.currentFocus
    val methodManager = activity.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
    assert(view != null)
    methodManager.hideSoftInputFromWindow(view!!.windowToken, InputMethodManager.HIDE_NOT_ALWAYS)
}

private fun showKeyboard(activity: Activity) {
    val view = activity.currentFocus
    val methodManager = activity.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
    assert(view != null)
    methodManager.showSoftInput(view, InputMethodManager.SHOW_IMPLICIT)
}

Java

public static void hideKeyboard(Activity activity) {
    View view = activity.getCurrentFocus();
    InputMethodManager methodManager = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
    assert methodManager != null && view != null;
    methodManager.hideSoftInputFromWindow(view.getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
}

private static void showKeyboard(Activity activity) {
    View view = activity.getCurrentFocus();
    InputMethodManager methodManager = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
    assert methodManager != null && view != null;
    methodManager.showSoftInput(view, InputMethodManager.SHOW_IMPLICIT);
}

尝试了很多，但这对我来说是有效的(kotlin):

        val dialog = builder.create()
        dialog.setOnShowListener {
            nameEditText.requestFocus()
            val s = ContextCompat.getSystemService(requireContext(), InputMethodManager::class.java)
            s?.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0)
        }

        dialog.setOnDismissListener {
            val s = ContextCompat.getSystemService(requireContext(), InputMethodManager::class.java)
            s?.toggleSoftInput(InputMethodManager.HIDE_IMPLICIT_ONLY, 0)
        }

        dialog.show()