我的方法使用了Android 11+的新方法，也支持旧版本:

fun Fragment.showKeyboard() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
        ViewCompat.getWindowInsetsController(requireView())?.show(WindowInsetsCompat.Type.ime())
    } else {
        val focusedView = view?.findFocus() ?: view?.apply { requestFocus() }
        val imm = (context?.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager)
        val isShowSucceeded = imm.showSoftInput(focusedView, InputMethodManager.SHOW_IMPLICIT)
        if(!isShowSucceeded) {
            imm.toggleSoftInputFromWindow(
                view?.windowToken, 0, InputMethodManager.HIDE_IMPLICIT_ONLY)
    }
}

}

edittext.setShowSoftInputOnFocus(真正的);是关于这个问题的最流畅的解决方案。

AlertDialog.Builder alertSearch = new AlertDialog.Builder(activity);
alertSearch.setIcon(R.drawable.ic_launcher);
alertSearch.setTitle("Search");
final EditText edittext = new EditText(activity);
edittext.setSingleLine();
edittext.setHint("...");
edittext.setText(SearchString);

在聚焦时设置键盘

edittext.setShowSoftInputOnFocus(true);

获得焦点

edittext.requestFocus();

And

alertSearch.setView(edittext);
alertSearch.setPositiveButton("OK", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
        // Do something
        act.recreate();
    }
});
alertSearch.show();

在AlertDialog中从EditText显示软键盘的问题可能是在AlertDialog.show()中，因为在显示AlertDialog之后应用了EditText。我不确定所有版本的API都是这样，但我认为解决方案来自API级别21，因为它来自AlertDialog.create()，它应该在AlertDialog.show()之前调用。

这是我对这种情况的最佳解决方案。首先，在某个地方创建:

    private int showKeyboard(View view) {
        final InputMethodManager inputManager = (InputMethodManager) requireActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
        if (inputManager != null) {
            boolean isShown = inputManager.showSoftInput(view, InputMethodManager.SHOW_IMPLICIT); // flag=InputMethodManager.SHOW_IMPLICIT ili =
            return (isShown) ? 1: -1;
        }
        return 0;
    }

然后，在AlertDialog之后。生成器生成器= new AlertDialog.Builder(requireContext());继续:

    EditText editText = new EditText(requireContext());
    builder.setView(editText);
    // ... put positive-negative buttons, and etc ...
    AlertDialog dialog = builder.create(); // Create dialog from builder
    dialog.setCancelable(false); // If you need
    Handler handler = new Handler();
    dialog.setOnShowListener(new DialogInterface.OnShowListener() {
        @Override
        public void onShow(DialogInterface dialog) { // 1. When a dialog is displayed
            editText.requestFocus();
            Runnable runnable = new Runnable() { // create one runnable
                int counter = 0;
                public void run() {
                    int status = showKeyboard(editText); // 2. Call func.above for keyboard, but...
                    if(status == -1 && counter < 10){ handler.postDelayed(this, 100); counter ++; } // ...if it inst shown call again after 100ms
                }
            };
            runnable.run(); // Execute runnable first time here
        }
    });
    dialog.show();

不要忘记导入android.os.Handler;等等;-)

感谢大家的投票。

这对我很有用。我为对话框设置了一个OnShowListener，在那个监听器中，我为文本字段设置了一个onFocusChangeListener，在那个FocusChangeListener中，我用100ms的延迟调用showSoftInput，然后删除FocusChangeListener，所以它只处理第一个焦点变化。

当调用dialog.show()时，OnShowListener被调用，它请求文本字段的焦点。当文本字段获得焦点时，将调用FocusChangeListener并最终显示键盘。

    val views = DialogBinding.inflate(layoutInflater) // layout with 'textfield'
    val dialog = MaterialAlertDialogBuilder(requireContext())
        .setTitle("Exercise")
        .setView(views.root)
        ...
        .create()
    dialog.setOnShowListener {
        views.textfield.onFocusChangeListener = View.OnFocusChangeListener { view, _ ->
            view.postDelayed({
                (view.context.getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager).showSoftInput(view, 0)
            }, 100)                
            views.textfield.onFocusChangeListener = null
        }
        views.repcount.requestFocus()
    }
    dialog.show()

<activity
    ...
    android:windowSoftInputMode="stateVisible" >
</activity>

or

getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);

来自其他答案的代码片段也可以工作，但将它们放在代码中的哪个位置并不总是很明显，特别是在使用AlertDialog时。Builder和遵循官方对话框教程，因为它不使用最终AlertDialog…或alertDialog.show()。

alertDialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);

更可取

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

因为如果焦点从EditText移开，SOFT_INPUT_STATE_ALWAYS_VISIBLE将隐藏键盘，而SHOW_FORCED将保持键盘显示，直到显式地关闭，即使用户返回到主屏幕或显示最近的应用程序。

下面是使用自定义布局和XML定义的EditText创建的AlertDialog的工作代码。它还设置键盘有一个“go”键，并允许它触发积极按钮。

alert_dialog.xml:

<RelativeLayout
android:id="@+id/dialogRelativeLayout"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content" >

    <!-- android:imeOptions="actionGo" sets the keyboard to have a "go" key instead of a "new line" key. -->
    <!-- android:inputType="textUri" disables spell check in the EditText and changes the "go" key from a check mark to an arrow. -->
    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginBottom="16dp"
        android:imeOptions="actionGo"
        android:inputType="textUri"/>

</RelativeLayout>

AlertDialog.java:

import android.app.Activity;
import android.app.Dialog;
import android.content.DialogInterface;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.DialogFragment;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatDialogFragment;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.WindowManager;
import android.widget.EditText;

public class CreateDialog extends AppCompatDialogFragment {
    // The public interface is used to send information back to the activity that called CreateDialog.
    public interface CreateDialogListener {
        void onCreateDialogCancel(DialogFragment dialog);    
        void onCreateDialogOK(DialogFragment dialog);
    }

    CreateDialogListener mListener;

    // Check to make sure that the activity that called CreateDialog implements both listeners.
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (CreateDialogListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement CreateDialogListener.");
        }
    }

    // onCreateDialog requires @NonNull.
    @Override
    @NonNull
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(getActivity());
        LayoutInflater customDialogInflater = getActivity().getLayoutInflater();

        // Setup dialogBuilder.
        alertDialogBuilder.setTitle(R.string.title);
        alertDialogBuilder.setView(customDialogInflater.inflate(R.layout.alert_dialog, null));
        alertDialogBuilder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                mListener.onCreateDialogCancel(CreateDialog.this);
            }
        });
        alertDialogBuilder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                mListener.onCreateDialogOK(CreateDialog.this);
            }
        });

        // Assign the resulting built dialog to an AlertDialog.
        final AlertDialog alertDialog = alertDialogBuilder.create();

        // Show the keyboard when the dialog is displayed on the screen.
        alertDialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);

        // We need to show alertDialog before we can setOnKeyListener below.
        alertDialog.show();

        EditText editText = (EditText) alertDialog.findViewById(R.id.editText);

        // Allow the "enter" key on the keyboard to execute "OK".
        editText.setOnKeyListener(new View.OnKeyListener() {
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                // If the event is a key-down event on the "enter" button, select the PositiveButton "OK".
                if ((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) {
                    // Trigger the create listener.
                    mListener.onCreateDialogOK(CreateDialog.this);

                    // Manually dismiss alertDialog.
                    alertDialog.dismiss();

                    // Consume the event.
                    return true;
                } else {
                    // If any other key was pressed, do not consume the event.
                    return false;
                }
            }
        });

        // onCreateDialog requires the return of an AlertDialog.
        return alertDialog;
    }
}