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()

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);

我有同样的问题，并解决了它与以下代码。我不确定它在有硬件键盘的手机上会有什么表现。

// TextEdit
final EditText textEdit = new EditText(this);

// Builder
AlertDialog.Builder alert = new AlertDialog.Builder(this);
alert.setTitle("Enter text");
alert.setView(textEdit);

alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        String text = textEdit.getText().toString();
        finish();
    }
});

alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        finish();
    }
});

// Dialog
AlertDialog dialog = alert.create();
dialog.setOnShowListener(new OnShowListener() {

    @Override
    public void onShow(DialogInterface dialog) {
        InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
        imm.showSoftInput(textEdit, InputMethodManager.SHOW_IMPLICIT);
    }
});

dialog.show();

这是一个很好的例子:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ScrollView
        android:id="@+id/scrollID"
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="1" >

        <LinearLayout
            android:id="@+id/test"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >
        </LinearLayout>
    </ScrollView>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:baselineAligned="true"
        android:orientation="horizontal"
        android:paddingBottom="5dp"
        android:paddingLeft="5dp"
        android:paddingRight="5dp"
        android:weightSum="1" >

        <EditText
            android:id="@+id/txtInpuConversation"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="0.5"
            android:hint="@string/edt_Conversation" >

            <requestFocus />
        </EditText>

        <Button
            android:id="@+id/btnSend"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="0.5"
            android:text="@string/btn_Conversation" />
    </LinearLayout>

</LinearLayout>

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()

您可以在AlertDialog的EditText上创建一个焦点侦听器，然后获取AlertDialog的窗口。从那里你可以通过调用setSoftInputMode来显示软键盘。

final AlertDialog dialog = ...;

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