如何在安卓按键上添加问号

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <!-- 添加问号按钮 -->
    <Button
        android:id="@+id/question_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="?"
        android:textSize="20sp"
        android:onClick="insertQuestionMark" />
</LinearLayout>

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 绑定自定义布局文件
        View customKeyboard = getLayoutInflater().inflate(R.layout.custom_keyboard, null);
        InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
        imm.setInputView(customKeyboard);
    }

    // 在按钮点击事件中插入问号字符
    public void insertQuestionMark(View view) {
        EditText editText = findViewById(R.id.edit_text);
        int cursorPosition = editText.getSelectionStart();
        editText.getText().insert(cursorPosition, "?");
    }
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapp">

    <application
        ...>

        <service
            android:name=".MyInputMethodService"
            android:label="@string/app_name"
            android:permission="android.permission.BIND_INPUT_METHOD">

            <meta-data
                android:name="android.view.im"
                android:resource="@xml/method" />
        </service>

        ...
    </application>

</manifest>