Menu-note-list
<!--    背景图功能  -->
    <item
        android:id="@+id/menu_a1"
        android:title="@string/menu_a1"/>
    <item
        android:id="@+id/menu_a2"
        android:title="@string/menu_a2"/>
    <item
        android:id="@+id/menu_a3"
        android:title="@string/menu_a3"/>
 
NotelistActivity
//背景图功能
    public int mode=-1;
//    私密模式
    public static int secret_mode = 0;
//        背景图功能
        getWindow().setBackgroundDrawableResource(R.drawable.a3);
        getWindow().setBackgroundDrawableResource(R.drawable.a2);
        getWindow().setBackgroundDrawableResource(R.drawable.a1);
//        背景功能
        if(mode==-1)
            menu.findItem(R.id.menu_a1).setVisible(false);
        else if (mode==0)
            menu.findItem(R.id.menu_a2).setVisible(false);
        else if (mode==1)
            menu.findItem(R.id.menu_a3).setVisible(false);

//            背景功能
            case R.id.menu_a1:{
                mode=-1;
                getWindow().setBackgroundDrawableResource(R.drawable.a1);
                break;
            }
            case R.id.menu_a2:{
                mode=0;
                getWindow().setBackgroundDrawableResource(R.drawable.a2);
                break;
            }
            case R.id.menu_a3:{
                mode=1;
                getWindow().setBackgroundDrawableResource(R.drawable.a3);
                break;
            }
Values_string
<!--    背景图功能 -->
    <string name="menu_a2">Background: a2</string>
    <string name="menu_a1">Background: a1</string>
    <string name="menu_a3">Background: a3</string>



        if(secret_mode == 1)menu.findItem(R.id.menu_secret).setVisible(false); else
            menu.findItem(R.id.menu_quit_secret).setVisible(false);
public void supportInvalidateOptionsMenu() {
    invalidateOptionsMenu(); // 最终调用 Activity 的原生方法
}
            case R.id.menu_secret: {    // 进入私密模式
                secret_mode = 1;  // 先临时设为1（用于对话框标题提示）
                AlertDialog.Builder dialog = new AlertDialog.Builder(NotesListActivity.this);
                dialog.setTitle("重要提醒")
                        .setMessage("您确认进入私密模式吗？")
                        .setCancelable(false)
                        .setPositiveButton("确认", (d, which) -> {
                            startAsyncNotesListQuery();
                            Toast.makeText(NotesListActivity.this, "您已进入私密模式", Toast.LENGTH_SHORT).show();
                        })
                        .setNegativeButton("取消", (d, which) -> {
                            secret_mode = 0;  // 恢复状态
                            supportInvalidateOptionsMenu();  // 强制刷新菜单 })
                        .show();
                break;}
            case R.id.menu_quit_secret: {    // 退出私密模式
                AlertDialog.Builder dialog = new AlertDialog.Builder(NotesListActivity.this);
                dialog.setTitle("重要提醒")
                        .setMessage("您确认退出私密模式吗？")
                        .setCancelable(false)
                        .setPositiveButton("确认", (d, which) -> {
                            secret_mode = 0;
                            startAsyncNotesListQuery();
                            supportInvalidateOptionsMenu();  // 刷新菜单
                            Toast.makeText(NotesListActivity.this, "您已退出私密模式", Toast.LENGTH_SHORT).show();
                        })
                        .setNegativeButton("取消", null)  // 无需操作
                        .show();
                break;
            }
Values_string
ShareActionProvider
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.note_list, menu);
    MenuItem enterSecret = menu.findItem(R.id.menu_secret);
    MenuItem quitSecret = menu.findItem(R.id.menu_quit_secret);
    enterSecret.setVisible(secret_mode == 0);  // 非私密模式时显示"进入"
    quitSecret.setVisible(secret_mode == 1);   // 私密模式时显示"退出"
    return true;
}
<!--    私密模式  -->
    <string name="Secret">secret model</string>
    <string name="Quit_Secret">quit secret model</string>
Menu_Sub_folder
<!--    私密模式  -->
    <item
        android:id="@+id/menu_secret"
        android:title="@string/Secret"/>
    <item
        android:id="@+id/menu_quit_secret"
        android:title="@string/Quit_Secret"/>
//    私密模式
    public static int secret_mode = 0;
private void startAsyncNotesListQuery() {
        String selection = (mCurrentFolderId == Notes.ID_ROOT_FOLDER) ? ROOT_FOLDER_SELECTION
                : NORMAL_SELECTION;
        if(secret_mode == 0) {
            mBackgroundQueryHandler.startQuery(FOLDER_NOTE_LIST_QUERY_TOKEN, null,
                    Notes.CONTENT_NOTE_URI, NoteItemData.PROJECTION, selection, new String[]{
                            String.valueOf(mCurrentFolderId)
                    }, NoteColumns.TYPE + " DESC," + NoteColumns.MODIFIED_DATE + " DESC");
        }
        else{
            String str1 = "111";
            String [] PROJECTION = new String [] {  //定义一个新的PROJECTION数组，只换掉SNIPPET
                    NoteColumns.ID,
                    NoteColumns.ALERTED_DATE,
                    NoteColumns.BG_COLOR_ID,
                    NoteColumns.CREATED_DATE,
                    NoteColumns.HAS_ATTACHMENT,
                    NoteColumns.MODIFIED_DATE,
                    NoteColumns.NOTES_COUNT,
                    NoteColumns.PARENT_ID,
//                    NoteColumns.SNIPPET,
                    str1,
                    NoteColumns.TYPE,
                    NoteColumns.WIDGET_ID,
                    NoteColumns.WIDGET_TYPE,
            };
            mBackgroundQueryHandler.startQuery(FOLDER_NOTE_LIST_QUERY_TOKEN, null,
                    Notes.CONTENT_NOTE_URI, PROJECTION, selection, new String[]{
                            String.valueOf(mCurrentFolderId)
                    }, NoteColumns.TYPE + " DESC," + NoteColumns.MODIFIED_DATE + " DESC");

        }
    }