android - 我们如何像在 onCreate() 中那样在 onOptionItemSelected 之外使用菜单项

Question

我在获取对 onOptionsItemSelected() 方法之外的菜单项的引用时遇到了问题。我希望这部分代码在我的 Activity 创建后立即执行，所以我试图在 onCreate() 中使用该菜单项，但它总是返回 空。任何帮助将不胜感激。

我正在尝试以下代码:

private Menu menu;

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

 updateMenu();

}

@Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_sub_task_detail, menu);

        this.menu = menu;
        menuItem = menu.findItem(R.id.markComplete);

        return true;

    }

    public void updateMenu(){

        menuItem = menu.findItem(R.id.markComplete);
        SharedPreferences sharedPreferences1 = getSharedPreferences("StatusValue", Context.MODE_PRIVATE);
        int count2 = sharedPreferences1.getInt("status", 0);
        if (count2 != 0){
          menuItem.setEnabled(false);

        }

        else {
            menuItem.setEnabled(true);
        }




    }



    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.

        SharedPreferences sharedPreferences1 = getSharedPreferences("StatusValue", Context.MODE_PRIVATE);
        int count2 = sharedPreferences1.getInt("status", 0);
        if (count2 != 0){

            menuItem.setEnabled(false);
        }

          int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        if (id == R.id.markComplete) {


            SQLiteDataBaseAdapter db = new SQLiteDataBaseAdapter(this);
          String taskname = task_name.getText().toString();
           int subTaskNumber1 = db.getSubTaskUID(taskname);
            int taskNumber = db.getTaskUID(position1);
            Log.d("Pana", "The value of Sub Task Number is " +subTaskNumber1);
            Long result = db.updateUserTable(1, subTaskNumber1, taskNumber);
            //Toast.makeText(this, "The value of result is " + result, Toast.LENGTH_LONG).show();

            // getting current Date and Time
            Calendar c = Calendar.getInstance();
            SimpleDateFormat df1 = new SimpleDateFormat("MM/dd/yyyy HH:mm");
            String formattedDate = df1.format(c.getTime());
            // formattedDate have current date/time
            Log.d("Pana", "Formatted Date is " + formattedDate);


            String[] dateTimeSplit = formattedDate.split(" ");
            String currDate = dateTimeSplit[0];
            String currTime = dateTimeSplit[1];

            subTask = db.getSubTask(position);
            String subTaskName = subTask.getSub_Task_Name();

           int UID = db.getSubTaskUID(subTaskName);


            db.updateEstCompTimeDateSubTask(UID, currTime, currDate);

            String[] actTimeDate = db.getActTimeDateSubTask(taskname);

            String actTime = actTimeDate[0];
            String actDate = actTimeDate[1];
            act_compDate.setText(actTime);
            act_compTime.setText(actDate);



            int count = db.checkOtherSubTask(taskNumber);

            if (count == 0){

                Toast.makeText(this, "There are no active Sub Tasks for the corresponding Task. Please create a new Sub Task or mark the corresponding task as completed", Toast.LENGTH_LONG).show();
            }

            int count1 = db.getStatus(taskNumber, subTaskNumber1);

            SharedPreferences sharedPreferences = getSharedPreferences("StatusValue", Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = sharedPreferences.edit();
            editor.putInt("status", count1);
            editor.commit();

            if (count1 != 0) {
                item.setEnabled(false);
            }


        }

        return super.onOptionsItemSelected(item);
    }

在这里，我想在我的 onCreate 方法中设置 ID 为 R.id.markComplete 的项目，但我无法获得对该项目的引用。欢迎所有建议。提前致谢。

Answer 1

不宜随心所欲。虽然您可以创建类字段

private Menu menu;

并在 onCreateOptionsMenu() 中捕获它的值

this.menu = menu;

已知 menu 的值突然变成null在 Activity 的某些点/Fragment生命周期。因此，建议您使用 menu 做任何您想做的事情。在onCreateOptionsMenu() , onPrepareOptionsMenu()和 onOptionsItemSelected()方法。这些方法是执行此操作的正确位置。

引用资料:

1. Menus .

2. Options Menu Tutorial .