我想要用長按選單來切換頁面，但是我呼叫MainActivity裡面切換的程式就閃退了

lvAlarmlist.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
                new AlertDialog.Builder(getContext()).setTitle("操作選項").setItems(new CharSequence[]{"刪除","修改"}, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        switch (which) {
                            case 0:
                                deleteAlarm(position);
                                break;
                            case 1:
                                MA.SetAlarm();
                                break;
                            default:
                                break;
                        }
                    }
                }).setNegativeButton("取消",null).show();

                return true;
            }
        });
    }
    private MainActivity MA;

選單部分，case 1的地方

public void SetAlarm(){
        System.out.println("1");
        //Intent intent = new Intent();
        //intent.setClass(MainActivity.this,SetAlarm.class);
        //startActivity(intent);
    }

MainActivity裡面的部分，經過實驗 一呼叫就爆炸