android - 从纵向切换到横向时保存 View 状态

Question

我使用 GridView 创建了一个简单的日历，每当我从纵向 View 切换到横向(或返回)时，它都不会保留状态。例如，我在纵向 View 中更改为一月，而在横向 View 中又回到了十二月。我试图解决这个问题并将这段代码添加到我的 OnCreate() 中:

    if(savedInstanceState != null && savedInstanceState.containsKey(CALENDAR)){
        mCalendar = (Calendar) savedInstanceState.getSerializable(CALENDAR);
   }else{
    mCalendar = Calendar.getInstance();
   }

并将此方法添加到类中:

@Override
    public void onSaveInstanceState(Bundle outState){
        super.onSaveInstanceState(outState);

        //Save the calendar instance in case the user changed it
        outState.putSerializable(CALENDAR, mCalendar);
    }

不幸的是，它不想工作，并且在更改手机方向时，几个月仍然会切换到初始版本。有人可以帮帮我吗？

---

代码:

public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_calendar);

    mCalendar = Calendar.getInstance(Locale.getDefault());
    month = mCalendar.get(Calendar.MONTH) + 1;
    year = mCalendar.get(Calendar.YEAR);

    previous = (Button) findViewById(R.id.b_prevMonth);
    next = (Button) findViewById(R.id.b_nextMonth);
    displayMonth = (TextView) findViewById(R.id.et_displayMonth);
    gv_daysOfWeek = (GridView) findViewById(R.id.gv_daysOfWeek);
    gv_calendar = (GridView) findViewById(R.id.gv_calendar);

    previous.setOnClickListener(this);
    next.setOnClickListener(this);
    displayMonth.setText(DateFormat.format(monthDisplay, mCalendar.getTime()));

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.weekdays_grid, R.id.grid_item_label, WEEK_DAYS);
    gv_daysOfWeek.setAdapter(adapter);

    setGridCellAdapter(month, year);

    if(savedInstanceState != null && savedInstanceState.containsKey(CALENDAR)){
        mCalendar = (Calendar) savedInstanceState.getSerializable(CALENDAR);
    }else{
        mCalendar = Calendar.getInstance();
    }
}

/**
 * Method responsible for intialising the adapter
 */
 private void setGridCellAdapter(int month, int year) {
     cellAdapter = new GridCellAdapter(getApplicationContext(),R.id.day_gridcell, month, year);
     mCalendar.set(year, month - 1 , mCalendar.get(Calendar.DAY_OF_MONTH));
     displayMonth.setText(DateFormat.format(monthDisplay, mCalendar.getTime()));
     cellAdapter.notifyDataSetChanged();
     gv_calendar.setAdapter(cellAdapter);
 }

Answer 1

在设置 GridView 之前之后您不会读取已保存的状态...更改您的代码以首先读取已保存的状态:

if(savedInstanceState != null && savedInstanceState.containsKey(CALENDAR)){
    mCalendar = (Calendar) savedInstanceState.getSerializable(CALENDAR);
}else{
    mCalendar = Calendar.getInstance(Locale.getDefault());
}
month = mCalendar.get(Calendar.MONTH) + 1;
year = mCalendar.get(Calendar.YEAR);

// Initialize your Buttons and such...

setGridCellAdapter(month, year);

删除任何其他试图在 onCreate() 中设置 mCalendar 的代码。