android - 在 viewpager 中保存 View 状态

Question

这是这个问题的跟进 ViewPager and fragments — what's the right way to store fragment's state? .我需要有人用代码来解释这部分答案。

另一种方法是覆盖 FragmentPageAdapter.instantiateItem(View, int) 并在返回之前保存对从 super 调用返回的 fragment 的引用(它具有查找 fragment 的逻辑，如果已经存在的话)。

我正在使用 PagerAdapter 将数据从游标加载到 viewpager。我已经覆盖了 PagerAdapter.intantiateItem。我所需要的只是能够保存被单击的按钮的状态。这是我的代码

    public class CustomQuestionPagerAdapter extends PagerAdapter {

private Cursor cursor;
private Cursor cursorCategory;
private LayoutInflater inflater;
private Context context;
private ArrayList<String> optionsArray; 
String rightAnswer;
String wrongAnswer1;
String wrongAnswer2;
Button option1;
Button option2;
Button option3;

public CustomQuestionPagerAdapter(Context context, Cursor cursor1, Cursor cursor2) {
    this.context = context;
    this.cursor = cursor1;
    this.cursorCategory = cursor2;
    this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

}        

public void swapCursor(Cursor cursor) {
    this.cursor = cursor;
}

public void swapAnotherCursor(Cursor cursor) {
    this.cursorCategory = cursor;
}


public void destroyItem(View view, int position, Object object) {
    ((ViewPager) view).removeView((ScrollView) object);
}

@Override
public int getCount() {
    if (cursor == null) {
        return 0;
    }else {
        return cursor.getCount();
    }
}



/* (non-Javadoc)
 * @see android.support.v4.view.PagerAdapter#instantiateItem(android.view.View, int)
 */


@Override
public Object instantiateItem(View view, int position) {

    cursor.moveToPosition(position);
    final ViewPager pager = (ViewPager) view.findViewById(R.id.pager_nav);
    ScrollView layout = (ScrollView) inflater.inflate(R.layout.question_activity, null);
    if (cursorCategory != null && cursorCategory.moveToFirst()){
        String s = cursorCategory.getString(cursorCategory.getColumnIndex("name"));
        ((TextView)layout.findViewById(R.id.text_category)).setText(s);
    }

    Typeface tpf = Typeface.createFromAsset(context.getAssets(), "Roboto-Light.ttf");
    String text = cursor.getString(cursor.getColumnIndex("question_text"));
    TextView question_text =  (TextView)layout.findViewById(R.id.text_question);
    question_text.setText(text);
    question_text.setTypeface(tpf);

    String qPos = Integer.toString(position + 1) + ".";
    TextView question_position = (TextView) layout.findViewById(R.id.text_position);
    question_position.setText(qPos);
    question_position.setTypeface(tpf);

    this.rightAnswer = cursor.getString(cursor.getColumnIndex(DBHelper.RIGHT_ANSWER));
    this.wrongAnswer1 = cursor.getString(cursor.getColumnIndex(DBHelper.WRONG_ANSWER1));
    this.wrongAnswer2 = cursor.getString(cursor.getColumnIndex(DBHelper.WRONG_ANSWER2));

    optionsArray = new ArrayList<String>();
    optionsArray.clear();
    optionsArray.add(this.rightAnswer);
    optionsArray.add(this.wrongAnswer1);
    optionsArray.add(this.wrongAnswer2);
    Collections.shuffle(optionsArray);

    option1 = (Button) layout.findViewById(R.id.button_option1);
    option1.setText((CharSequence) this.optionsArray.get(0));

    option2 = (Button) layout.findViewById(R.id.button_option2);
    option2.setText((CharSequence) this.optionsArray.get(1));

    option3 = (Button) layout.findViewById(R.id.button_option3);
    option3.setText((CharSequence) this.optionsArray.get(2));


    final Button next = (Button) layout.findViewById(R.id.next_button);
    next.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            int j = getItem(+1) + 1;
            Toast.makeText(context, context.getResources().getString(R.string.question_no) + " " + j, Toast.LENGTH_SHORT).show();
            pager.setCurrentItem(getItem(+1), true);
            next.setBackgroundColor(0xffeeeeee); // i need to save this new bacground color
        }

        private int getItem(int i) {
            return i += pager.getCurrentItem();
        }
    });

我也试过这个答案，但没有用 Saving Fragment state in ViewPager

提前致谢。

Answer 1

PagerAdapter 不会在状态恢复时自动保存和恢复 View 。
您需要等效于 FragmentStatePagerAdapter 但对于 View 。您可以选择是自己实现还是扩展已有的组件。 GitHub 上有一些:例如 https://github.com/NightlyNexus/ViewStatePagerAdapter .
如果您需要回收 View 支架，甚至还有来自伟大的 Jake Wharton 的 View 寻呼机适配器 https://github.com/JakeWharton/salvage .我使用前者，因为它更适合我的情况，只需将 PageAdapter 替换为新的 ViewStatePagerAdapter 并覆盖 createView(ViewGroup, int) 和 destroyView(ViewGroup, int)。
检查这个例子真的很容易理解。