维持Backpress事件 [英] Maintain Backpress Event

问题描述

您好，



我有一个片段，其中包含自定义ListView，所有ListView事件都在片段类本身处理。现在，当我单击ListView项目时，我再次根据条件填充相同的ListView。但是，如果我按下后退按钮，我想再次在上一个状态下填写ListView。



这可能吗？如果有，怎么样？



下面是ListView的片段代码

  public   class  HomeFragment  extends 片段{
 
 字符串 CourseName [] = { 特殊课程，< span class =code-string> 工程，  BScIT，  BScCS}; 
 字符串 UniversityEngArray [] = { 孟买，  Pune， 德里， 拉贾斯坦邦}; 
 字符串 UniversityBScITArray [] = { 孟买，  Pune， 德里， 拉贾斯坦邦}; 
整数ImageId [] = {
 R.drawable.letters，
 R.drawable.lettere，
 R.drawable.letterb，
 R.drawable.letterb 
}; 
  private  ListView lv; 
 CustomList customList; 
 
  //   Listview适配器 
 ArrayAdapter< String>适配器; 
 
  public  HomeFragment（）{
  //  必需的空公共构造函数 
} 
 
  @覆盖 
  public   void  onCreate（Bundle savedInstanceState）{
  super .onCreate(savedInstanceState）; 
 
} 
 
  @ Override  
  public 查看onCreateView（LayoutInflater inflater，ViewGroup容器，
 Bundle savedInstanceState）{
查看rootView = inflater.inflate（R.layout.fragment_home，container，false）; 
 
 customList =  new  CustomList（getActivity（），CourseName，ImageId）; 
 lv =（ListView）rootView.findViewById（R.id.listView1）; 
 lv.setAdapter（customList）; 
 lv.setOnItemClickListener（ new  AdapterView.OnItemClickListener（）{
  @ Override  
  public   void  onItemClick（AdapterView<？> parent，View view， int  position， long  id）{
  //   Toast.makeText（getActivity（），You Clicked at+ CourseName [+ position]，Toast.LENGTH_SHORT）.show（）;  
  if （CourseName [+ position] .toString（）。equalsIgnoreCase（ 工程））{
 customList = new CustomList（getActivity（），UniversityEngArray，ImageId）; 
 lv.setAdapter（customList）; 
} 
  else   if （CourseName [+ position] .toString（）。equalsIgnoreCase（  BScIT））{
 customList = new CustomList（getActivity（），UniversityBScITArray，ImageId）; 
 lv.setAdapter（customList）; 
} 
} 
}）; 
 
  //  为此片段的布局充气 
  return  rootView; 
} 
 
  @覆盖 
  public   void  onAttach（活动活动）{
  super  .onAttach（activity）; 
} 
 
  @覆盖 
  public   void  onDetach（）{
  super  .onDetach（）; 
} 

解决方案

当然可以，但是你应该有一个带历史记录的状态机。最好是操纵数据，而不是UI。 UI应该简单地从数据中填充UI，比如来自历史的数据。由于历史可能需要大量数据，因此您可能需要保留它。抱歉，进一步的细节取决于您对数据的使用，数据库的使用或其他等等。

-SA

Hello,

I have a Fragment Which has a Custom ListView and All the ListView Events is Handled in Fragment Class Itself. Now When I Click On The ListView Item I Am Populating Same ListView Again Based On Condition. But If I Press Back Button I Want to again Fill ListView on Previous State.

Is this Possible? If yes how?

Below is the Code For Fragment With ListView

public class HomeFragment extends Fragment {

    String CourseName[]={"Special Courses","Engineering","BScIT","BScCS"};
    String UniversityEngArray[]={"Mumbai","Pune","Delhi","Rajasthan"};
    String UniversityBScITArray[]={"Mumbai","Pune","Delhi","Rajasthan"};
    Integer ImageId[]={
            R.drawable.letters,
            R.drawable.lettere,
            R.drawable.letterb,
            R.drawable.letterb
    };
    private ListView lv;
    CustomList customList;

    // Listview Adapter
    ArrayAdapter<String> adapter;

    public HomeFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_home, container, false);

        customList = new CustomList(getActivity(), CourseName, ImageId);
        lv = (ListView) rootView.findViewById(R.id.listView1);
        lv.setAdapter(customList);
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                //Toast.makeText(getActivity(), "You Clicked at " + CourseName[+position], Toast.LENGTH_SHORT).show();
                if(CourseName[+position].toString().equalsIgnoreCase("Engineering")){
                    customList =new CustomList(getActivity(),UniversityEngArray,ImageId);
                    lv.setAdapter(customList);
                }
                else if(CourseName[+position].toString().equalsIgnoreCase("BScIT")){
                    customList =new CustomList(getActivity(),UniversityBScITArray,ImageId);
                    lv.setAdapter(customList);
                }
            }
        });

        // Inflate the layout for this fragment
        return rootView;
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
    }

    @Override
    public void onDetach() {
        super.onDetach();
    }

解决方案

Of course it's possible, but then you should have a state machine with History. It's better to manipulate data, not UI. The UI should simple populate UI from data, say, data from history. As history may need a lot of data, you may need to persist it. Sorry, but further detail depends on what you have for data, the use of databases or something else, and so on.

—SA

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