Question

我有一个包含5个成员变量的类Place。单击按钮用户，输入一个新的Place对象，我将其放在listview中。我正在使用LinkedHashset来防止重复，但我仍然可以在listview中看到双重输入。请建议。我的代码：

public class OneFragment extends Fragment {
    private Button mButton;



    List<String> inputStrings = new ArrayList<String>();
    List<Place> placeList=new ArrayList<Place>();
    LinkedHashSet<Place> hashPlace=new LinkedHashSet<Place>();
    LinkedHashSet<String> hashSet=new LinkedHashSet<String>();

    private ListView mListView=null;
    private PlaceAdapter mPlaceAdapter;





    public OneFragment() {
    }

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

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.fragment_one, container, false);
        input=(EditText)view.findViewById(R.id.input);
                mListView=(ListView)view.findViewById(R.id.myListView);
        mButton=(Button)view.findViewById(R.id.submit);

        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String str = input.getText().toString();


                String shopName = Character.toString(str.charAt(0));
                  String  catName = Character.toString(str.charAt(1));
                String offerName = Character.toString(str.charAt(2));
                String expName = Character.toString(str.charAt(3));
                 String imageName = Character.toString(str.charAt(4)); 
                    Place plc=new Place(shopName,offerName,imageName,catName,expName);

//Check duplication
                if (hashPlace.add(plc)){
                placeList=new ArrayList<Place>(hashPlace);}

                Place mPlaces[] = placeList.toArray(new Place[placeList.size()]);

                mPlaceAdapter = new PlaceAdapter(getActivity(), R.layout.row, mPlaces, OneFragment.this);

                if (mListView != null) {
                    mListView.setAdapter(mPlaceAdapter);
                }

            }

        });

        return view;
    }

}

添加地方类：

public class Place implements Serializable {
    public String mPlace;
    public String mOffer;
    public String mImage;
    public String mCat;
    public String mExp;

    public Place(){

    }
    public Place(String place, String offer, String image,String cat,String exp) {
        this.mPlace = place;
        this.mOffer = offer;
        this.mImage = image;
        this.mCat=cat;
        this.mExp=exp;
    }

    public String getPlace() {
        return mPlace;
    }

    public void setPlace(String place) {
        mPlace = place;
    }

    public String getOffer() {
        return mOffer;
    }

    public void setOffer(String offer) {
        mOffer = offer;
    }

    public String getImage() {
        return mImage;
    }

    public void setImage(String image) {
        mImage = image;
    }

    public String getCat() {
        return mCat;
    }

    public void setCat(String cat) {
        mCat = cat;
    }

    public String getExp() {
        return mExp;
    }

    public void setExp(String exp) {
        mExp = exp;
    }

    @Override
    public boolean equals(Object object) {
        boolean result = false;
        if (object == null || object.getClass() != getClass()) {
            result = false;
        } else {
            Place place= (Place) object;
            if (this.mPlace== place.getPlace()
                    && this.mCat == place.getCat()) {
                result = true;
            }
        }
        return result;
    }

    @Override
    public int hashCode() {
        return super.hashCode();
    }
}

Answer 1

要使LinkedHashSet正常工作，必须覆盖hashcode和equals方法。在你的情况下，你必须在Place class中进行。

Answer 2

我有一个使用HashSet的解决方案。如果这对您有用，请告诉我，我没有布局文件或适配器等信息来正确测试。

public class OneFragment extends Fragment implements View.OnClickListener {

    private Button mButton;
    private EditText mInput;
    private ListView mListView;

    private HashSet<Place> mPlaces;
    private PlaceAdapter mPlaceAdapter;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Create hash set
        mPlaces = new HashSet<>();

        // Create adapter based on hash set
        mPlaceAdapter = new PlaceAdapter(getActivity(), R.layout.row, mPlaces, OneFragment.this);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_one, container, false);
        // Initialise the view objects
        initViews(view);
        return view;
    }

    private void initViews(View view) {
        // Find the views from the resource file
        mListView = (ListView) view.findViewById(R.id.myListView);
        mInput    = (EditText) view.findViewById(R.id.input);
        mButton   = (Button) view.findViewById(R.id.submit);

        // Set the lists adapter
        mListView.setAdapter(mPlaceAdapter);
        // Attach on click listener
        mButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.submit:
                // On click of mButton
                String str = mInput.getText().toString();

                String shopName  = "" + str.charAt(0);
                String catName   = "" + str.charAt(1);
                String offerName = "" + str.charAt(2);
                String expName   = "" + str.charAt(3);
                String imageName = "" + str.charAt(4);

                // If the place was not already in the hash map, the 'add' method will return true.
                if (mPlaces.add(new Place(shopName, offerName, imageName, catName, expName))) {
                    // Update the adapter / list view only if a new place is added.
                    mPlaceAdapter.notifyDataSetChanged();
                }
        }
    }
}

Answer 3

@Override protected Void doInBackground（Void ... voids）{

        HttpHandler sh = new HttpHandler();

        String jsonStr = sh.makeServiceCall(Utils.SERVER_URL);

        Log.e(TAG, "Response from url: " + jsonStr);

        if (jsonStr != null) {
            try {
                JSONObject jsonObject = new JSONObject(jsonStr);
                JSONArray result = jsonObject.getJSONArray("result");

                for (int i = 0; i < result.length(); i++) {

                    JSONObject data = result.getJSONObject(i);
                    String day = data.getString("day");

                    dataModels.add(day);

                    LinkedHashSet<String> lhs = new LinkedHashSet<String>();
                    lhs.addAll(dataModels);
                    // Removing ArrayList elements
                    dataModels.clear();
                    dataModels.addAll(lhs);
                }

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return null;
    }

我使用LinkedHashset来防止在自定义对象的Arraylist中重复输入，但重复发生

3 个答案: