Question

我正在尝试根据父微调器的选定项设置微调器的值。但leagueAdapter.clear();以某种方式将我的属性leagueValues（作为List传递给我的SpinnerAdapter作为第三个参数）。我只想删除微调器中的所有当前值并设置新值。但是调用clear()会删除leagueValues的所有值，因此getLeaguesByCountry中的for循环会返回一个空列表。

缩短代码：

public class AddBetActivity extends MainActivity implements OnItemSelectedListener {
    // spinners
    Spinner countrySpinner;
    // ...

    // values
    List<DataObject> countryValues = new ArrayList<DataObject>();
    List<DataObject> leagueValues = new ArrayList<DataObject>();
    // ...

    // adapters
    SpinnerAdapter countryAdapter;
    // ...

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_bet);

        // spinners
        countrySpinner = (Spinner) findViewById(R.id.country);
        // ...


        // load data
        loadData();

        // set listener for button onClick
        findViewById(R.id.submit).setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        validate();
                    }
                });
    }

    protected void setListener() {
        countrySpinner.setOnItemSelectedListener(this);
        // ...
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
        switch(parent.getId()) {
            case R.id.country:
                DataObject country = countryAdapter.getItem(pos);
                if (country.getID() != 0) {
                    // get new values
                    ArrayList<League> list = getLeaguesByCountry(country.getID());

                    // clear old values
                    leagueAdapter.clear();

                    // add new values
                    leagueAdapter.addAll(list);

                    // notify adapter
                    leagueAdapter.notifyDataSetChanged();
                    leagueSpinner.setVisibility(View.VISIBLE);
                }
                else {
                    leagueSpinner.setVisibility(View.INVISIBLE);
                }
            break;

            // ...
        }
    }


    public void onNothingSelected(AdapterView<?> arg0) {
        // TO-DO
    }

    public void loadData() {
        DataUtil.post("GetBetData", params, new JsonHttpResponseHandler() {
            public void onSuccess(int statusCode, Header[] headers, JSONObject response) {
                try {
                    // get arrays
                    JSONArray countries = response.getJSONArray("countries");
                    // ...


                    // add default value
                    countryValues.add(new DataObject(0, getString(R.string.default_country)));
                    // add countries
                    for(int i=0; i<countries.length(); i++) {
                        JSONObject country = countries.getJSONObject(i);
                        countryValues.add(new DataObject(country.getInt("countryID"), country.getString("name")));
                    }

                    // ...
                }
                catch (JSONException e) {
                     Log.e("ERROR", e.getMessage());
                }

                countryAdapter = new SpinnerAdapter(getApplicationContext(), R.layout.spinner_style, countryValues);
                countrySpinner.setAdapter(countryAdapter);

                leagueAdapter = new SpinnerAdapter(getApplicationContext(), R.layout.spinner_style, leagueValues);
                leagueSpinner.setAdapter(leagueAdapter);

                // ...

                // set on select listener
                setListener();
            }
        });     
    }


    public void validate() {        
        // TO-DO
    }

    public ArrayList<League> getLeaguesByCountry(int countryID) {
        ArrayList<League> list = new ArrayList<League>();

        for(League league: leagueValues) {
            if (league.getCountry() == countryID)
                list.add(league);
        }
        return list;
    }



}

修改我尝试添加另一个属性List<League> tempLeagueValues = new ArrayList<League>();，我在loadData方法

中添加了值

        tempLeagueValues = leagueValues;

        countryAdapter = new SpinnerAdapter(getApplicationContext(), R.layout.spinner_style, countryValues);
        countrySpinner.setAdapter(countryAdapter);

        leagueAdapter = new SpinnerAdapter(getApplicationContext(), R.layout.spinner_style, leagueValues);
        leagueSpinner.setAdapter(leagueAdapter);

我也在我的getLeaguesByCountry方法中使用它：

public ArrayList<League> getLeaguesByCountry(int countryID) {
    ArrayList<League> list = new ArrayList<League>();

    for(League league: tempLeagueValues) {
        if (league.getCountry() == countryID)
            list.add(league);
    }
    return list;
}

第二次在countrySpinner中选择项目时，tempLeagueValues为空。怎么会这样？

Answer 1

clear()方法正在做它应该做的事情。

您需要保留一组可能的值才能恢复。

public ArrayList<League> getLeaguesByCountry(int countryID) {
    ArrayList<League> list = new ArrayList<League>();

    for(League league: savedLeagueValues) {
        if (league.getCountry() == countryID)
            list.add(league);
    }
    return list;
}

使用：

savedLeagueValues = new ArrayList<League>(leagueValues);
// this is a java "trick" to directly copy values from an array to another

能够恢复它们。

Adapter.clear删除list属性的值

1 个答案: