java - 从 ArrayList> 填充 Spinner

Question

我试图从我存储 JSON 响应的 ArrayList 填充 Spinner。

我不知道该怎么做。我需要带有项目列表的微调器，并且当选择项目时才能获取该项目的值。

非常感谢。

@Override
    protected void onPostExecute(Void aVoid) {
       ArrayAdapter<ArrayList<HashMap<String,String>>> adapter = new ArrayAdapter<>(
                MainActivity.this, android.R.layout.simple_spinner_item, array.size());

        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        spinner.setAdapter(adapter);


        super.onPostExecute(aVoid);
    }

更改为:

 @Override
    protected void onPostExecute(Void aVoid) {
       ArrayAdapter<ArrayList<HashMap<String,String>>> adapter = new ArrayAdapter<ArrayList<HashMap<String, String>>>(
                MainActivity.this, android.R.layout.simple_spinner_item, Collections.singletonList(valutetList));

        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        spinner.setAdapter(adapter);


        super.onPostExecute(aVoid);
    }

现在我只得到一件元素，例如:

{"currency_code": "AUD", "median_rate": "4.634211", "selling_rate": "4.648114", "buying_rate": "4.620308", "unit_value": 1}

我的完整代码:

public class MainActivity extends AppCompatActivity {

private String TAG = MainActivity.class.getSimpleName();


ArrayList<HashMap<String, String>> valutetList;
Spinner spinner;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    spinner = findViewById(R.id.spFrom);
    valutetList = new ArrayList<>();
    new getRates().execute();
}

private class getRates extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        Toast.makeText(MainActivity.this, "Json Data is downloading", Toast.LENGTH_LONG).show();
    }

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

        HttpHandler httpHandler = new HttpHandler();
        String url = "http://hnbex.eu/api/v1/rates/daily/?date=2018-05-05";
        String jsonStr = httpHandler.makeServiceCall(url);

        Log.e(TAG, "Response from url: " + jsonStr);
        if (jsonStr != null) try {

            JSONArray valute = new JSONArray(jsonStr);
            for (int i = 0; i < valute.length(); i++) {
                HashMap<String, String> map = new HashMap<>();

                JSONObject jsonobject = valute.getJSONObject(i);
                String code = jsonobject.getString("currency_code");
                String selling = jsonobject.getString("selling_rate");
                String buying = jsonobject.getString("buying_rate");
                String median = jsonobject.getString("median_rate");
                String value = jsonobject.getString("unit_value");
                map.put("currency_code", code);
                map.put("selling_rate", selling);
                map.put("buying_rate", buying);
                map.put("median_rate", median);
                map.put("unit_value", value);

                valutetList.add(map);
            }


        } catch (final JSONException e) {
            Log.e(TAG, "Json parsing error: " + e.getMessage());
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(),
                            "Json parsing error: " + e.getMessage(),
                            Toast.LENGTH_LONG).show();
                }
            });

        }
        else {
            Log.e(TAG, "Couldn't get json from server.");
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(),
                            "Couldn't get json from server. Check LogCat for possible errors!",
                            Toast.LENGTH_LONG).show();
                }
            });
        }

        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        ArrayAdapter<ArrayList<HashMap<String, String>>> adapter = new ArrayAdapter<>(
                MainActivity.this, android.R.layout.simple_selectable_list_item, Collections.singletonList(valutetList));

        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);

        super.onPostExecute(aVoid);
    }
}

}

我不知道如何填充微调器。

Answer 1

尝试这个解决方案，可能会对您有所帮助。对于json数组文件，我将其更改为字符串。

第一步，创建辅助类(StackHelper.class)

public class StackHelper {
String code, selling, buying, median, value;

public StackHelper() {
}

public String getCode() {
    return code;
}

public void setCode(String code) {
    this.code = code;
}

public String getSelling() {
    return selling;
}

public void setSelling(String selling) {
    this.selling = selling;
}

public String getBuying() {
    return buying;
}

public void setBuying(String buying) {
    this.buying = buying;
}

public String getMedian() {
    return median;
}

public void setMedian(String median) {
    this.median = median;
}

public String getValue() {
    return value;
}

public void setValue(String value) {
    this.value = value;
}

@Override
public String toString () {
    return code;
}}

然后在Activity(StackActivity.class)中

public class StackActivity extends AppCompatActivity {

private String TAG = StackActivity.class.getSimpleName();
Spinner spinnerStack;
List <StackHelper> stackHelperList = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_stack);
    spinnerStack = findViewById(R.id.spFrom);
    spin();

    spinnerStack.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

        public void onItemSelected(AdapterView<?> arg0, View view, int position, long id) {
            String selling = ((StackHelper) spinnerStack.getSelectedItem ()).getSelling ();
            String buying = ((StackHelper) spinnerStack.getSelectedItem ()).getBuying ();
            String median = ((StackHelper) spinnerStack.getSelectedItem ()).getMedian ();
            String value = ((StackHelper) spinnerStack.getSelectedItem ()).getValue ();
            Toast.makeText(StackActivity.this,
                    "Selling : " + selling+"\n" +
                            "Buying : " + buying+"\n" +
                            "Median : " + median+"\n" +
                            "Value : " + value, Toast.LENGTH_SHORT).show();
        }
        public void onNothingSelected(AdapterView<?> arg0) { }
    });
}

private void spin () {
    stackHelperList = new ArrayList<>();

    try {
        String jsonStr = "[{\"unit_value\": 1, \"median_rate\": \"4.656778\", \"currency_code\": \"AUD\", \"buying_rate\": \"4.642808\", \"selling_rate\": \"4.670748\"}, {\"unit_value\": 1, \"median_rate\": \"4.811651\", \"currency_code\": \"CAD\", \"buying_rate\": \"4.797216\", \"selling_rate\": \"4.826086\"}, {\"unit_value\": 1, \"median_rate\": \"0.290560\", \"currency_code\": \"CZK\", \"buying_rate\": \"0.289688\", \"selling_rate\": \"0.291432\"}, {\"unit_value\": 1, \"median_rate\": \"0.994420\", \"currency_code\": \"DKK\", \"buying_rate\": \"0.991437\", \"selling_rate\": \"0.997403\"}, {\"unit_value\": 100, \"median_rate\": \"2.356911\", \"currency_code\": \"HUF\", \"buying_rate\": \"2.349840\", \"selling_rate\": \"2.363982\"}, {\"unit_value\": 100, \"median_rate\": \"5.677144\", \"currency_code\": \"JPY\", \"buying_rate\": \"5.660113\", \"selling_rate\": \"5.694175\"}, {\"unit_value\": 1, \"median_rate\": \"0.767955\", \"currency_code\": \"NOK\", \"buying_rate\": \"0.765651\", \"selling_rate\": \"0.770259\"}, {\"unit_value\": 1, \"median_rate\": \"0.701279\", \"currency_code\": \"SEK\", \"buying_rate\": \"0.699175\", \"selling_rate\": \"0.703383\"}, {\"unit_value\": 1, \"median_rate\": \"6.204487\", \"currency_code\": \"CHF\", \"buying_rate\": \"6.185874\", \"selling_rate\": \"6.223100\"}, {\"unit_value\": 1, \"median_rate\": \"8.395712\", \"currency_code\": \"GBP\", \"buying_rate\": \"8.370525\", \"selling_rate\": \"8.420899\"}, {\"unit_value\": 1, \"median_rate\": \"6.194629\", \"currency_code\": \"USD\", \"buying_rate\": \"6.176045\", \"selling_rate\": \"6.213213\"}, {\"unit_value\": 1, \"median_rate\": \"3.787414\", \"currency_code\": \"BAM\", \"buying_rate\": \"3.776052\", \"selling_rate\": \"3.798776\"}, {\"unit_value\": 1, \"median_rate\": \"7.407537\", \"currency_code\": \"EUR\", \"buying_rate\": \"7.385314\", \"selling_rate\": \"7.429760\"}, {\"unit_value\": 1, \"median_rate\": \"1.736169\", \"currency_code\": \"PLN\", \"buying_rate\": \"1.730960\", \"selling_rate\": \"1.741378\"}]";

        JSONArray jsonArray = null;
        jsonArray = new JSONArray(jsonStr);
        for (int i = 0; i < jsonArray.length(); i++) {
            JSONObject jsonobject = jsonArray.getJSONObject(i);
            String code = jsonobject.getString("currency_code");
            String selling = jsonobject.getString("selling_rate");
            String buying = jsonobject.getString("buying_rate");
            String median = jsonobject.getString("median_rate");
            String value = jsonobject.getString("unit_value");

            StackHelper stackHelper = new StackHelper();
            stackHelper.setCode(code);
            stackHelper.setSelling(selling);
            stackHelper.setBuying(buying);
            stackHelper.setMedian(median);
            stackHelper.setValue(value);
            stackHelperList.add(stackHelper);

        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
    ArrayAdapter<StackHelper> dataAdapter = new ArrayAdapter<StackHelper>(this,
            android.R.layout.simple_selectable_list_item,stackHelperList);
    dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinnerStack.setAdapter(dataAdapter);

}}