我正在構建貨幣轉換器(從API獲取,動態填充列表以創建可用貨幣,選擇兩種貨幣並返回匯率,這似乎是通過練習的權利)。Java onItemSelectedListener和Spinner不返回任何東西
我一直在試圖讓Spinner工作,但儘管我盡了最大的努力,但我無法讓偵聽器在我從列表中選擇一個值時做任何事情。當我點擊某個值時,日誌確實會返回一些內容(請參閱下文),但我不知道它的含義,以及爲什麼它不會返回我想要的System.out.println("yay")
呼叫。
d/OpenGLRenderer:帶手柄0x95c21270" 上0xa7040980 (DropDownListView)endAllActiveAnimators
陣列適配器正常填充從ArrayList<string>
我從API獲得和JSON
對象旋轉器列表。偵聽器代碼基於我對SO迄今爲止發現的例子看起來是正確的。
我不知道它是在我的代碼的順序問題?還是其他什麼東西。
package com.timlee.currencymate;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
public class MainActivity extends AppCompatActivity {
// public variables
String uRLResultString = "";
ArrayList <String> currencies = new ArrayList<String>();
Spinner currencyOneSpinner;
Spinner currencyTwoSpinner;
// get data from api
public class DownloadTask extends AsyncTask <String, Void, String> {
@Override
protected String doInBackground(String... urls) {
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL(urls[0]);
urlConnection = (HttpURLConnection)url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while (data != -1) {
char current = (char) data;
uRLResultString += current;
data = reader.read();
}
return uRLResultString;
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
//System.out.println(result);
//if get current list then run this, else run something else
getCurrencyList();
}
}
//gets the list of currecies
public void getCurrencyList() {
try {
JSONObject jsonObject = new JSONObject(uRLResultString);
String base = jsonObject.getString("base");
String rates = jsonObject.getString("rates");
currencies.add(base);
System.out.println(rates);
JSONObject jSonObj = new JSONObject(rates);
Iterator<String> keys = jSonObj.keys();
while (keys.hasNext()) {
String key = (String)keys.next();
currencies.add(key);
if (jSonObj.get(key) instanceof JSONObject) {
}
}
Collections.sort(currencies, String.CASE_INSENSITIVE_ORDER);
} catch (JSONException e) {
e.printStackTrace();
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
currencies = new ArrayList<String>();
String currencyURL = "http://api.fixer.io/latest?base=AUD";
DownloadTask task = new DownloadTask();
task.execute(currencyURL);
// apply Array Adapter and listener
currencyOneSpinner = (Spinner)findViewById(R.id.spinnerCurrencyOne);
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>(this,android.R.layout.simple_spinner_item,currencies);
currencyOneSpinner.setAdapter(arrayAdapter);
currencyOneSpinner.setOnItemSelectedListener (new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
System.out.println("yay");
return;
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
System.out.println("neyh");
return;
}
});
}
}
謝謝你Dustblue。解決方案是我需要通知在AsyncTask中更改的數據集。如果我只應用了arrayadapter視圖更改,問題依然存在。我不明白爲什麼通知電話會影響聽衆,但我很感激您的額外建議是解決方案。 –
不客氣。當列表更新時,更新微調器。根據文檔,它「通知附屬的觀察者,基礎數據已經改變,任何反映數據集的視圖都應該刷新自己。」這就是爲什麼它會影響你的聽衆。別忘了接受我的回答!謝謝。 – dustblue