我正在使用Android应用程序，该应用程序使用API中的信息并将其显示在列表视图中。它有效，但我无法弄清楚如何正确实现Swipe to Refresh。现在它刷新时不会更新列表TextView字段中的数据，但会在下面添加更多数据。我对此非常陌生，并希望能帮助您解决这个问题。
这是我到目前为止的代码。
MainActivity.java
public class MainActivity extends AppCompatActivity {
private String TAG = MainActivity.class.getSimpleName();
private ProgressDialog pDialog;
private ListView lv;
ArrayList<HashMap<String, String>> coinList;
ArrayList<HashMap<String, String>> priceList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Swipe Refresh tests
final SwipeRefreshLayout swipeView = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh_layout);
swipeView.setEnabled(false);
ListView lView = (ListView) findViewById(R.id.list);
ArrayAdapter<String> adp = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, R.id.list);
lView.setAdapter(adp);
swipeView.setOnRefreshListener(
new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
swipeView.setRefreshing(true);
( new Handler()).postDelayed(new Runnable() {
@Override
public void run() {
swipeView.setRefreshing(false);
}
}, 1000);
new GetStats().execute();
}
});
lView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int i) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (firstVisibleItem == 0)
swipeView.setEnabled(true);
else
swipeView.setEnabled(false);
}
});
///// END OF SWIPE REFRESH TEST CODE ////
coinList = new ArrayList<>();
priceList = new ArrayList<>();
lv = (ListView) findViewById(R.id.list); // Needs to be here seemingly!!
new GetStats().execute();
}
// Async task class to get JSON over HTTP call
private class GetStats extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute () {
super.onPreExecute();
// Progress Dialog
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Please Wait...");
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
HttpHandler sh = new HttpHandler();
// URL request and response
String url = "URL";
String url2 = "URL";
String jsonStr = sh.makeServiceCall(url);
String jsonStr2 = sh.makeServiceCall(url2);
Log.e(TAG, "Response from url: " + jsonStr);
Log.e(TAG, "Response from url2: " + jsonStr2);
if (jsonStr != null) {
try { /// BEGINNING of Parsing Try
JSONObject jsonObj = new JSONObject(jsonStr);
// Get JSON Object "getuserallbalances"
JSONObject userBalances = jsonObj.getJSONObject("getuserallbalances");
// Get JSON Array "data"
JSONArray data = userBalances.getJSONArray("data");
// Loop through all data
for (int i = 0; i < data.length(); i++) {
JSONObject d = data.getJSONObject(i);
String coin = d.getString("coin");
String confirmed = d.getString("confirmed");
String unconfirmed = d.getString("unconfirmed");
String aeConfirmed = d.getString("ae_confirmed");
String aeUnconfirmed = d.getString("ae_unconfirmed");
String exchange = d.getString("exchange");
//Convert to BigDecimal
BigDecimal dConfirmed = new BigDecimal(confirmed);
BigDecimal dUnconfirmed = new BigDecimal(unconfirmed);
BigDecimal dAeConfirmed = new BigDecimal(aeConfirmed);
BigDecimal dAeUnconfirmed = new BigDecimal(aeUnconfirmed);
BigDecimal dExchange = new BigDecimal(exchange);
// Temp HashMap for single coin
HashMap<String, String> coins = new HashMap<>();
// Add each child node to HashMap key => value
coins.put("coin", coin.toUpperCase());
coins.put("confirmed", "Confirmed: " + dConfirmed);
coins.put("exchange", "Exchange: " + dExchange);
coins.put("unconfirmed", "Unconfirmed: " + dUnconfirmed);
coins.put("ae_confirmed", "AE Confirmed: " + dAeConfirmed);
coins.put("ae_unconfirmed", "AE Unconfirmed: " + dAeUnconfirmed);
// Add to list
coinList.add(coins);
}
} catch (final JSONException e) { /// END of Parsing TRY
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!",
Toast.LENGTH_LONG).show();
}
});
}
// Second API call (CoinMarketCap)
if (jsonStr2 != null) {
try { /// BEGINNING of Parsing Try
// Get JSON Array
JSONArray jsonArr = new JSONArray(jsonStr2);
// Loop through all data
for (int i = 0; i < jsonArr.length(); i++) {
JSONObject p = jsonArr.getJSONObject(i);
String id = p.getString("id");
String price_usd = p.getString("price_usd");
// Temp HashMap for single coin
HashMap<String, String> prices = new HashMap<>();
// Add each child node to HashMap key => value
prices.put("id", id.toUpperCase());
prices.put("perice_usd", price_usd);
// Add to list
priceList.add(prices);
}
} catch (final JSONException e) { /// END of Parsing TRY
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!",
Toast.LENGTH_LONG).show();
}
});
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
// Update parsed JSON into ListView
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, coinList,
R.layout.list_item, new String[]{"coin", "confirmed",
"exchange", "unconfirmed", "ae_confirmed", "ae_unconfirmed"}, new int[]{R.id.coin,
R.id.confirmed, R.id.exchange, R.id.unconfirmed, R.id.ae_confirmed, R.id.ae_unconfirmed});
lv.setAdapter(adapter);
}
}
}
activity_main.xml中
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.v4.widget.SwipeRefreshLayout
android:id="@+id/swipe_refresh_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ListView
android:id="@+id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</android.support.v4.widget.SwipeRefreshLayout>
</RelativeLayout>
希望这有一定意义，并且真的会给予任何帮助！如果我可以做到这一点，我可能会有更多的问题，但现在一次只有一件事。 ：P
谢谢！ ：）
答案 0 :(得分：0)
在调用异步任务时，在刷卡刷新侦听器中，每次都在创建新的适配器。只需在数据上调用notifyDataChanged即可。
在您的后台任务中，首先检查您的priceList中是否已存在数据，然后不要在列表中添加该项目。
或者您可以先清除列表，然后将json中的所有结果添加到价目表中。
以下是在刷卡刷新时清除列表的代码：
public class MainActivity extends AppCompatActivity {
private String TAG = MainActivity.class.getSimpleName();
private ProgressDialog pDialog;
private ListView lv;
ListAdapter adapter;
ArrayList<HashMap<String, String>> coinList;
ArrayList<HashMap<String, String>> priceList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Swipe Refresh tests
final SwipeRefreshLayout swipeView = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh_layout);
swipeView.setEnabled(false);
ListView lView = (ListView) findViewById(R.id.list);
adapter = new SimpleAdapter(
MainActivity.this, coinList,
R.layout.list_item, new String[]{"coin", "confirmed",
"exchange", "unconfirmed", "ae_confirmed", "ae_unconfirmed"}, new int[]{R.id.coin,
R.id.confirmed, R.id.exchange, R.id.unconfirmed, R.id.ae_confirmed, R.id.ae_unconfirmed});
lView.setAdapter(adapter);
swipeView.setOnRefreshListener(
new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
swipeView.setRefreshing(true);
( new Handler()).postDelayed(new Runnable() {
@Override
public void run() {
swipeView.setRefreshing(false);
}
}, 1000);
new GetStats().execute();
}
});
lView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int i) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (firstVisibleItem == 0)
swipeView.setEnabled(true);
else
swipeView.setEnabled(false);
}
});
///// END OF SWIPE REFRESH TEST CODE ////
coinList = new ArrayList<>();
priceList = new ArrayList<>();
lv = (ListView) findViewById(R.id.list); // Needs to be here seemingly!!
new GetStats().execute();
}
// Async task class to get JSON over HTTP call
private class GetStats extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute () {
super.onPreExecute();
// Progress Dialog
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Please Wait...");
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
HttpHandler sh = new HttpHandler();
// URL request and response
String url = "https://miningpoolhub.com/index.php?page=api&action=getuserallbalances&api_key=MyApiKey";
String url2 = "https://api.coinmarketcap.com/v1/ticker/";
String jsonStr = sh.makeServiceCall(url);
String jsonStr2 = sh.makeServiceCall(url2);
Log.e(TAG, "Response from url: " + jsonStr);
Log.e(TAG, "Response from url2: " + jsonStr2);
if (jsonStr != null) {
try {
coinList.clear(); /// BEGINNING of Parsing Try
JSONObject jsonObj = new JSONObject(jsonStr);
// Get JSON Object "getuserallbalances"
JSONObject userBalances = jsonObj.getJSONObject("getuserallbalances");
// Get JSON Array "data"
JSONArray data = userBalances.getJSONArray("data");
// Loop through all data
for (int i = 0; i < data.length(); i++) {
JSONObject d = data.getJSONObject(i);
String coin = d.getString("coin");
String confirmed = d.getString("confirmed");
String unconfirmed = d.getString("unconfirmed");
String aeConfirmed = d.getString("ae_confirmed");
String aeUnconfirmed = d.getString("ae_unconfirmed");
String exchange = d.getString("exchange");
//Convert to BigDecimal
BigDecimal dConfirmed = new BigDecimal(confirmed);
BigDecimal dUnconfirmed = new BigDecimal(unconfirmed);
BigDecimal dAeConfirmed = new BigDecimal(aeConfirmed);
BigDecimal dAeUnconfirmed = new BigDecimal(aeUnconfirmed);
BigDecimal dExchange = new BigDecimal(exchange);
// Temp HashMap for single coin
HashMap<String, String> coins = new HashMap<>();
// Add each child node to HashMap key => value
coins.put("coin", coin.toUpperCase());
coins.put("confirmed", "Confirmed: " + dConfirmed);
coins.put("exchange", "Exchange: " + dExchange);
coins.put("unconfirmed", "Unconfirmed: " + dUnconfirmed);
coins.put("ae_confirmed", "AE Confirmed: " + dAeConfirmed);
coins.put("ae_unconfirmed", "AE Unconfirmed: " + dAeUnconfirmed);
Coin coinObj= new Coin(/*pass the arguments*/);
// Add to list
coinList.add(coins);
}
} catch (final JSONException e) { /// END of Parsing TRY
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!",
Toast.LENGTH_LONG).show();
}
});
}
// Second API call (CoinMarketCap)
if (jsonStr2 != null) {
try {
priceList.clear(); /// BEGINNING of Parsing Try
// Get JSON Array
JSONArray jsonArr = new JSONArray(jsonStr2);
// Loop through all data
for (int i = 0; i < jsonArr.length(); i++) {
JSONObject p = jsonArr.getJSONObject(i);
String id = p.getString("id");
String price_usd = p.getString("price_usd");
// Temp HashMap for single coin
HashMap<String, String> prices = new HashMap<>();
// Add each child node to HashMap key => value
prices.put("id", id.toUpperCase());
prices.put("perice_usd", price_usd);
// Add to list
priceList.add(prices);
}
} catch (final JSONException e) { /// END of Parsing TRY
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!",
Toast.LENGTH_LONG).show();
}
});
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
// Update parsed JSON into ListView
// ListAdapter adapter = new SimpleAdapter(
// MainActivity.this, coinList,
// R.layout.list_item, new String[]{"coin", "confirmed",
// "exchange", "unconfirmed", "ae_confirmed", "ae_unconfirmed"}, new int[]{R.id.coin,
// R.id.confirmed, R.id.exchange, R.id.unconfirmed, R.id.ae_confirmed, R.id.ae_unconfirmed});
adapter.notifyDataSetChanged();
}
}
}