我正在开发一个应用程序，并且在一个屏幕上显示从数据库中提取的订单。这些订单中通常包含一些物品。
我可以毫无问题地提取并显示数据，但是我正在努力实现一种自动刷新活动的方式，以便显示新订单（例如，每15秒刷新一次）。
我玩过一个处理程序，每15秒运行一次displayOrders（）方法，但结果导致每15秒再次发布相同的订单。
这是我的代码：
public class ChefScreen extends AppCompatActivity {
ListView listView;
List<ChefOrderList> listOrders;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chef_screen);
listView = findViewById(R.id.list_chef_orders);
listOrders = new ArrayList<>();
displayOrders();
}
private void displayOrders(){
String url = "hidden";
StringRequest stringRequest = new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONObject obj = new JSONObject(response);
JSONArray array = obj.getJSONArray("orders");
for (int i = 0; i < array.length(); i++) {
final JSONObject orderObj = array.getJSONObject(i);
ChefOrderList c = new ChefOrderList(orderObj.getString("menu_item_name"), orderObj.getString("item_type"), orderObj.getString("order_date_time"),
orderObj.getInt("quantity_ordered"), orderObj.getInt("order_id"));
listOrders.add(c);
}
ChefOrderAdapter adapter = new ChefOrderAdapter(listOrders, getApplicationContext());
listView.setAdapter(adapter);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(ChefScreen.this, "Oops!" +error.toString(), Toast.LENGTH_LONG).show();
}
}){
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String, String> params = new HashMap<>();
params.put("menuid", "0");
return params;
}
};
MySingleton.getInstance(this).addToRequestQueue(stringRequest);
}
}
适配器：
private List<ChefOrderList> chefOrderList1;
private Context context;
private Button completeOrder;
public ChefOrderAdapter(List<ChefOrderList> M, Context C){
super(C, R.layout.listcheforders, M);
this.chefOrderList1 = M;
this.context = C;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
LayoutInflater layoutInflater = LayoutInflater.from(context);
View view = layoutInflater.inflate(R.layout.listcheforders,null,true);
TextView orderNumber = view.findViewById(R.id.tvOrderNumber);
TextView itemType = view.findViewById(R.id.tvItemType);
TextView itemName = view.findViewById(R.id.tvItemName);
TextView orderQuantity = view.findViewById(R.id.tvItemQty);
TextView orderTime = view.findViewById(R.id.tvDateTime);
completeOrder = view.findViewById(R.id.btnComplete);
ChefOrderList chefOrderList = chefOrderList1.get(position);
itemName.setText(chefOrderList.getName());
orderQuantity.setText("Qty: " +chefOrderList.getQty());
if(position>0){
ChefOrderList prevChefOrderList = chefOrderList1.get(position-1);
if(chefOrderList.getOrder() != (prevChefOrderList.getOrder())){
orderNumber.setText("Order: " +chefOrderList.getOrder());
orderTime.setText(chefOrderList.getDate());
completeOrder.setVisibility(View.VISIBLE);
completeOrder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
completeOrder(position);
}
});
}
if(!chefOrderList.getType().equals(prevChefOrderList.getType())){
itemType.setText(chefOrderList.getType());
}
} else {
itemType.setText(chefOrderList.getType());
orderNumber.setText("Order: " +chefOrderList.getOrder());
orderTime.setText(chefOrderList.getDate());
completeOrder.setVisibility(View.VISIBLE);
completeOrder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
completeOrder(position);
}
});
}
return view;
}
private void completeOrder(final int position){
String url = "http://mgourley03.web.eeecs.qub.ac.uk/RestaurantApp/clearOrder.php";
StringRequest stringRequest = new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
if(response.trim().equals("success")){
Toast.makeText(context, "Order completed!", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(context, "Clear order failed!", Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(context, "Error!" +error.toString(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String, String> params = new HashMap<>();
params.put("orderid", String.valueOf(chefOrderList1.get(position).getOrder()));
return params;
}
};
MySingleton.getInstance(context).addToRequestQueue(stringRequest);
}
有人能建议一种方法来使活动每15秒刷新一次，并且仅显示单个订单的列表（而不是每次刷新时都显示一些订单）
答案 0 :(得分：0)
有很多方法可以处理这种情况，但首先，我将使用游标适配器列出您的数据。