我正在开发一个Android应用程序,其中显示受冠状病毒影响的国家/地区列表,确诊病例总数和总死亡人数。我正在使用JSON
API来获取数据并使用RecyclerView
显示它。该应用程序运行良好,并且我得到了所有国家/地区的清单以及各自的案件数。我想添加一个搜索选项,以便用户可以过滤列表并找到特定的国家。我怎么做?我是编程新手,如果有人可以帮忙,那就太好了。这是代码片段
MainActivity.java
private RecyclerView mRecyclerView;
private Corona_Stats_Adapter mCorona_Stats_Adapter;
private TextView mErrorDisplay;
private ProgressBar mProgressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.corona_stats);
mRecyclerView = (RecyclerView)findViewById(R.id.Corona_stats_recycler);
mErrorDisplay = (TextView) findViewById(R.id.tv_error_message_display);
LinearLayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setHasFixedSize(true);
mCorona_Stats_Adapter = new Corona_Stats_Adapter();
mRecyclerView.setAdapter(mCorona_Stats_Adapter);
mProgressBar = (ProgressBar)findViewById(R.id.pb_loading_indicator) ;
loadCoronaData();
}
private void loadCoronaData(){
showCoronaDataView();
//String Country = String.valueOf(mSearchQuery.getText());
new Fetch_data().execute();
}
private void showCoronaDataView(){
mErrorDisplay.setVisibility(View.INVISIBLE);
mRecyclerView.setVisibility(View.VISIBLE);
}
private void showErrorMessage(){
mRecyclerView.setVisibility(View.INVISIBLE);
mErrorDisplay.setVisibility(View.VISIBLE);
}
public class Fetch_data extends AsyncTask<Void,Void,String[]> {
@Override
protected void onPreExecute() {
super.onPreExecute();
mProgressBar.setVisibility(View.VISIBLE);
}
@Override
protected String[] doInBackground(Void... voids) {
URL covidRequestURL = NetworkUtils.buildUrl();
try {
String JSONCovidResponse = NetworkUtils.getResponseFromHttpUrl(covidRequestURL);
String[] simpleJsonCovidData = CovidJSON_Utils.getSimpleStringFromJson(MainActivity.this, JSONCovidResponse);
return simpleJsonCovidData;
} catch (IOException | JSONException e) {
e.printStackTrace();
return null;
}
}
@Override
protected void onPostExecute(String[] coronaData) {
mProgressBar.setVisibility(View.INVISIBLE);
if(coronaData !=null){
showCoronaDataView();
mCorona_Stats_Adapter.setCoronaData(coronaData);
} else{
showErrorMessage();
}
}
}
}
[RecyclerView适配器类Corona_stats_Adapter.java
public class Corona_Stats_Adapter extends RecyclerView.Adapter<Corona_Stats_Adapter.Corona_Stats_AdapterViewHolder>
{
private Context context;
// private List<Country> countryList;
// private List<Country> countryListFiltered;
private String[] mCoronaData;
public Corona_Stats_Adapter(){
}
@NonNull
@Override
public Corona_Stats_AdapterViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
Context context = viewGroup.getContext();
int LayoutIdForListItem =R.layout.corona_stats_list_item;
LayoutInflater inflater =LayoutInflater.from(context);
boolean ShouldAttachToParentImmediately = false;
View view = inflater.inflate(LayoutIdForListItem,viewGroup,ShouldAttachToParentImmediately);
return new Corona_Stats_AdapterViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull Corona_Stats_AdapterViewHolder corona_stats_adapterViewHolder, int position) {
String coronaStats = mCoronaData[position];
corona_stats_adapterViewHolder.mCoronaTextView.setText(coronaStats);
}
@Override
public int getItemCount() {
if(null == mCoronaData) return 0;
return mCoronaData.length;
// return countryListFiltered.size();
}
public class Corona_Stats_AdapterViewHolder extends RecyclerView.ViewHolder {
public final TextView mCoronaTextView;
public Corona_Stats_AdapterViewHolder(@NonNull View view) {
super(view);
mCoronaTextView = (TextView) view.findViewById(R.id.tv_corona_data);
}
}
public void setCoronaData(String[] coronaData){
mCoronaData = coronaData;
notifyDataSetChanged();
}
}
在CovidJSON_Utils.java中解析JSON数据
public final class CovidJSON_Utils {
public static String[] getSimpleStringFromJson(Context context, String codivJsonString)
throws JSONException {
final String COV_COUNTRY = "Countries";
final String COV_CONFIRMED = "confirmed";
final String COV_DEATHS = "deaths";
final String COV_MESSAGE_CODE = "code";
String[] parsedCovidData = null;
JSONObject covidJsonObject = new JSONObject(codivJsonString);
if (covidJsonObject.has(COV_MESSAGE_CODE)) {
int errorCode = covidJsonObject.getInt(COV_MESSAGE_CODE);
switch (errorCode) {
case HttpURLConnection.HTTP_OK:
break;
case HttpURLConnection.HTTP_NOT_FOUND:
return null;
default:
return null;
}
}
JSONArray countryCovidArray = covidJsonObject.getJSONArray(COV_COUNTRY);
parsedCovidData = new String[countryCovidArray.length()];
for (int i = 0; i < countryCovidArray.length(); i++) {
JSONObject countryJSONObject = countryCovidArray.getJSONObject(i);
String Country = countryJSONObject.getString("Country");
String Confirmed = String.valueOf(countryJSONObject.getInt("TotalConfirmed"));
String Deaths = String.valueOf(countryJSONObject.getInt("TotalDeaths"));
parsedCovidData[i] = Country + "- Cases " + Confirmed + "- Deaths " + Deaths;
}
return parsedCovidData;
}
}
问题在于MainActivity.Oncreate方法中的以下初始化
mCorona_Stats_Adapter = new Corona_Stats_Adapter(this,countries);
使用更新的国家/地区数据在onPostExecute方法中初始化适配器。
希望这会对您有所帮助。
从服务器获取数据后,您必须设置arraylist以更新适配器中的国家/地区数据。
Public void setCoronaData (Arraylist coronaData) {
countryList = coronaData;
notifyDataSetChanged ();
}