我有一个包含 ListView 的 fragment (homePageFrag) 。当我尝试使用 URL 中的 JSON 数据填充它时，它不起作用。 ListView 是空的。但是，当我从 ArrayList 提供静态数据时，它就会出现。
我想要实现的是从 URL 获取的 JSON 数据填充 Fragment 内的 ListView 。 HP_JSON_Download 按预期工作，我在 Activity 中使用 ListView，但在 fragment 中，它没有显示任何数据。
homePageFrag.java
public class homePageFrag extends Fragment implements HP_JSON_Download.download_complete {
boolean open = false; Context applicationContext;
public ListView list;
public ArrayList<HPEntity> countries = new ArrayList<HPEntity>();
public HP_ListAdapter adapter;
private final String bus_id[] = {"a1"};
private final String bus_destination[] = {"A1"};
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//returning our layout file
View view = inflater.inflate(R.layout.homepage_lv, container, false);
list = (ListView) view.findViewById(R.id.homepageListView);
adapter = new HP_ListAdapter(this);
list.setAdapter(adapter);
HP_JSON_Download download_data = new HP_JSON_Download((HP_JSON_Download.download_complete) this);
download_data.download_data_from_link("http://www.xyz.in/MyApi/Api.php");
return view;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
//you can set the title for your toolbar here for different fragments different titles
getActivity().setTitle("E-RTC");
}
public void get_data(String data) {
Toast.makeText(getApplicationContext(),"xx",Toast.LENGTH_SHORT).show();
try {
JSONArray data_array=new JSONArray(data);
for (int i = 0 ; i < data_array.length() ; i++) {
JSONObject obj=new JSONObject(data_array.get(i).toString());
HPEntity add=new HPEntity();
add.name = obj.getString("id");
add.code = obj.getString("name");
countries.add(add);
}
adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
public Context getApplicationContext() {
return applicationContext;
}
}
HP_ListAdapter.java
public class HP_ListAdapter extends BaseAdapter {
homePageFrag main;
Context mContext;
public HP_ListAdapter(Context mContext) {
this.mContext = mContext;
}
HP_ListAdapter(homePageFrag main) {
this.main = main;
}
@Override
public int getCount() {
return main.countries.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
static class ViewHolderItem {
TextView name;
TextView code;
}
@Override
public View getView(int position, View convertView, ViewGroup parent){
ViewHolderItem holder = new ViewHolderItem();
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.homepage_item, null);
holder.name = (TextView) convertView.findViewById(R.id.busID);
holder.code = (TextView) convertView.findViewById(R.id.busNAME);
convertView.setTag(holder);
} else {
holder = (ViewHolderItem) convertView.getTag();
}
holder.name.setText(this.main.countries.get(position).name);
holder.code.setText(this.main.countries.get(position).code);
return convertView;
}
}
HPEntity.java
public class HPEntity {
String name;
String code;
}
HP_JSON_Download.java
public class HP_JSON_Download implements Runnable {
public download_complete caller;
public interface download_complete {
void get_data(String data);
}
HP_JSON_Download(download_complete caller) {
this.caller = caller;
}
private String link;
public void download_data_from_link(String link) {
this.link = link;
Thread t = new Thread(this);
t.start();
}
public void run() {
threadMsg(download(this.link));
}
private void threadMsg(String msg) {
if (!msg.equals(null) && !msg.equals("")) {
Message msgObj = handler.obtainMessage();
Bundle b = new Bundle();
b.putString("message", msg);
msgObj.setData(b);
handler.sendMessage(msgObj);
}
}
private final Handler handler = new Handler() {
public void handleMessage(Message msg) {
String Response = msg.getData().getString("message");
caller.get_data(Response);
}
};
public static String download(String url) {
URL website;
StringBuilder response = null;
try {
website = new URL(url);
HttpURLConnection connection = (HttpURLConnection) website.openConnection();
connection.setRequestProperty("charset", "utf-8");
BufferedReader in = new BufferedReader(
new InputStreamReader(
connection.getInputStream()));
response = new StringBuilder();
String inputLine;
while ((inputLine = in.readLine()) != null)
response.append(inputLine);
in.close();
} catch (Exception e) {
return "";
}
return response.toString();
}
}
最佳答案
我建议你像这样修改你的适配器。
public class HP_ListAdapter extends BaseAdapter {
public ArrayList<HPEntity> countries = new ArrayList<HPEntity>();
Context mContext;
public HP_ListAdapter(Context mContext, ArrayList<HPEntity> countries) {
this.mContext = mContext;
this.countries = countries;
}
@Override
public int getCount() {
return countries.size();
}
@Override
public Object getItem(int position) {
return countries.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
static class ViewHolderItem {
TextView name;
TextView code;
}
@Override
public View getView(int position, View convertView, ViewGroup parent){
ViewHolderItem holder = new ViewHolderItem();
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.homepage_item, null);
holder.name = (TextView) convertView.findViewById(R.id.busID);
holder.code = (TextView) convertView.findViewById(R.id.busNAME);
convertView.setTag(holder);
} else {
holder = (ViewHolderItem) convertView.getTag();
}
holder.name.setText(this.countries.get(position).name);
holder.code.setText(this.countries.get(position).code);
return convertView;
}
}
现在从 Fragment 中的 onCreateView 函数初始化适配器，如下所示。您使用 this 将错误的上下文传递给适配器初始化。您应该使用 getActivity() 来代替。
adapter = new HP_ListAdapter(getActivity(), countries);
关于java - 如何从 PHP JSON 数据填充 ListView fragment ？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48918557/