我正在制作一个使用OWM 5天3小时预报API显示天气的android应用程序，该ui包含用于输入城市名称的EditText，用于启动通话过程的按钮，将显示5个条目（五天）和每天条目的列表视图包括另一个列表视图，该列表视图每天显示每3个小时的脱脂和温度，
我可以看到几天的列表视图，但是看不到每小时数据的嵌套列表视图。我的类包括：MainActivity，用于显示每小时3小时天气的WeatherAdapter，用于显示日期条目的DayAdapter以及JsonToWeather数据类，该数据类从Json响应中提取数据，并仅针对特定一天创建数据数组列表。我试图记录错误，并通过注释突出显示了错误位置。
主要活动 ：
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private String responseJSON = null;
ListView listView;
ArrayList<WeatherData> weatherDataArrayList;
WeatherAdapter weatherAdapter = null;
EditText cityName;
String city = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.dayList);
cityName = (EditText) findViewById(R.id.cityName);
Button load = (Button) findViewById(R.id.loadButton);
load.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
city = cityName.getText().toString();
Log.d(TAG, "onClick: city is : " + city);
if(city == null){
Toast toast = null;
toast.makeText(MainActivity.this,"Please Enter a city before continuing",Toast.LENGTH_LONG);
toast.show();
} else {
String url = "http://api.openweathermap.org/data/2.5/forecast?q=" + (city.toLowerCase()) + "&units=metric&appid=8b10912e19fde267f36f6cb785ee7efd";
Log.d(TAG, "onCreate: staring download task");
DownloadJSON downloadJSON = new DownloadJSON();
downloadJSON.execute(url);
Log.d(TAG, "onCreate: after downloadtask");
}
}
});
if(weatherDataArrayList == null){
Log.d(TAG, "onCreate: ArrayList is Still null");
}
}
private class DownloadJSON extends AsyncTask<String, Void, String>{
private static final String TAG = "DownloadJSON";
private String downloadJSON(String url){
StringBuilder jsonResult = new StringBuilder();
try{
URL apiURL = new URL(url);
HttpURLConnection connection = (HttpURLConnection) apiURL.openConnection();
int responseCode = connection.getResponseCode();
Log.d(TAG, "downloadJSON: Response code "+ responseCode);
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
int charReader;
char[] inputBuffer = new char[500];
while(true){
charReader = reader.read(inputBuffer);
if(charReader < 0){
break;
}
if(charReader > 0){
jsonResult.append(String.copyValueOf(inputBuffer, 0, charReader));
}
}
reader.close();
return jsonResult.toString();
}catch (MalformedURLException e){
Log.e(TAG, "downloadJSON: URL is Invalid");
}catch (IOException e){
Log.e(TAG, "downloadJSON: IO Error");
}
return null;
}
@Override
protected String doInBackground(String... strings) {
Log.d(TAG, "doInBackground: url is : " + strings[0]);
String jsonResponse = downloadJSON(strings[0]);
if(jsonResponse == null){
Log.e(TAG, "doInBackground: Error downloading");
}
return jsonResponse;
}
@Override
protected void onPostExecute(String jsonResponse) {
super.onPostExecute(jsonResponse);
Log.d(TAG, "onPostExecute: json received is : " + jsonResponse);
if(jsonResponse != null){
JsonToWeatherData jtwd = new JsonToWeatherData();
weatherDataArrayList = jtwd.extractor(jsonResponse);
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
String date1 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date2 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date3 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date4 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date5 = simpleDateFormat.format(calendar.getTime());
ArrayList<String> days = new ArrayList<>();
days.add(date1);
days.add(date2);
days.add(date3);
days.add(date4);
days.add(date5);
DayAdapter day = new DayAdapter(MainActivity.this,R.layout.layout_day_card,days,weatherDataArrayList);
listView.setAdapter(day);
} else {
Log.d(TAG, "onPostExecute: no json recieved, city is Wrong");
Toast toast = Toast.makeText(MainActivity.this,"Please provide a valid city!",Toast.LENGTH_LONG);
toast.show();
}
}
}
}
WeatherAdapter :
public class WeatherAdapter extends ArrayAdapter<WeatherData> {
private static final String TAG = "WeatherAdapter";
private final int layoutResourceID;
private LayoutInflater layoutInflater;
private ArrayList<WeatherData> block;
public WeatherAdapter(@NonNull Context context, int resource, ArrayList<WeatherData> block) {
super(context, resource, block);
this.layoutResourceID = resource;
this.block = block;
this.layoutInflater = LayoutInflater.from(context);
Log.d(TAG, "WeatherAdapter: called constructor");
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
if(convertView == null){
convertView = layoutInflater.inflate(layoutResourceID,parent,false);
}
Log.d(TAG, "getView: entered");
WeatherData weatherData = block.get(position);
TextView temp = (TextView) convertView.findViewById(R.id.temperature);
temp.setText(weatherData.getTemp());
TextView shortDesc = (TextView) convertView.findViewById(R.id.descrip);
shortDesc.setText(weatherData.getShortDesc());
return convertView;
}
}
DayAdapter :
public class DayAdapter extends ArrayAdapter<String> {
private static final String TAG = "DayAdapter";
private ArrayList<String> dayBlock;
private LayoutInflater layoutInflater;
private int layoutresourceID;
private ArrayList<WeatherData> dayWeather, fullBlock;
private Context context;
JsonToWeatherData json = new JsonToWeatherData();
public DayAdapter(@NonNull Context context, int resource, @NonNull ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock) {
super(context, resource, dayBlock);
this.context = context;
this.dayBlock = dayBlock;
this.fullBlock = weatherBlock;
layoutInflater = LayoutInflater.from(context);
this.layoutresourceID = resource;
if(fullBlock == null){
Log.e(TAG, "DayAdapter: full block is null");
}
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
if (convertView == null){
convertView = layoutInflater.inflate(layoutresourceID,parent,false);
}
TextView date = (TextView) convertView.findViewById(R.id.date);
TextView minTempFoDay = (TextView) convertView.findViewById(R.id.minTempOfDay);
TextView maxTempFoDay = (TextView) convertView.findViewById(R.id.maxTempOfDay);
ListView weatherHolderListView = (ListView) convertView.findViewById(R.id.wHoldLV);
String dateString = dayBlock.get(position);
dayWeather = json.extractByDate(fullBlock,dateString);
if(fullBlock == null){
Log.d(TAG, "getView: fullblock is null");
}
if(dayWeather == null){
Log.d(TAG, "getView: dayweather array is null");
} else {
Log.d(TAG, "getView: dayweather is not null");
}
String test = dayWeather.get(position).getTemp(); // error occured here
Log.d(TAG, "getView: test string : " + test);
date.setText(dateString);
DecimalFormat df = new DecimalFormat(".##");
float mint = 500, maxt = 0;
String mint1 = "", maxt1 = "";
for(WeatherData data : dayWeather){
if(mint > Float.parseFloat(data.getMinTemp())){
mint = Float.parseFloat(data.getMinTemp());
mint1 = df.format(mint);
Log.d(TAG, "getView: mint : " + mint);
}
if (maxt > Float.parseFloat(data.getMaxTemp())){
maxt = Float.parseFloat(data.getMaxTemp());
maxt1 = df.format(maxt);
}
}
minTempFoDay.setText(mint1);
maxTempFoDay.setText(maxt1);
WeatherAdapter weatherAdapter = new WeatherAdapter(context,R.layout.weather_holder,dayWeather);
weatherHolderListView.setAdapter(weatherAdapter);
return convertView;
}
}
JsonToWeatherData:
public class JsonToWeatherData {
private static final String TAG = "JsonToWeatherData";
public ArrayList<WeatherData> extractor(String jsonData){
Log.d(TAG, "extractor: in the method");
if(jsonData == null){
return null; // if there is no json data is received
} else {
ArrayList<WeatherData> weatherDataArrayList = new ArrayList<WeatherData>();
Log.d(TAG, "extractor: in the else field");
try{
Log.d(TAG, "extractor: in try block");
JSONObject root = new JSONObject(jsonData);
int count = root.getInt("cnt");
JSONArray wList = root.getJSONArray("list");
for (int i = 0; i < count; ++i){
WeatherData weather = new WeatherData();
JSONObject wBlock = wList.getJSONObject(i);
weather.setDate(wBlock.getString("dt_txt"));
JSONObject mainObj = wBlock.getJSONObject("main");
weather.setTemp(String.valueOf(mainObj.getDouble("temp")));
weather.setMinTemp(String.valueOf(mainObj.getDouble("temp_min")));
weather.setMaxTemp(String.valueOf(mainObj.getDouble("temp_max")));
weather.setHumidity(String.valueOf(mainObj.getInt("humidity")));
JSONArray warray = wBlock.getJSONArray("weather");
JSONObject weatherObj = warray.getJSONObject(0);
weather.setDescription(weatherObj.getString("description"));
weather.setShortDesc(weatherObj.getString("main"));
weather.setIconID(weatherObj.getString("icon"));
weatherDataArrayList.add(weather);
Log.d(TAG, "extractor: temp field is :" + weather.getTemp());
}
}catch (JSONException e){
e.printStackTrace();
}
return weatherDataArrayList;
}
}
public ArrayList<WeatherData> extractByDate(ArrayList<WeatherData> fullList,String date){
ArrayList<WeatherData> dayweatherList = new ArrayList<WeatherData>();
for( WeatherData weather : fullList ){
if( ( weather.getDate().substring(0,9) ).equals(date) ){
dayweatherList.add(weather);
}
}
return dayweatherList;
}
}
我该怎么办？
错误信息 ： （
08-19 23：11：39.914 12148-12148 / com.jugalmistry.apps.fivedaysofweather D / DayAdapter：getView：dayweather不为空
08-19 23：11：39.916 12148-12148 / com.jugalmistry.apps.fivedaysofweather D / AndroidRuntime：关闭VM
08-19 23：11：39.918 12148-12148 / com.jugalmistry.apps.fivedaysofweather E / AndroidRuntime：FATAL EXCEPTION：main
流程：com.jugalmistry.apps.fivedaysofweather，PID：12148
java.lang.IndexOutOfBoundsException：索引：0，大小：0
在java.util.ArrayList.get（ArrayList.java:411）
在com.jugalmistry.apps.fivedaysofweather.DayAdapter.getView（DayAdapter.java:58）
最佳答案
我试图用下面的完整代码来帮助您。
我还建议您实施ViewHolder模式ViewHolder pattern example以提高性能。
public class MainActivity extends AppCompatActivity
{
private static final String TAG = "MainActivity";
EditText cityName;
String city = null;
ListView dayListView;
ArrayList<WeatherData> weatherDataArrayList;
DayAdapter dayAdapter;
//private String responseJSON = null;
//WeatherAdapter weatherAdapter = null; // Creating this adapter within the DayAdapter
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cityName = (EditText) findViewById(R.id.cityName);
Button load = (Button) findViewById(R.id.loadButton);
dayListView = (ListView) findViewById(R.id.dayList);
load.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
city = cityName.getText().toString();
Log.d(TAG, "onClick: city is : " + city);
if (city == null)
{
Toast toast = null;
toast.makeText(MainActivity.this,"Please Enter a city before continuing",Toast.LENGTH_LONG);
toast.show();
}
else
{
String url = "http://api.openweathermap.org/data/2.5/forecast?q=" + (city.toLowerCase()) + "&units=metric&appid=8b10912e19fde267f36f6cb785ee7efd";
Log.d(TAG, "onCreate: staring download task");
DownloadJSON downloadJSON = new DownloadJSON();
downloadJSON.execute(url);
Log.d(TAG, "onCreate: after downloadtask");
}
}
});
}
public void SetDayListData(ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock)
{
if (dayAdapter == null)
{
dayAdapter = new DayAdapter(MainActivity.this,R.layout.layout_day_card, days, weatherDataArrayList);
dayListView.setAdapter(dayAdapter);
}
else
{
//created a new method "UpdateData" just to update the data in the adapter
dayAdapter.UpdateData(days, weatherDataArrayList);
dayAdapter.notifyDataSetChanged();
}
}
private class DownloadJSON extends AsyncTask<String, Void, String>
{
private static final String TAG = "DownloadJSON";
private String downloadJSON(String url)
{
StringBuilder jsonResult = new StringBuilder();
try
{
URL apiURL = new URL(url);
HttpURLConnection connection = (HttpURLConnection) apiURL.openConnection();
int responseCode = connection.getResponseCode();
Log.d(TAG, "downloadJSON: Response code "+ responseCode);
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
int charReader;
char[] inputBuffer = new char[500];
while (true)
{
charReader = reader.read(inputBuffer);
if (charReader < 0)
{
break;
}
if (charReader > 0)
{
jsonResult.append(String.copyValueOf(inputBuffer, 0, charReader));
}
}
reader.close();
return jsonResult.toString();
}
catch (MalformedURLException e)
{
Log.e(TAG, "downloadJSON: URL is Invalid");
}
catch (IOException e)
{
Log.e(TAG, "downloadJSON: IO Error");
}
return null;
}
@Override
protected String doInBackground(String... strings)
{
Log.d(TAG, "doInBackground: url is : " + strings[0]);
String jsonResponse = downloadJSON(strings[0]);
if (jsonResponse == null)
{
Log.e(TAG, "doInBackground: Error downloading");
}
return jsonResponse;
}
@Override
protected void onPostExecute(String jsonResponse)
{
super.onPostExecute(jsonResponse);
Log.d(TAG, "onPostExecute: json received is : " + jsonResponse);
if (jsonResponse != null)
{
JsonToWeatherData jtwd = new JsonToWeatherData();
weatherDataArrayList = jtwd.extractor(jsonResponse);
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
String date1 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date2 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date3 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date4 = simpleDateFormat.format(calendar.getTime());
calendar.add(Calendar.DATE,1);
String date5 = simpleDateFormat.format(calendar.getTime());
ArrayList<String> days = new ArrayList<>();
days.add(date1);
days.add(date2);
days.add(date3);
days.add(date4);
days.add(date5);
SetDayListData(days, weatherDataArrayList);
}
else
{
Log.d(TAG, "onPostExecute: no json recieved, city is Wrong");
Toast toast = Toast.makeText(MainActivity.this,"Please provide a valid city!",Toast.LENGTH_LONG);
toast.show();
}
}
}
}
public class DayAdapter extends ArrayAdapter<String>
{
private static final String TAG = "DayAdapter";
private Context context;
private LayoutInflater layoutInflater;
private int layoutresourceID;
private ArrayList<String> dayBlock;
private ArrayList<WeatherData> dayWeather, weatherBlock;
JsonToWeatherData json = new JsonToWeatherData();
public DayAdapter(@NonNull Context context, int resource, @NonNull ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock)
{
super(context, resource, dayBlock);
this.context = context;
this.dayBlock = dayBlock;
this.weatherBlock = weatherBlock;
layoutInflater = LayoutInflater.from(context);
this.layoutresourceID = resource;
if (weatherBlock == null)
{
Log.e(TAG, "DayAdapter: full block is null");
}
}
@Override
public int getCount()
{
return dayBlock.getSize();
}
public void UpdateData(@NonNull ArrayList<String> dayBlock, ArrayList<WeatherData> weatherBlock)
{
this.dayBlock = dayBlock;
this.weatherBlock = weatherBlock;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent)
{
if (convertView == null)
{
convertView = layoutInflater.inflate(layoutresourceID,parent,false);
}
if (weatherBlock == null)
{
Log.d(TAG, "getView: weatherBlock is null");
return convertView;
}
TextView date = (TextView) convertView.findViewById(R.id.date);
TextView minTempFoDay = (TextView) convertView.findViewById(R.id.minTempOfDay);
TextView maxTempFoDay = (TextView) convertView.findViewById(R.id.maxTempOfDay);
ListView weatherHolderListView = (ListView) convertView.findViewById(R.id.wHoldLV);
String dateString = dayBlock.get(position);
dayWeather = json.extractByDate(weatherBlock, dateString);
if (dayWeather == null)
{
Log.d(TAG, "getView: dayweather array is null");
return convertView;
}
if (position > dayWeather.getSize() - 1)
{
Log.d(TAG, "getView: the position is too great for the dayWeather array");
return convertView;
}
String test = dayWeather.get(position).getTemp(); // error occured here
Log.d(TAG, "getView: test string : " + test);
date.setText(dateString);
DecimalFormat df = new DecimalFormat(".##");
float mint = 500, maxt = 0;
String mint1 = "", maxt1 = "";
for (WeatherData data : dayWeather)
{
if (mint > Float.parseFloat(data.getMinTemp()))
{
mint = Float.parseFloat(data.getMinTemp());
mint1 = df.format(mint);
Log.d(TAG, "getView: mint : " + mint);
}
if (maxt > Float.parseFloat(data.getMaxTemp()))
{
maxt = Float.parseFloat(data.getMaxTemp());
maxt1 = df.format(maxt);
}
}
minTempFoDay.setText(mint1);
maxTempFoDay.setText(maxt1);
WeatherAdapter weatherAdapter = new WeatherAdapter(context, R.layout.weather_holder, dayWeather);
weatherHolderListView.setAdapter(weatherAdapter);
return convertView;
}
}
关于java - ListView 内的 ListView 不起作用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/51920488/