我有1个活动，1个片段涉及这个。 在片段中，我声明了公共类FetchWeatherTask：
public class FetchWeatherTask extends AsyncTask<String,Void,String[]>{
private final String LOG_TAG = FetchWeatherTask.class.getSimpleName();
@Override
protected void onPostExecute(String[] result) {
if (result != null){
mForecastAdapter.clear();
for(String dayForecastStr : result)
mForecastAdapter.add(dayForecastStr);
}
}
//region JSON PARSING SNIPPET
//*****************************************************************************************************************************
/* The date/time conversion code is going to be moved outside the asynctask later,
* so for convenience we're breaking it out into its own method now.
*/
private String getReadableDateString(long time){
// Because the API returns a unix timestamp (measured in seconds),
// it must be converted to milliseconds in order to be converted to valid date.
SimpleDateFormat shortenedDateFormat = new SimpleDateFormat("EEE MMM dd");
return shortenedDateFormat.format(time);
}
/**
* Prepare the weather high/lows for presentation.
*/
private String formatHighLows(double high, double low) {
String unitType = prefs.getString(
getString(R.string.pref_default_unit_key),
getString(R.string.pref_default_temp));
// For presentation, assume the user doesn't care about tenths of a degree.
long roundedHigh = Math.round(high);
long roundedLow = Math.round(low);
String highLowStr = roundedHigh + "/" + roundedLow;
return highLowStr;
}
/**
* Take the String representing the complete forecast in JSON Format and
* pull out the data we need to construct the Strings needed for the wireframes.
*
* Fortunately parsing is easy: constructor takes the JSON string and converts it
* into an Object hierarchy for us.
*/
private String[] getWeatherDataFromJson(String forecastJsonStr, int numDays)
throws JSONException {
// These are the names of the JSON objects that need to be extracted.
final String OWM_LIST = "list";
final String OWM_WEATHER = "weather";
final String OWM_TEMPERATURE = "temp";
final String OWM_MAX = "max";
final String OWM_MIN = "min";
final String OWM_DESCRIPTION = "main";
JSONObject forecastJson = new JSONObject(forecastJsonStr);
JSONArray weatherArray = forecastJson.getJSONArray(OWM_LIST);
// OWM returns daily forecasts based upon the local time of the city that is being
// asked for, which means that we need to know the GMT offset to translate this data
// properly.
// Since this data is also sent in-order and the first day is always the
// current day, we're going to take advantage of that to get a nice
// normalized UTC date for all of our weather.
Time dayTime = new Time();
dayTime.setToNow();
// we start at the day returned by local time. Otherwise this is a mess.
int julianStartDay = Time.getJulianDay(System.currentTimeMillis(), dayTime.gmtoff);
// now we work exclusively in UTC
dayTime = new Time();
String[] resultStrs = new String[numDays];
for(int i = 0; i < weatherArray.length(); i++) {
// For now, using the format "Day, description, hi/low"
String day;
String description;
String highAndLow;
// Get the JSON object representing the day
JSONObject dayForecast = weatherArray.getJSONObject(i);
// The date/time is returned as a long. We need to convert that
// into something human-readable, since most people won't read "1400356800" as
// "this saturday".
long dateTime;
// Cheating to convert this to UTC time, which is what we want anyhow
dateTime = dayTime.setJulianDay(julianStartDay+i);
day = getReadableDateString(dateTime);
// description is in a child array called "weather", which is 1 element long.
JSONObject weatherObject = dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0);
description = weatherObject.getString(OWM_DESCRIPTION);
// Temperatures are in a child object called "temp". Try not to name variables
// "temp" when working with temperature. It confuses everybody.
JSONObject temperatureObject = dayForecast.getJSONObject(OWM_TEMPERATURE);
double high = temperatureObject.getDouble(OWM_MAX);
double low = temperatureObject.getDouble(OWM_MIN);
highAndLow = formatHighLows(high, low);
resultStrs[i] = day + " - " + description + " - " + highAndLow;
}
for (String s : resultStrs) {
//Log.v(LOG_TAG, "Forecast Entry: " + s);
}
return resultStrs;
}
//endregion
@Override
protected String[] doInBackground(String... params) {
if(params.length == 0)
return null;
//region HTTPConnection Snippet
// **********************************************************************************************************************************************************************************
// These two need to be declared outside the try/catch
// so that they can be closed in the finally block.
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
// Will contain the raw JSON response as a string.
String forecastJsonStr = null;
String format ="json";
String units = "metric";
int numDays = 7;
String apiKey ="b1b15e88fa797225412429c1c50c122a";
try {
// Construct the URL for the OpenWeatherMap query
// Possible parameters are avaiable at OWM's forecast API page, at
// http://openweathermap.org/API#forecast
//region URI_BUILDER
//***********************************************************************************************************************
final String FORECAST_BASE_URL =
"http://api.openweathermap.org/data/2.5/forecast/daily?";
final String QUERY_PARAM = "q";
final String FORMAT_PARAM ="mode";
final String UNITS_PARAM = "units";
final String DAYS_PARAM = "cnt";
final String API_KEY_PARAM="appid";
Uri buildUri = Uri.parse(FORECAST_BASE_URL).buildUpon()
.appendQueryParameter(QUERY_PARAM,params[0])
.appendQueryParameter(FORMAT_PARAM,format)
.appendQueryParameter(UNITS_PARAM,units)
.appendQueryParameter(DAYS_PARAM,Integer.toString(numDays))
.appendQueryParameter(API_KEY_PARAM,apiKey).build();
//Log.v(LOG_TAG, "BuiltURI: " + buildUri.toString());
URL url = new URL(buildUri.toString());
//endregion
// Create the request to OpenWeatherMap, and open the connection
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// Read the input stream into a String
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
// Nothing to do.
forecastJsonStr = null;
}
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
// Since it's JSON, adding a newline isn't necessary (it won't affect parsing)
// But it does make debugging a *lot* easier if you print out the completed
// buffer for debugging.
buffer.append(line + "\n");
}
if (buffer.length() == 0) {
// Stream was empty. No point in parsing.
forecastJsonStr = null;
}
forecastJsonStr = buffer.toString();
//(LOG_TAG, "Forecast JSON String: " + forecastJsonStr);
} catch (IOException e) {
Log.e("PlaceholderFragment", "Error ", e);
// If the code didn't successfully get the weather data, there's no point in attemping
// to parse it.
forecastJsonStr = null;
} finally{
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("PlaceholderFragment", "Error closing stream", e);
}
}
}
//endregion
try{
return getWeatherDataFromJson(forecastJsonStr,numDays);
}
catch (JSONException e){
Log.e(LOG_TAG, e.getMessage(), e);
e.printStackTrace();
}
return null;
}
}
然后在onOptionsItemSelected方法的MainActivity中实现此类：
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
startActivity(new Intent(this, SettingsActivity.class));
return true;
}
if (id == R.id.action_refresh) {
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
String location = prefs.getString(getString(R.string.pref_location_key),
getString(R.string.pref_default_location));
FetchWeatherTask weatherTask = new FetchWeatherTask();
weatherTask.execute(location);
return true;
}
return super.onOptionsItemSelected(item);
}
}
IDE建议改变weatherTaks的声明，使其变为静态。这确实解决了这个方法的错误，虽然我无法使用其他方法，如：
String unitType = prefs.getString(
的getString（R.string.pref_units_key）， 的getString（R.string.pref_units_metric））;
内部getString会说＆＃34;不能在静态方法上使用非静态方法＆＃34; （我不记录确切的单词，但这意味着什么）
恢复主要目标：我如何在其他活动中使用公共类，即使它被标记为公开，我甚至导入了我的包：
import com.example.diomonogatarilaptop.sunshine.MainActivityFragment;
感谢您阅读
编辑：片段代码
package com.example.diomonogatarilaptop.sunshine;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.text.format.Time;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
public class MainActivityFragment extends Fragment {
public final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
public static ArrayAdapter<String> mForecastAdapter;
public MainActivityFragment() {
}
private void updateWeather(){
FetchWeatherTask weatherTask = new FetchWeatherTask();
String location = prefs.getString(getString(R.string.pref_location_key),
getString(R.string.pref_default_location));
weatherTask.execute(location);
}
@Override
public void onStart(){
super.onStart();
updateWeather();
}
//region AsyncTask Weather Fetcher
//********************************************************************************************************************************************************************************************
public class FetchWeatherTask extends AsyncTask<String,Void,String[]>{
private final String LOG_TAG = FetchWeatherTask.class.getSimpleName();
@Override
protected void onPostExecute(String[] result) {
if (result != null){
mForecastAdapter.clear();
for(String dayForecastStr : result)
mForecastAdapter.add(dayForecastStr);
}
}
//region JSON PARSING SNIPPET
//*****************************************************************************************************************************
/* The date/time conversion code is going to be moved outside the asynctask later,
* so for convenience we're breaking it out into its own method now.
*/
private String getReadableDateString(long time){
// Because the API returns a unix timestamp (measured in seconds),
// it must be converted to milliseconds in order to be converted to valid date.
SimpleDateFormat shortenedDateFormat = new SimpleDateFormat("EEE MMM dd");
return shortenedDateFormat.format(time);
}
/**
* Prepare the weather high/lows for presentation.
*/
private String formatHighLows(double high, double low) {
String unitType = prefs.getString(
getString(R.string.pref_default_unit_key),
getString(R.string.pref_default_temp));
// For presentation, assume the user doesn't care about tenths of a degree.
long roundedHigh = Math.round(high);
long roundedLow = Math.round(low);
String highLowStr = roundedHigh + "/" + roundedLow;
return highLowStr;
}
/**
* Take the String representing the complete forecast in JSON Format and
* pull out the data we need to construct the Strings needed for the wireframes.
*
* Fortunately parsing is easy: constructor takes the JSON string and converts it
* into an Object hierarchy for us.
*/
private String[] getWeatherDataFromJson(String forecastJsonStr, int numDays)
throws JSONException {
// These are the names of the JSON objects that need to be extracted.
final String OWM_LIST = "list";
final String OWM_WEATHER = "weather";
final String OWM_TEMPERATURE = "temp";
final String OWM_MAX = "max";
final String OWM_MIN = "min";
final String OWM_DESCRIPTION = "main";
JSONObject forecastJson = new JSONObject(forecastJsonStr);
JSONArray weatherArray = forecastJson.getJSONArray(OWM_LIST);
// OWM returns daily forecasts based upon the local time of the city that is being
// asked for, which means that we need to know the GMT offset to translate this data
// properly.
// Since this data is also sent in-order and the first day is always the
// current day, we're going to take advantage of that to get a nice
// normalized UTC date for all of our weather.
Time dayTime = new Time();
dayTime.setToNow();
// we start at the day returned by local time. Otherwise this is a mess.
int julianStartDay = Time.getJulianDay(System.currentTimeMillis(), dayTime.gmtoff);
// now we work exclusively in UTC
dayTime = new Time();
String[] resultStrs = new String[numDays];
for(int i = 0; i < weatherArray.length(); i++) {
// For now, using the format "Day, description, hi/low"
String day;
String description;
String highAndLow;
// Get the JSON object representing the day
JSONObject dayForecast = weatherArray.getJSONObject(i);
// The date/time is returned as a long. We need to convert that
// into something human-readable, since most people won't read "1400356800" as
// "this saturday".
long dateTime;
// Cheating to convert this to UTC time, which is what we want anyhow
dateTime = dayTime.setJulianDay(julianStartDay+i);
day = getReadableDateString(dateTime);
// description is in a child array called "weather", which is 1 element long.
JSONObject weatherObject = dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0);
description = weatherObject.getString(OWM_DESCRIPTION);
// Temperatures are in a child object called "temp". Try not to name variables
// "temp" when working with temperature. It confuses everybody.
JSONObject temperatureObject = dayForecast.getJSONObject(OWM_TEMPERATURE);
double high = temperatureObject.getDouble(OWM_MAX);
double low = temperatureObject.getDouble(OWM_MIN);
highAndLow = formatHighLows(high, low);
resultStrs[i] = day + " - " + description + " - " + highAndLow;
}
for (String s : resultStrs) {
//Log.v(LOG_TAG, "Forecast Entry: " + s);
}
return resultStrs;
}
//endregion
@Override
protected String[] doInBackground(String... params) {
if(params.length == 0)
return null;
//region HTTPConnection Snippet
// **********************************************************************************************************************************************************************************
// These two need to be declared outside the try/catch
// so that they can be closed in the finally block.
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
// Will contain the raw JSON response as a string.
String forecastJsonStr = null;
String format ="json";
String units = "metric";
int numDays = 7;
String apiKey ="b1b15e88fa797225412429c1c50c122a";
try {
// Construct the URL for the OpenWeatherMap query
// Possible parameters are avaiable at OWM's forecast API page, at
// http://openweathermap.org/API#forecast
//region URI_BUILDER
//***********************************************************************************************************************
final String FORECAST_BASE_URL =
"http://api.openweathermap.org/data/2.5/forecast/daily?";
final String QUERY_PARAM = "q";
final String FORMAT_PARAM ="mode";
final String UNITS_PARAM = "units";
final String DAYS_PARAM = "cnt";
final String API_KEY_PARAM="appid";
Uri buildUri = Uri.parse(FORECAST_BASE_URL).buildUpon()
.appendQueryParameter(QUERY_PARAM,params[0])
.appendQueryParameter(FORMAT_PARAM,format)
.appendQueryParameter(UNITS_PARAM,units)
.appendQueryParameter(DAYS_PARAM,Integer.toString(numDays))
.appendQueryParameter(API_KEY_PARAM,apiKey).build();
//Log.v(LOG_TAG, "BuiltURI: " + buildUri.toString());
URL url = new URL(buildUri.toString());
//endregion
// Create the request to OpenWeatherMap, and open the connection
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// Read the input stream into a String
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
// Nothing to do.
forecastJsonStr = null;
}
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
// Since it's JSON, adding a newline isn't necessary (it won't affect parsing)
// But it does make debugging a *lot* easier if you print out the completed
// buffer for debugging.
buffer.append(line + "\n");
}
if (buffer.length() == 0) {
// Stream was empty. No point in parsing.
forecastJsonStr = null;
}
forecastJsonStr = buffer.toString();
//(LOG_TAG, "Forecast JSON String: " + forecastJsonStr);
} catch (IOException e) {
Log.e("PlaceholderFragment", "Error ", e);
// If the code didn't successfully get the weather data, there's no point in attemping
// to parse it.
forecastJsonStr = null;
} finally{
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("PlaceholderFragment", "Error closing stream", e);
}
}
}
//endregion
try{
return getWeatherDataFromJson(forecastJsonStr,numDays);
}
catch (JSONException e){
Log.e(LOG_TAG, e.getMessage(), e);
e.printStackTrace();
}
return null;
}
}
//endregion
//region onCreateView
//***********************************************************************************************************************************
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment, container, false);
//region Where the data is
mForecastAdapter = new ArrayAdapter<String>(
getActivity(),
R.layout.list_item_forecast,
R.id.list_item_forecast_textview,
new ArrayList<String>());
ListView lista = (ListView)rootView.findViewById(R.id.listview_forecast);
lista.setAdapter(mForecastAdapter);
//region onClickListener manda tostas
lista.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String forecast = mForecastAdapter.getItem(position);
Intent intent = new Intent(getContext(), DetailActivity.class)
.putExtra(Intent.EXTRA_TEXT, forecast);
startActivity(intent);
}
});
//endregion
//endregion
return rootView;
}
//endregion
}
答案 0 :(得分：0)
这是因为你试图实例化一个内部类而不引用外部类的实例。你应该这样做，
new MainFragment(). new FetchWeatherTask();
但是你可能已经创建了一个MainFragment实例（让我们说它的mainFragment）然后你应该使用它：
mainFragment. new FetchWeatherTask();