在我的Android应用程序中，我使用OpenWeatherMap服务，我是android的新手。我将JSON日期解析为我的应用程序的屏幕，但我对SQLite有点困惑，因为我从未使用过它而且我使用Fragment。（我发现很多教程都是使用Activity，有些东西不能用Fragment工作）任何人都可以告诉我如何做下一件事：
1) I want to save date which I parsed to database when network is available.
2) When network is not available take last date from database and show it in screen.
感谢您的帮助！
WeatherDB.java
public class WeatherDB extends SQLiteOpenHelper {
public WeatherDB(Context context){
super(context, "WeatherDB", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table WeatherTable ("+ "cityField text,"
+ "updatedField text,"
+ "detailsField text"
+ "currentTemperatureField text"
+ "weatherIcon text"
+ "sunrise text"
+ "sunset text" + ");");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
WeatherFragment.java
public class WeatherFragment extends Fragment{
Typeface weatherFont;
TextView cityField;
TextView updatedField;
TextView detailsField;
TextView currentTemperatureField;
TextView weatherIcon;
TextView sunrise;
TextView sunset;
Button tButton;
boolean isCelsius;
double temp;
Handler handler;
WeatherDB weatherDB;
public WeatherFragment(){
handler = new Handler();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_weather, container, false);
//Initialize button
cityField = (TextView)view.findViewById(R.id.city_field);
updatedField = (TextView)view.findViewById(R.id.updated_field);
detailsField = (TextView)view.findViewById(R.id.details_field);
currentTemperatureField = (TextView)view.findViewById(R.id.temperature_field);
weatherIcon = (TextView)view.findViewById(R.id.weather_icon);
sunrise = (TextView)view.findViewById(R.id.sunrise);
sunset = (TextView)view.findViewById(R.id.sunset);
//tButton = Change to ºC and ºF buttons
tButton = (Button)view.findViewById(R.id.temp_toggle_button);
tButton.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View v) {
if( isCelsius ) {
// convert temp to Fahrenheit
temp = (temp * ((double) 9/5)) + 32;
currentTemperatureField.setText(String.format("%.2f ºF", temp));
tButton.setText(R.string.button_celsius);
isCelsius = false;
} else {
// convert temp to Celsius
temp = (temp - 32) * ((double) 5/9);
currentTemperatureField.setText(String.format("%.2f ºC", temp));
tButton.setText(R.string.button_fahrenheit);
isCelsius = true;
}
}
});
weatherIcon.setTypeface(weatherFont);
setHasOptionsMenu(true);
weatherDB = new WeatherDB(getActivity());
return view;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
weatherFont = Typeface.createFromAsset(getActivity().getAssets(), "fonts/weather.ttf");
updateWeatherData(new CityPreference(getActivity()).getCity());
}
/*----------------------------------------------------------------------------------------------
* Method: updateWeatherData( final String city)
* Parameter: final String city: city that will be looked for in the Open Weather Maps API
* Description: Creates the thread used by renderWeather to update the weather data
* ---------------------------------------------------------------------------------------------
*/
private void updateWeatherData(final String city){
new Thread(){
public void run(){
final JSONObject json = RemoteFetch.getJSON(getActivity(), city);
if(json == null){
handler.post(new Runnable(){
public void run(){
Toast.makeText(getActivity(), getActivity().getString(R.string.place_not_found), Toast.LENGTH_LONG).show();
}
});
} else {
handler.post(new Runnable(){
public void run(){
renderWeather(json);
}
});
}
}
}.start();
}
/*
* ---------------------------------------------------------------------------------------------
* Method: renderWeather
* Parameter: - JSONObject json: object containing the weather data from Open Weather Map's API
* Description: Uses the inputted JSONObject to write the relevant weather data to the text
* views.
* ---------------------------------------------------------------------------------------------
*/
private void renderWeather(JSONObject json){
try {
cityField.setText(json.getString("name").toUpperCase(Locale.US) +
", " +
json.getJSONObject("sys").getString("country"));
JSONObject details = json.getJSONArray("weather").getJSONObject(0);
JSONObject main = json.getJSONObject("main");
detailsField.setText(
details.getString("description").toUpperCase(Locale.US) +
"\n" + "Humidity: " + main.getString("humidity") + "%" +
"\n" + "Pressure: " + main.getString("pressure") + " hPa");
currentTemperatureField.setText(String.format("%.2f", main.getDouble("temp"))+ "ºC");
temp = main.getDouble("temp");
isCelsius = true;
DateFormat df = DateFormat.getDateTimeInstance();
String updatedOn = df.format(new Date(json.getLong("dt")*1000));
updatedField.setText("Last update: " + updatedOn);
setWeatherIcon(details.getInt("id"), json.getJSONObject("sys").getLong("sunrise") * 1000, json.getJSONObject("sys").getLong("sunset") * 1000);
//Sunrise
String javaTimestampSunrise = new SimpleDateFormat("HH:mm").format(new Date(json.getJSONObject("sys").getLong("sunrise")*1000L));
sunrise.setText("Sunrise\n " + javaTimestampSunrise);
//Sunset
String javaTimestampSunset = new SimpleDateFormat("HH:mm").format(new Date(json.getJSONObject("sys").getLong("sunset")*1000L));
sunset.setText("Sunset\n " + javaTimestampSunset);
}catch(Exception e){
Log.e("SimpleWeather", "One or more fields not found in the JSON data");
}
}
/*----------------------------------------------------------------------------------------------
* Method: setWeatherIcon(int actualId, long sunrise, long sunset)
* Parameters: - int actualId: Open Weather Map's id for the inputted weather condition
* - long sunrise: The time when the sunrise occurs in the inputted city
* - long sunset: The time when the sunset occurs in the inputted city
* Description: Called by renderWeather to set the weather icon (in the main/assets/fonts
* folder) based on the current time of day and weather conditions.
*----------------------------------------------------------------------------------------------
*/
private void setWeatherIcon(int actualId, long sunrise, long sunset){
int id = actualId / 100;
String icon = "";
if(actualId == 800){
long currentTime = new Date().getTime();
if(currentTime>=sunrise && currentTime<sunset) {
icon = getActivity().getString(R.string.weather_sunny);
} else {
icon = getActivity().getString(R.string.weather_clear_night);
}
} else {
switch(id) {
case 2 : icon = getActivity().getString(R.string.weather_thunder);
break;
case 3 : icon = getActivity().getString(R.string.weather_drizzle);
break;
case 7 : icon = getActivity().getString(R.string.weather_foggy);
break;
case 8 : icon = getActivity().getString(R.string.weather_cloudy);
break;
case 6 : icon = getActivity().getString(R.string.weather_snowy);
break;
case 5 : icon = getActivity().getString(R.string.weather_rainy);
break;
}
}
weatherIcon.setText(icon);
}
/*
* ---------------------------------------------------------------------------------------------
* Method: updateWeatherData(final String city)
* Parameter: String city: The city that will the search will be changed to
* Description: Calls updateWeather(city) to change the weather information in the View to the
* specified city's weather information.
* ---------------------------------------------------------------------------------------------
*/
public void changeCity(String city){
new CityPreference(getActivity()).setCity(city);
updateWeatherData(city);
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.menu_weather, menu);
MenuItem item = menu.findItem(R.id.change_city);
item.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.change_city:
showInputDialog();
//Your stuff
break;
}
return false;
}
});
super.onCreateOptionsMenu(menu, inflater);
}
/*
* ---------------------------------------------------------------------------------------------
* Method: showInputDialog():
* Description: Creates the "Change City" option on the Action Bar
* ---------------------------------------------------------------------------------------------
*/
private void showInputDialog(){
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View dialogView = inflater.inflate(R.layout.dialog_city_weather, null);
builder.setView(dialogView);
final EditText input = (EditText) dialogView.findViewById(R.id.input_location);
input.setInputType(InputType.TYPE_CLASS_TEXT);
builder.setPositiveButton("GET STARTED", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
changeCity(input.getText().toString());
}
});
builder.show();
}
}