Java tutorial
/* * Copyright (C) 2015 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.alboteanu.android.sunshine.app; import android.annotation.TargetApi; import android.app.Activity; import android.content.Intent; import android.content.SharedPreferences; import android.content.res.TypedArray; import android.database.Cursor; import android.net.Uri; import android.os.Build; import android.os.Bundle; import android.preference.PreferenceManager; import android.support.v4.app.Fragment; import android.support.v4.app.LoaderManager; import android.support.v4.content.CursorLoader; import android.support.v4.content.Loader; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.util.AttributeSet; import android.util.Log; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.view.ViewTreeObserver; import android.widget.AbsListView; import android.widget.TextView; import com.alboteanu.android.sunshine.app.data.WeatherContract; import com.alboteanu.android.sunshine.app.sync.SunshineSyncAdapter; /** * Encapsulates fetching the forecast and displaying it as a {@link android.support.v7.widget.RecyclerView} layout. */ public class ForecastFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor>, SharedPreferences.OnSharedPreferenceChangeListener { public static final String LOG_TAG = ForecastFragment.class.getSimpleName(); private ForecastAdapter mForecastAdapter; private RecyclerView mRecyclerView; private boolean mUseTodayLayout, mAutoSelectView; private int mChoiceMode; private boolean mHoldForTransition; private long mInitialSelectedDate = -1; private static final String SELECTED_KEY = "selected_position"; private static final int FORECAST_LOADER = 0; // For the forecast view we're showing only a small subset of the stored data. // Specify the columns we need. private static final String[] FORECAST_COLUMNS = { // In this case the id needs to be fully qualified with a table name, since // the content provider joins the location & weather tables in the background // (both have an _id column) // On the one hand, that's annoying. On the other, you can search the weather table // using the location set by the user, which is only in the Location table. // So the convenience is worth it. WeatherContract.WeatherEntry.TABLE_NAME + "." + WeatherContract.WeatherEntry._ID, WeatherContract.WeatherEntry.COLUMN_DATE, WeatherContract.WeatherEntry.COLUMN_SHORT_DESC, WeatherContract.WeatherEntry.COLUMN_MAX_TEMP, WeatherContract.WeatherEntry.COLUMN_MIN_TEMP, WeatherContract.LocationEntry.COLUMN_LOCATION_SETTING, WeatherContract.WeatherEntry.COLUMN_WEATHER_ID, WeatherContract.LocationEntry.COLUMN_COORD_LAT, WeatherContract.LocationEntry.COLUMN_COORD_LONG }; // These indices are tied to FORECAST_COLUMNS. If FORECAST_COLUMNS changes, these // must change. static final int COL_WEATHER_ID = 0; static final int COL_WEATHER_DATE = 1; static final int COL_WEATHER_DESC = 2; static final int COL_WEATHER_MAX_TEMP = 3; static final int COL_WEATHER_MIN_TEMP = 4; static final int COL_LOCATION_SETTING = 5; static final int COL_WEATHER_CONDITION_ID = 6; static final int COL_COORD_LAT = 7; static final int COL_COORD_LONG = 8; /** * A callback interface that all activities containing this fragment must * implement. This mechanism allows activities to be notified of item * selections. */ public interface Callback { /** * DetailFragmentCallback for when an item has been selected. */ public void onItemSelected(Uri dateUri, ForecastAdapter.ForecastAdapterViewHolder vh); } public ForecastFragment() { } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Add this line in order for this fragment to handle menu events. setHasOptionsMenu(true); } @Override public void onResume() { SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity()); sp.registerOnSharedPreferenceChangeListener(this); super.onResume(); } @Override public void onPause() { SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(getActivity()); sp.unregisterOnSharedPreferenceChangeListener(this); super.onPause(); } @Override public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { inflater.inflate(R.menu.forecastfragment, menu); } @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(); // if (id == R.id.action_refresh) { // updateWeather(); // return true; // } if (id == R.id.action_map) { openPreferredLocationInMap(); return true; } return super.onOptionsItemSelected(item); } @Override public void onInflate(Activity activity, AttributeSet attrs, Bundle savedInstanceState) { super.onInflate(activity, attrs, savedInstanceState); TypedArray a = activity.obtainStyledAttributes(attrs, R.styleable.ForecastFragment, 0, 0); mChoiceMode = a.getInt(R.styleable.ForecastFragment_android_choiceMode, AbsListView.CHOICE_MODE_NONE); mAutoSelectView = a.getBoolean(R.styleable.ForecastFragment_autoSelectView, false); mHoldForTransition = a.getBoolean(R.styleable.ForecastFragment_sharedElementTransitions, false); a.recycle(); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_main, container, false); // Get a reference to the RecyclerView, and attach this adapter to it. mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerview_forecast); // Set the layout manager mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); View emptyView = rootView.findViewById(R.id.recyclerview_forecast_empty); // use this setting to improve performance if you know that changes // in content do not change the layout size of the RecyclerView mRecyclerView.setHasFixedSize(true); // The ForecastAdapter will take data from a source and // use it to populate the RecyclerView it's attached to. mForecastAdapter = new ForecastAdapter(getActivity(), new ForecastAdapter.ForecastAdapterOnClickHandler() { @Override public void onClick(Long date, ForecastAdapter.ForecastAdapterViewHolder vh) { String locationSetting = Utility.getPreferredLocation(getActivity()); ((Callback) getActivity()).onItemSelected( WeatherContract.WeatherEntry.buildWeatherLocationWithDate(locationSetting, date), vh); } }, emptyView, mChoiceMode); // specify an adapter (see also next alboteanu) mRecyclerView.setAdapter(mForecastAdapter); final View parallaxView = rootView.findViewById(R.id.parallax_bar); if (null != parallaxView) { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) { mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() { @TargetApi(Build.VERSION_CODES.HONEYCOMB) @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); int max = parallaxView.getHeight(); if (dy > 0) { parallaxView.setTranslationY(Math.max(-max, parallaxView.getTranslationY() - dy / 2)); } else { parallaxView.setTranslationY(Math.min(0, parallaxView.getTranslationY() - dy / 2)); } } }); } } /* final AppBarLayout appbarView = (AppBarLayout)rootView.findViewById(R.id.appbar); if (null != appbarView) { ViewCompat.setElevation(appbarView, 0); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() { @TargetApi(Build.VERSION_CODES.LOLLIPOP) @Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { if (0 == mRecyclerView.computeVerticalScrollOffset()) { appbarView.setElevation(0); } else { appbarView.setElevation(appbarView.getTargetElevation()); } } }); } }*/ // If there's instance state, mine it for useful information. // The end-goal here is that the user never knows that turning their device sideways // does crazy lifecycle related things. It should feel like some stuff stretched out, // or magically appeared to take advantage of room, but data or place in the app was never // actually *lost*. if (savedInstanceState != null) { mForecastAdapter.onRestoreInstanceState(savedInstanceState); } mForecastAdapter.setUseTodayLayout(mUseTodayLayout); return rootView; } @Override public void onActivityCreated(Bundle savedInstanceState) { // We hold for transition here just in-case the activity // needs to be re-created. In a standard return transition, // this doesn't actually make a difference. if (mHoldForTransition) { getActivity().supportPostponeEnterTransition(); } getLoaderManager().initLoader(FORECAST_LOADER, null, this); super.onActivityCreated(savedInstanceState); } // since we read the location when we create the loader, all we need to do is restart things void onLocationChanged() { getLoaderManager().restartLoader(FORECAST_LOADER, null, this); } private void openPreferredLocationInMap() { // Using the URI scheme for showing a location found on a map. This super-handy // intent can is detailed in the "Common Intents" page of Android's developer site: // http://developer.android.com/guide/components/intents-common.html#Maps if (null != mForecastAdapter) { Cursor c = mForecastAdapter.getCursor(); if (null != c) { c.moveToPosition(0); String posLat = c.getString(COL_COORD_LAT); String posLong = c.getString(COL_COORD_LONG); Uri geoLocation = Uri.parse("geo:" + posLat + "," + posLong); Intent intent = new Intent(Intent.ACTION_VIEW); intent.setData(geoLocation); if (intent.resolveActivity(getActivity().getPackageManager()) != null) { startActivity(intent); } else { Log.d(LOG_TAG, "Couldn't call " + geoLocation.toString() + ", no receiving apps installed!"); } } } } @Override public void onSaveInstanceState(Bundle outState) { // When tablets rotate, the currently selected list item needs to be saved. mForecastAdapter.onSaveInstanceState(outState); super.onSaveInstanceState(outState); } @Override public Loader<Cursor> onCreateLoader(int i, Bundle bundle) { // This is called when a new Loader needs to be created. This // fragment only uses one loader, so we don't care about checking the id. // To only show current and future dates, filter the query to return weather only for // dates after or including today. // Sort order: Ascending, by date. String sortOrder = WeatherContract.WeatherEntry.COLUMN_DATE + " ASC"; String locationSetting = Utility.getPreferredLocation(getActivity()); Uri weatherForLocationUri = WeatherContract.WeatherEntry.buildWeatherLocationWithStartDate(locationSetting, System.currentTimeMillis()); return new CursorLoader(getActivity(), weatherForLocationUri, FORECAST_COLUMNS, null, null, sortOrder); } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { mForecastAdapter.swapCursor(data); updateEmptyView(); if (data.getCount() == 0) { getActivity().supportStartPostponedEnterTransition(); } else { mRecyclerView.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() { @Override public boolean onPreDraw() { // Since we know we're going to get items, we keep the listener around until // we see Children. if (mRecyclerView.getChildCount() > 0) { mRecyclerView.getViewTreeObserver().removeOnPreDrawListener(this); int position = mForecastAdapter.getSelectedItemPosition(); if (position == RecyclerView.NO_POSITION && -1 != mInitialSelectedDate) { Cursor data = mForecastAdapter.getCursor(); int count = data.getCount(); int dateColumn = data.getColumnIndex(WeatherContract.WeatherEntry.COLUMN_DATE); for (int i = 0; i < count; i++) { data.moveToPosition(i); if (data.getLong(dateColumn) == mInitialSelectedDate) { position = i; break; } } } if (position == RecyclerView.NO_POSITION) position = 0; // If we don't need to restart the loader, and there's a desired position to restore // to, do so now. mRecyclerView.smoothScrollToPosition(position); RecyclerView.ViewHolder vh = mRecyclerView.findViewHolderForAdapterPosition(position); if (null != vh && mAutoSelectView) { mForecastAdapter.selectView(vh); } if (mHoldForTransition) { getActivity().supportStartPostponedEnterTransition(); } return true; } return false; } }); } } @Override public void onDestroy() { super.onDestroy(); if (null != mRecyclerView) { mRecyclerView.clearOnScrollListeners(); } } @Override public void onLoaderReset(Loader<Cursor> loader) { mForecastAdapter.swapCursor(null); } public void setUseTodayLayout(boolean useTodayLayout) { mUseTodayLayout = useTodayLayout; if (mForecastAdapter != null) { mForecastAdapter.setUseTodayLayout(mUseTodayLayout); } } public void setInitialSelectedDate(long initialSelectedDate) { mInitialSelectedDate = initialSelectedDate; } /* Updates the empty list view with contextually relevant information that the user can use to determine why they aren't seeing weather. */ private void updateEmptyView() { if (mForecastAdapter.getItemCount() == 0) { TextView tv = (TextView) getView().findViewById(R.id.recyclerview_forecast_empty); if (null != tv) { // if cursor is empty, why? do we have an invalid location int message = R.string.empty_forecast_list; @SunshineSyncAdapter.LocationStatus int location = Utility.getLocationStatus(getActivity()); switch (location) { case SunshineSyncAdapter.LOCATION_STATUS_SERVER_DOWN: message = R.string.empty_forecast_list_server_down; break; case SunshineSyncAdapter.LOCATION_STATUS_SERVER_INVALID: message = R.string.empty_forecast_list_server_error; break; case SunshineSyncAdapter.LOCATION_STATUS_INVALID: message = R.string.empty_forecast_list_invalid_location; break; default: if (!Utility.isNetworkAvailable(getActivity())) { message = R.string.empty_forecast_list_no_network; } } tv.setText(message); } } } @Override public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) { if (key.equals(getString(R.string.pref_location_status_key))) { updateEmptyView(); } } }