Java tutorial
/* * Copyright (C) 2014 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.udacity.android.student.project.app; import android.database.Cursor; import android.net.Uri; import android.os.Bundle; 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.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.widget.AdapterView; import android.widget.ListView; import com.udacity.android.student.project.app.data.CourseTable.CatalogCursor; import com.udacity.android.student.project.app.sync.SyncAdapter; import static com.udacity.android.student.project.app.data.ApplicationContentProvider.buildCourseUri; import static com.udacity.android.student.project.app.data.ApplicationContentProvider.getContentUri; import static com.udacity.android.student.project.app.data.CourseTable.CatalogCursor.CODE; /** * Encapsulates fetching the course catalog and displaying it as a {@link ListView} layout. */ public class CatalogFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor> { public static final String LOG_TAG = CatalogFragment.class.getSimpleName(); private CourseAdapter mCourseAdapter; private ListView mListView; private int mPosition = ListView.INVALID_POSITION; private static final String SELECTED_KEY = "selected_position"; private static final int CATALOG_LOADER = 0; //Note - I have used my preferred solution this type of problem // - using enumerations to hide the underlying indices. // The original implementation from Sunshine has been commented out here. // for more details, see CourseTable // 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); } public CatalogFragment() { } @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 onCreateOptionsMenu(Menu menu, MenuInflater inflater) { inflater.inflate(R.menu.catalogfragment, 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 View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // The CourseAdapter will take data from a source and // use it to populate the ListView it's attached to. mCourseAdapter = new CourseAdapter(getActivity(), null, 0); View rootView = inflater.inflate(R.layout.fragment_main, container, false); // Get a reference to the ListView, and attach this adapter to it. mListView = (ListView) rootView.findViewById(R.id.listview_catalog); mListView.setAdapter(mCourseAdapter); // We'll call our MainActivity mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) { // CursorAdapter returns a cursor at the correct position for getItem(), or null // if it cannot seek to that position. Cursor cursor = (Cursor) adapterView.getItemAtPosition(position); if (cursor != null) { String selectedCode = CODE.getString(cursor); Uri uriForActivityDetails = buildCourseUri(selectedCode); Log.i(LOG_TAG, "SELECTED " + selectedCode + " uri " + uriForActivityDetails); ((Callback) getActivity()).onItemSelected(uriForActivityDetails); } mPosition = position; } }); // 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 && savedInstanceState.containsKey(SELECTED_KEY)) { // The listview probably hasn't even been populated yet. Actually perform the // swapout in onLoadFinished. mPosition = savedInstanceState.getInt(SELECTED_KEY); } return rootView; } @Override public void onActivityCreated(Bundle savedInstanceState) { getLoaderManager().initLoader(CATALOG_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() { updateWeather(); getLoaderManager().restartLoader(CATALOG_LOADER, null, this); } private void updateWeather() { SyncAdapter.syncImmediately(getActivity()); } /* 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 != mCourseAdapter) { Cursor c = mCourseAdapter.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:" + 50 + "," + 0); 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. // When no item is selected, mPosition will be set to Listview.INVALID_POSITION, // so check for that before storing. if (mPosition != ListView.INVALID_POSITION) { outState.putInt(SELECTED_KEY, mPosition); } 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. // Sort order: Ascending, by course code - TODO for completeness, could also add provider field to cursor fields and here final String sortOrder = CatalogCursor.CODE.getFieldName() + " ASC"; return new CursorLoader(getActivity(), getContentUri(), CatalogCursor.getFieldNames(), null, null, sortOrder); } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { mCourseAdapter.swapCursor(data); if (mPosition != ListView.INVALID_POSITION) { // If we don't need to restart the loader, and there's a desired position to restore // to, do so now. mListView.smoothScrollToPosition(mPosition); } } @Override public void onLoaderReset(Loader<Cursor> loader) { mCourseAdapter.swapCursor(null); } }