Java tutorial
/* * Copyright (C) 2012 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.sorin.cloudcog.xivelypull; import java.io.IOException; import java.util.List; import java.util.Locale; import android.annotation.SuppressLint; import android.app.AlertDialog; import android.app.Dialog; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.location.Address; import android.location.Geocoder; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.os.AsyncTask; import android.os.Build; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.provider.Settings; import android.support.v4.app.DialogFragment; import android.support.v4.app.FragmentActivity; import android.view.View; import android.widget.Button; import android.widget.TextView; import android.widget.Toast; import com.sorin.cloudcog.R; @SuppressLint("ValidFragment") public class LocationActivity extends FragmentActivity { private TextView mLatLng; private TextView mAddress; private Button mFineProviderButton; private Button mBothProviderButton; private LocationManager mLocationManager; private Handler mHandler; private boolean mGeocoderAvailable; private boolean mUseFine; private boolean mUseBoth; // Keys for maintaining UI states after rotation. private static final String KEY_FINE = "use_fine"; private static final String KEY_BOTH = "use_both"; // UI handler codes. private static final int UPDATE_ADDRESS = 1; private static final int UPDATE_LATLNG = 2; private static final int TEN_SECONDS = 10000; private static final int TEN_METERS = 10; private static final int TWO_MINUTES = 1000 * 60 * 2; /** * This sample demonstrates how to incorporate location based services in * your app and process location updates. The app also shows how to convert * lat/long coordinates to human-readable addresses. */ @SuppressLint("NewApi") @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.map_coordinates); // Restore apps state (if exists) after rotation. if (savedInstanceState != null) { mUseFine = savedInstanceState.getBoolean(KEY_FINE); mUseBoth = savedInstanceState.getBoolean(KEY_BOTH); } else { mUseFine = false; mUseBoth = false; } mLatLng = (TextView) findViewById(R.id.latlng); mAddress = (TextView) findViewById(R.id.address); // Receive location updates from the fine location provider (gps) only. mFineProviderButton = (Button) findViewById(R.id.provider_fine); // Receive location updates from both the fine (gps) and coarse // (network) location // providers. mBothProviderButton = (Button) findViewById(R.id.provider_both); // The isPresent() helper method is only available on Gingerbread or // above. mGeocoderAvailable = Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD && Geocoder.isPresent(); // Handler for updating text fields on the UI like the lat/long and // address. mHandler = new Handler() { public void handleMessage(Message msg) { switch (msg.what) { case UPDATE_ADDRESS: mAddress.setText((String) msg.obj); break; case UPDATE_LATLNG: mLatLng.setText((String) msg.obj); break; } } }; // Get a reference to the LocationManager object. mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); } // Restores UI states after rotation. @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putBoolean(KEY_FINE, mUseFine); outState.putBoolean(KEY_BOTH, mUseBoth); } @Override protected void onResume() { super.onResume(); setup(); } @Override protected void onStart() { super.onStart(); // Check if the GPS setting is currently enabled on the device. // This verification should be done during onStart() because the system // calls this method // when the user returns to the activity, which ensures the desired // location provider is // enabled each time the activity resumes from the stopped state. LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); final boolean gpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER); if (!gpsEnabled) { // Build an alert dialog here that requests that the user enable // the location services, then when the user clicks the "OK" button, // call enableLocationSettings() new EnableGpsDialogFragment().show(getSupportFragmentManager(), "enableGpsDialog"); } } // Method to launch Settings private void enableLocationSettings() { Intent settingsIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS); startActivity(settingsIntent); } // Stop receiving location updates whenever the Activity becomes invisible. @Override protected void onStop() { super.onStop(); mLocationManager.removeUpdates(listener); } // Set up fine and/or coarse location providers depending on whether the // fine provider or // both providers button is pressed. private void setup() { Location gpsLocation = null; Location networkLocation = null; mLocationManager.removeUpdates(listener); mLatLng.setText(R.string.unknown); mAddress.setText(R.string.unknown); // Get fine location updates only. if (mUseFine) { mFineProviderButton.setBackgroundResource(R.drawable.button_active); mBothProviderButton.setBackgroundResource(R.drawable.button_inactive); // Request updates from just the fine (gps) provider. gpsLocation = requestUpdatesFromProvider(LocationManager.GPS_PROVIDER, R.string.not_support_gps); // Update the UI immediately if a location is obtained. if (gpsLocation != null) updateUILocation(gpsLocation); } else if (mUseBoth) { // Get coarse and fine location updates. mFineProviderButton.setBackgroundResource(R.drawable.button_inactive); mBothProviderButton.setBackgroundResource(R.drawable.button_active); // Request updates from both fine (gps) and coarse (network) // providers. gpsLocation = requestUpdatesFromProvider(LocationManager.GPS_PROVIDER, R.string.not_support_gps); networkLocation = requestUpdatesFromProvider(LocationManager.NETWORK_PROVIDER, R.string.not_support_network); // If both providers return last known locations, compare the two // and use the better // one to update the UI. If only one provider returns a location, // use it. if (gpsLocation != null && networkLocation != null) { updateUILocation(getBetterLocation(gpsLocation, networkLocation)); } else if (gpsLocation != null) { updateUILocation(gpsLocation); } else if (networkLocation != null) { updateUILocation(networkLocation); } } } /** * Method to register location updates with a desired location provider. If * the requested provider is not available on the device, the app displays a * Toast with a message referenced by a resource id. * * @param provider * Name of the requested provider. * @param errorResId * Resource id for the string message to be displayed if the * provider does not exist on the device. * @return A previously returned {@link android.location.Location} from the * requested provider, if exists. */ private Location requestUpdatesFromProvider(final String provider, final int errorResId) { Location location = null; if (mLocationManager.isProviderEnabled(provider)) { mLocationManager.requestLocationUpdates(provider, TEN_SECONDS, TEN_METERS, listener); location = mLocationManager.getLastKnownLocation(provider); } else { Toast.makeText(this, errorResId, Toast.LENGTH_LONG).show(); } return location; } // Callback method for the "fine provider" button. public void useFineProvider(View v) { mUseFine = true; mUseBoth = false; setup(); } // Callback method for the "both providers" button. public void useCoarseFineProviders(View v) { mUseFine = false; mUseBoth = true; setup(); } private void doReverseGeocoding(Location location) { // Since the geocoding API is synchronous and may take a while. You // don't want to lock // up the UI thread. Invoking reverse geocoding in an AsyncTask. (new ReverseGeocodingTask(this)).execute(new Location[] { location }); } private void updateUILocation(Location location) { // We're sending the update to a handler which then updates the UI with // the new // location. Message.obtain(mHandler, UPDATE_LATLNG, location.getLatitude() + ", " + location.getLongitude()) .sendToTarget(); // Bypass reverse-geocoding only if the Geocoder service is available on // the device. if (mGeocoderAvailable) doReverseGeocoding(location); } private final LocationListener listener = new LocationListener() { @Override public void onLocationChanged(Location location) { // A new location update is received. Do something useful with it. // Update the UI with // the location update. updateUILocation(location); } @Override public void onProviderDisabled(String provider) { } @Override public void onProviderEnabled(String provider) { } @Override public void onStatusChanged(String provider, int status, Bundle extras) { } }; /** * Determines whether one Location reading is better than the current * Location fix. Code taken from * http://developer.android.com/guide/topics/location * /obtaining-user-location.html * * @param newLocation * The new Location that you want to evaluate * @param currentBestLocation * The current Location fix, to which you want to compare the new * one * @return The better Location object based on recency and accuracy. */ protected Location getBetterLocation(Location newLocation, Location currentBestLocation) { if (currentBestLocation == null) { // A new location is always better than no location return newLocation; } // Check whether the new location fix is newer or older long timeDelta = newLocation.getTime() - currentBestLocation.getTime(); boolean isSignificantlyNewer = timeDelta > TWO_MINUTES; boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES; boolean isNewer = timeDelta > 0; // If it's been more than two minutes since the current location, use // the new location // because the user has likely moved. if (isSignificantlyNewer) { return newLocation; // If the new location is more than two minutes older, it must be // worse } else if (isSignificantlyOlder) { return currentBestLocation; } // Check whether the new location fix is more or less accurate int accuracyDelta = (int) (newLocation.getAccuracy() - currentBestLocation.getAccuracy()); boolean isLessAccurate = accuracyDelta > 0; boolean isMoreAccurate = accuracyDelta < 0; boolean isSignificantlyLessAccurate = accuracyDelta > 200; // Check if the old and new location are from the same provider boolean isFromSameProvider = isSameProvider(newLocation.getProvider(), currentBestLocation.getProvider()); // Determine location quality using a combination of timeliness and // accuracy if (isMoreAccurate) { return newLocation; } else if (isNewer && !isLessAccurate) { return newLocation; } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) { return newLocation; } return currentBestLocation; } /** Checks whether two providers are the same */ private boolean isSameProvider(String provider1, String provider2) { if (provider1 == null) { return provider2 == null; } return provider1.equals(provider2); } // AsyncTask encapsulating the reverse-geocoding API. Since the geocoder API // is blocked, // we do not want to invoke it from the UI thread. private class ReverseGeocodingTask extends AsyncTask<Location, Void, Void> { Context mContext; public ReverseGeocodingTask(Context context) { super(); mContext = context; } @Override protected Void doInBackground(Location... params) { Geocoder geocoder = new Geocoder(mContext, Locale.getDefault()); Location loc = params[0]; List<Address> addresses = null; try { addresses = geocoder.getFromLocation(loc.getLatitude(), loc.getLongitude(), 1); } catch (IOException e) { e.printStackTrace(); // Update address field with the exception. Message.obtain(mHandler, UPDATE_ADDRESS, e.toString()).sendToTarget(); } if (addresses != null && addresses.size() > 0) { Address address = addresses.get(0); // Format the first line of address (if available), city, and // country name. String addressText = String.format("%s, %s, %s", address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "", address.getLocality(), address.getCountryName()); // Update address field on UI. Message.obtain(mHandler, UPDATE_ADDRESS, addressText).sendToTarget(); } return null; } } /** * Dialog to prompt users to enable GPS on the device. */ private class EnableGpsDialogFragment extends DialogFragment { @Override public Dialog onCreateDialog(Bundle savedInstanceState) { return new AlertDialog.Builder(getActivity()).setTitle(R.string.enable_gps) .setMessage(R.string.enable_gps_dialog) .setPositiveButton(R.string.enable_gps, new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { enableLocationSettings(); } }).create(); } } }