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.adampmarshall.speedo; 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.graphics.Typeface; import android.location.Geocoder; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; 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.*; import android.widget.TextView; import android.widget.Toast; public class LocationActivity extends FragmentActivity { private TextView mSpeed; private LocationManager mLocationManager; private static Handler mHandler; private boolean mGeocoderAvailable; private boolean mUseFine; private boolean mUseBoth; private GmeterView mGmeterView; // 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_SPEED = 1; private static final int ONE_SECOND = 1000; private static final int TEN_METERS = 10; /** * 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.activity_main); // Restore apps state (if exists) after rotation. if (savedInstanceState != null) { mUseFine = savedInstanceState.getBoolean(KEY_FINE); mUseBoth = savedInstanceState.getBoolean(KEY_BOTH); } else { mUseFine = false; mUseBoth = true; } mSpeed = (TextView) findViewById(R.id.speed); Typeface font = Typeface.createFromAsset(getAssets(), "DS-DIGI.TTF"); mSpeed.setTypeface(font); // 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_SPEED: mSpeed.setText((String) msg.obj); break; } } }; // Get a reference to the LocationManager object. mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); mGmeterView = (GmeterView) findViewById(R.id.gmeter); } // 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"); } } @Override public boolean onCreateOptionsMenu(Menu menu) { MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.activity_main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle item selection switch (item.getItemId()) { case R.id.gmeter_view: setContentView(R.layout.activity_gmeter); return true; case R.id.speedo_view: setContentView(R.layout.activity_main); return true; default: return super.onOptionsItemSelected(item); } } // 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); mSpeed.setText(R.string.unknown); // Get fine location updates only. if (mUseFine) { // 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) { // 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, ONE_SECOND, 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 updateUILocation(Location location) { // We're sending the update to a handler which then updates the UI with // the new // location. Message.obtain(mHandler, UPDATE_SPEED, Math.round(location.getSpeed() * 3.6) + "").sendToTarget(); } private final LocationListener listener = new LocationListener() { 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); } public void onProviderDisabled(String provider) { } public void onProviderEnabled(String provider) { } 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 > ONE_SECOND; boolean isSignificantlyOlder = timeDelta < -ONE_SECOND; 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); } /** * 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() { public void onClick(DialogInterface dialog, int which) { enableLocationSettings(); } }).create(); } } }