I've put together a small collection of Android recipes. For each of these recipes,
this is an instance of
Context (more specifically,
Activity or
Service) unless otherwise noted. Enjoy :)
IntentsOne of the coolest things about Android is
Intents. The two most common uses of Intents are starting an Activity (open an email, contact, etc.) and starting an Activity for a result (scan a barcode, take a picture to attach to an email, etc.). Intents are specified primarily using action strings and URIs. Here are some things you can do with the
android.intent.action.VIEWaction and
startActivity().
Intent intent = new Intent(Intent.ACTION_VIEW);
// Choose a value for uri from the following.
// Search Google Maps: geo:0,0?q=query
// Show contacts: content://contacts/people
// Show a URL: http://www.google.com
intent.setData(Uri.parse(uri));
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
Other useful action/URI pairs include:
Intent.ACTION_DIAL, tel://8675309Intent.ACTION_CALL, tel://8675309
More interesting things are available when you use
startActivityForResult(). For example, to scan a barcode:
Intent intent = new Intent("com.google.zxing.client.android.SCAN");
startActivityForResult(intent, 0);Then, add
onActivityResult to your activity.
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK && requestCode == 0) {
Bundle extras = data.getExtras();
String result = extras.getStringExtra("SCAN_RESULT");
// ...
}
}
Taking a picture is done like so:
Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
startActivityForResult(intent, 0);
// ...
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK && requestCode == 0) {
String result = data.toURI();
// ...
}
}Check out the
OpenIntents registry for more information.
WifiThe
WifiManager can be used to enable and disable wifi. Where
enabled is a boolean, it's as easy as:
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
wifi.setWifiEnabled(enabled);
NotificationsText notifications (called
Toast) which appear briefly above all activities are also easy:
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
You can increase the time the notification is displayed by using
Toast.LENGTH_LONG instead.
Alert and Input DialogsSometimes it's useful to prompt the user for input. An easy way to do that without creating a new layout is to use
AlertDialog.Builder.
AlertDialog.Builder alert = new AlertDialog.Builder(this);
alert.setTitle(title);
alert.setMessage(message);
// You can set an EditText view to get user input besides
// which button was pressed.
final EditText input = new EditText(this);
alert.setView(input);
alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
String value = input.getText();
// Do something with value!
}
});
alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
// Canceled.
}
});
alert.show();
LocationUse the
LocationManager to start up the GPS and listen for location updates.
LocationManager locator = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
LocationListener mLocationListener = new LocationListener() {
public void onLocationChanged(Location location) {
if (location != null) {
location.getAltitude();
location.getLatitude();
location.getLongitude();
location.getTime();
location.getAccuracy();
location.getSpeed();
location.getProvider();
}
}
public void onProviderDisabled(String provider) {
// ...
}
public void onProviderEnabled(String provider) {
// ...
}
public void onStatusChanged(String provider, int status, Bundle extras) {
// ...
}
};
// You need to specify a Criteria for picking the location data source.
// The criteria can include power requirements.
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_COARSE); // Faster, no GPS fix.
criteria.setAccuracy(Criteria.ACCURACY_FINE); // More accurate, GPS fix.
// You can specify the time and distance between location updates.
// Both are useful for reducing power requirements.
mLocationManager.requestLocationUpdates(mLocationManager.getBestProvider(criteria, true),
MIN_LOCATION_UPDATE_TIME, MIN_LOCATION_UPDATE_DISTANCE, mLocationListener,
getMainLooper());
You can also get the phone's last known location using the
LocationManager. This is faster than setting up a
LocationListener and waiting for a fix.
// Start with fine location.
Location l = locator.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (l == null) {
// Fall back to coarse location.
l = locator.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
}
SMSSending a text is done with the
SmsManager.
SmsManager m = SmsManager.getDefault();
String destination = "8675309";
String text = "Hello, Jenny!";
m.sendTextMessage(destination, null, text, null, null);
VibrateYou can vibrate the phone for a specified duration like so:
(Vibrator) getSystemService(Context.VIBRATOR_SERVICE).vibrate(milliseconds);
SensorsAccessing sensor data is done using the
SensorManager.
SensorManager mSensorManager = (SensorManager) getSystemService(Activity.SENSOR_SERVICE);
private final SensorListener mSensorListener = new SensorListener() {
public void onAccuracyChanged(int sensor, int accuracy) {
// ...
}
public void onSensorChanged(int sensor, float[] values) {
switch (sensor) {
case SensorManager.SENSOR_ORIENTATION:
float azimuth = values[0];
float pitch = values[1];
float roll = values[2];
break;
case SensorManager.SENSOR_ACCELEROMETER:
float xforce = values[0];
float yforce = values[1];
float zforce = values[2];
break;
case SensorManager.SENSOR_MAGNETIC_FIELD:
float xmag = values[0];
float ymag = values[1];
float zmag = values[2];
break;
}
}
};
// Start listening to all sensors.
mSensorManager.registerListener(mSensorListener, mSensorManager.getSensors());
// ...
// Stop listening to sensors.
mSensorManager.unregisterListener(mSensorListener);
Silence RingerYou can use the
AudioManager to enable and disable silent mode.
mAudio = (AudioManager) getSystemService(Activity.AUDIO_SERVICE);
mAudio.setRingerMode(AudioManager.RINGER_MODE_SILENT);
// or...
mAudio.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
