BroadCast Receiver

Android apps can send or receive broadcast messages from the Android system and other Android apps.

Apps can register to receive specific broadcasts. When a broadcast is sent, the system automatically routes broadcasts to apps that have subscribed to receive that particular type of broadcast.

System broadcasts

The system automatically sends broadcasts when various system events occur, such as when the system switches in and out of airplane mode. System broadcasts are sent to all apps that are subscribed to receive the event.

Receiving broadcasts

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Apps can receive broadcasts in two ways: through manifest-declared receivers and context-registered receivers.

Manifest-declared receivers

If you declare a broadcast receiver in your manifest, the system launches your app (if the app is not already running) when the broadcast is sent.

Note: If your app targets API level 26 or higher, you cannot use the manifest to declare a receiver for implicit broadcasts (broadcasts that do not target your app specifically), except for a few implicit broadcasts that are exempted from that restriction. In most cases, you can use scheduled jobsinstead.

To declare a broadcast receiver in the manifest, perform the following steps:

1. Specify the <receiver> element in your app's manifest.

   <receiver android:name=".MyBroadcastReceiver"  android:exported="true">
       <intent-filter>
           <action android:name="android.intent.action.BOOT_COMPLETED"/>
           <action android:name="android.intent.action.INPUT_METHOD_CHANGED" />
       </intent-filter>
   </receiver>

   The intent filters specify the broadcast actions your receiver subscribes to.
2. Subclass BroadcastReceiver and implement onReceive(Context, Intent). The broadcast receiver in the following example logs and displays the contents of the broadcast:

   public class MyBroadcastReceiver extends BroadcastReceiver {
       private static final String TAG = "MyBroadcastReceiver";
       @Override
       public void onReceive(Context context, Intent intent) {
           StringBuilder sb = new StringBuilder();
           sb.append("Action: " + intent.getAction() + "\n");
           sb.append("URI: " + intent.toUri(Intent.URI_INTENT_SCHEME).toString() + "\n");
           String log = sb.toString();
           Log.d(TAG, log);
           Toast.makeText(context, log, Toast.LENGTH_LONG).show();
       }
   }

The system package manager registers the receiver when the app is installed. The receiver then becomes a separate entry point into your app which means that the system can start the app and deliver the broadcast if the app is not currently running.

The system creates a new BroadcastReceiver component object to handle each broadcast that it receives. This object is valid only for the duration of the call to onReceive(Context, Intent). Once your code returns from this method, the system considers the component no longer active.

Context-registered receivers

To register a receiver with a context, perform the following steps:

1. Create an instance of BroadcastReceiver.

   BroadcastReceiver br = new MyBroadcastReceiver();
2. Create an IntentFilter and register the receiver by calling registerReceiver(BroadcastReceiver, IntentFilter):

   IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
   filter.addAction(Intent.ACTION_AIRPLANE_MODE_CHANGED);
   this.registerReceiver(br, filter);

   Note: To register for local broadcasts, call LocalBroadcastManager.registerReceiver(BroadcastReceiver, IntentFilter) instead

3. To stop receiving broadcasts, call unregisterReceiver(android.content.BroadcastReceiver). Be sure to unregister the receiver when you no longer need it or the context is no longer valid.

sdg
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Date Convertor

    public static String getDate(String _Date){

//        String _Date = "2010-09-29 08:45:22";

//        String _Date = "2018-05-02T00:00:00+0000";
        SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");

        SimpleDateFormat fmt2 = new SimpleDateFormat("dd/MM/yyyy"); 

       try {
            Date date = fmt.parse(_Date);

            return fmt2.format(date);        }
        catch(ParseException pe) {

            return "Date";        }