Codice di J-Time: ricostruzione.

Ora costruiamo un'interfaccia di base che lancia l'activity principale la quale poi si rilancia automaticamente a intervalli di tempo predefiniti.

MainActivity:

public class MainActivity extends AppCompatActivity {

    private AlarmManager alarmManager;
    private Intent intent;
    private PendingIntent pendingIntent;
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button=(Button) findViewById(R.id.button);
        intent=new Intent(getApplicationContext(),Seconda.class);
        alarmManager=(AlarmManager)getSystemService(Context.ALARM_SERVICE);
        pendingIntent=PendingIntent.getActivity(getApplicationContext(),0,intent,0);

        button.setOnClickListener(new Button.OnClickListener(){

            @Override
            public void onClick(View view) {
                alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime()+5*1000,pendingIntent);
                finish();

            }
        });
    }



}

Seconda:

public class Seconda extends AppCompatActivity {

    private AlarmManager alarmManager;
    private Intent intent;
    private PendingIntent pendingIntent;
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_seconda);

        intent=new Intent(getApplicationContext(),Seconda.class);
        alarmManager=(AlarmManager)getSystemService(Context.ALARM_SERVICE);
        pendingIntent=PendingIntent.getActivity(getApplicationContext(),0,intent,0);

        button=(Button) findViewById(R.id.button2);

        button.setOnClickListener(new Button.OnClickListener(){

            @Override
            public void onClick(View view) {
                finish();
            }
        });
    }

    @Override
    public void onDestroy(){
        super.onDestroy();
        alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime()+5*1000,pendingIntent);
    }

Manifest (con il codice per non far apparire la finestra fra i Recent Tasks):

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.antonello.j_time">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Seconda"
            android:autoRemoveFromRecents="true"></activity>
    </application>

</manifest> 

La finestra viene egregiamente rimossa dalla finestra dei Recent Tasks.