android - Handle ToggleButton in onResume()

Question

I have written a program in which I am using Timer and controlling that timer using Toggle states.

Toggle's default state is OFF, once I make changes in toggle state from OFF to ON Timer starts, and when I again change to OFF it stops the Timer as per requirement.

But problem starts when my Timer is ON and I switch to other activity and then again come back to ToggleActivity and then do changes in toggle state from ON to OFF - it still runs Timer...

Note: when I use finish() or back press, in place of Intent to come back to ToggleActivity everything works fine, but when I use Intent facing such issues..

ToggleActivity.java:

public class ToggleActivity extends Activity implements OnCheckedChangeListener {

    ToggleButton toggleButton;
    TextView text;

    Timer timer;
    TimerTask timerTask;
    final Handler handler = new Handler();

    Button btnSwitchActivity;

    boolean toggleState;
    SharedPreferences sharedPreferences;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        setContentView(R.layout.activity_toggle);           

        toggleButton = (ToggleButton) findViewById(R.id.toggleButton);
        text = (TextView) findViewById(R.id.textView1);
        btnSwitchActivity = (Button) findViewById(R.id.btnSwitchActivity);

        sharedPreferences = getApplicationContext().getSharedPreferences("toggleState",0);

        btnSwitchActivity.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent intentSwitchActivity = new Intent(ToggleActivity.this, SwitchActivity.class);
                startActivity(intentSwitchActivity);
                }
            });

        }

        @Override
        public void onCheckedChanged(CompoundButton arg0, boolean isChecked) {      

            if(isChecked)
            {               
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putBoolean("toggleState", true);
                editor.commit();

                text.setText("ON");

                startTimer();

            } else 
            {       

                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putBoolean("toggleState", false);
                editor.commit();

                text.setText("OFF");

                if (timer != null) {
                    timer.cancel();
                    timer = null;
                }
            }

        }


        public void startTimer() {

            timer = new Timer();            
            initializeTimerTask();          
            timer.schedule(timerTask, 1000, 5000);

        }

        public void stoptimertask(View v) {

            if (timer != null) {
                timer.cancel();
                timer = null;
            }

        }

        public void initializeTimerTask() {

            timerTask = new TimerTask() {

                public void run() {

                    handler.post(new Runnable() {

                        public void run() {
                            Calendar calendar = Calendar.getInstance();
                            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd:MMMM:yyyy HH:mm:ss a");
                            final String strDate = simpleDateFormat.format(calendar.getTime());

                            int duration = Toast.LENGTH_SHORT;  
                            Toast toast = Toast.makeText(getApplicationContext(), strDate, duration);
                            toast.show();
                        }

                    });

                }

            };

        }

        public void onResume() {
            super.onResume();

            toggleState = sharedPreferences.getBoolean("toggleState", false);
            Log.v("toggleState", Boolean.toString(toggleState));

            if (toggleState) {
                toggleButton.setChecked(true);
                text.setText("ON");
            } else {
                toggleButton.setChecked(false);
                text.setText("OFF");
            }

            toggleButton.setChecked(toggleState);
            toggleButton.setOnCheckedChangeListener(this);         
        }

        @Override
         protected void onPause() {
            super.onPause();             
            toggleButton.setOnCheckedChangeListener(null);
          } 

}

SwitchActivity.java

public class SwitchActivity extends Activity {

    Button btnToggleActivity;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_switch);

        btnToggleActivity = (Button) findViewById(R.id.btnToggleActivity);
        btnToggleActivity.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent intent = new Intent(SwitchActivity.this, ToggleActivity.class);
                startActivity(intent);

                /**
                 * if i use finish instead of Intent to switch to ToggleActivity 
                 * my Timer works fine
                 */
                // finish
            }
        });
    }    
}

activity_toggle.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:gravity="center"
    android:background="#ffffff"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context=".ToggleActivity" >

    <ToggleButton
        android:id="@+id/toggleButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/toggle_selector"
        android:checked="false"
        android:text=""
        android:textOff=""
        android:textOn="" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"        
        android:layout_marginTop="20dp"
        android:layout_marginBottom="20dp"
        android:text="@string/string_toggle_off"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <Button 
        android:id="@+id/btnSwitchActivity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/string_btn_switch"/>

</LinearLayout>

activity_switch.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:background="#ffffff"
    android:orientation="vertical" >

    <Button 
        android:id="@+id/btnToggleActivity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/string_btn_goback"
        />

</LinearLayout>

Answer 1

"But problem starts when my Timer is ON and I switch to other activity and then again come back to Toggle activity"...

You DO not come back. As @Fabin Paul mentioned you just create a new instance of ToggleActivity. So in the scenario when you launch the app, then move to SwitchActivity and back by clicking the button, the back stack looks as follows:

ToggleActivity(1) -> SwitchActivity -> ToggleActivity(2)

"...and then do changes in toggle state from ON to OFF - it still runs Timer..."

You switch off the timer of the second instance of ToggleActivity. The one that is running belongs to the first ToggleActivity's instance.

"when I use finish(); or back press, in place of Intent to come back to ToggleActivity everything works fine..."

Yes, it does, because you don't create the second instance of ToggleActivity and your logic works correctly.

The easiest way to get the desired behavior is to add android:launchMode="singleInstance" to the ToggleActivity's tag of the manifest.