I have an alarm clock application, and I've just added code to exit the program when using the Back button from the main activity. However, when I do so, the last action the user took is undone. For example, if the user creates three alarms, then presses the back button, only two alarms will show up.
This is the Back button code, from Main Activity:
@Override
public void onBackPressed() {
moveTaskToBack(true);
android.os.Process.killProcess(android.os.Process.myPid());
System.exit(1);
}
And just in case, here's all the code from both activities I'm testing:
MainActivity.java (The only activity that has this Back button functionality, deliberately)
public class MainActivity extends AppCompatActivity {
ListView alarmListView;
ArrayList<Alarm> alarmList = new ArrayList<Alarm>();
AlarmAdapter alarmAdapter;
String filename = "alarmList";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
alarmListView = findViewById(R.id.alarmListView);
// Credit to Mitch Woodbright for helping with this section, and other try/catch blocks.
try
{
ArrayList<Alarm> alarm = (ArrayList<Alarm>) getIntent().getSerializableExtra("alarmList");
for(Alarm elements : alarm){
alarmList.add(elements);
}
writeAlarmList(alarmList);
}
catch (NullPointerException e){
System.out.println("AlarmList is empty.");
}
try {
alarmList = readAlarmList();
}
catch (NullPointerException e) {
}
alarmAdapter = new AlarmAdapter(MainActivity.this, alarmList){
@Override
public void onUpdateClick(int position, ArrayList<Alarm> alarmList) {
super.onUpdateClick(position, alarmList);
Intent updateAlarmIntent = new Intent(MainActivity.this,
CreateAlarmActivity.class);
updateAlarmIntent.putExtra("alarmList", alarmList);
updateAlarmIntent.putExtra("position", position);
startActivity(updateAlarmIntent);
}
};
alarmListView.setAdapter(alarmAdapter);
alarmAdapter.notifyDataSetChanged();
alarmListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent updateAlarmIntent = new Intent(MainActivity.this, CreateAlarmActivity.class);
updateAlarmIntent.putExtra("alarmList", alarmList);
updateAlarmIntent.putExtra("position", position);
startActivity(updateAlarmIntent);
}
});
// writeAlarmList(alarmList);
}
protected void onStart() {
super.onStart();
alarmList = readAlarmList();
}
protected void onResume() {
super.onResume();
alarmList = readAlarmList();
}
protected void onPause() {
super.onPause();
writeAlarmList(alarmList);
}
protected void onStop() {
super.onStop();
writeAlarmList(alarmList);
}
@Override
public void onBackPressed() {
// Thanks to Mitch for this line.
moveTaskToBack(true);
android.os.Process.killProcess(android.os.Process.myPid());
System.exit(1);
}
// Create alarm when user presses FAB on activity_main.xml.
public void createNewAlarm(View view) {
Intent createAlarmIntent = new Intent(this, CreateAlarmActivity.class);
createAlarmIntent.putExtra("alarmList", alarmList);
startActivity(createAlarmIntent);
}
public void testAlarmActivated(View view){
//Intent activateAlarmIntent = new Intent(this, AlarmActivatedActivity.class);
//startActivity(activateAlarmIntent);
while(alarmList.size() > 0){
alarmList.remove(0);
}
Intent deleteEverythingIntent = new Intent(MainActivity.this, MainActivity.class);
deleteEverythingIntent.putExtra("alarmList", alarmList);
startActivity(deleteEverythingIntent);
}
public void writeAlarmList(ArrayList<Alarm> alarmList){
try {
FileOutputStream fos = openFileOutput(filename, Context.MODE_PRIVATE);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(alarmList);
oos.close();
}
catch (FileNotFoundException e){
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
}
public ArrayList<Alarm> readAlarmList(){
try {
FileInputStream fis = openFileInput(filename);
ObjectInputStream ois = new ObjectInputStream(fis);
ArrayList<Alarm> alarmList = (ArrayList<Alarm>) ois.readObject();
ois.close();
return alarmList;
}
catch (FileNotFoundException e) {
ArrayList<Alarm> alarmList = new ArrayList<Alarm>();
System.out.println("File not found. Making empty list.");
return alarmList;
}
catch (IOException e) {
e.printStackTrace();
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
catch (NullPointerException e) {
ArrayList<Alarm> alarmList = new ArrayList<Alarm>();
System.out.println("Null pointer exception. Making empty list.");
return alarmList;
}
ArrayList<Alarm> alarmList = new ArrayList<Alarm>();
return alarmList;
}
}
CreateAlarmActivity.java (The activity which does the creating/updating/deleting of alarms)
public class CreateAlarmActivity extends AppCompatActivity {
// If the alarm is being created, position = -1.
int position = -1;
int alarmHour;
int alarmMinute;
boolean isPm;
int snoozeTimer;
int[] daysActive;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_create_alarm);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
alarmList = (ArrayList<Alarm>)getIntent().getSerializableExtra("alarmList");
try {
// If we're updating an alarm, return the position of the alarm to update.
position = (int)getIntent().getSerializableExtra("position");
}
// Else, keep going.
catch (NullPointerException e){
}
Button hourButton = findViewById(R.id.buttonHours);
Button minuteButton = findViewById(R.id.buttonMinutes);
Button isPmButton = findViewById(R.id.buttonAmPm);
Button snoozeTimerButton = findViewById(R.id.buttonSnoozeTimer);
Button sundayButton = findViewById(R.id.buttonSunday);
Button mondayButton = findViewById(R.id.buttonMonday);
Button tuesdayButton = findViewById(R.id.buttonTuesday);
Button wednesdayButton = findViewById(R.id.buttonWednesday);
Button thursdayButton = findViewById(R.id.buttonThursday);
Button fridayButton = findViewById(R.id.buttonFriday);
Button saturdayButton = findViewById(R.id.buttonSaturday);
// If creating a new alarm, initialise data as default.
if (position == -1){
alarmHour = 6;
alarmMinute = 0;
isPm = false;
snoozeTimer = 10;
daysActive = new int[] {0, 0, 0, 0, 0, 0, 0};
}
// If updating an alarm, grab the defaults we already had.
else {
Alarm tempAlarm = alarmList.get(position);
alarmHour = tempAlarm.hour;
alarmMinute = tempAlarm.minute;
isPm = tempAlarm.isPm;
snoozeTimer = tempAlarm.snoozeTimer;
daysActive = tempAlarm.daysActive;
}
// Set buttons to what they should be.
hourButton.setText(Integer.toString(alarmHour));
snoozeTimerButton.setText(Integer.toString(snoozeTimer));
if (alarmMinute < 10){
minuteButton.setText("0" + Integer.toString(alarmMinute));
}
else {
minuteButton.setText(Integer.toString(alarmMinute));
}
if (!isPm){
isPmButton.setText("am");
}
else {
isPmButton.setText("pm");
}
setDayColor(sundayButton, daysActive[0]);
setDayColor(mondayButton, daysActive[1]);
setDayColor(tuesdayButton, daysActive[2]);
setDayColor(wednesdayButton, daysActive[3]);
setDayColor(thursdayButton, daysActive[4]);
setDayColor(fridayButton, daysActive[5]);
setDayColor(saturdayButton, daysActive[6]);
}
ArrayList<Alarm> alarmList = new ArrayList<Alarm>();
// Add one to the hour of the alarm.
public void changeHour(View view) {
Button btn = findViewById(R.id.buttonHours);
if (alarmHour == 12){
alarmHour = 0;
}
else {
alarmHour++;
}
btn.setText(Integer.toString(alarmHour));
}
// Add one to the minute of the alarm.
public void changeMinute(View view) {
Button btn = findViewById(R.id.buttonMinutes);
if (alarmMinute == 59) {
alarmMinute = 0;
}
else {
alarmMinute++;
}
if (alarmMinute < 10) {
// Ensure minute 1 becomes 01, e.g, 6:01 am.
btn.setText("0" + Integer.toString(alarmMinute));
}
else {
btn.setText(Integer.toString(alarmMinute));
}
}
public void changeAmPm(View view) {
Button btn = findViewById(R.id.buttonAmPm);
if (isPm == true) {
isPm = false;
btn.setText("am");
}
else {
isPm = true;
btn.setText("pm");
}
}
public void changeSnoozeTimer(View view) {
Button btn = findViewById(R.id.buttonSnoozeTimer);
if (snoozeTimer == 15){
snoozeTimer = 1;
}
else {
snoozeTimer++;
}
btn.setText(Integer.toString(snoozeTimer));
}
public void finishAlarm(View view){
EditText alarmName = findViewById(R.id.alarmName);
String name = alarmName.getText().toString();
Alarm alarm = new Alarm(name, alarmHour, alarmMinute, isPm, daysActive, snoozeTimer);
// If we're creating an alarm.
if (position == -1) {
try {
alarmList.add(alarm);
} catch (Exception e) {
}
}
// Else, we're updating one.
else {
try {
// Set the alarm we're updating to the new alarm.
alarmList.set(position, alarm);
} catch (Exception e) {
}
}
Intent finishAlarmIntent = new Intent(this, MainActivity.class);
finishAlarmIntent.putExtra("alarmList", alarmList);
startActivity(finishAlarmIntent);
}
public void cancelAlarm(View view){
Intent cancelAlarmIntent = new Intent(this, MainActivity.class);
cancelAlarmIntent.putExtra("alarmList", alarmList);
startActivity(cancelAlarmIntent);
}
public void deleteAlarm(View view) {
// If creating a new alarm, deleting is the same as cancelling.
if (position == -1) {
Intent cancelAlarmIntent = new Intent(this, MainActivity.class);
cancelAlarmIntent.putExtra("alarmList", alarmList);
startActivity(cancelAlarmIntent);
}
else {
// Remove the alarm.
alarmList.remove(position);
Intent cancelAlarmIntent = new Intent(this, MainActivity.class);
cancelAlarmIntent.putExtra("alarmList", alarmList);
startActivity(cancelAlarmIntent);
}
}
public void changeSunday(View view) {
Button btn = findViewById(R.id.buttonSunday);
daysActive[0] = switchDay(daysActive[0]);
setDayColor(btn, daysActive[0]);
}
public void changeMonday(View view) {
Button btn = findViewById(R.id.buttonMonday);
daysActive[1] = switchDay(daysActive[1]);
setDayColor(btn, daysActive[1]);
}
public void changeTuesday(View view) {
Button btn = findViewById(R.id.buttonTuesday);
daysActive[2] = switchDay(daysActive[2]);
setDayColor(btn, daysActive[2]);
}
public void changeWednesday(View view) {
Button btn = findViewById(R.id.buttonWednesday);
daysActive[3] = switchDay(daysActive[3]);
setDayColor(btn, daysActive[3]);
}
public void changeThursday(View view) {
Button btn = findViewById(R.id.buttonThursday);
daysActive[4] = switchDay(daysActive[4]);
setDayColor(btn, daysActive[4]);
}
public void changeFriday(View view) {
Button btn = findViewById(R.id.buttonFriday);
daysActive[5] = switchDay(daysActive[5]);
setDayColor(btn, daysActive[5]);
}
public void changeSaturday(View view) {
Button btn = findViewById(R.id.buttonSaturday);
daysActive[6] = switchDay(daysActive[6]);
setDayColor(btn, daysActive[6]);
}
// Helper method to switch the daysActive from 0 to 1 or from 1 to 0.
public int switchDay(int day) {
if (day == 0){
return 1;
}
return 0;
}
// Helper method to set the color of a daysActive button when updating the alarm.
public void setDayColor(Button btn, int day) {
if (day == 1) {
// Source: https://stackoverflow.com/questions/2173936/how-to-set-background-color-of-a-view
// Credit goes to EddieB for the below line.
btn.getBackground().setColorFilter(Color.parseColor("#00ff00"), PorterDuff.Mode.DARKEN);
} else {
// Source: https://stackoverflow.com/questions/14802354/how-to-reset-a-buttons-background-color-to-default
// Credit goes to Ivo for the below line.
btn.getBackground().clearColorFilter();
}
}
}
