Develop Reference

Back button stuck in endless loop?

My app is currently stuck in an endless loop with the physical back button. The program is set up to load a splash screen and then transition to a main menu. Once at the main menu the user can switch to another activity of their choice. For example: The new game activity. Once the user is at the new game activity I want them to be able to hit the back button and have it take them to the main menu. Once back at the main menu, if they hit the back button again I would like it to exit the game.
This is what I am using for each activity:
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
startActivity(new Intent(NewGameActivity.this, MenuActivity.class));
}
return super.onKeyDown(keyCode, event);
}
It works properly and takes the user back to the main menu without a problem. But if the user hits the back button again once at the main menu it will take them to the screen they just escaped from. So it just loops back to the previous screen every time.
This is how the main menu is set up:
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
stopService(new Intent(MenuActivity.this, BGMusicService.class));
MenuActivity.this.finish();
}
return super.onKeyDown(keyCode, event);
}
If I press the back button as soon as the main menu loads the first time it will work properly and close the game. It only messes up if I've hit the back button previously to get from one screen to the main menu.
Update:
Okay that kind of worked. When I hit the back button at the main screen the music stops and it acts like it's trying to close the app but it flashes back to the main screen again. I have to hit it twice every time.

You should call finish() inside the onKeyDown method of your activities so your current activity is actually removed from the stack.
Something like this should work:
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_BACK)
{
startActivity(new Intent(NewGameActivity.this, MenuActivity.class));
finish();
}
return super.onKeyDown(keyCode, event);
}

First (from comments) add return true; within the if statements (to indicate that you have handled the event), like so:
// Main menu code
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
stopService(new Intent(MenuActivity.this, BGMusicService.class));
MenuActivity.this.finish();
return true; // Add me!
}
return super.onKeyDown(keyCode, event);
}
Additionally, I believe because you're "starting" the menu activity again, you have to clear the back stack (the order of activities used so far) before opening it. You should be able to achieve this using Intent.FLAG_ACTIVITY_CLEAR_TOP (or maybe Intent.FLAG_ACTIVITY_CLEAR_TASK). Something like this:
// Other activity code
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
Intent menuIntent = new Intent(NewGameActivity.this, MenuActivity.class);
menuIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); // Add me!
startActivity(menuIntent);
return true; // Add me, too!
}
return super.onKeyDown(keyCode, event);
}

You haven't called finish() in your other activities so when you call finish() on the menu it just closes itself and the other activity is exposed

Navigation inside tab in android

I have a tab activity, which contains 4 tabs and each one contain activities. In the fourth tab i have got a list activity. it will list a number of options. when we click and option it will go to another activity. and when i press back button from that activity the application exits. But actually i want to go back to the list of options.
Can any body help me to get rid of this
Regards
Pramod

Override the back button with this code
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
//Enter code here telling it what you want to do when you hit back
return true;
}
return super.onKeyDown(keyCode, event);
}
Hope that helps!!

Override the onPause() of the Activity you mentioned above "when we click and option it will go to another activity" to go to the Activity of the Tab containing the options via Intent with its class.

Use getParent() to the activity & use the below to so that you will be able add up view by clearing up existing views & adding new views to the top.
Window window = getLocalActivityManager().startActivity(Id,intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));

All the tabs reside inside the activity, so when the backkey has been pressed the complete activity goes into background, so if you want to navigate to a particular activity override the onkeydown method and navigate to the particular tab
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
MyActivity mMyActivity;
mMyActivity = (MyActivity) this.getParent();
mMyActivity.switchTab(tabnumber);
return true;
}
return super.onKeyDown(keyCode, event); }

Android Home button click ignoring saved state?

Can I ignore the previous stage of application after tapping Home button in android?
So that I can get the application from initial screen.

Use like this.If now you are in LastActivity and you want to go back to the First Activity and there is more activity in between then if you want to go first from last use
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(autoSearch)
if (keyCode == KeyEvent.KEYCODE_HOME) {
Log.d("click","HOMEButtonclicked");
LastActivity.this.startActivity(new Intent(LastActivity.this, FirstActivity.class));
moveTaskToBack(false);
return true;
}
return super.onKeyDown(keyCode, event);
}

Opening softkeyboard again when entering activity from back button

I use android:windowSoftInputMode="stateVisible|adjustPan" in my manifest file to open the softkeyboard when the main activity is launched.
This works great, apart from when i come back to the main activity from another using the back button; The softkeyboard does not reappear.
How do i make the softkeyboard appear when coming back to the main activity?
Thanks for any help in advance.

On back button it just remove the current activity from the stack and show the previous activity that is why softkeyboard is not getting opened . you can override the onKeyDown() method and on back button you can call your activity again.
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
// start your activity again here
Log.d(this.getClass().getName(), "back button pressed");
}
return super.onKeyDown(keyCode, event);
}

What is the command to return to your main screen in an app?

How do I have an app return to the 'Home' screen when the user is on a different class and they click the back/return button on their phone?
Right now, when they access a different class and hit the back button, it goes back to the Home screen on the Droid rather than the Home screen on the app - how do I get it to go back to the Home Screen on the app?
Thanks!

Use OnBackPressed() method of Activity class.
Make conditions like :
public void onBackPressed(){
if(conditon)
{
detailInfoList.setVisibility(View.VISIBLE);//or anything that you want to show
}
}

you can't,
the home button is the only you can't prevent form closing your app. Its done so that you can't block the user inside your applications (like a virus).
the other keys like back menu and research are possible
in your activity
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(event.getAction() == MotionEvent.ACTION_DOWN){
if(keyCode == 82){
Log.i("jason","released on menu");
//change view
//return so that the other behavior (leaving the activity) is not tirggered
return false;
}
}
Log.i("jason","actual key code "+keyCode);
return super.onKeyDown(keyCode, event);
}