Override back button to act like home button

Question

On pressing the back button  I d like my application to go into the stopped state  rather than the destroyed state   In the Android docs it states         not all activities have the behavior that they are destroyed when BACK is pressed  When the user starts playing music in the Music application and then presses BACK  the application overrides the normal back behavior  preventing the player activity from being destroyed  and continues playing music  even though its activity is no longer visible   How do I replicate this functionality in my own application   I think there must be three possibilities      Capture the back button press  as below  and then call whatever method s  the home button calls      Override public boolean onKeyDown int keyCode  KeyEvent event        if   keyCode    KeyEvent KEYCODE BACK             Log d this getClass   getName     back button pressed              return super onKeyDown keyCode  event      Capture the back button press and then spoof a home button press    Capture the back button press  then start an Activity of the home screen  effectively putting my application s Activity into the stopped state    Edit  I know about services and am using one in the application to which this problem is related  This question is specifically about putting the Activity into the stopped state rather than the destroyed state on pressing the back button

User · Accepted Answer

Most of the time you need to create a Service to perform something in the background, and your visible Activity simply controls this Service. (I'm sure the Music player works in the same way, so the example in the docs seems a bit misleading.) If that's the case, then your Activity can finish as usual and the Service will still be running.

A simpler approach is to capture the Back button press and call moveTaskToBack(true) as follows:

// 2.0 and above
@Override
public void onBackPressed() {
    moveTaskToBack(true);
}

// Before 2.0
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        moveTaskToBack(true);
        return true;
    }
    return super.onKeyDown(keyCode, event);
}

I think the preferred option should be for an Activity to finish normally and be able to recreate itself e.g. reading the current state from a Service if needed. But moveTaskToBack can be used as a quick alternative on occasion.

NOTE: as pointed out by Dave below Android 2.0 introduced a new onBackPressed method, and these recommendations on how to handle the Back button.

User · Answer

try to override void onBackPressed   defined in android app Activity class

User · Answer

Override onBackPressed   after android 2 0  Such as    Override public void onBackPressed         moveTaskToBack true

User · Answer

If you want to catch the Back Button have a look at this post on the Android Developer Blog   It covers the easier way to do this in Android 2 0 and the best way to do this for an application that runs on 1 x and 2 0   However  if your Activity is Stopped it still may be killed depending on memory availability on the device   If you want a process to run with no UI you should create a Service  The documentation says the following about Services      A service doesn t have a visual user interface  but rather runs in the background for an indefinite period of time  For example  a service might play background music as the user attends to other matters  or it might fetch data over the network or calculate something and provide the result to activities that need it    These seems appropriate for your requirements

User · Answer

I have use  Mirko N  answser using made the new Custom EditText   public class EditViewCustom extends EditText        Button cancelBtn      RelativeLayout titleReleLayout      public EditViewCustom Context context  AttributeSet attrs  int defStyle            super context  attrs  defStyle              public EditViewCustom Context context  AttributeSet attrs            super context  attrs              public EditViewCustom Context context            super context              public void setViews Button cancelBtn RelativeLayout titleReleLayout           this cancelBtn   cancelBtn          this titleReleLayout   titleReleLayout              Override     public boolean onKeyPreIme int keyCode  KeyEvent event            if  event getKeyCode      KeyEvent KEYCODE BACK                Log d  KEYCODE BACK   KEYCODE BACK                cancelBtn setVisibility View GONE               this setFocusableInTouchMode false               this setFocusable false               titleReleLayout setVisibility View VISIBLE                return super onKeyPreIme keyCode  event                        return super onKeyPreIme keyCode  event              Then set data from your activity   searchEditView setViews cancelBtn  titleRelativeLayout     Thank you

User · Answer

Working example    Make sure don t call super onBackPressed      Override public void onBackPressed        Log d  CDA    onBackPressed Called       Intent setIntent   new Intent Intent ACTION MAIN      setIntent addCategory Intent CATEGORY HOME      setIntent setFlags Intent FLAG ACTIVITY NEW TASK      startActivity setIntent       In this way your Back Button act like Home button   It doesn t finishes your activity but take it to background  Second way is to call  moveTaskToBack true   in onBackPressed and be sure to remove super onBackPressed

User · Answer

if it helps someone else  I had an activity with 2 layouts that I toggled on and off for visibilty  trying to emulate a kind of page1   page2 structure  if they were on page 2 and pressed the back button I wanted them to go back to page 1  if they pressed the back button on page 1 it should still work as normal  Its pretty basic but it works   Override public void onBackPressed        check if page 2 is open     RelativeLayout page2layout    RelativeLayout findViewById R id page2layout       if page2layout getVisibility      View VISIBLE           togglePageLayout       my method to toggle the views         return       else          super onBackPressed       allows standard use of backbutton for page 1            hope it helps someone  cheers

User · Answer

Use the following code   public void onBackPressed             Intent intent   new Intent        intent setAction Intent ACTION MAIN       intent addCategory Intent CATEGORY HOME       startActivity intent

User · Answer

I ve tried all the above solutions  but none of them worked for me  The following code helped me  when trying to return to MainActivity in a way that onCreate gets called   Intent FLAG ACTIVITY CLEAR TOP is the key      Override   public void onBackPressed           Intent intent   new Intent this  MainActivity class         intent setFlags Intent FLAG ACTIVITY NEW TASK   Intent FLAG ACTIVITY CLEAR TOP         startActivity intent

User · Answer

Even better  how about OnPause      Called as part of the activity lifecycle when an activity is going into the background  but has not  yet  been killed  The counterpart to onResume     When activity B is launched in front of activity A  this callback will be invoked on A  B will not be created until A s onPause   returns  so be sure toenter code here not do anything lengthy here   This callback is mostly used for saving any persistent state the activity is editing and making sure nothing is lost if there are not enough resources to start the new activity without first killing this one    This is also a good place to do things like stop animations and other things that consume a noticeable amount of CPU in order to make the switch to the next activity as fast as possible  or to close resources that are exclusive access such as the camera

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