I have added an onDestroy in my Main activity
#Override
protected void onDestroy() {
if (BTAdapter.isEnabled()) {
BTAdapter.disable();
}
this.unregisterReceiver(receiver);
super.onDestroy();
}
In my Main Activity I start another activity through Navigation Drawer
if (id == R.id.nav_devices) {
intent = new Intent("com.navigationwithrssi.RSSIActivity");
startActivity(intent);
}
But when I come back to my Main Activity (using the default back button in Toolbar), the RSSIActivity automatically disables Bluetooth Adapter.
I just want my Main Activity to be able to do that, is there any way to do that?
I got my problem fixed. It was actually pretty easy, on the tutorial about Providing Up Navigation on developer.android.com
I just put this code in my onOptionsItemSelected method
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
Also I made the launch mode of my Parent Activity as <singleTop>
android:launchMode="singleTop"
What it does is rather than creating a new instance of your parent activity, it just brings it to the top of the stack.
Related
I just started android programming and I created 3 activities.A button in each activity will open another.I can navigate from my 2nd activity back to my first but I can't navigate from my third activity back to my second.Here's what I tried but the app crashes when I click on the back button. I guess it's trying to jump from the third activity to the second. If it helps my second activity's java file is called CountryDetails.java
public class WikiPage extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_web);
getSupportActionBar().setTitle(R.string.title_activity_wikipedia_details);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
}
Simply call onBackPressed() instead of NavUtils.navigateUpFromSameTask(this)
Remove NavUtils.navigateUpFromSameTask(this);
You should use onBackPressed() only.
Called when the activity has detected the user's press of the back
key. The default implementation simply finishes the current activity,
but you can override this to do whatever you want.
case android.R.id.home:
onBackPressed();
return true;
Use onBackPressed() instead of NavUtils.navigateUpFromSameTask(this) for activity backstake manage
I've a Preference activity for a options menu in my Android app.
I've enabled the Up \ Back navigation on the ActionBar and I need to come back to the previous activity that called the Options menu.
For the Preference activity, I could use in the manifest:
android:parentActivityName="mypackage.com.MainActivity"
but how come back to other activies ? The Options menu is called from 4 different activities.
public class Prefs extends PreferenceActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
ActionBar actionBar = getActionBar();
// Enabling Up / Back navigation
actionBar.setDisplayHomeAsUpEnabled(true);
}
}
Make sure that you have declared the parent activity in the manifest like this...
<activity
android:name="com.myapp.SetPreferenceActivity"
android:parentActivityName="com.myapp.MainActivity"
>
and then make sure to add the case into your onOptionsItemSelected method...
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
//Take me back to the main activity
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
if you prefer to have the up button point to a custom activity, you can just use an intent.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
Intent changeActivity = new Intent(this,OtherActivity.class);
startActivity(changeActivity);
return true;
}
return super.onOptionsItemSelected(item);
}
The default behaviour of the Back button is that it will get you back to the calling activity. The system maintains a back stack of activities while the user navigates the application. Do you need to override this functionality? Please be more specific.
Solved in this way:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
}
return true;
}
Activity A ===click button===> Activity B
When press back button, Activity A is not recreated.
When press home as up button, Activity A is recreated.
So I save state when A.onSaveInstanceState(Bundle outState)
, and use state when A.onRestoreInstanceState(Bundle savedInstanceState).
Saving and Using works fine (except home as up button)
.
However,
When pressed home as up button,
system recreate Activity A, and savedInstanceState is gone.
How can I use Saved Instance State?
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// I do not want this...
// Home as up button is to navigate to Home-Activity not previous acitivity
super.onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}
In the onCreate() enable the home button.
#Override
public void onCreate(Bundle savedInstanceState) {
...
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
In the onOptionItemSelected() method do this.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
This should enable Up navigation. If you want the parent activity to be restored with a savedInstanceState. You should set launchMode="singleTop" in the parent activity in Manifest file.
For more info check out http://developer.android.com/: Providing Up Navigation
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
I used finish() insteed of NavUtils;
As #Joachim mentioned in a comment, there is a difference between R.id.home and android.R.id.home. In my case, I have been using R.id.home, which did not work, and android.R.id.home did work.
I am seeing the up caret but nothing happens when I click it. Where do i tell it to goto home and set which activity is Home?
You need the line:
getActionBar().setDisplayHomeAsUpEnabled(true);
put that in onCreate();
That will make it clickable. The you will need to handle the click event. This is done by overriding onOptionsItemSelected()
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
default:
return super.onOptionsItemSelected(item);
}
}
If you want to use NavUtils, (which I have seen used by the ADT plugin when it makes Activities) you can replace change the implementation like so:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
NavUtils.navigateUpFromSameTask(this);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
Don't forget to
import android.support.v4.app.NavUtils;
Also, you can add this to your Activity node:
<activity
android:name=".SomeActivity"
android:label="#string/activity_label" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.mypackage.MainActivity" />
</activity>
NavUtils is usually the better approach. For more information, see the official Android Guidelines.
In your onCreate you have:
getActionBar().setDisplayHomeAsUpEnabled(true);
And then use:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
Updated to address comments below, which correctly point out my original answer was not correct for all cases. The "home/up" button have are supposed to take you the Home Activity or the Parent Activity, respectively. From the ActionBar documents --
By default, your application icon appears in the action bar on the
left side. If you'd like, you can enable the icon to behave as an
action item. In response to user action on the icon, your application
should do one of two things:
Go to the application "home" activity, or
Navigate "up" the application's structural hierarchy
Implementing "Home" is straightforward. Launch an intent to the home activity (usually your main launch activity) of your app, clearing the backstack to the existing instance if one exists--
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
Intent intent = new Intent(this, HomeActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
"up" is similar, except you should use
getActionBar().setDisplayHomeAsUpEnabled(true);
in your onCreate to get the icon to show as "up" instead of "home", and launch an instance of the parent activity.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
Intent parentActivityIntent = new Intent(this, MyParentActivity.class);
parentActivityIntent.addFlags(
Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(parentActivityIntent);
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
In both case, for Activities that can be launched from outside your application, you should add FLAG_ACTIVITY_NEW_TASK to launch into a new task instead of the callers task.
"Up" can get more complicated if your Activity can be launched from another app, and want to build a back stack for your application to get back to the root. See for this guide for more info.
My original answer, shown below, is considered bad form in the guide because it it treats the home/up button as 'back'. It will take you to the activity that invoked this activity, which is not necessarily the home or parent. It works well as 'up' for apps that have strict tree hierarchy of activities because an given activity was always launched by its parent.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
I'm using the Actionbar and it's "up" button to return from a detail activity to the main activity, which works fine. Similarly, the user can press the system "back" button to return to the main activity.
In my main activity, in onCreate() data is downloaded from the internet to display upon app start. I noticed that when I use the Actionbar "up" button to go from detail to main activity, onCreate() is run, re-downloading the data. But onCreate() is not run when I use the system "back" button, therefore immediately showing the main activity view.
The code I use in the detail activity to implement the "up" button is:
switch (item.getItemId()) {
case android.R.id.home:
Intent intent = new Intent(this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
return true;
I would like the "up" button to behave like the "back" button and not rerun onCreate(). But I'm unsure how to make this happen, or which code path the "back" button implements to return to the main activity.
Thanks!
Instead of starting a whole new activity simply finish the details activity you are in
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
Then you will return to the previous activity on the activity stack (your main activity) and onCreate shouldn't be called
If you want Up to do exactly what Back does, you can do this:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
default:
break;
}
return super.onOptionsItemSelected(item);
}
Note that the default implementation of onBackPressed() just calls finish(), but onBackPressed can be overridden.
I think a better solution can be found in this post.
Calling finish() works in specific situations but may not always produce the behavior described in the documentation e.g:
By calling
Intent intent = NavUtils.getParentActivityIntent(this);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
NavUtils.navigateUpTo(this, intent);
you'll return to the parent activity in the state in which you left it. If you have a flat app structure, it'll still act just like the Back button.
for a real "home" functionality , you should see the api demos ,under "App/Activity/Reorder Activities" .
the reason : what if you have something like this : activity1->activity2->activity3 , and now you wish to go to activity1 by pressing the home button on the action bar?
I believe the simplest way is to override the "getParentActivityIntent" method of the detail activity adding the flag "Intent.FLAG_ACTIVITY_CLEAR_TOP":
#Nullable
#Override
public Intent getParentActivityIntent() {
Intent intent = super.getParentActivityIntent();
if (intent != null) {
return super.getParentActivityIntent().addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
}
return intent;
}
There is another solution which can be in hand for somebody. I had the same double-behavior when user pressed Back and ActionbarBack buttons. I was fine with Back btn behaviour. I didn't want an activity to be recreated. So I overrode the method
#Override
public boolean onSupportNavigateUp() {
onBackPressed();
return true;
}
Works fine for me