I would like to check programmatically whether an sd card is installed, and if yes, give the user the choice to switch between external and internal storage.
I have my other static settings organized inside a preferences.xml.
It seems that I have to rewrite all the settings of the xml file in code if I start to work with preferences more dynamically.
Or is there an option to enhance the preferences from the xml with preferences from code which get used just once needed?
Thanks
Add this to manifest for install app on sd card if is possible:
android:installLocation="preferExternal">
To verify is sd card writable and readable use this method:
private boolean isExternalStorageWritable() {
return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);}
To get folder of appfiles on sdCard (externalStorageVolumes[0] is primary folder):
File[] externalStorageVolumes =
ContextCompat.getExternalFilesDirs(getApplicationContext(), null);
Oficial documentation
I found out myself, it looks a bit clumsy, but it works.
Once again: My problem is that I have certain setting options pre configured in an xml file as described here:
Preferences with XML
Here is my preferences.xml:
<PreferenceScreen xmlns:app="http://schemas.android.com/apk/res-auto">
<PreferenceCategory app:title="#string/download_header">
<SwitchPreferenceCompat
app:key="dl_background"
app:title="#string/background_behaviour"
app:defaultValue="false"/>
<ListPreference
app:title="#string/dl_qual"
app:defaultValue="#string/low_qual"
app:key="dl_qual"
app:entries="#array/dl_qual_arry"
app:entryValues="#array/dl_qual_arry"/>
</PreferenceCategory>
<PreferenceCategory app:title="#string/tc_header">
<SwitchPreferenceCompat
app:key="tc_installed"
app:title="#string/tc_behaviour"
app:defaultValue="false"/>
<ListPreference
app:title="#string/dl_dir_root"
app:key="dl_dir_root"/>
</PreferenceCategory>
</PreferenceScreen>
Here you can define arrays which map to ListPrefrence objects.
Each option list is then populated from a resource xml file holding the actual list entries.
I used this approach for the first ListPreference "dl_qual" above.
This is the resource.xml file:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string-array name="dl_qual_arry">
<item>Higher quality (128kbps)</item>
<item>Lower quality (64kbps)</item>
</string-array>
</resources>
But then I had the idea to insert a ListPreference where the values of the options list are only known at runtime.
This is my second ListPreference above "dl_dir_root".
I was too lazy to rewrite (and read how to do it in advance) the complete settings activity from code.
So I ended up with this SettingsFragment inside my SettingsActivity:
public static class SettingsFragment extends PreferenceFragmentCompat {
#Override
public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
//First, lets check whether we have initialized preferences already
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getContext());
String selectedDir = prefs.getString("dl_dir_root", "INIT");
setPreferencesFromResource(R.xml.root_preferences, rootKey);
PreferenceScreen root = getPreferenceScreen();
ListPreference dlDirRoot = root.findPreference("dl_dir_root");
CharSequence[] arryValues = BBCWorldServiceDownloaderUtils.getStoragePaths(getContext());
CharSequence[] arryEntrys = BBCWorldServiceDownloaderUtils.getStoragePaths(getContext());
dlDirRoot.setEntries(arryEntrys);
dlDirRoot.setEntryValues(arryValues);
if(selectedDir.equals("INIT")) {
//Initialize value/index
dlDirRoot.setDefaultValue(arryValues[0]);
dlDirRoot.setValueIndex(0);
}
else{
//Position at already selected value/index
dlDirRoot.setDefaultValue(selectedDir);
dlDirRoot.setValue(selectedDir);
dlDirRoot.setValueIndex(dlDirRoot.findIndexOfValue(selectedDir));
}
}
}
The pre defined xml is applied first, then the ListPreference object for "dl_dir_root" is acessed and the options are added:
ListPreference dlDirRoot = root.findPreference("dl_dir_root");
CharSequence[] arryValues = BBCWorldServiceDownloaderUtils.getStoragePaths(getContext());
CharSequence[] arryEntrys = BBCWorldServiceDownloaderUtils.getStoragePaths(getContext());
dlDirRoot.setEntries(arryEntrys);
dlDirRoot.setEntryValues(arryValues);
The rest is checking/keeping state between the calls to the activity.
If anyone knows of a more elegant way, I would be curious.
Best
Matthias
First of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, I'm a little frustrated)
Most of them come with the advice to use android:id instead of just id in the XML file. I did.
From others, I learned, that View.findViewById works different than Activity.findViewById. I handled that, too.
In my location_layout.xml, I use:
<FrameLayout .... >
<some.package.MyCustomView ... />
<LinearLayout ... >
<TextView ...
android:id="#+id/txtLat" />
...
</LinearLayout>
</FrameLayout>
In my Activity I do:
...
setContentView( R.layout.location_layout );
and in my custom view class:
...
TextView tv = (TextView) findViewById( R.id.txtLat );
which returns null. Doing this, my Activity works fine. So maybe it's because of the Activity.findViewById and View.findViewById differences. So I stored the context passed to the customs view constructor locally and tried:
...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );
which also returned null.
Then, I changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: it didn't solve anything.
So what the heck am I doing wrong?
I'll appreciate any comments.
which returns null
Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.
Possibly, you are calling findViewById before calling setContentView?
If that's the case, try calling findViewById AFTER calling setContentView
Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.
FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.
This would be wrong
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context);
}
This is correct
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context,attrs);
}
Alongside the classic causes, mentioned elsewhere:
Make sure you've called setContentView() before findViewById()
Make sure that the id you want is in the view or layout you've given to setContentView()
Make sure that the id isn't accidentally duplicated in different layouts
There is one I have found for custom views in standard layouts, which goes against the documentation:
In theory you can create a custom view and add it to a layout (see here). However, I have found that in such situations, sometimes the id attribute works for all the views in the layout except the custom ones. The solution I use is:
Replace each custom view with a FrameLayout with the same layout properties as you would like the custom view to have. Give it an appropriate id, say frame_for_custom_view.
In onCreate:
setContentView(R.layout.my_layout);
FrameView fv = findViewById(R.id.frame_for_custom_layout);
MyCustomView cv = new MyCustomView(context);
fv.addView(cv);
which puts the custom view in the frame.
In my case, I had 2 activites in my project, main.xml and main2.xml. From the beginning, main2 was a copy of main, and everything worked well, until I added new TextView to main2, so the R.id.textview1 became available for the rest of app. Then I tried to fetch it by standard calling:
TextView tv = (TextView) findViewById( R.id.textview1 );
and it was always null. It turned out, that in onCreate constructor I was instantiating not main2, but the other one. I had:
setContentView(R.layout.main);
instead of
setContentView(R.layout.main2);
I noticed this after I arrived here, on the site.
#Override
protected void onStart() {
// use findViewById() here instead of in onCreate()
}
A answer for those using ExpandableListView and run into this question based on it's title.
I had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.
You can use something like the following in your implementations of the getChildView() and getGroupView() methods.
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_layout, null);
}
I found this here.
FWIW, I don't see that anyone solved this in quite the same way as I needed to. No complaints at compile time, but I was getting a null view at runtime, and calling things in the proper order. That is,
findViewById()
after
setContentView().
The problem turned out that my view is defined in content_main.xml, but in my activity_main.xml, I lacked this one statement:
<include layout="#layout/content_main" />
When I added that to activity_main.xml, no more NullPointer.
I'm pretty new to Android/Eclipse, by mistake I added the UI stuff to activity_main.xml instead of fragment_main.xml. Took me some hours to figure that out...
I had this same problem. I was using a third-party library that allows you to override their adapter for a GridView and to specify your own layout for each GridView cell.
I finally realized what was happening. Eclipse was still using the library's layout xml file for each cell in the GridView, even though it gave no indication of this. In my custom adapter, it indicated that it was using the xml resource from my own project even though at runtime, it wasn't.
So what I did was to make sure my custom xml layouts and ids were different from those still sitting in the library, cleaned the project and then it started reading the correct custom layouts that were in my project.
In short, be careful if you're overriding a third-party library's adapter and specifying your own layout xml for the adapter to use. If your layout inside your project has the same file name as that in the library, you might encounter a really difficult-to-find bug!
In my particular case, I was trying to add a footer to a ListView. The following call in onCreate() was returning null.
TextView footerView = (TextView) placesListView.findViewById(R.id.footer);
Changing this to inflate the footer view instead of finding it by ID solved this issue.
View footerView = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.footer_view, null, false);
Just wanted to throw my specific case in here. Might help someone down the line.
I was using the directive in my Android UI XML like this:
Parent view:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:visibility="gone" />
Child view (retry_button):
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/retry"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
.findViewById(R.id.retry) would always return null. But, if I moved the ID from the child view into the include tag, it started working.
Fixed parent:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:id="#+id/retry"
android:visibility="gone" />
Fixed child:
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
In my case, I was using ExpandableListView and I had set android:transcriptMode="normal". This was causing few children in expandable group to disappear and I used to get NULL exception when ever I used scroll the list.
For me I had two xml layouts for the same activity - one in portrait mode and one in landscape. Of course I had changed the id of an object in the landscape xml but had forgotten to make the same change in the portrait version. Make sure if you change one you do the same to the other xml or you will not get an error until you run/debug it and it can't find the id you didn't change. Oh dumb mistakes, why must you punish me so?
Set the activity content from a layout resource.
ie.,setContentView(R.layout.basicXml);
In addition of the above solutions you make sure the
tools:context=".TakeMultipleImages"
in the layout is same value in the mainfest.xml file :
android:name=".TakeMultipleImages" for the same activity element.
it is occur when use copy and paste to create new activity
I have the same problem, but I think its worth sharing with you guys.
If you have to findViewById in custom layout, for example:
public class MiniPlayerControllBar extends LinearLayout {
//code
}
you cannot get the view in constructor.
You should call findViewById after view has inflated.
Their is a method you can override onFinishInflate
My case is none like above, no solutions worked. I assume my view was too deep into layout hierarchy. I moved it one level up and it was not null anymore.
INFLATE THE LAYOUT !! (which contains the id)
In my case findViewById() returned null, because the layout in which the element was written, was not inflated...
Eg.
fragment_layout.xml
<ListView
android:id="#+id/listview">
findViewById(R.id.listview) returned null, because I had not done
inflater.inflate(R.layout.fragment_layout, ..., ...);
before it.
Hope this answer helps some of y'all.
In my case I had inflated the layout but the child views were returning null. Originally I had this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) findViewById(R.id.pbListviewFooter);
tvText = (TextView) findViewById(R.id.tvListviewFooter);
...
}
However, when I changed it to the following it worked:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) footerView.findViewById(R.id.pbListviewFooter);
tvText = (TextView) footerView.findViewById(R.id.tvListviewFooter);
...
}
The key was to specifically reference the already inflated layout in order to get the child views. That is, to add footerView:
footerView.findViewById...
It crashed for me because one of fields in my activity id was matching with id in an other activity. I fixed it by giving a unique id.
In my loginActivity.xml password field id was "password". In my registration activity I just fixed it by giving id r_password, then it returned not null object:
password = (EditText)findViewById(R.id.r_password);
In my experience, it seems that this can also happen when your code is called after OnDestroyView (when the fragment is on the back stack.) If you are updating the UI on input from a BroadCastReceiver, you ought to check if this is the case.
findViewById also can return null if you're inside a Fragment. As described here: findViewById in Fragment
You should call getView() to return the top level View inside a Fragment. Then you can find the layout items (buttons, textviews, etc)
In my case, findViewById returned null when I moved the call from a parent object into an adapter object instantiated by the parent. After trying tricks listed here without success, I moved the findViewById back into the parent object and passed the result as a parameter during instantiation of the adapter object.
For example, I did this in parent object:
Spinner hdSpinner = (Spinner)view.findViewById(R.id.accountsSpinner);
Then I passed the hdSpinner as a parameter during creation of the adapter object:
mTransactionAdapter = new TransactionAdapter(getActivity(),
R.layout.transactions_list_item, null, from, to, 0, hdSpinner);
I was facing a similar problem when I was trying to do a custom view for a ListView.
I solved it simply by doing this:
public View getView(int i, View view, ViewGroup viewGroup) {
// Gets the inflater
LayoutInflater inflater = LayoutInflater.from(this.contexto);
// Inflates the layout
ConstraintLayout cl2 = (ConstraintLayout)
inflater.inflate(R.layout.custom_list_view, viewGroup, false);
//Insted of calling just findViewById, I call de cl2.findViewById method. cl2 is the layout I have just inflated.
TextView tv1 = (TextView)cl2.findViewById(cl2);
Ways to debug and find the issue:
Comment out all findViewById in your activity.
Comment out everything except onCreate and setContentView
Run the project and see if any layout is set
In my case, I was using activity_main.xml in both my app module and also my library module. So when I performed the above steps, instead of the layout which I designed in the library, the layout inside app module was inflated.
So I changed the activity_main.xml file name to activity_main_lib.xml.
So make sure you do not have any duplicate layout names in your whole project.
The issue for me was that I had two layouts with the same file name activity_main.xml. (The layouts were in different libraries but in the same app) The issue was solved by renaming one of them to a unique name.
For me it returned null because the given control was (programmatically) hidden. When I put a condition to call findViewByID(id) only when the control is visible, it started working again.
For me it was only null when using Evaluate Expression or the Debug Watch View of the IDE.
This is a scaled down version of the actual problem. To recreate the difficulty I am facing.
I have taken the example from the official website developer.android.com to cite my problem.
Building a Flexible UI
MainActivity has 2 layouts. One is for the default(portrait in small screen devices) layout in the layout folder. The other layout for both large-screen and landscape mode, kept in layout-large and layout-land folder.
Default layout for activity_main.xml contains only one FrameLayout (R.id.fragment_container) in which I add and replace 2 fragments that I create, dynamically.
The other layout is same for both the layout-land and layout-large folders. It has 2 static fragments [R.id.headlines_fragment - to display a list of headlines] and [R.id.article_fragment - to display the details when headlines are selected]. Horizontally placed. One on the left to show the lists and the one on the right to show details.
This is the code for MainActivity.java which controls all the fragments :
public class MainActivity extends Activity implements OnHeadLineSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.news_article);
if(findViewById(R.id.fragment_container) != null) {
if(savedInstanceState != null) {
return;
}
HeadlinesFragment firstFragment = new HeadlinesFragment();
firstFragment.setArguments(getIntent().getExtras());
getFragmentManager().beginTransaction().add(R.id.fragment_container, firstFragment).commit();
}
}
#Override
public void onArticleSelected(int position) {
ArticleFragment articleFrag = (ArticleFragment) getFragmentManager().findFragmentById(R.id.article_fragment);
if(articleFrag != null && articleFrag.isVisible()) {
articleFrag.updateArticleView(position);
} else {
articleFrag = new ArticleFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction().replace(R.id.fragment_container, articleFrag);
transaction.addToBackStack(null);
transaction.commit();
}
}
}
As soon as the activity is started, I check if fragment_container that is the FrameLayout is present or not. If it is not present, then the layout with the 2 fragments has been loaded. Hence no need to add the fragments dynamicaly as they are already present.
Otherwise, I check if the savedInstanceState is null or not. If null, then I create a new HeadlinesFragment and add it to the frame. If it is not null, then it means that the activity has already been created previously, and hence the HeadlinesFragment must have been added already. No need to add it again. So, return.
And onArticleSelected() method replaces the existing fragment in the frame with the ArticleFragment, or if in the other layout, it simply updates the fragment as it is already present. It is called from the HeadlinesFragment when an item is selected.
Now, this all works perfectly well if we enter the activity in portrait mode and then change the orientation. No problem. Flawless.
But if we enter the activity in the landscape mode, as soon as I change the orientation to the portrait mode, a blank screen is shown.
The reason being, the onCreate() is called, and the savedInstanceState returns as not null. Hence, the HeadlinesFragment is not created and added to the frame.
And yes, if I remove that check, then the app works fine, but that will mean that a new HeadlinesFragment is created and added to the frame each time and gets stacked on top of eachother. Which is not at all desirable.
I cannot implement this by just finding out the orientation and applying the appropriate layout. Because, in large-screen devices, even if it is in portrait mode, it is supposed to show both the fragments at once.
I have tried many convoluted logic. But nothing seems to work. Any help is appreciated.
Entering activity in portrait mode
1> List Items are shown.
2> Clicking items replaces the fragment with the ArticleFragment (details).
3> Changing the orientation, shows both side by side. Everything works.
--->
Entering activity in landscape mode
1> Both the list and details are shown. Everything works.
2> But as soon as the orientation changes, you get the blank screen. As Headlines fragment is not created and added.
-->
It would be really helpful if someone could guide me as to how I can solve this problem. And as the actual project is huge, and this logic has already been implemented, a drastic change in logic is not an option anymore as that will mean re writting thousands of lines of code. Thank you. :)
Ok. I got the problem. The problem is we are using Fragments in xml layouts in large devices.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment android:name="com.example.android.fragments.HeadlinesFragment"
android:id="#+id/headlines_fragment"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent" />
<fragment android:name="com.example.android.fragments.ArticleFragment"
android:id="#+id/article_fragment"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="match_parent" />
</LinearLayout>
So android is trying to catch the Fragments in savedInstanceState in MainActivity. When screen rotates, system tries to restore the above Fragments even though different layout loads in potrait mode. And so system considers that the article_fragment is also available on the right side and it tries to update it on click on the Headline.
So, What's the solution ?
I have changed a little code in MainActivity and nothing else :-)
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(null);
setContentView(R.layout.news_articles);
// Check whether the activity is using the layout version with
// the fragment_container FrameLayout. If so, we must add the first fragment
if (findViewById(R.id.fragment_container) != null) {
// However, if we're being restored from a previous state,
// then we don't need to do anything and should return or else
// we could end up with overlapping fragments.
/*if (savedInstanceState != null) {
return;
}*/
// Create an instance of ExampleFragment
HeadlinesFragment firstFragment = new HeadlinesFragment();
// In case this activity was started with special instructions from an Intent,
// pass the Intent's extras to the fragment as arguments
firstFragment.setArguments(getIntent().getExtras());
// Add the fragment to the 'fragment_container' FrameLayout
getSupportFragmentManager().beginTransaction()
.add(R.id.fragment_container, firstFragment).commit();
}
}
So what I have done just I told the system that I don't want any thing restored by using super.onCreate(null); so its restoring nothing now.
About the blank screen you are getting
Whenever you start activity in landscape mode. It loads large display by default. Without entering into if satement. Because it can't get fragment_container in landscape mode. And then you rotate screen to load portrait layout and system gets savedInstanceState != null and it returns without loading HeadlinesFragment. So you get bank screen.
So I have commented If statement as you can notice.
/*if (savedInstanceState != null) {
return;
}*/
So now It load everything correctly.
No issue
Download the code sample from this Developer site and modify it according to your needs.
Build Dynamic UI with fragments
Its super and reliable code.
I'm sure there are reasons why the Fragment was rendered correctly in Portrait -> Landscape and not in the reverse but one thing is very clear about the Activity lifecycle
Called when the activity is starting. This is where most
initialization should go: calling setContentView(int) to inflate the
activity's UI, using findViewById(int) to programmatically interact
with widgets in the UI, calling managedQuery(android.net.Uri,
String[], String, String[], String) to retrieve cursors for data
being displayed, etc.
Note the part that says This is where most initialization should go. By exiting after checking that savedInstanceState is null, you're leaving it up to the super class to restore your Fragment which is not a good idea considering the previous view was destroyed.
My advice, inspect the content of savedInstanceState instead of just checking if it is null. Ensure that it contains enough data to restore your previous state, if not initialize your Fragment.
The best practices with Fragments involve implementing all necessary methods to monitor the state.
Here, I'm trying to start an activity on different devices (Android Tablet and Android Phone). Is there a way to use if statement to check which activity should to load based on the devices?
Here's my code:
Button buttonGo = (Button) findViewById(R.id.button_goToActivity);
buttonGo.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
if (tablet device) {
startActivity(new Intent(MainActivity.this, TabletActivity.class));
} else {
startActivity(new Intent(MainActivity.this, AndroidPhoneActivity.class));
}
});
Thanks for your effort...
In order to achieve that you must use Fragment not an Activity. the Design Philosophy of Fragments is exactly what you want. you can take a look at Example to see how it is implemented. This is a master-detail app with two Fragments, when device in a portrait mode or it is not a tablet it just shows master, otherwise it also shows detail beside the master and when you select an item from the list you will see the details without going to other Activity.
Firstly as Android Best Practice it is adviced to use Fragments rather than Activity to achieve your requirement.
But if you are keen on using Activity, then below is the solution to find device type and load different activities.
1) Have 2 values folders: values -> strings.xml and values-sw600dp -> strings.xml
2) Create string value in both the xml
<string name="device_type">PHONE</string> in values -> strings.xml
<string name="device_type">TABLET</string> in values-sw600dp -> strings.xml
3) create a method to check if current device is Phone or not
public boolean isPhone() {
String deviceType = getResource().getString(R.string.device_type);
if (deviceType.equalsIgnoreCase("PHONE") {
return true;
} else {
return false;
}
}
4) Depending on the device load your activity as you have already done in your above code snippet
Let me know if this helps...
Most likely, you should not have two separate activities here. Instead, you should have two different layouts for the same activity. The layout for phones should be in the regular res/layout folder and the layout for tablets should be in the res/layout-large folder. Read Supporting Different Screens for more details.
If you are using same fuctionality for Tablet Activity and Phone activity then you do not need two activities for this purpose. You need to make two different Layout xml for Tablet as well as Phone.
Make a Layout folder named : layout-large and layout-xlarge.
Now copy the xml file from normal layout folder and paste in both new layout folders.
No need to change the name of xml file.
Now Adjust xml file of layout-large and layot-xlarge as you want to make design for tablet.
Now on running application Tablet and phone bot will pick xml according to there size and screen density.
Note : the functionality should be same.
And if: you want to show different screen with different functionality for phone and tablet then. use this code for check.
if ((getResources().getConfiguration().screenLayout &
Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_LARGE) {
}
Hope this wll help you.