Develop Reference

Using Sliding Tabs with Toolbar

I've started to change from using ActionBarActivity to AppCompatActivity, but I've also started using the Toolbar as well instead of a standard ActionBar.
However, in one of my activities which has a swiping tab type of layout, the following line seems to be deprecated:
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
Although I have looked at some other answers on Stack Overflow regarding this, is there any built-in way of changing this to support using the Toolbar. If so, could you explain exactly how I would go about changing it? How would deprecated methods like onTabSelected be changed?
Also, I've noticed that the Google Play Music app has what looks like an extended toolbar/section underneath the tabs (see this image for what I am talking about). How would I be able to have that type of layout?
Thanks in advance.

So after a few days of lots of research, and looking through GitHub, I finally managed to solve my problem.
Steps to updating the ActionBar tabs to Toolbar tabs using AppCompatActivity:
UPDATE: After Friday 29th May 2015:
Thankfully, using a TabLayout with the Toolbar has become much simpler since the announcement of the Android Design Support Library in Google I/O 2015.
We no longer need to download custom view classes, and this is something Google really should have done a long time ago.
From the Android Developers' Blogspot post on the Android Design Support Library:
Tabs:
Switching between different views in your app via tabs is not a new concept to material design and they are equally at home as a top level navigation pattern or for organizing different groupings of content within your app (say, different genres of music).
The Design library’s TabLayout implements both fixed tabs, where the view’s width is divided equally between all of the tabs, as well as scrollable tabs, where the tabs are not a uniform size and can scroll horizontally. Tabs can be added programmatically:
TabLayout tabLayout = ...;
tabLayout.addTab(tabLayout.newTab().setText("Tab 1"));
However, if you are using a ViewPager for horizontal paging between tabs, you can create tabs directly from your PagerAdapter’s getPageTitle() and then connect the two together using setupWithViewPager(). This ensures that tab selection events update the ViewPager and page changes update the selected tab.
Prior to Google I/O 2015:
Firstly, I downloaded the SlidingTabLayout.java and SlidingTabStrip.java files from Google's I/O Conference app on GitHub. These would be the views that would be used in the tab layout, so I created a folder with my other Java activities called 'view' and placed them there.
Next, I edited my activity layout .xml to look a bit like this:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:ads="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.mycompany.myapp.MyActivity" >
<!-- This is the Toolbar with the tabs underneath -->
<LinearLayout android:id="#+id/detail_headerBar"
style="#style/HeaderBar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<include android:id="#+id/detail_toolbar" layout="#layout/toolbar" />
<com.mycompany.myapp.view.SlidingTabLayout
android:id="#+id/sliding_tabs"
android:background="?attr/colorPrimary"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
<!-- This is the ViewPager (which I had used before) and
it would be responsible for the swiping to change layouts -->
<android.support.v4.view.ViewPager
android:id="#+id/view_pager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#id/detail_headerBar"
android:layout_above="#+id/detail_adView" />
<!-- I also had an AdView in my layout,
but this is not necessary for creating tab layouts -->
<com.google.android.gms.ads.AdView
android:id="#+id/detail_adView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
ads:adSize="SMART_BANNER"
ads:adUnitId="#string/banner_ad_unit_id" >
</com.google.android.gms.ads.AdView>
</RelativeLayout>
The line which references the Toolbar (<include android:id="#+id/detail_toolbar" layout="#layout/toolbar" />), is referencing the following layout (for those who aren't sure how to use the Toolbar yet):
<android.support.v7.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/toolbar"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:minHeight="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
And in both of the .xml layout files above, ?attr/colorPrimary, refers to the primary colour of my app (which I had defined in a style).
Also, in the first layout, the style I had mentioned as #style/HeaderBar refers to the following:
<style name="HeaderBar">
<item name="android:background">?colorPrimary</item>
<item name="android:elevation">4dp</item>
<!-- You may have to override this in a v21 version of this file -->
</style>
Before I started setting up the layouts in Java, I had to make sure to change the package names in SlidingTabLayout.java and SlidingTabStrip.java corresponding to where they were placed. In my case, I used: package com.mycompany.myapp.view; in both of these files.
Now, in my Activity (which was extending AppCompatActivity), I first added the following in the onCreate method:
Toolbar toolbar = (Toolbar) findViewById(R.id.detail_toolbar);
setSupportActionBar(toolbar);
This would be reponsible for displaying the Toolbar.
Then I setup the ViewPager and SlidingTabLayout parts:
mViewPager = (ViewPager) findViewById(R.id.view_pager);
mViewPager.setAdapter(new ViewPagerAdapter(getSupportFragmentManager()));
mSlidingTabLayout = (SlidingTabLayout) findViewById(R.id.sliding_tabs);
mSlidingTabLayout.setSelectedIndicatorColors(getResources().getColor(R.color.tab_line));
mSlidingTabLayout.setDistributeEvenly(true);
mSlidingTabLayout.setViewPager(mViewPager);
The colour 'tab_line' was a colour I had declared in color.xml which would be the colour of the tab line indicator. Also note that the variables above were global which I defined previously in this activity:
SlidingTabLayout mSlidingTabLayout;
ViewPager mViewPager;
The final thing to do was to setup the ViewPagerAdapter which I had called eariler. This would be responsible for changing the page depending on which tab was selected. I used the following:
public class ViewPagerAdapter extends FragmentPagerAdapter {
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public int getCount() {
// Returns the number of tabs
return 3;
}
#Override
public Fragment getItem(int position) {
// Returns a new instance of the fragment
switch (position) {
case 0:
return new FragmentOne();
case 1:
return new FragmentTwo();
case 2:
return new FragmentThree();
}
return null;
}
#Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
I hope this was a thorough enough answer for those who are having the same trouble as I did, when switching from ActionBarActivity to AppCompatActivity and starting to use Toolbar instead of ActionBar. If there is anything that is unclear, feel free to comment below.

Using ViewPager with Tabs without actionBar

I am using the google example called EffectiveNavigation to create a ViewPager with tabs. The problem is that in the manifest, for my main activity, I have set
android:theme="#android:style/Theme.Holo.NoActionBar.Fullscreen"
So that my app has no actionBar. Therefore I am getting a NullPointerException at
final ActionBar actionBar = getActionBar();//null from getActionBar()
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);//NullPointerException
Now, all I want is to be able to create a simple ViewPager with tabs. That's it. Nothing grand. I am using the google example because it is what I found.
Basically in the google example, they are using the statusBar to hold the tabs. How else might I hold the tabs? Anything less than a good example or instruction on how to modify the goggle example is not going to be much help as I don't know much about ViewPagers. The link to the google example is http://developer.android.com/training/implementing-navigation/lateral.html
A simple workaround the statusBar might be enough.

Using the ActionBar to hold the tabs is actually deprecated because, even if your app does have action bar, it may lead to NullPointerException. Good news are the TabLayout from the Design package brings you the possibility to easily create a ViewPager with tabs. Just write this in the XML of your Activity (or Fragment):
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<android.support.design.widget.TabLayout
android:id="#+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top" />
</android.support.v4.view.ViewPager>
And once you have your Adapter for the ViewPager, include this code in the onCreate method of your Activity (or Fragment) after the setContentView method:
ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(new MyPagerAdapter(getSupportFragmentManager()));
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(viewPager);
Hope it helps ;)

I found a fix. Basically in onCreate, before setContentView, I call
requestWindowFeature(Window.FEATURE_ACTION_BAR);
Then everything works fine.

To anyone else arriving here finding that #learner's solution doesn't work for them, take a look at http://thepseudocoder.wordpress.com/2011/10/13/android-tabs-viewpager-swipe-able-tabs-ftw/

Some issues and difficulties in PagerTabStrip

I have implemented a scrollable tab + swipe, everything works fine.
However I have some issues related to the current PagerTabStrip :
1. I can't make the current title Bold
2. Can't choose the default tab I want to display (e.g : the tab with position 2) when rendering the view, like the tabs in the Google Play app
3. The first and last tab have respectively a margin on the left and the right, can I set it to 0dp ?
This is what I could do for styling the tabs :
Java :
strip = (PagerTabStrip) findViewById(R.id.pager_tab_strip);
strip.setTabIndicatorColorResource(R.color.light_blue);
strip.setDrawFullUnderline(true);
Layout :
<android.support.v4.view.PagerTabStrip
android:id="#+id/pager_tab_strip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
android:background="#drawable/pagertitle_border_bottom"
android:paddingBottom="15dp"
android:paddingTop="15dp"
android:textColor="#color/light_blue" />
Can anyone help me with the 3 points ? Thank you.

Well, I actually found a proper solution for that. Forget about PagerTabStrip ;)
Apparently, Google released a sample app that features the exact source code they used in Google Play app. It's super easy to use. Download the sample app and copy two files from there: SlidingTabLayout.java and SlidingTabStrip.java.
Then in your layout XML, add the following above the ViewPager (change com.example to your package name):
<com.example.SlidingTabLayout
android:id="#+id/sliding_tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<android.support.v4.view.ViewPager
android:id="#+id/pager"
android:layout_marginTop="5dp"
android:layout_weight="1.5"
android:layout_width="match_parent"
android:background="#android:color/white"
android:layout_height="0dp"/>
And add the following to the activity after you initialize the ViewPager:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(new GridPagerAdapter(getSupportFragmentManager()));
// Initialize the SlidingTabLayout. Note that the order is important. First init ViewPager and Adapter and only then init SlidingTabLayout
mSlidingTabLayout = (SlidingTabLayout) findViewById(R.id.sliding_tabs);
mSlidingTabLayout.setViewPager(mViewPager);
}
SlidingTabLayout's API allows you to easily do basic styling such as, changing the tab color, the divider color, the indicator color, etc.
One more important thing, the SlidingTabLayout that Google provided works well when you have many tabs. But, if you have, for example, three tabs, you'll see that all the tabs are aligned to the left and there's a big gap between the last tab and the width of the view.
To overcome this, modify SlidingTabLayout.java after line 173 just below TextView textView = new TextView(context); add the following line:
textView.setLayoutParams(new LinearLayout.LayoutParams(0, LinearLayout.LayoutParams.WRAP_CONTENT, 1f));
Now the space among the tabs will be divided correctly:

Have a look at this. This guy explains very clearly how to use Sliding Tab Layout
Understanding Sliding Tab Layout
For any customization
Change the code in the class SlidingTabLayout.java

Different Fragment view for tablet

I have created an app using the Android Wizard and using a ViewPager to contain all three of my fragments. The main activity is contained in a "activity_main.xml" and contains a ViewPager which inturn contains a PagerTitleStrip. My MainActivity extends the FragmentActivity from support library.
I have checked the Supporting Multiple Screens on Android Developers. I created a folder called "layout-sw600dp" and added another "activity_main.xml" in there. I added my Fragments in there inside a LinearLayout. When I run this on a 7" tablet, my app force closes with a NPE at this line, mViewPager.setAdapter(mSectionsPagerAdapter);.
I understand that I get this NPE here because it is invoking my xml from sw600dp folder, but how do I specify multiple fragments in a single view for tablets?
Any help or pointers will be appreciated.
Edit - Added some source code, tried to keep only relevant data to keep the post short
As you can find below, most of the code is generated by the wizard/adt-plugin.
layout/activity_main.xml
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
layout-sw600dp/activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<fragment
android:id="#+id/fragment_one"...
<fragment
android:id="#+id/fragment_two"...
MainActivity.java
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding tab.
// We can also use ActionBar.Tab#select() to do this if we have a reference to the
// Tab.
mViewPager.setOnPageChangeListener(...

It sounds like on the tablet you don't want a ViewPager, you just want to display all the fragments, so you don't have a ViewPager in that layout. So when you try to set mViewPager it's setting as null because there is no ViewPager in that layout. so, your options, if I have seen the situation correctly, are to add a dummy ViewPager to the tablet layout (Don't recommend), or to add an if statement. Remember that mViewPager will be set to null anytime the user is on a tablet, so any code you have involving will throw an error if it's not inside an if statement like the one below.
if(mViewPager!=null){
mViewPager.setAdapter(mSectionsPagerAdapter)
}

ViewPagerIndicator's TitlePageIndicator stopping fragments from showing and causing swiping to not work

I'm seeing a very strange error when trying to use ViewPagerIndicator (http://viewpagerindicator.com/). I've narrowed it down to the TitlePageIndicator that is part of that library.
When I use the TitlePageIndicator, I am unable to swipe between tabs, and my fragments don't show up (although they are created and ran, the button in the upper right is created by the fragment that should be showing). It looks like this: http://imgur.com/RJaI9 (Sorry, new user so I can't inline pictures)
But without, my fragments appear correctly and I'm able to swipe between them. http://imgur.com/bboSd
I have no idea why this is happening. I'm using the latest ViewPagerIndicator library, but I'm thinking maybe it has something to do with how I imported it? I followed the instructions on the website:
created the new android project in eclipse from existing source, imported the compatibility library, then added it to my project in the android project properties.
Any help would be greatly appreciated, I've been stuck on this for 2 weeks :(
Code:
Layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<com.viewpagerindicator.TitlePageIndicator
android:id="#+id/titles"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<android.support.v4.view.ViewPager
android:id="#+id/grocery_pager"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
/>
</LinearLayout>
FragmentActivity (From ActionBarSherlock):
public class GroceryActivity extends BaseFragmentActivity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_grocerylist);
// Set the pager with an adapter
ViewPager pager = (ViewPager) findViewById(R.id.grocery_pager);
pager.setAdapter(new GroceryViewPagerAdapter(getSupportFragmentManager()));
// Bind the title indicator to the adapter
//When these next two lines are commented out, everything works
TitlePageIndicator titleIndicator = (TitlePageIndicator) findViewById(R.id.titles);
titleIndicator.setViewPager(pager);
}
}

I ended up finding the problem:
In my linear layout, I did not set the orientation of the layout. For some silly reason I thought the orientation field had to do with the orientation of the device, and not the layout itself. Adding the orientation:vertical field made everything work.
Hopefully this helps someone!