Android Basic Fragment Example

Simple example of an activity using two fragments.

If there's space the screen is split in half and the two fragments are shown simultaneously

Compile

# Optional
ANDROID_HOME=/home/.../android/sdk; export ANDROID_HOME
./gradlew compileDebug

Test

# Make sure emulator is running or connected to real device
./gradlew connectedInstrumentTest

Code highlights

Layouts are defined as follows:

* In small screens res/layout/main\_activity.xml

    <?xml version="1.0" encoding="utf-8"?>
    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />


* In large screen res/layout-large/main\_activity.xml

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/frags"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:baselineAligned="false">

        <fragment
            android:id="@+id/friends_frag"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            class="course.labs.fragmentslab.FriendsFragment" />

        <fragment
            android:id="@+id/feed_frag"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="3"
            class="course.labs.fragmentslab.FeedFragment" />

    </LinearLayout>

On the activity's onCreate add the fragment to the Fragment Manager if single pane mode.

    if (!isInTwoPaneMode())
        ...

        // TODO 1 - add the FriendsFragment to the fragment_container
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.fragment_container, mFriendsFragment);
        fragmentTransaction.commit();

    else
        // Otherwise, save a reference to the FeedFragment for later use
        mFeedFragment = (FeedFragment) getFragmentManager().findFragmentById(R.id.feed_frag);

On the activity's onItemSelected:

onItemSelected(int position) /* Clicked one of the twitter accounts */
    ...

    // If there is no FeedFragment instance, then create one
    if (mFeedFragment == null)
        mFeedFragment = new FeedFragment();

    if (!isInTwoPaneMode()) {

        // TODO 2 - replace the fragment_container with the FeedFragment
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fragment_container, mFeedFragment);
        fragmentTransaction.addToBackStack(null); /* To put the fragment on the "back" stack */
        fragmentTransaction.commit();

        // execute transaction now
        getFragmentManager().executePendingTransactions();
    }