Android Fragment Transitions

Activity and fragment transitions in Lollipop (Android 5.0) are built on some relatively new Android features called transitions. Introduced in KitKat, the transition framework provides a series of convenient APIs to provide animations between different UI states of an application. This framework is built around two key concepts: scenes and transitions. A scene defines a given state of the application UI, while a transition defines the animated change between two scenes.

When a scene changes, a transition has two main responsibilities:

• Capture the state of each view in the starting and ending scenes.
• Create an animator that animates the differences between the views that need animation from one scene to another.

Example

This example explains how to use fragment transitions to create custom animations. Let's start by following these steps:

Below is the content of the res/layout/activity_main.xml file, which includes a FrameLayout and a Button.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <FrameLayout
        android:id="@+id/fragment1"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <Button
        android:id="@+id/new_fragment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add New Fragment" />

</LinearLayout>

Below is the content of the res/anim/fragment_stack.xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/text"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"/>
</LinearLayout>

Below is the content of the res/animator/fragment_slide_left_enter.xml file, which includes the set method and animator object tags.

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="100dp" android:valueTo="0dp"
        android:valueType="floatType"
        android:propertyName="translationX"
        android:duration="@android:integer/config_mediumAnimTime" />

    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="0.0" android:valueTo="1.0"
        android:valueType="floatType"
        android:propertyName="alpha"
        android:duration="@android:integer/config_mediumAnimTime" />
</set>

Below is the content of the res/animator/fragment_slide_left_exit.xml file, which includes the set method and animator object tags.

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="0dp" android:valueTo="-100dp"
        android:valueType="floatType"
        android:propertyName="translationX"
        android:duration="@android:integer/config_mediumAnimTime" />

    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="1.0" android:valueTo="0.0"
        android:valueType="floatType"
        android:propertyName="alpha"
        android:duration="@android:integer/config_mediumAnimTime" />
</set>

Below is the content of the res/animator/fragment_slide_right_enter.xml file, which includes the set method and animator object tags.

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="-100dp" android:valueTo="0dp"
        android:valueType="floatType"
        android:propertyName="translationX"
        android:duration="@android:integer/config_mediumAnimTime" />

    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="0.0" android:valueTo="1.0"
        android:valueType="floatType"
        android:propertyName="alpha"
        android:duration="@android:integer/config_mediumAnimTime" />
</set>

Below is the content of the res/animator/fragment_slide_right_exit.xml file, which includes the set method and animator object tags.

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="0dp" android:valueTo="100dp"
        android:valueType="floatType"
        android:propertyName="translationX"
        android:duration="@android:integer/config_mediumAnimTime" />

    <objectAnimator
        android:interpolator="@android:interpolator/decelerate_quint"
        android:valueFrom="1.0" android:valueTo="0.0"
        android:valueType="floatType"
        android:propertyName="alpha"
        android:duration="@android:integer/config_mediumAnimTime" />
</set>

Here is the content of the src/cn.uprogrammer.fragmentcustomanimation/MainActivity.java file, including button listeners, CountingFragment, and onCreateView():

package cn.uprogrammer.fragmentcustomanimation;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentTransaction;
import android.os.Bundle;

import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;

import android.widget.Button;
import android.widget.TextView;

/**
 * Demonstrates the use of custom animations in fragment transactions.
 */
public class MainActivity extends Activity {
    int mStackLevel = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button button = (Button)findViewById(R.id.new_fragment);

        button.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                addFragmentToStack();
            }
        });

        if (savedInstanceState == null) {
            // Add initial fragment
            Fragment newFragment = CountingFragment.newInstance(mStackLevel);
            FragmentTransaction ft = getFragmentManager().beginTransaction();
            ft.add(R.id.fragment1, newFragment).commit();
        }
        else {
            mStackLevel = savedInstanceState.getInt("level");
        }
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt("level", mStackLevel);
    }

    void addFragmentToStack() {
        mStackLevel++;

        // Instantiate a new fragment
        Fragment newFragment = CountingFragment.newInstance(mStackLevel);

        // Add the fragment to the activity, putting it in the back stack
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.setCustomAnimations(R.animator.fragment_slide_left_enter,
                R.animator.fragment_slide_left_exit,
                R.animator.fragment_slide_right_enter,
                R.animator.fragment_slide_right_exit);
        ft.replace(R.id.fragment1, newFragment);
        ft.addToBackStack(null);
        ft.commit();
    }

    public static class CountingFragment extends Fragment {
        int mNum;
        /**
         * Create a new instance of CountingFragment, providing "num" as an argument.
         */
        static CountingFragment newInstance(int num) {
            CountingFragment f = new CountingFragment();

            Bundle args = new Bundle();
            args.putInt("num", num);
            f.setArguments(args);
            return f;
        }

        /**
         * When creating, retrieve this instance's number from its arguments.
         */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            mNum = getArguments() != null ? getArguments().getInt("num") : 1;
        }
        /**
         * The fragment's UI is just a TextView showing its number.
         */
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.fragment_stack, container, false);
            View tv = v.findViewById(R.id.text);
            ((TextView)tv).setText("Fragment #" + mNum);
            tv.setBackgroundDrawable(getResources().getDrawable(android.R.drawable.gallery_thumb));
            return v;
        }
    }
}

Here is the content of the AndroidManifest.xml file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.uprogrammer.fragmentcustomanimation"
    android:versionCode="1"
    android:versionName="1.0" >

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

        </activity>

    </application>
</manifest>

Let's run the modified Fragment Custom Animation application. I assume you have already created an AVD when setting up the environment. Open the activity file in your project and click on the toolbar.