At some point you may find yourself needing to implement a splash screen for your Android app. Reasons for doing so include matching an existing design for iOS, performing necessary background work at start up, or simply for the visual appeal alone. It should be noted that splash screens are certainly not required in your app. In fact, some feel that they should be avoided entirely. Still, it is not uncommon to come across Android apps that utilize a splash screen.
This article provides a detailed outline for implementing a splash screen on Android. While the implementation is relatively straight forward, there are a few details that often get overlooked. We've also provided a working sample project that can be run on your device or emulator.
First, create an Activity named SplashActivity.
public class SplashActivity extends Activity {
...
}It's important that we extend from Activity and not ActionBarActivity. This will exclude the ActionBar from being visible on our splash screen. Next, declare SplashActivity as the launcher activity in the app's manifest file.
<activity
android:name=".SplashActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>Our splash screen will now be the initial screen shown when the app launches.
The layout for a splash screen is typically very simple. For our purposes, we will show an ImageView in the center of the screen.
<RelativeLayout 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:background="@android:color/white"
tools:context="com.ibm.mil.splashscreendemo.SplashActivity">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:src="@drawable/splash_logo"
android:contentDescription="@string/splash_logo_desc" />
</RelativeLayout>Inside onCreate(Bundle) we will initialize a Handler and its corresponding Runnable that will be responsible for starting the app's main activity after a specified duration.
private Handler mHandler;
private Runnable mRunnable;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
mHandler = new Handler();
mRunnable = new Runnable() {
@Override
public void run() {
startActivity(new Intent(SplashActivity.this, MainActivity.class));
finish();
}
};
}Handler is part of the android.os package and it easily allows developers to utilize a message queue for a thread without having to deal with synchronization and the lower-level threading APIs in Java. In our case, we will use the Handler to invoke our Runnable object at a later point in time on the main UI thread without blocking other operations from occurring in the meantime.
The implementation of run() is straightforward: the app's main activity (called MainActivity in the example) is started via an Intent. The call to finish() marks SplashActivity as done and subsequently removes itself from the app's back stack. This prevents the user from seeing the splash screen again if they back out of the app via the system's back button.
From onResume(), the method postDelayed(Runnable, long) is invoked on mHandler and is passed both our Runnable instance and a timed delay which is measured in milliseconds. This will enqueue mRunnable onto the thread's message queue and then dequeue it for execution after our specified delay.
private static final long SPLASH_DURATION = 2500L;
...
@Override
protected void onResume() {
super.onResume();
mHandler.postDelayed(mRunnable, SPLASH_DURATION);
}We will also remove mRunnable from the Handler in onPause() to ensure it doesn't execute when SplashActivity is no longer in a resumed state.
@Override
protected void onPause() {
super.onPause();
mHandler.removeCallbacks(mRunnable);
}Optionally, we can allow the user to dismiss the splash screen prematurely. In onCreate(Bundle) we can add an OnClickListener to the root view of our layout.
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
...
// allow user to click and dismiss the splash screen prematurely
View rootView = findViewById(android.R.id.content);
rootView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(SplashActivity.this, MainActivity.class));
finish();
}
});
}Now when the user taps anywhere on the screen, the splash screen will be dismissed. If you wish to include this functionality, you should move the body of the onClick(View) method to a private helper method since it is indentical to the code used in run() of our Runnable.
And that encompasses all of the necessary components for properly implementing a basic splash screen. The next section describes how to additionally perform background work when the splash screen is present.
A common approach is to perform some background work at start up while the splash screen is active. This can be helpful if there is data shown on the home screen that needs to be retrieved from a network or external memory device. A valid alternative is to display a progress bar or dialog to indicate to the user that a long standing operation is being performed. While a splash screen inhibits the user's progress through the app, we get the benefit of hiding expensive operations from the user.
For example, let's assume we wanted to download an image from the network (e.g. a user's profile image that is shown on the home screen). We can create an AsyncTask that will do exactly this:
public class ImageLoader extends AsyncTask<String, Void, Bitmap> {
private static final String TAG = ImageLoader.class.getName();
@Override
protected Bitmap doInBackground(String... urls) {
// make network call to fetch image
Bitmap bitmap = null;
try {
bitmap = BitmapFactory.decodeStream(new URL(urls[0]).openStream());
} catch (Exception e) {
e.printStackTrace();
cancel(true);
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap result) {
Log.i(TAG, "Image successfully downloaded.");
if (result != null) {
// do something with the bitmap
...
}
}
@Override
protected void onCancelled() {
Log.i(TAG, "Image download not successful.");
}
}doInBackground(String...) runs on its own thread and performs the actual network call for fetching the image. Both onPostExecute(Bitmap) and onCancelled() will run on the thread that the ImageLoader was invoked from, which is the main thread in our case.
For demonstration purposes we've written our own AsyncTask for retrieving the image. Excellent libraries already exist that perform this operation and more. Note that making a network call requires the INTERNET permission to be added to the manifest file.
The basis for the implementation of the splash screen will be identical to the splash screen we developed in the previous section. For brevity, we can simply extend SplashActivity and augment onCreate(Bundle) to include the execution of our AsyncTask.
public class WorkerSplashActivity extends SplashActivity {
private static final String IMAGE_URL = ...
private ImageLoader mImageLoader;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mImageLoader = new ImageLoader();
mImageLoader.execute(IMAGE_URL);
}
...
}Executing ImageLoader inside of onCreate(Bundle) allows the background work to start as soon as the activity is created. Consequently, we can cancel the task in onDestroy() if it's still running in order to allow the operation to continue in the background even if the activity is no longer visible.
@Override
protected void onDestroy() {
super.onDestroy();
if (mImageLoader.getStatus() != AsyncTask.Status.FINISHED) {
mImageLoader.cancel(true);
}
}That is the extent of performing background work while the splash screen is present. The next section explores some of the pitfalls that developers can encounter with a splash screen.
There are a handful of oversights that developers often make when implementing a splash screen. For example, we make sure to remove our Runnable from the Handler in onPause() and then effectively restart the splash screen duration each time onResume() is called.
@Override
protected void onResume() {
super.onResume();
mHandler.postDelayed(mRunnable, SPLASH_DURATION);
}
@Override
protected void onPause() {
super.onPause();
mHandler.removeCallbacks(mRunnable);
}If instead we moved the invocation of postDelayed(Runnable, long) to onCreate(Bundle) and didn't bother removing the Runnable callback in onPause(), the Runnable would end up being executed even if the app was in the background. As a result, MainActivity would suddenly appear on the user's screen even though the app was no longer in an active state.
// DON'T DO THIS!
@Override
protected void onCreate(Bundle savedInstanceState) {
...
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
startActivity(new Intent(SplashActivity.this, MainActivity.class));
finish();
}
}, SPLASH_DURATION);
}It's also important that we employ a Handler to delay the execution of our code contained in the Runnable.
mHandler.postDelayed(mRunnable, SPLASH_DURATION);If the main thread is put to sleep in order to simulate the delay, then the user would be blocked from performing any UI actions while the splash screen is visible. This includes the system back button to exit our app.
// DON'T DO THIS
try {
Thread.sleep(SPLASH_DURATION);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
startActivity(this, MainActivity.class);
finish();
}Likewise, it's essential that we use an AsyncTask to perform any background work. Without it, not only do we block the main thread, but we also increase the likelihood of an ANR (Application Not Responding) message being shown to the user. This happens when the system can't respond to an input event for a minimum of 5 seconds.
*The Dreaded ANR Dialog*
Another consideration is how the AsyncTask interacts with our splash screen. A good approach is to have the splash screen remain visible for a specified duration, like how we did in the first section, and then cancel the background task if it takes too long.
@Override
protected void onDestroy() {
super.onDestroy();
if (mImageLoader.getStatus() != AsyncTask.Status.FINISHED) {
mImageLoader.cancel(true);
}
}It is not a good idea to have the duration of our splash screen dependent on the background work being completed. Many types of tasks, such as those involving network calls, can take an undetermined amount of time to complete and having a timeout mechanism is important.
Splash screens, while simple on the surface, take special consideration in order to implement properly. Missing even the smallest detail can lead to a poor user experience. Hopefully this article has revealed which areas you need to examine carefully. And while this article does cover the subject at length, it certainly isn't comprehensive. Several more enhancements could be imagined for a splash screen.
John Petitto is a software engineer focused on Android development at IBM's Mobile Innovation Lab in Austin, TX. Check out more blog articles from the MIL team and visit our GitHub page to see our growing list of open source projects.