My android application has multiple Activities. I need to perform a few things when the Application resumes (Application not Activity).
Android application provides onCreate callback but no onResume callback.
Is there any way I can identify that my application has resumed?
Applications do not get paused or resumed, only individual activities do. You can think of the Application class as of a static object that gets created before any of your activities (that's why it has a onCreate() function) and gets destroyed when the system kills the process (no onDestroy() involved here).
Using the Application Class
Depending on what you're doing in your initialization you could consider creating a new class that extends Application and moving your initialization code into an overridden onCreate method within that class.
public class MyApplicationClass extends Application < @Override public void onCreate() < super.onCreate(); // TODO Put your application initialization code here. >> The onCreate in the application class is only called when the entire application is created, so the Activity restarts on orientation or keyboard visibility changes won't trigger it.
It's good practice to expose the instance of this class as a singleton and exposing the application variables you're initializing using getters and setters.
NOTE: You'll need to specify the name of your new Application class in the manifest for it to be registered and used:
Reacting to Configuration Changes [UPDATE: this is deprecated since API 13; see the recommended alternative]
As a further alternative, you can have your application listen for events that would cause a restart – like orientation and keyboard visibility changes – and handle them within your Activity.
Start by adding the android:configChanges node to your Activity's manifest node
Then within the Activity override the onConfigurationChanged method and call setContentView to force the GUI layout to be re-done in the new orientation.
@Override public void onConfigurationChanged(Configuration newConfig)
To fix the OutOfMemory error, you should do something like this:
BitmapFactory.Options options = new BitmapFactory.Options(); options.inSampleSize = 8; Bitmap preview_bitmap = BitmapFactory.decodeStream(is, null, options); This inSampleSize option reduces memory consumption.
Here's a complete method. First it reads image size without decoding the content itself. Then it finds the best inSampleSize value, it should be a power of 2, and finally the image is decoded.
// Decodes image and scales it to reduce memory consumption private Bitmap decodeFile(File f) < try < // Decode image size BitmapFactory.Options o = new BitmapFactory.Options(); o.inJustDecodeBounds = true; BitmapFactory.decodeStream(new FileInputStream(f), null, o); // The new size we want to scale to final int REQUIRED_SIZE=70; // Find the correct scale value. It should be the power of 2. int scale = 1; while(o.outWidth / scale / 2 >= REQUIRED_SIZE && o.outHeight / scale / 2 >= REQUIRED_SIZE) < scale *= 2; >// Decode with inSampleSize BitmapFactory.Options o2 = new BitmapFactory.Options(); o2.inSampleSize = scale; return BitmapFactory.decodeStream(new FileInputStream(f), null, o2); > catch (FileNotFoundException e) <> return null; >