LifecycleLoggingActivity.java

package vandy.mooc.common;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

/**
 * This abstract class extends the Activity class and overrides lifecycle
 * callbacks for logging various lifecycle events.
 */
public abstract class LifecycleLoggingActivity extends Activity {
    /**
     * Debugging tag used by the Android logger.
     */
    protected final String TAG = 
        getClass().getSimpleName();

    /**
     * Hook method called when a new instance of Activity is created. One time
     * initialization code should go here e.g. UI layout, some class scope
     * variable initialization. if finish() is called from onCreate no other
     * lifecycle callbacks are called except for onDestroy().
     * 
     * @param savedInstanceState
     *            object that contains saved state information.
     */
    @Override
	protected void onCreate(Bundle savedInstanceState) {
        // Always call super class for necessary
        // initialization/implementation.
        super.onCreate(savedInstanceState);

        if (savedInstanceState != null) {
            // The activity is being re-created. Use the
            // savedInstanceState bundle for initializations either
            // during onCreate or onRestoreInstanceState().
            Log.d(TAG, "onCreate(): activity re-created");

        } else {
            // Activity is being created anew. No prior saved
            // instance state information available in Bundle object.
            Log.d(TAG, "onCreate(): activity created anew");
        }

    }

    /**
     * Hook method called after onCreate() or after onRestart() (when the
     * activity is being restarted from stopped state). Should re-acquire
     * resources relinquished when activity was stopped (onStop()) or acquire
     * those resources for the first time after onCreate().
     */
    @Override
	protected void onStart() {
        // Always call super class for necessary
        // initialization/implementation.
        super.onStart();
        Log.d(TAG, "onStart() - the activity is about to become visible");
    }

    /**
     * Hook method called after onRestoreStateInstance(Bundle) only if there is
     * a prior saved instance state in Bundle object. onResume() is called
     * immediately after onStart(). onResume() is called when user resumes
     * activity from paused state (onPause()) User can begin interacting with
     * activity. Place to start animations, acquire exclusive resources, such as
     * the camera.
     */
    @Override
	protected void onResume() {
        // Always call super class for necessary
        // initialization/implementation and then log which lifecycle
        // hook method is being called.
        super.onResume();
        Log.d(TAG,
              "onResume() - the activity has become visible (it is now \"resumed\")");
    }

    /**
     * Hook method called when an Activity loses focus but is still visible in
     * background. May be followed by onStop() or onResume(). Delegate more CPU
     * intensive operation to onStop for seamless transition to next activity.
     * Save persistent state (onSaveInstanceState()) in case app is killed.
     * Often used to release exclusive resources.
     */
    @Override
	protected void onPause() {
        // Always call super class for necessary
        // initialization/implementation and then log which lifecycle
        // hook method is being called.
        super.onPause();
        Log.d(TAG,
              "onPause() - another activity is taking focus (this activity is about to be \"paused\")");
    }

    /**
     * Called when Activity is no longer visible. Release resources that may
     * cause memory leak. Save instance state (onSaveInstanceState()) in case
     * activity is killed.
     */
    @Override
	protected void onStop() {
        // Always call super class for necessary
        // initialization/implementation and then log which lifecycle
        // hook method is being called.
        super.onStop();
        Log.d(TAG,
              "onStop() - the activity is no longer visible (it is now \"stopped\")");
    }

    /**
     * Hook method called when user restarts a stopped activity. Is followed by
     * a call to onStart() and onResume().
     */
    @Override
	protected void onRestart() {
        // Always call super class for necessary
        // initialization/implementation and then log which lifecycle
        // hook method is being called.
        super.onRestart();
        Log.d(TAG, "onRestart() - the activity is about to be restarted()");
    }

    /**
     * Hook method that gives a final chance to release resources and stop
     * spawned threads. onDestroy() may not always be called-when system kills
     * hosting process
     */
    @Override
	protected void onDestroy() {
        // Always call super class for necessary
        // initialization/implementation and then log which lifecycle
        // hook method is being called.
        super.onDestroy();
        Log.d(TAG, "onDestroy() - the activity is about to be destroyed");
    }

}