However, there are cases where a back button isn’t ideal to the situation. Imagine the user pressing “back” 15 times to get to the main page of your app. Or, in an eCommerce app, the user having access to the “make payment” screen once again after the payment has been successful.

In such cases, a way to redirect the user to return to the home screen is necessary. This is where android’s FLAG_ACTIVITY_SINGLE_TOP and FLAG_ACTIVITY_CLEAR_TOP intent flags come in handy.

The use case we consider today is where there are several activities A, B, C, D, E etc and the user navigates through these multiple times – A > B > C > D > E. After E, we need to return to B, but remove the whole activity stack so that only A and B remain.

Below is a simple tutorial on how to implement this.

Step 1:

In the AndroidManifest.xml of your application, identify the activity you want to return to. In my case, I call it MainActivity. In the corresponding <activity> tag, specify the launchMode attribute to singleTop.

Step 2:

If you want to navigate in a single click from activity E (eg: DeeplyNestedActivity) directly to activity B (eg: MainActivity) and close all other activities in between , then define a Button in the DeeplyNestedActivity and add an OnClickListener to it. In the onClick method of the button, add the following code -

Button goHomeButton;
		goHomeButton = (Button) findViewById(R.id.go_home);
		goHomeButton.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				Intent intent = new Intent(DeeplyNestedActivity.this, MainActivity.class);
		                intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_CLEAR_TOP);
		                startActivity(intent);
			}
		});

And DONE. Your app will navigate back to its home activity when this button is clicked.

1) Image Splitting

I use Photoshop, so the method here is for photoshop users, there should be some online resources available for doing the same thing on GIMP.

Load image in photoshop and select the splice tool (the tool looks like a small pen-knife)
Right click on the image and choose “Divide Splice”. A dialog opens which asks you how many vertical and horizontal splices you require – i prefer choosing a size that makes each splice smaller than 320×480.
Once that is done, go to File > Save for Web  (or Alt+Shift+Ctrl+S) > hit the Save button and in the dialog that opens, choose “HTML and Images (*.html)” where it asks you to specify Save as Type.

A html page along with an image folder would have been created for you at the specified location.

2) Adding these to android assets

Place the html page (lets call it bigimage.html and the images folder in the assets folder of your android project), you can later access it from your application by specifying the path as file:///android_asset/bigimage.html

3) Rendering the image

in the onCreate() method of your activity, create a WebView element and show the html page.

		WebView webView = new WebView(this);

		setContentView(webView);

		try {
			webView.loadUrl("file:///android_asset/bigimage.html");
			webView.getSettings().setLoadsImagesAutomatically(true);
			webView.getSettings().setBuiltInZoomControls(true); // zooming
																// controls
			webView.setInitialScale(25); // sets the scale to 25% you may
											// specify whatever suits you best
		} catch (Exception e) {
			e.printStackTrace();
		}

Thats it, the rendering is superfast and no more out of memory errors. I parsed an image that was 3500×1500 px in less than a second.

Google now uses the stackoverflow android tag as an additional forum for answering developer queries.

Presented here is a list of tutorials/resources that I had come across during my study of the various aspects of android.

1) Starting with the most basic -

Installing an apk file on the google android phone
and using various hardware devices

2) Maps in android

A hello world tutorial
Detecting and zooming on doubletaps in a map
Driving directions

3) Auto-start, background threads and push notifications

Auto Start
Push-notifications
Background-services
Multithreading

4) REST

Part 1 – getting the json data
Part 2 – parsing the objects created to a custom adapter
Part 3 – Lazy loading of images

Another REST example

5) SOAP

SOAP using the KSOAP-2 library

6) MVC in android

MVC

More links and useful tutorials will be posted here as and when i explore newer features of this wonderful platform. Next stop – apps for android using HTML/CSS and JavaScript