Posts in the “android” category

Today I’m proud announce that I’ve written an Android application named “Just Be”:

Just Be is a simple but useful “mindfulness reminders” app that helps bring you back to the present moment.

To use Just Be, all you have to do is a) configure the reminders that you want to see, b) optionally add your favorite background images, and c) set a notification schedule, and Just Be will send you notifications (mindfulness reminders) on that schedule.

I’d write more about it here, but I’ve already written about it at JustBe.cc, so please see that website for more information, including a short video.

I just got back into using an Android AsyncTask, and it took me a little while to re-load the concepts in my head. I used AsyncTask’s a few years ago, but haven’t used them since.

To help remember how they work, I created a little AsyncTask example project, and I’ve included all of the source code for that project here. I’ll show all of the source code for my classes and configuration files, and then explain the code at the end.

I recently had a problem with an Android emulator, and for some reason I wasn't able to delete the Android app I was developing. I knew you could delete Android apps from the command line, but I had no need to do this until now.

After reading a few docs, I found that I could delete my Android app from the command line using the adb command, like this:

If you ever need to get the root data directory of your Android application (app) from within your Java code, I can confirm that this approach works:

File rootDataDir = getActivity().getFilesDir();

When I log that directory like this:

Log.i(TAG, rootDataDir.toString());

it prints this output for my application:

/data/data/com.alvinalexander.mynewapp/files

where com.alvinalexander.mynewapp is the package name for my new Android app.

It turns out that it’s easy to create and use a static array of strings in Android. Of course you can do this in Java code, as I describe in my Java string array tutorial, but for Android I’m talking about doing this in XML.

In short, this is how you define a static string array in an Android XML file:

Android Toast FAQ: How do I create a Toast message in Android? (Or, Can you share some Android Toast message syntax examples?)

Here's one example of the Android Toast syntax:

Toast.makeText(ProjectActivity.this, "Your message here" , Toast.LENGTH_SHORT).show();

and here's a second example, this time referring to the Android application context as the first method parameter:

Android FAQ: What is Android doing when it says “optimizing apps” after an Android system upgrade (and reboot)?

The short story is that Android is doing what it says, creating an optimized version of each app for the new version of Android you just upgraded to. This process makes each app start as fast as possible with the new Android version.

My main project right now (through Valley Programming of Broomfield, Colorado) is porting my Back To Now mindfulness reminder app (formerly named Just Be) to run on both Android and iOS. It’s great to have a toolkit where I can write an app for Android and iOS using one set of code.

As an Android developer, you can normally use the adb push command to copy files from your computer’s hard drive to an Android device. However, I just ran into a problem where I couldn’t copy files to my Android emulator’s “data” directory, i.e., the /data/data filesystem. When I tried to copy a file using this command:

$ adb push foo.jpg /data/data/com.alvinalexander.myapp/files

I got this Android error:

SQLite FAQ: Can you show me how the SQLite ALTER TABLE syntax works?

At the time of this writing you can use the SQLite ALTER TABLE syntax for two purposes:

1. Add a column to the end of an existing SQLite database table
2. Change the name of a database table.

For other changes you'll have to follow some workaround procedures (discussed below).

Android/SQLite FAQ: I've created an instance of a SQLiteOpenHelper object, but the onCreate method isn't getting called, what's wrong? (onCreate is not getting called, and my database tables are not being created.)

SQLite FAQ - How do I create a UNIQUE constraint on multiple fields in a SQLite database table?

Just specify the unique constraint in your create table declaration, as shown here:

If you’re working with an Android application, this source code seems to work to load an image from a file:

Bitmap bitmap = BitmapFactory.decodeFile(pathToPicture);

The Bitmap and BitmapFactory classes are located in the android.graphics package:

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

Assuming that your pathToPicture is correct, you can then add this bitmap image to an ImageView like this:

Before I completely delete this code from my current Android application, I want to make a copy of it here. It was intended to show a series of quotes (text phrases) in a “Grid” (GridView), but (a) I never got it working as desired, and (b) I decided I didn’t want it in my application anyway.

Here’s the source code for the Java controller/fragment class:

XO Play is a “thinking man’s” football game that I created for Android devices. It’s for those of us who enjoy thinking about football strategy, of how to take advantage of our strengths and our opponents’ weaknesses, and how to call plays to win games. If you’ve ever watched a football game and thought, “I can call plays better than this guy,” XO Play is for you.

Version 1.4

Version 1.4 introduces four game levels you can choose from:

The UI still needs a lot of work, but I like the idea of having an Inconceivable mode in the next version of my XO Play Android football game.

I’m working on a very small Android “notifications” app where I a) display a notification using a background service, b) the user taps the notification, which c) takes them to a view that shows the full text of the notification. To get this to work, I need to send the full text along with the notification. However, this didn’t work easily. The text that was shown by my full view would be updated once, then never again.

After a lot of googling and trial and error, I finally got this approach in my sendNotification method working:

I need a new tablet, and I just might bite the bullet on the Amazon Fire 10 HD today (Black Friday, 2018). For my Android development I don’t like that it’s based on Android 5, but $100 (33% off its regular price) for a tablet with decent performance is hard to pass up for my current needs.

I was just working on centering some components in an Android LinearLayout and came upon this helpful advice:

android:gravity takes care of its children,
android:layout_gravity takes care of itself

So, in my case, where I wanted to center two buttons horizontally in a LinearLayout, I used android:gravity="center".

Android Button FAQ: How do I add a listener to a Button in Android?

To add a click (tap) listener to a button in Android, just get a reference to the button (typically using findViewById), then call the setOnClickListener method of the button, like this: