Tutorial : How to have two buttons on each side of the screen

Sometimes, things are quite confusing in the Android World.

I wanted to have one two buttons, on each side of the screen ( the famous next and previous buttons ).
I though it would be really easy to do.
I was wrong...

I had already done something quite similar for multiple column list view ( here ), but the trick I actually used for the multiple column view was not applicable here.
For the multiple column view, I could use a text view with a left aligned text, and another big text view taking all the remaining space with right aligned text.
As the textviews are invisibles ( only the text inside was visible ), the trick was unnoticable.


So now, my first try was to put my buttons in a linear layout, and have one with a right gravity, and another with a left gravity.
But it just failed : the two buttons were on the right, or the two buttons were on the left, but I couldn't obtain the result I wanted.

Finally, after some hours struggling with the documentations, some blogs, and the samples from the 1.1 SDK ( and my cat, but that is another story ), I found a way :

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
<Button
android:id="@+id/button_previous"
android:layout_height="wrap_content"
android:layout_width="110px"
android:layout_alignParentLeft="true"
android:textSize="15sp"
android:typeface="monospace"
android:textColor="#ffFFffFF"
android:background="@drawable/textview"
android:text="@string/PreviousButton"
>
</Button>
<Button
android:id="@+id/button_next"
android:layout_height="wrap_content"
android:layout_width="110px"
android:layout_alignParentRight="true"
android:textSize="15sp"
android:typeface="monospace"
android:textColor="#ffFFffFF"
android:background="@drawable/textview"
android:text="@string/NextButton"
>
</Button>
</RelativeLayout>

So I discovered the alignParentRight / alignParentLeft tags !

What are the lessons learned :
* Android GUI is not always as easy as planned
* The linear Layout, that is often the first choice, is often the wrong choice. Relative Layout is much more flexible.
* Where are the API Demos samples in the 1.5 SDK ?

Cupcake finally coming for orange in France ?

Here, in France, Orange have sold the HTC Dream ( the G1 ) for several months.

But the Android version that came with the Phone was the 1.1...
And no update came since google had released Cupcake.

So I was quite surprised when Google send developers a mail to explain that "deployment of Android 1.5 is nearly complete"...

It looks like my phone is one of the last without Cupcake.
But now it looks like an update is finally coming 'in early august'...

I really hope so !

A C programmer in Android world : discovering Java allocations

I'm mainly, in my day world, a C / C++ programmer.

So I'm used with this language and sometimes, I feel like I would prefer to use another, more modern language !

So I was quite happy to try Java. I saw Java as a kind of modern, cleaner C++, with some nice features, and a more improved object model.

But for the 'WordProspector' game, in the process of taking the database out, and replacing it with 'something' else, more lighter (see here ), I found a serious limitation of this Java object model...

The issue :

As 'WordProspector' is a word game, it is shipped with a word dictionary.

At first, I stored the dictionary as a SQL database, as it was simpler for me at that time.

but when I found how memory costly it is, I decided to switch to another way to store it.

So I came up with a kind of tree with a letter for each node.

In my effort to compress the dictionary as much as possible, I found a way to store each node as a 8 bits integer plus a 16 bits integer, so it was 3 bytes.

So I had a Node class, with simply a byte and a short.

But I had a big number of node instances in my tree : something like 300 000 nodes.

So when I loaded the tree, I started by allocating all the nodes.

Allocating the nodes with java was something like :

NodeArray = new Node[nbNodes];

for ( int i = 0; i <>

NodeArray[i] = new Node();

When I tried it on the emulator... It took several minutes... Then the program crashed...

Too much allocations of this size !

I was amazed that I just couldn't easily create this really simple array !!

Then I discovered that allocations of simple type arrays didn't demand to allocate each element !

So finally, I get rid of my nice Node class, save the whole thing as a byte array, and interpret, on the fly, the byte array as a byte plus a short.

With that, the allocation is as fast as it could be :

NodeArray = new byte[nbNodes * 3];

Conclusion:

With this allocation issue, I had to get rid of my Node class, I just have a big array of bytes.

Acces to member are much more complicated, the code that was once so simple is now much more complex.

Add on this issue the fact that what I really wanted was an unsigned short, and not a short.

My code is now full of bits manipulation to create and interpret some bytes as unsigned short, or as bytes, depending of the situation.

With C/C++, I would never have this problem, and I would have a clean object code !

Tutorial : How to access a Android database by using a command line.

When your start dealing with a database in your program, it is really important and useful to be able to access it directly, outside your program, to check what the program has just done, and to debug.

And it is important also on Android.

Here is how to do that :

1) Launch the emulator (or connect your real device to your PC ). I usually launch one of my program from Eclipse for this.

2) Launch a command prompt in the android tools directory.

3) type adb shell.

This will launch an unix shell on your emulator / connected device.

4) go to the directory where your database is :

cd data/data

here you have the list of all the applications on your device

Go in your application directory ( beware, Unix is case sensitive !! )

cd com.alocaly.LetterGame

and descend in your databases directory :

cd databases

Here you can find all your databases. In my case, there is only one ( now ) : SCORE_DB

5) Launch sqlite on the database you want to check / change :

sqlite3 SCORE_DB

From here, you can check what tables are present :

.tables

6) enter any SQL instruction you want :

select * from Score;

This is quite simple, but every time I need it, I don't know where to find it.

Developing with Python on Android : a dream comes true ?

Google still innovates and offers as many tools as they can to us developers !

I'm a big fan of Python, and several times, I wanted to try things on my phone, but without having a development PC around me.
Now they combines both of my implicit wishes, and we can develop in python (and LUA, BeanShell, and other langages to come ) from the mobile !!
I'm really excited about that.

Next question is :
Could I embed my python script that I developed on my phone in a real Java application ?
That would be awesome : it would mean I really could develop parts of my application from my phone, or even have a scripted part of my application that could evolve without a PC !!!

Waaaa...

Thank you, Mr google !!!


Google Open Source Blog: Introducing Android Scripting Environment

Edit :

Sadly, this application is for Cupcake only, so I can't use it...

I will have to wait for Cupcake to be avalaible on my phone.

That makes me wonder how many phone are still stuck with the 1.1 OS ?

From what I've read, in the US, the update is finished, so there should be no 1.1 left.

But outside US ???