Saturday, August 22, 2009

Android : Sliding Drawer Example

If you have lot’s of stuff to put on your screen for a single activity, you should probably go for the SlidingDrawer widget. It is very simple to use, and looks cute. Here are the steps that you need to do for bringing up the sliding drawer on your activity.

Here is a sample application displaying how to code up a sliding drawer. It's pretty simple, and I don't think it needs more explanation.

<SlidingDrawer android:id="@+id/slidingDrawer1"
        android:layout_width="fill_parent" android:layout_height="fill_parent"
        android:topOffset="50dip" android:handle="@+id/handle"

The sample project sets up a Sliding Drawer at the bottom of the screen. You can change it to appear at place of the screen. You just need to change/adjust some properties of the SlidingDrawer.
  • The orientation property can be set to either "horizontal" and "vertical"
  • There are properties like "topOffset", "bottonOffset", "rightOffset" and "leftOffset" with which you can position your drawer anywhere.
  • With a few more changes, you can attach backgrounds/images to the whole SlidingDrawer. For example, I have added a color background to the content of the Sliding Drawer.
Update: Here is the link to the source code which shows how to cook up a simple sliding drawer.

Thursday, August 13, 2009

FileWriter in Android

This is a pretty handy API that you can use to write a string of information to a file on the device. It doesn’t need a StreamWriter or BufferedWriter or FileOutputStream. It is short and sweet.
            FileWriter fWriter;
                 fWriter = new FileWriter(“\sdcard\filename.txt”);
             }catch(Exception e){
The flush() and close() calls are important here, and also make sure that the “sdcard” is mounted. Else, you can use a path such as “data\data\com\yourpackage\filename.txt” which would create a file in the data directory of your package.

Scrollview in Android

I never noticed, or realised how an application’s UI would render when the orientation changed, since most of the time I tested my apps on the emulator. But one fine day, when a friend of mine walked in and asked to change the orientation, I shocked to see that the layouts didn’t fit in the landscape view.
Well, the solution!!!
Wrap your layouts in a parent ScrollView, so that, when the orientation changes, you will be able to at-least scroll and view the whole layout. How the UI looks, is however a different concern.

Relative Layouts vs Linear Layouts

From the very first day, I hated Relative Layouts. I struggled with layouts in general during my initial days till I figured out that Linear Layouts can create any kind of complex layout you need. By using only the Linear Layouts, you can create whatever you want. I had always wondered what was the purpose of the other available layouts.
I was a fan of the Linear Layouts till the day I hit the dead end. With SDK 1.5, pressing for the limit up to which your view hierarchy can be deep, problems started with my existing apps. I was able to remove the errors by removing a layout or two. And then, there was a case, where, I couldn’t remove a level. I was hitting the StackOverflow exception all the time. Frustrated, I posted my query to Google Groups, and guess what, Romain Guy responded, asking me to remove or simplify my view hierarchy. Well, if I were to listen to him, it would mean converting some Linear Layouts to Relative Layouts. And since I didn’t understand Relative Layouts then, I though it was a big big ask. But I tried, and guess what, now my UI is faster, simpler and I don’t get that StackOverflow exception.
I have now realized that though it is easy to use LinearLayouts, but RelativeLayouts not only make your UI load faster, but also is easier to render (at least for me). I have changed all my Linear Layouts to Relative ones, wherever possible.
I also watched the Google I/O videos that gave me a lot of information regarding how to code for Android platform. One of them I would like to mention in my next blog would be about the ListView, the most widely used widget, and i guess, the most wrongly used as well.
Keep droiding….