Android development tricks

This is a summay of the tricks I have learned making an application called courseApp project.  This application was developed in the Mobile Information Systems that I took at University of Oslo. Eclipse is a very good tool to use for Android development. To start with you need to download Andriod SDK. After installing both of these(and ofcourse Java Development Kit, JDK which is a pre-requirement for both of these), you need to make Eclipse and Android SDK talk together. This is done by a plugin called “ADT plugin for Eclipse” from Google. You can read more about how to install this plugin by clicking hereIn case of Android SDK installation(the exe file) doesn’t recognize JDK on your computer, you can simply download the zip file and extract it. Don’t forget appending that folder to the %PATH% environment variable. Now some more tips follows :

background color for your layout :

add the following code to your layout XML code(#ff32cf is the color code)

[java]android:background=”#ff23cf”[/java]

Background Image for your layout :
1- Add the image you want to the layout folder of your project.
2- Add the following code to your layout XML code

[java]android:background=”@drawable/bbg”[/java]

EditText features :
one of the features I want to talk about is android:singleLine which is very useful. If you want to get some info from the user, this text box is a good tool to use, but make sure you set the SingleLine variable to true. If not if they paste a 20 lines of text by mistake your whole GUI gets out of shape. Also if you want to use this for example to write an email text, then this should be set to false as you want it to contain several lines. The good thing about several lines EditText is that they do have scrolling function.

[java]<EditText … android:singleLine=”true”>//Single Line box for getting email address
</span><span style=”font-family: Consolas, Monaco, ‘Courier New’, Courier, monospace; font-size: 12px; line-height: 18px; white-space: pre;”><EditText … android:singleLine=”false”>//Multi Line box for getting email text[/java]

in case you want limit the number of lines of an EditText:

[java]<span style=”font-family: monospace; font-size: 12px; line-height: 18px; white-space: pre;”><EditText android:layout_width=”fill_parent”</span>
<pre><code>            android:layout_height=”wrap_content” android:gravity=”center”
android:singleLine=”false” android:lines=”5″
android:layout_marginLeft=”10dip” android:layout_marginRight=”10dip”
/></code><span style=”font-family: Georgia, ‘Times New Roman’, ‘Bitstream Charter’, Times, serif; font-size: 13px; line-height: 19px; white-space: normal;”>[/java]

 

Simple Item List :
Setting up a simple Item list with an already filled Arrayadapter.

[java]

static final String[] COUNTRIES = new String[] {“Afghanistan”, “Albania”, “Algeria”, “American Samoa”, “Andorra”,”Angola”, “…”}
<pre>setListAdapter(new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, COUNTRIES));
getListView().setTextFilterEnabled(true);</pre>
[/java]

Drop Down List :
In Android drop down list is a little bit complicated to give value to. You first need to add one Spinner to your layout and then connect it to

[java] String[] Countries = { “India”, “France”, “Japan”, “China”, “U.S” };

// //////////////////Countries Spinner/////////////////////////////////
SpinnerCountries = (Spinner) findViewById(R.id.Spinner01);

// //////////////////////////////////////////////////////////////
// create an arrayAdapter an assign it to the spinner
AdapterCountries = new ArrayAdapter<CharSequence>(this,
android.R.layout.simple_spinner_item);
AdapterCountries
.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
SpinnerCountries.setAdapter(AdapterCountries);

int lenCountries = Countries.length;

for (int i = 0; i < lenCountries; i++) {
// test += Areas[i] + “n”;
AdapterCountries.add(Countries[i]);
}[/java]

source

Disabling the Landscape Mode :
You have two ways to do this, either in the code, or in the XML layout file :

XML :

[java]</span><span style=”font-family: monospace; font-size: 12px; line-height: 18px; white-space: pre;”><activity android:name=”.SomeActivity”</span>
<pre>
<pre><code>              android:label=”@string/app_name”
android:screenOrientation=”portrait”></code>[/java]

OR in the code :

[java][/java][/java]

setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);     //  Fixed Portrait orientation[/java]

Layouts in Android :
LinearLayout :
LinearLayout aligns all children in a single direction — vertically or horizontally, depending on how you define the orientation attribute. All children are stacked one after the other, so a vertical list will only have one child per row, no matter how wide they are, and a horizontal list will only be one row high (the height of the tallest child, plus padding). A LinearLayout respects margins between children and the gravity (right, center, or left alignment) of each child.

TableLayout :
TableLayout positions its children into rows and columns. TableLayout containers do not display border lines for their rows, columns, or cells. The table will have as many columns as the row with the most cells. A table can leave cells empty, but cells cannot span columns, as they can in HTML.

RelativeLayout
RelativeLayout lets child views specify their position relative to the parent view or to each other (specified by ID). So you can align two elements by right border, or make one below another, centered in the screen, centered left, and so on. Elements are rendered in the order given, so if the first element is centered in the screen, other elements aligning themselves to that element will be aligned relative to screen center. Also, because of this ordering, if using XML to specify this layout, the element that you will reference (in order to position other view objects) must be listed in the XML file before you refer to it from the other views via its reference ID.