After going through the Part 1 and Part 2 of “How To: Building Android Application”, we will go explore more on the android sample and some tips to improve the performance of the emulator.

Playing with Android Sample Application

In this tutorial, we will setup the Android sample application which will help you play with most of the android components.

Step1: click on File->New->Other and then select Android->Android Sample Project

click Next and Finish.

in case you see “ This target has no samples. Please select another target.” message, you should click Windows->Android SDK Manager and select the sample and other versions (if needed) and Install the packages. This step will take a while. After that is done, retry Step 1.

useful emulator Shortcuts:

Alt+Enter maximizes the emulator. Nice for demos.

Ctrl+F11 changes the orientation of the emulator.

F8 turns network on / off.

F6 to turn on / off the trackball

Performance Considerations

Try to use a smaller resolution for your emulator as for example HVGA. The emulator gets slower the more pixels its needs to render as it is using software rendering.
While creating device (e.g. myDevice), set the flag "Enabled" for Snapshots. This will save the state of the emulator and let it start much faster.

This is in the continuation of my previous post “How To: Building Android Application with easy steps–Part 1”. In this tutorial, we will go over creating the sample application using the environment we have already setup.

Here is the details of the application we will build:
Number Counting: providing the buttons to increment/decrement the number present in the text box

Step 1: create Android project

Select File → New → Other → Android → Android Project and create the Android project named

com.hashfold.android.numbercounting

click Next and select the Android SDK version on which your application will be build and compiled.

note: selecting the Android 2.1 is the best options as 90% of Android devices till date are based on this version.

Click next and make sure the information filled is matching with below:

and then click Finish

note: numbercountingActivity is the name of the activity which will get started when the application starts

here is the final project view after above steps:

Step 2: writing application code

so far we have completed creating the project space. Now its time to do some coding and creating the GUI components.

2.1 AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.hashfold.android.numbercounting"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="7" />

<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name="com.hashfold.android.numbercountingActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

2.2 strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="details">number counting application</string>
<string name="hello">Hello! number counting!</string>
<string name="app_name">NumberCounting</string>
<color name="bgcolor">#000000</color>
</resources>

2.3 main.xml layout – the GUI component

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent" android:background="@color/bgcolor">
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content" android:text="@string/hello" />
<LinearLayout android:id="@+id/LinearLayout01"
android:layout_height="wrap_content" android:layout_width="fill_parent">
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_weight="1"
android:text="+" android:id="@+id/Plus"></Button>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_weight="1"
android:id="@+id/Minus" android:text="-"></Button>
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_weight="1"
android:id="@+id/Value" android:text="value"></TextView>
<Button android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_weight="1"
android:text="Ok" android:id="@+id/Ok"></Button>
</LinearLayout>

</LinearLayout>

2.4 numbercountingActivity.java

package com.hashfold.android;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import com.hashfold.android.numbercounting.R;

public class numbercountingActivity extends Activity implements OnClickListener
{
Button Plus, Minus, Ok;
TextView Value;
int score = 0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Plus = (Button) findViewById(R.id.Plus);
Minus = (Button) findViewById(R.id.Minus);
Ok = (Button) findViewById(R.id.Ok);
Value = (TextView) findViewById(R.id.Value);

Plus.setOnClickListener(this);
Minus.setOnClickListener(this);
Ok.setOnClickListener(this);

}

public void onClick(View v)
{
boolean showText = false;

switch(v.getId())
{
case R.id.Plus: score++; showText = true; break;
case R.id.Minus: score--; showText = true; break;
case R.id.Ok: showText = true; break;
}
if(showText)
Value.setText(String.valueOf(score));
}
}

The R.java is the resource file which is auto generated based on strings.xml and other related resource changes.

Step 3: running the application

setup the run configuration: click on Run->Run configurations

and then click on ‘New launch configuration’ and then fill in the information needed as below:

now click on Apply button and then Run button to run the application.

It will take a while in starting up the Android device emulator with the device select in above step “myDevice”.

Once the device is started, it will look like below: