Google Android Tutorial

Demo 5 - RadioButtons

The next standard control is the RadioButton, within a RadioGroup.

To be placed in tools\demo\res\layout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="wrap_content">
	<RadioGroup android:id="@+id/group1" android:layout_width="fill_parent"
		android:layout_height="wrap_content" android:orientation="vertical">
		<RadioButton android:id="@+id/radio1" android:text="madras"
			android:layout_width="wrap_content" android:layout_height="wrap_content" />
		<RadioButton android:id="@+id/radio2" android:text="bombay"
			android:layout_width="wrap_content" android:layout_height="wrap_content" />
	</RadioGroup>
	<Button android:id="@+id/button1" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:text="Button" />
	<TextView android:id="@+id/label1" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:text="where" />
	<EditText android:id="@+id/text1" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:text="" android:textSize="18sp"
		android:layout_x="70px" android:layout_y="182px" />
</LinearLayout>

The following Java code should be placed in tools\demo\src\mypack\mydemo

package mypack.mydemos;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.widget.*;

public class demo extends Activity

{

	TextView label1;

	RadioGroup group1;

	RadioButton radio1, radio2;

	Button button1;

	EditText text1;

	@Override
	protected void onCreate(Bundle icicle)

	{

		super.onCreate(icicle);

		setContentView(R.layout.main);

		group1 = (RadioGroup)

		findViewById(R.id.group1);

		radio1 = (RadioButton)

		findViewById(R.id.radio1);

		radio2 = (RadioButton)

		findViewById(R.id.radio2);

		button1 = (Button) findViewById(R.id.button1);

		text1 = (EditText) findViewById(R.id.text1);

		text1.setText("radio");

		label1 = (TextView) findViewById(R.id.label1);

		label1.setText("where?");

		button1.setOnClickListener(new clicker());

	}

	// ...inner class ---follows ->

	class clicker implements Button.OnClickListener

	{

		public void onClick(View v)

		{

			if (v == button1)

			{

				if (radio1.isChecked())

				{
					text1.setText("madras");
				}

				if (radio2.isChecked())

				{
					text1.setText("bombay");
				}

			}

		}

	}

	// ----inner class ends here ---

}

You would have observed that I am naming all my java files as 'demo.java'. May be confusing at first but I am doing so with a purpose. First of all, the emulator screen gets cluttered with too many buttons if we go on adding my examples. What I have done is :

I have created a folder as d:\android\mydemos.

In mydemos folder, I have created subfolders such as (ex1,ex2 etc). But, within each folder, I have demo.java & main.xml.

This way, we can easily test each of our demos  by uniform procedure. In my system, I had the problem of insufficient memory. And, by the above step, I was able to test all my programs by the same name.

Here is an important tip however, if you choose to name the source files and xml files differently and want to reduce the clutter.

Demo 6 - Gallery 

Interestingly, there is a ready-made control in the toolbox, named 'gallery'. Let us now learn to use this control, though the syntax is a bit difficult. This time, we will need demo.java, main.xml and also another folder in tools\demo\res\drawable. This special folder is to be created by us. You can read 'img' instead of 'drawable'. So, we place all the image files to be displayed in the gallery, in this folder.

Let us as usual create the xml file by using DroidDraw as follows.

<?xml version="1.0" encoding="utf-8"?>
<Gallery xmlns:android="http://schemas.android.com/apk/res/android"
	android:id="@+id/gallery" android:layout_width="fill_parent"
	android:layout_height="fill_parent" android:layout_alignParentBottom="true"
	android:layout_alignParentLeft="true" android:gravity="center_vertical"
	android:spacing="5" />

The following class is to be placed in tools\demo\mypack\mydemos

package mypack.mydemos;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.*;
import android.widget.AdapterView.OnItemClickListener;

public class example extends Activity

{

	@Override
	public void onCreate(Bundle icicle) {

		super.onCreate(icicle);
		setContentView(R.layout.main);
		Gallery gallery = (Gallery)
		findViewById(R.id.gallery);
		gallery.setAdapter(new ImageAdapter(this));
		gallery.setOnItemClickListener(new OnItemClickListener()
		{

			public void onItemClick(AdapterView parent,
			View v,
			int position,
			long id)

			{

				Toast.makeText(example.this, "" + position,
				Toast.LENGTH_SHORT).show();
			}

		});

	}

	public class ImageAdapter extends BaseAdapter
	{

		public ImageAdapter(Context c)
		{
			mContext = c;
		}

		public int getCount()
		{
			return mImageIds.length;
		}

		public Object getItem(int position)
		{
			return position;
		}

		public long getItemId(int position)
		{
			return position;
		}

		public View getView(int position, View
		convertView, ViewGroup parent)
		{
			ImageView i = new ImageView(mContext);
			i.setImageResource(mImageIds[position]);
			i.setScaleType(ImageView.ScaleType.FIT_XY);
			i.setLayoutParams(new Gallery.LayoutParams(160, 200));
			return i;
		}

		public float getAlpha(boolean focused, int offset)
		{
			return Math.max(0, 1.0f - (0.2f * Math.abs(offset)));
		}

		public float getScale(boolean focused, int offset)
		{
			return Math.max(0, 1.0f - (0.2f *
			Math.abs(offset)));
		}
		private Context mContext;
		private Integer[] mImageIds = {
		R.drawable.cindy,
		R.drawable.clinton,
		R.drawable.ford,
		R.drawable.cybil,
		R.drawable.demi,
		R.drawable.colin,
		R.drawable.david,
		R.drawable.drew
		};

	}

}

How to uninstall an application from the emulator?

• Make sure your emulator is running
• Open a dos box in the android/tools folder  d:\android\tools>adb shell 
• You will get the shell prompt
   #cd /data/app
   #ls
   (It will list all the *.apk installed in your emulator)
  # rm  example.apk
  ( if you want to remove 'example')
  #exit
• You will see the application getting removed from the emulator at the same moment

That completes the first part of my introductory tutorial on Android SDK.