Android Intents Example in ListView

In my last article, I have shown you a basic example of intent. In this article, I will show you a more practical example of Intents. Scenario is that a list item itself contains more information in the form of a list.

When the list item is selected, it should open another list.

In the customized list example, I showed you a list with your favorite cartoon characters. Once you select a character, it should open another list with related characters.

ListView layout will hold the main characters.

cartoon_list_view.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/taskListParent"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </ListView>

</LinearLayout>

List item layout contains just a text field. We will dynamically set the cartoon’s image using setCompoundDrawablesWithIntrinsicBounds.

cartoon_list_item_view.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/name" />

</LinearLayout>

Our model contains Cartoon bean. It has reference to the image resource and the related cartoons object.

Cartoon:

package com.javarticles.android;

import java.util.List;

public class Cartoon {
	private String mName;
	private int mCartoonPicRes;
	private List<Cartoon> mOtherCartoons;
	
	public Cartoon(String name, int picRes, List<Cartoon> otherCartoons) {
		mName = name;
		mCartoonPicRes = picRes;
		mOtherCartoons = otherCartoons;
	}
	
	public Cartoon(String name, int picRes) {
		mName = name;
		mCartoonPicRes = picRes;
	}

	public String getName() {
		return mName;
	}

	public int getCartoonPicRes() {
		return mCartoonPicRes;
	}

	public List<Cartoon> getOtherCartoons() {
		return mOtherCartoons;
	}	
}

In the getView, we set the cartoon image using setCompoundDrawablesWithIntrinsicBounds.

CartoonListAdapter:

package com.javarticles.android;

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class CartoonListAdapter extends ArrayAdapter<Cartoon> {
	private List<Cartoon> cartoonItems;
	private Context context;

	public CartoonListAdapter(Context context, int textViewResourceId,
			List<Cartoon> cartoonItems) {
		super(context, textViewResourceId, cartoonItems);
		this.context = context;
		this.cartoonItems = cartoonItems;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {

		View view = convertView;
		if (view == null) {
			LayoutInflater vi = (LayoutInflater) context
					.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
			view = vi.inflate(R.layout.cartoon_list_item_view, null);
		}

		Cartoon cartoon = cartoonItems.get(position);

		if (cartoon != null) {
			// name
			TextView nameTextView = (TextView) view.findViewById(R.id.name);
			nameTextView.setText(cartoon.getName());

			nameTextView.setCompoundDrawablesWithIntrinsicBounds(0,
					cartoon.getCartoonPicRes(), 0, 0);
		}

		return view;
	}
}

CartoonListActivity represents the main list view. Let’s go through the steps followed in onCreate.

Call setContentView to set the list view’s layout.
Create CartoonListAdapter adapter and set it to the list view using setListAdapter. This contains the list of Cartoon objects to display.
Set an item listener using listView.setOnItemClickListener to start the list activity that will display the related cartoons.
In the item listener callback, OnItemClickListener.onItemClick, we explicitly pass in the related list activity class OtherCartoonsListActivity to Intent during its creation.
```
Intent intent = new Intent(CartoonListActivity.this, OtherCartoonsListActivity.class);
```
In the Intent object, we put in an extra value, to let the related list activity know which cartoon was selected.
The extra value contains “cartoon” as key and name of the selected cartoon as the value.
```
intent.putExtra("cartoon", cartoonSelected.getName());
```
We call startActivity(intent) to start the related list activity.

CartoonListActivity:

package com.javarticles.android;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;

public class CartoonListActivity extends ListActivity {
	private CartoonListAdapter cartoonListAdapter;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.cartoon_list_view);		
		cartoonListAdapter = new CartoonListAdapter(this,
				R.layout.cartoon_list_item_view, new ArrayList(CARTOONS.values()));
		setListAdapter(cartoonListAdapter);	
		ListView listView = getListView();
		listView.setOnItemClickListener(new OnItemClickListener(){

			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				Intent intent = new Intent(CartoonListActivity.this, OtherCartoonsListActivity.class);				
				Cartoon cartoonSelected = cartoonListAdapter.getItem(position);
				intent.putExtra("cartoon", cartoonSelected.getName());
				startActivity(intent);
				finish();
			}});
	}	
	
	public static List getOtherCartoonList(String character) {
		Cartoon cartoon = CARTOONS.get(character);
		return cartoon.getOtherCartoons();
	}

	private static final Map<String, Cartoon> CARTOONS = new HashMap<String, Cartoon>();

	static {
		List tintinCartoons = new ArrayList(4);
		tintinCartoons.add(new Cartoon("Snowy", R.drawable.snowy_small));
		tintinCartoons.add(new Cartoon("Captain Haddock",
				R.drawable.captain_haddock_small));
		tintinCartoons.add(new Cartoon("Thomson & Thopson",
				R.drawable.thomson_thompson_small));
		tintinCartoons.add(new Cartoon("Professor Calculus",
				R.drawable.professor_calculus_small));
		Cartoon tintin = new Cartoon("Tintin", R.drawable.tintin_thumb,
				tintinCartoons);

		List asterixCartoons = new ArrayList(4);
		asterixCartoons.add(new Cartoon("Obelix", R.drawable.obelix_small));
		asterixCartoons.add(new Cartoon("Bicarbonatofsoda",
				R.drawable.bicarbonatofsoda_small));
		asterixCartoons.add(new Cartoon("Idefix", R.drawable.idefix_small));
		asterixCartoons.add(new Cartoon("Troubadix", R.drawable.troubadix_small));
		Cartoon asterix = new Cartoon("Asterix", R.drawable.asterix_thumb,
				asterixCartoons);
		
		CARTOONS.put("Tintin", tintin);
		CARTOONS.put("Asterix", asterix);
	}
}

In OtherCartoonsListActivity, we get the Intent object passed in from the parent list activity and then get the extra value to know the cartoon selected.

Intent intent = getIntent();
String cartoon = intent.getStringExtra("cartoon");

Once we know the cartoon selected, we will get its related cartoons, create the adapter and set it to the list view.

List cartoonList = CartoonListActivity.getOtherCartoonList(cartoon);
cartoonListAdapter = new CartoonListAdapter(this, R.layout.cartoon_list_item_view, cartoonList);
setListAdapter(cartoonListAdapter);

OtherCartoonsListActivity:

package com.javarticles.android;

import java.util.List;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

public class OtherCartoonsListActivity extends ListActivity {
	private CartoonListAdapter cartoonListAdapter;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		// set the layout of the Activity
		setContentView(R.layout.cartoon_list_view);
		
		// get the intent that we have passed from ActivityOne
		Intent intent = getIntent();

		// get the extra value
		String cartoon = intent.getStringExtra("cartoon");
		Log.d("otherCartoon", "Get other cartoons for " + cartoon);
		List cartoonList = CartoonListActivity.getOtherCartoonList(cartoon);
		cartoonListAdapter = new CartoonListAdapter(this, R.layout.cartoon_list_item_view, cartoonList);
		setListAdapter(cartoonListAdapter);
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);		
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		switch (id) {
		case R.id.back:
			startActivity(new Intent(this, CartoonListActivity.class));
			finish();
		}
		return super.onOptionsItemSelected(item);
	}
}

To return back to the main list, you need to click on the back button from the action bar.

case R.id.back:
    startActivity(new Intent(this, CartoonListActivity.class));
    finish();

Let’s launch the app and test it.
The first page is the main List:

Main List

On selecting Asterix, related characters of Asterix are shown in the child list:

Child List of Asterix

On selecting TinTin, related characters of Tintin are shown in the child list:

Child List of Tintin

Download Source Code

In this article, I showed you how to use intent to display child lists.
intentExample.zip