Display Views android exam

So far all the views you have seen are used to display text information. For displaying images, you can use the ImageView, Gallery and ImageSwitcher views.

Gallery and ImageView Views

The Gallery is a view that shows items (such as images) in a center-locked, horizontal scrolling list. Figure 8 shows the Gallery view used in the Android Market.

Figure 8: The Gallery view used in the Android Market

To see how the Gallery view works, add a new file to the res/layout folder and name it as displayview.xml and populate it with the following elements:

<?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"
    >  
 
    <TextView   
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:text="Images of San Francisco" /> 
 
    <Gallery
        android:id="@+id/gallery1"
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" />          
    <ImageView
        android:id="@+id/image1"
        android:layout_width="320px" 
        android:layout_height="250px"
        android:scaleType="fitXY" />
 
</LinearLayout>

Add a new file to the res/values folder and name it as attrs.xml. Populate it with the following:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="Gallery1">
        <attr name="android:galleryItemBackground" />
    </declare-styleable>
</resources>

The Gallery1 style is used to apply to images displayed in the Gallery view so that the each image has a border around it (see Figure 9).

Figure 9: Gallery view, with borders on images

Add a few images to the res/drawable folder (see Figure 10).

Figure 10: Adding images

Add a new class to the src/net.learn2develop.AndroidViews folder and name it as DisplayViewsExample.java. Populate it as follows:

package net.learn2develop.AndroidViews;
 
import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
 
public class DisplayViewsExample extends Activity
{    
    //---the images to display---
    Integer[] imageIDs = {
            R.drawable.pic1,
            R.drawable.pic2,
            R.drawable.pic3,
            R.drawable.pic4,
            R.drawable.pic5,
            R.drawable.pic6,
            R.drawable.pic7                    
    };
 
    @Override    
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.displayview);
 
        Gallery gallery = (Gallery) findViewById(R.id.gallery1);
 
        gallery.setAdapter(new ImageAdapter(this));        
        gallery.setOnItemClickListener(new OnItemClickListener() 
        {
            public void onItemClick(AdapterView parent, 
            View v, int position, long id) 
            {                
                Toast.makeText(getBaseContext(), 
                        "pic" + (position + 1) + " selected", 
                        Toast.LENGTH_SHORT).show();
            }
        });
    }
 
    public class ImageAdapter extends BaseAdapter 
    {
        private Context context;
        private int itemBackground;
 
        public ImageAdapter(Context c) 
        {
            context = c;
            //---setting the style---
            TypedArray a = obtainStyledAttributes(R.styleable.Gallery1);
            itemBackground = a.getResourceId(
                R.styleable.Gallery1_android_galleryItemBackground, 0);
            a.recycle();                    
        }
 
        //---returns the number of images---
        public int getCount() {
            return imageIDs.length;
        }
 
        //---returns the ID of an item--- 
        public Object getItem(int position) {
            return position;
        }            
 
        public long getItemId(int position) {
            return position;
        }
 
        //---returns an ImageView view---
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView = new ImageView(context);
            imageView.setImageResource(imageIDs[position]);
            imageView.setScaleType(ImageView.ScaleType.FIT_XY);
            imageView.setLayoutParams(new Gallery.LayoutParams(150, 120));
            imageView.setBackgroundResource(itemBackground);
            return imageView;
        }
    }    
}

You create the ImageAdapter class (which extends the BaseAdapter class) so that it can bind to the Gallery view with a series of ImageView views. The ImageView view is used to display images.
When an image in the Gallery view is selected (or clicked), the position of the image selected is displayed.
Modify the AndroidManifest.xml file to register the new activity:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="net.learn2develop.AndroidViews"
      android:versionCode="1"
      android:versionName="1.0.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".ViewsActivity" 
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>        
 
        <activity android:name=".DisplayViewsExample"
                  android:label="@string/app_name" />                            
 
    </application>
</manifest>

Modify the ViewsActivity.java file as follows to start the DisplayViewsExample activity:

public class ViewsActivity extends Activity 
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
 
        startActivity(new Intent(this, DisplayViewsExample.class));
 
    }
}

Press F11 to debug the application on the Android emulator. Figure 11 shows the Gallery view in action. You can scroll through the list of thumbnail images by swiping it. When an image is selected, the name of the image selected will be displayed by the Toast class.

Figure 11: The Gallery view in action

If you want to display the selected image in an ImageView view, modify the onItemClick() method so that the selected image is shown in the ImageView (image1) view:

public void onItemClick(AdapterView parent, 
            View v, int position, long id) 
            {                
                //---display the images selected---
                ImageView imageView = (ImageView) findViewById(R.id.image1);                
                imageView.setImageResource(imageIDs[position]);
            }

When an image is selected, it will now be displayed in the ImageView view below (see Figure 12).

Figure 12: Selected image displayed in ImageView view