Gallery, Using Gallery widget

Here is a exercise to implement a picture view using Gallery, a view that shows items in a center-locked, horizontally scrolling list.

Basically, this exercise follow the Android Tutorial, Hello Gallery.Create a Android Application, HelloGallery. 

Copy some images, in .png format, into res/drawable/ directory. Named a,b,...,e.png in my case.

Android supports bitmap resource files in a few different formats: png (preferred), jpg (acceptable), gif (discouraged). The bitmap file itself is compiled and referenced by the file name without the extension (so res/drawable/my_picture.png would be referenced as R.drawable.my_picture).

Create res/values/attrs.xml to define Theme_android_galleryItemBackground.

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

Modify main.xml to have a Gallery in the screen.

<?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="wrap_content"
/>

Now open the java file and insert the following code into it.

public class HellogalleryActivity extends Activity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

   super.onCreate(savedInstanceState);

   setContentView(R.layout.main);

   Gallery g = (Gallery) findViewById(R.id.gallery);

   g.setAdapter(new ImageAdapter(this));

   g.setOnItemClickListener(new OnItemClickListener() {

       public void onItemClick(AdapterView<?> parent,

           View v, int position, long id) {

           Toast.makeText(HellogalleryActivity.this, "" + position,

               Toast.LENGTH_SHORT).show();

       }

   });

}

public class ImageAdapter extends BaseAdapter {

   int mGalleryItemBackground;

   private Context mContext;

   private Integer[] mImageIds = {

           R.drawable.a,

R.drawable.b,

           R.drawable.c,

R.drawable.d,

           R.drawable.e,R.drawable.f,

           R.drawable.g,R.drawable.h

   };

   public ImageAdapter(Context c) {

       mContext = c;

       TypedArray a = obtainStyledAttributes(R.styleable.Theme);

       mGalleryItemBackground = a.getResourceId(                  

                   

R.styleable.Theme_android_galleryItemBackground,

                   0);

       a.recycle();

   }

   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.setLayoutParams(new Gallery.LayoutParams(150, 100));

       i.setScaleType(ImageView.ScaleType.FIT_XY);

       i.setBackgroundResource(mGalleryItemBackground);

       return i;

   }

}

}