范例HelloGallery

Android docs中的范例，简单翻译整理如下。
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1、创建新项目，名称HelloGallery；

2、准备一些图片文件，放到res/drawable/目录下；

3、修改res/layout/目录下main.xml，内容如下：

<?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"
/>

4、在res/values/目录下，新建文件attrs.xml，内容如下：

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

5、打开HelloGallery.java，修改后的代码如下：

public class HelloGallery 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(HelloGallery.this, "" + position, Toast.LENGTH_SHORT).show();
			}
		});
	}

	public class ImageAdapter extends BaseAdapter {

		int mGalleryItemBackground;
		private Context mContext;

		// 图片资源的名称需要根据准备的图片名称进行修改
		private Integer[] mImageIds = {
				R.drawable.expo01, R.drawable.expo02, R.drawable.expo03, R.drawable.expo04, R.drawable.expo05,
				R.drawable.expo06, R.drawable.expo07, R.drawable.expo08
		};

		public ImageAdapter(Context c) {
			mContext = c;
			TypedArray a = obtainStyledAttributes(R.styleable.HelloGallery);
			mGalleryItemBackground = a.getResourceId(R.styleable.HelloGallery_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;
		}
	}
}

6、运行项目，即可看到运行效果，如下图所示：