android学习笔记23：幻灯片

使用gallary和imageswitcher可以在android中实现如windows中的幻灯片图片浏览效果。

用gallary作为下面的图片选择部分，imageSwitcher作为图片显示部分

<?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">
<!-- 定义一个ImageSwitcher组件 -->
<ImageSwitcher android:id="@+id/switcher"
	android:layout_width="320dp"
	android:layout_height="320dp"
	/>
<!-- 定义一个Gallery组件 -->
<Gallery android:id="@+id/gallery"
	android:layout_width="fill_parent"
	android:layout_height="wrap_content"
	android:layout_marginTop="25dp" 
	android:unselectedAlpha="0.6"
	android:spacing="3pt"
	/>	
</LinearLayout>

自定义一个BaseAdapter作为Gallary的数据源，设置一个setOnItemSelectedListener作为监听器，实时改变imageSwitcher中为图片，用TyoedArray保存Gallery中的属性值。

public class GallaryTest extends Activity
{
	int[] imageIds = new int[]
	{
		R.drawable.shuangzi, R.drawable.shuangyu,
		R.drawable.chunv, R.drawable.tiancheng, R.drawable.tianxie,
		R.drawable.sheshou, R.drawable.juxie, R.drawable.shuiping,
		R.drawable.shizi, R.drawable.baiyang, R.drawable.jinniu,
		R.drawable.mojie };

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		final Gallery gallery = (Gallery) findViewById(R.id.gallery);
		// 获取显示图片的ImageSwitcher对象
		final ImageSwitcher switcher = (ImageSwitcher) 
			findViewById(R.id.switcher);
		// 为ImageSwitcher对象设置ViewFactory对象
		switcher.setFactory(new ViewFactory()
		{
			@Override
			public View makeView()
			{
				ImageView imageView = new ImageView(GallaryTest.this);
				imageView.setBackgroundColor(0xff0000);
				imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
				imageView.setLayoutParams(new ImageSwitcher.LayoutParams(
					LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
				return imageView;
			}
		});
		// 设置图片更换的动画效果
		switcher.setInAnimation(AnimationUtils.loadAnimation(this,
			android.R.anim.fade_in));
		switcher.setOutAnimation(AnimationUtils.loadAnimation(this,
			android.R.anim.fade_out));
		// 创建一个BaseAdapter对象，该对象负责提供Gallery所显示的图片
		BaseAdapter adapter = new BaseAdapter()
		{
			@Override
			public int getCount()
			{
				return imageIds.length;
			}
			@Override
			public Object getItem(int position)
			{
				return position;
			}
			@Override
			public long getItemId(int position)
			{
				return position;
			}

			// 该方法的返回的View就是代表了每个列表项
			@Override
			public View getView(int position, View convertView, ViewGroup parent)
			{
				// 创建一个ImageView
				ImageView imageView = new ImageView(GallaryTest.this);
				imageView
					.setImageResource(imageIds[position % imageIds.length]);
				// 设置ImageView的缩放类型
				imageView.setScaleType(ImageView.ScaleType.FIT_XY); //把图片 不按比例 扩大/缩小到View的大小显示
				imageView.setLayoutParams(new Gallery.LayoutParams(75, 100));
				//用TyoedArray保存Gallery中的属性值
				TypedArray typedArray = obtainStyledAttributes(
					R.styleable.Gallery);
				imageView.setBackgroundResource(typedArray.getResourceId(
					R.styleable.Gallery_android_galleryItemBackground, 0));
				return imageView;
			}
		};
		gallery.setAdapter(adapter);
		gallery.setOnItemSelectedListener(new OnItemSelectedListener()
		{
			// 当Gallery选中项发生改变时触发该方法
			@Override
			public void onItemSelected(AdapterView<?> parent, View view,
				int position, long id)
			{
				switcher.setImageResource(imageIds[position % imageIds.length]);
			}

			@Override
			public void onNothingSelected(AdapterView<?> parent)
			{
			}
		});
	}
}