android ImageSwitcher 切换图片

ImageSwitcher可切换显示图片，实现类似windows图片查看器，上一张，下一张的功能，直接上代码：

public class ActivityMain extends Activity implements ViewSwitcher.ViewFactory{

    private ImageSwitcher switcher;
    private Button forward;
    private Button next;
    //图片索引
    private int index = 0;
    //显示的图片资源
    private List<Drawable> list = new ArrayList<Drawable>();

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        forward = (Button) findViewById(R.id.forward);
        next = (Button) findViewById(R.id.next);

        switcher = (ImageSwitcher) findViewById(R.id.image);

        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            String path = Environment.getExternalStorageDirectory().getAbsolutePath()+"/test";
            File folder = new File(path);
            for(File file : folder.listFiles()){
                list.add(Drawable.createFromPath(file.getAbsolutePath()));
            }
        }
       //必须设置switcher的ViewFactory
        switcher.setFactory(this);
        if(list.size() > 0){
            switcher.setImageDrawable(list.get(0));
        }

       //上一张
        forward.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view) {
                index -- ;
                if(index < 0) {
                  index = list.size() - 1;
                }
                switcher.setImageDrawable(list.get(index));
            }
        });
        //下一张
        next.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view) {
                index ++ ;
                if(index >= list.size()) {
                  index = 0;
                }
                switcher.setImageDrawable(list.get(index));
            }
        });
    }
    //用于显示图片
    @Override
    public View makeView() {
        return new ImageView(this);
    }
}

布局文件：

 

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
            android:orientation="vertical"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent">
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                  android:orientation="vertical"
                  android:layout_width="fill_parent"
                  android:layout_height="fill_parent"
            >
        <ImageSwitcher
                android:id="@+id/image"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                />
        <Button
                android:id="@+id/forward"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:text="forward"
                />
        <Button
                android:id="@+id/next"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:text="next"
                />

    </LinearLayout>
</ScrollView>