用开源项目PhotoView实现图片的双指缩放和双击放大缩小

项目地址：https://github.com/chrisbanes/PhotoView

　　用开源项目有个好处，一是实现简单，二是bug少。那么我们就来说下这个项目能够实现的效果：

1.单个图片的双指缩放，双击放大缩小

PhotoViewAttacher mAttacher;
    ImageView mImageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Any implementation of ImageView can be used!
        mImageView = (ImageView) findViewById(R.id.iv_photo);

        // Set the Drawable displayed
        Drawable bitmap = getResources().getDrawable(R.drawable.ic_launcher);
        mImageView.setImageDrawable(bitmap);

        // Attach a PhotoViewAttacher, which takes care of all of the zooming
        // functionality.
        mAttacher = new PhotoViewAttacher(mImageView);

2.图片的旋转效果，可以精准指定旋转的度数

    private PhotoView photo;
    private final Handler handler = new Handler();
    private boolean rotating = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        photo = new PhotoView(this);
        photo.setImageResource(R.drawable.wallpaper);
        setContentView(photo);

     photo.setRotationBy(10);
    }    

3.放入viewpager来做照片浏览，浏览中可以放大和缩小（这里的viewpager可以设置是否允许左右滑动，如果不用这功能，就直接用普通的viewpager）

private static final String ISLOCKED_ARG = "isLocked";

    private ViewPager mViewPager;
    private MenuItem menuLockItem;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_pager);
        mViewPager = (HackyViewPager) findViewById(R.id.view_pager);
        setContentView(mViewPager);

        mViewPager.setAdapter(new SamplePagerAdapter());

        if (savedInstanceState != null) {
            boolean isLocked = savedInstanceState.getBoolean(ISLOCKED_ARG, false);
            ((HackyViewPager) mViewPager).setLocked(isLocked);
        }
    }

    static class SamplePagerAdapter extends PagerAdapter {

        private static final int[] sDrawables = { R.drawable.wallpaper, R.drawable.wallpaper, R.drawable.wallpaper,
                R.drawable.wallpaper, R.drawable.wallpaper, R.drawable.wallpaper };

        @Override
        public int getCount() {
            return sDrawables.length;
        }

        @Override
        public View instantiateItem(ViewGroup container, int position) {
            //定义可以缩放的图片对象
            PhotoView photoView = new PhotoView(container.getContext());
            photoView.setImageResource(sDrawables[position]);

            // Now just add PhotoView to ViewPager and return it
            container.addView(photoView, LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

            return photoView;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }

    }

这是官方文档的例子

ImageView mImageView;
PhotoViewAttacher mAttacher;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Any implementation of ImageView can be used!
    mImageView = (ImageView) findViewById(R.id.iv_photo);

    // Set the Drawable displayed
    Drawable bitmap = getResources().getDrawable(R.drawable.wallpaper);
    mImageView.setImageDrawable(bitmap);

    // Attach a PhotoViewAttacher, which takes care of all of the zooming functionality.
    mAttacher = new PhotoViewAttacher(mImageView);
}

// If you later call mImageView.setImageDrawable/setImageBitmap/setImageResource/etc then you just need to call
attacher.update();

下面给出的源码是我修改过的，我把原来的放大两次变成了放大一次，然后再双击的话就缩小到原图。至于单击直接退出的效果我给出一个思路，点击一个缩略图后开启一个activity，用渐变的效果显示。在这个弹出的activity放一个可以缩放的图片，然后给这个图片加个监听器（源码中我已经加了），点击后这个activity渐变消失。很简单吧~ 不过这里面需要注意的是缩略图的设置还有弹出activity时很可能要用进度条来等待网络图片

源码下载：http://download.csdn.net/detail/shark0017/7710153