利用LoaderManager加载相册图片

封装了一个类用于加载本地相册

LoaderManager类可以在子线程里进行加载
在activity里面一般可以通过getLoaderManager()方法取得该对象，surpport.v4包的FragmentActivity里获得该对象的方法是getSupportLoaderManager()，我这个类是后者这种情况，具体代码如下

public class LoadLocalPhoto implements LoaderManager.LoaderCallbacks<Cursor>{    //读取图片文件的参数    private static final String STORE_IMAGES[] = {            MediaStore.Images.Media.DATA,            MediaStore.Images.Media.DISPLAY_NAME,            MediaStore.Images.Media.DATE_ADDED,            MediaStore.Images.Media._ID    };    public FragmentActivity activity;    private LoadFinishCallback loadFinishCallback;    //构造方法传入当前的Activity    public LoadLocalPhoto(FragmentActivity activity){        this.activity = activity;        activity.getSupportLoaderManager().initLoader(0,null,this);    }    @Override    public android.support.v4.content.Loader<Cursor> onCreateLoader(int id, Bundle args) {        return new CursorLoader(activity, MediaStore.Images.Media.EXTERNAL_CONTENT_URI,                STORE_IMAGES, null, null, STORE_IMAGES[2] + " DESC");    }    //加载完成调用此方法    @Override    public void onLoadFinished(android.support.v4.content.Loader<Cursor> loader, Cursor data) {        if (data==null){            return;        }        List<ImageFolder> folderList = new ArrayList<>();        int count = data.getCount();        if (count>0){            data.moveToFirst();            do {                String path = data.getString(data.getColumnIndexOrThrow(MediaStore.Images.Thumbnails.DATA));                File imageFile = new File(path);                File folderFile = imageFile.getParentFile();                ImageFolder folder = new ImageFolder();                folder.path = folderFile.getAbsolutePath();                folder.name = folderFile.getName();                if (!folderList.contains(folder)){                    List<String> imageList = new ArrayList<>();                    imageList.add(path);                    folder.images = imageList;                    folderList.add(folder);                }else {                    ImageFolder folder1 = folderList.get(folderList.indexOf(folder));                    folder1.images.add(path);                }            }while (data.moveToNext());        }        //接口调用        loadFinishCallback.finish(folderList);    }    public void setLoadFinishCallback(LoadFinishCallback loadFinishCallback) {        this.loadFinishCallback = loadFinishCallback;    }    @Override    public void onLoaderReset(android.support.v4.content.Loader<Cursor> loader) {    }    public interface LoadFinishCallback{        void finish(List<ImageFolder> folderList);    }}

里面的ImageFolder是随便写的一个bean类：

public class ImageFolder {    public String name;    public String path;    public List<String> images;    @Override    public boolean equals(Object o) {        try {            ImageFolder other = (ImageFolder) o;            return this.path.equalsIgnoreCase(other.path);        }catch (ClassCastException e){            e.printStackTrace();        }        return super.equals(o);    }}

之后在代码里面就可以很简单的使用了：

 @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        new LoadLocalPhoto(this).setLoadFinishCallback(new LoadLocalPhoto.LoadFinishCallback() {            @Override            public void finish(List<ImageFolder> folderList) {                //获取到文件数据就可用进行一系列操作，比如给listview设置adapter                listview.setAdapter(new Adapter(folderList));            }        });    }