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));
}
});
}

最后

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