1、CursorLoader使用Demo
public class MainActivity extends Activity implements LoaderManager.LoaderCallbacks<Cursor> {
String TITLE = MediaStore.Audio.Media.TITLE;
String SINGER = MediaStore.Audio.Media.ARTIST;
String SONGURL = MediaStore.Audio.Media.DATA;
Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
private LoaderManager loaderManager;
private Cursor myCursor;
private ListView lv;
private SimpleCursorAdapter adapter;
private String songUrl;
/**
* 创建loader之后, 会在子线程执行loadInBackground()方法进行加载数据
*/
@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
CursorLoader loader = new CursorLoader(this, uri, null, null, null,null);
return loader;
}
/**
* loader加载数据完成,返回一个cursor对象,供我们查询数据
*/
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
myCursor = cursor;
Cursor oldCursor = adapter.swapCursor(cursor);
Log.e("tag", "onLoadFinished: " + oldCursor);
}
/**
* loader重置时回调,需要释放对这个loader数据有引用的cursor
*/
@Override
public void onLoaderReset(Loader<Cursor> loader) {
adapter.swapCursor(null);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
intiData();
loaderManager = getLoaderManager();
//调用该方法后会回调onCreateLoader来创建loader对象
loaderManager.initLoader(1, null, this);
}
private void intiData() {
lv = (ListView) findViewById(R.id.lv);
adapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_2, null,
new String[] {TITLE, SINGER }, new int[] { android.R.id.text1, android.R.id.text2 },
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
myCursor.moveToPosition(position);
songUrl = myCursor.getString(myCursor.getColumnIndex(SONGURL));
Log.e("tag", "clickStart: " + songUrl);
}
});
}
public void clickStart(View view) {
Intent i = new Intent(MainActivity.this, MusicService.class);
i.setAction("pause");
// i.putExtra("id", songUrl);
startService(i);
Log.e("tag", "clickStart: ");
// Log.e("tag", "clickStart: " );
}
public void clickStop(View view) {
Intent i = new Intent(MainActivity.this, MusicService.class);
i.setAction("stop");
startService(i);
}
}
2、AsyncTaskLoader详细使用DEMO
基于上篇的Fragments 代码，添加Loaders功能，实现加载应用程序数据到界面上，DEMO的运行效果如下：
核心代码为
应用程序的数据对象类：
private final AppListLoader mLoader;
private final ApplicationInfo mInfo;
private final File mApkFile;
private String mLable;
private Drawable mIcon;
private boolean mMounted;
public AppEntry(AppListLoader loader, ApplicationInfo info) {
mLoader = loader;
mInfo = info;
mApkFile = new File(info.sourceDir);
}
public ApplicationInfo getApplicationInfo() {
return mInfo;
}
public String getLable() {
return mLable;
}
public Drawable getIcon() {
if (mIcon == null) {
if (mApkFile.exists()) {
mIcon = mInfo.loadIcon(mLoader.mPm);
return mIcon;
} else {
mMounted = false;
}
} else if (!mMounted) {
if (mApkFile.exists()) {
mMounted = true;
mIcon = mInfo.loadIcon(mLoader.mPm);
return mIcon;
}
} else {
return mIcon;
}
return mLoader.getContext().getResources().getDrawable(
android.R.drawable.sym_def_app_icon);
}
@Override
public String toString() {
// TODO Auto-generated method stub
return mLable.toString();
}
void loadLable(Context mContext) {
if (mLable == null || !mMounted) {
if (!mApkFile.exists()) {
mMounted = false;
mLable = mInfo.packageName;
} else {
mMounted = true;
CharSequence lable = mInfo.loadLabel(mContext
.getPackageManager());
mLable = lable != null ? lable.toString()
: mInfo.packageName;
}
}
}
}
实现AsyncTaskLoader 加载数据
final InterestingConfigChanges mLastConfig = new InterestingConfigChanges();
final PackageManager mPm;
List<AppEntry> mApps;
packageIntentReceiver mPackageObserver;
public AppListLoader(Context context) {
super(context);
// TODO Auto-generated constructor stub
mPm = getContext().getPackageManager();
}
@Override
public List<AppEntry> loadInBackground() {
// TODO Auto-generated method stub
List<ApplicationInfo> apps = mPm
.getInstalledApplications(PackageManager.GET_UNINSTALLED_PACKAGES
| PackageManager.GET_DISABLED_COMPONENTS);
if (apps == null)
apps = new ArrayList<ApplicationInfo>();
final Context mContext = getContext();
List<AppEntry> entries = new ArrayList<AppEntry>(apps.size());
for (ApplicationInfo info : apps) {
AppEntry entry = new AppEntry(this, info);
entry.loadLable(mContext);
entries.add(entry);
}
Collections.sort(entries, ALPHA_COMPARATOR);
return entries;
}
@Override
public void deliverResult(
List<com.xuzhi.fragment.FragmentDemoActivity.AppEntry> data) {
// TODO Auto-generated method stub
if (isReset()) {
if (data != null) {
//释放资源处理
}
}
List<AppEntry> oladApps=data;
mApps=data;
if(isStarted()){
super.deliverResult(data);
}
if(oladApps!=null){
//释放资源
}
}
protected void onStartLoading() {
if(mApps!=null)
deliverResult(mApps);
if(mPackageObserver==null)
mPackageObserver=new packageIntentReceiver(this);
boolean configChange=mLastConfig.applyNewConfig(getContext().getResources());
if(takeContentChanged()|| mApps== null || configChange){
forceLoad();
}
};
@Override
public void onCanceled(
List<com.xuzhi.fragment.FragmentDemoActivity.AppEntry> data) {
// TODO Auto-generated method stub
super.onCanceled(data);
cancelLoad();
}
@Override
protected void onReset() {
// TODO Auto-generated method stub
super.onReset();
onStopLoading();
if(mApps!=null){
//释放资源
mApps=null;
}
if(mPackageObserver!=null){
getContext().unregisterReceiver(mPackageObserver);
mPackageObserver=null;
}
}
}
实现数据源：
private LayoutInflater mInflater;
public AppListAdapter(Context context) {
// TODO Auto-generated constructor stub
super(context, android.R.layout.simple_list_item_2);
mInflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void setData(List<AppEntry> data){
clear();
if(data!=null){
addAll(data);
}
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View view;
if(convertView==null){
view=mInflater.inflate(R.layout.list_item_icon_text, parent,false);
}else{
view=convertView;
}
AppEntry item=getItem(position);
((ImageView)view.findViewById(R.id.icon)).setImageDrawable(item.getIcon());
((TextView)view.findViewById(R.id.text)).setText(item.getLable());
return view;
}
}
在Activity 或者Fragments 里面实现接口：
public static class DetailsFragment extends ListFragment implements OnQueryTextListener,LoaderCallbacks<List<AppEntry>>
实现接口里面的函数：
// TODO Auto-generated method stub
return false;
}
public boolean onQueryTextSubmit(String query) {
// TODO Auto-generated method stub
return false;
}
public Loader<List<com.xuzhi.fragment.FragmentDemoActivity.AppEntry>> onCreateLoader(
int id, Bundle args) {
// TODO Auto-generated method stub
return new AppListLoader(getActivity());
}
/**
* Load 完成后
*/
public void onLoadFinished(
Loader<List<com.xuzhi.fragment.FragmentDemoActivity.AppEntry>> arg0,
List<com.xuzhi.fragment.FragmentDemoActivity.AppEntry> arg1) {
// TODO Auto-generated method stub
mAdapter.setData(arg1);
if (isResumed()) {
setListShown(true);
} else {
setListShownNoAnimation(true);
}
}
/**
* Loader 重置时
*/
public void onLoaderReset(
Loader<List<com.xuzhi.fragment.FragmentDemoActivity.AppEntry>> arg0) {
// TODO Auto-generated method stub
mAdapter.setData(null);
}
得到LoaderManager初始化Loader，启动加载在Fragment 的onActivityCreated回调方法上添加，本DEMO的DetailsFragment类添加：
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
mAdapter = new AppListAdapter(getActivity());
setListAdapter(mAdapter);
// Start out with a progress indicator.
setListShown(false);
// Prepare the loader. Either re-connect with an existing one,
// or start a new one.
getLoaderManager().initLoader(0, null, this);
}
参考资料：