四平公司做网站,网络营销推广方案思路,wordpress qq 群,中国建设网官方网站硅灰Loaders#xff0c;获取数据的东西。 总体流程是#xff1a;通过getLoaderManager().initLoader(0,null,this)获得Loader#xff0c;如果没有#xff0c;那么就会调用接口函数获取#xff0c;注意#xff1a;有ID#xff0c;所以要在获取的接口函数里进行相应的选择。 会… Loaders获取数据的东西。 总体流程是通过getLoaderManager().initLoader(0,null,this)获得Loader如果没有那么就会调用接口函数获取注意有ID所以要在获取的接口函数里进行相应的选择。 会自动更新数据 一个主要依赖Activity或者Fragment存在的。 通过getLoaderManager().initLoader(0,null,this)方法初始化LOADER。 要继承LoaderManager.LoaderCallbacks包括 LoaderManager.LoaderCallbacks includes these methods: onCreateLoader() — Instantiate and return a new Loader for the given ID.onLoadFinished() — Called when a previously created loader has finished its load.onLoaderReset() — Called when a previously created loader is being reset, thus making its data unavailable.These methods are described in more detail in the following sections. 第一个用于创建LOADER一般来说只有init的时候ID对应的LOADER不在的时候才会运行该方法。 第二个一般用来获取数据后的填充适配器。 第三个用于重置。 Loader可以自定义一般使用继承AsyncTaskLoader的类。 /*** A custom Loader that loads all of the installed applications.*/
public static class AppListLoader extends AsyncTaskLoaderListAppEntry {final InterestingConfigChanges mLastConfig new InterestingConfigChanges();final PackageManager mPm;ListAppEntry mApps;PackageIntentReceiver mPackageObserver;public AppListLoader(Context context) {super(context);// Retrieve the package manager for later use; note we dont// use context directly but instead the save global application// context returned by getContext().mPm getContext().getPackageManager();}/*** This is where the bulk of our work is done. This function is* called in a background thread and should generate a new set of* data to be published by the loader.*/Override public ListAppEntry loadInBackground() {// Retrieve all known applications.ListApplicationInfo apps mPm.getInstalledApplications(PackageManager.GET_UNINSTALLED_PACKAGES |PackageManager.GET_DISABLED_COMPONENTS);if (apps null) {apps new ArrayListApplicationInfo();}final Context context getContext();// Create corresponding array of entries and load their labels.ListAppEntry entries new ArrayListAppEntry(apps.size());for (int i0; iapps.size(); i) {AppEntry entry new AppEntry(this, apps.get(i));entry.loadLabel(context);entries.add(entry);}// Sort the list.Collections.sort(entries, ALPHA_COMPARATOR);// Done!return entries;}/*** Called when there is new data to deliver to the client. The* super class will take care of delivering it; the implementation* here just adds a little more logic.*/Override public void deliverResult(ListAppEntry apps) {if (isReset()) {// An async query came in while the loader is stopped. We// dont need the result.if (apps ! null) {onReleaseResources(apps);}}ListAppEntry oldApps mApps;mApps apps;if (isStarted()) {// If the Loader is currently started, we can immediately// deliver its results.super.deliverResult(apps);}// At this point we can release the resources associated with// oldApps if needed; now that the new result is delivered we// know that it is no longer in use.if (oldApps ! null) {onReleaseResources(oldApps);}}/*** Handles a request to start the Loader.*/Override protected void onStartLoading() {if (mApps ! null) {// If we currently have a result available, deliver it// immediately.deliverResult(mApps);}// Start watching for changes in the app data.if (mPackageObserver null) {mPackageObserver new PackageIntentReceiver(this);}// Has something interesting in the configuration changed since we// last built the app list?boolean configChange mLastConfig.applyNewConfig(getContext().getResources());if (takeContentChanged() || mApps null || configChange) {// If the data has changed since the last time it was loaded// or is not currently available, start a load.forceLoad();}}/*** Handles a request to stop the Loader.*/Override protected void onStopLoading() {// Attempt to cancel the current load task if possible.cancelLoad();}/*** Handles a request to cancel a load.*/Override public void onCanceled(ListAppEntry apps) {super.onCanceled(apps);// At this point we can release the resources associated with apps// if needed.onReleaseResources(apps);}/*** Handles a request to completely reset the Loader.*/Override protected void onReset() {super.onReset();// Ensure the loader is stoppedonStopLoading();// At this point we can release the resources associated with apps// if needed.if (mApps ! null) {onReleaseResources(mApps);mApps null;}// Stop monitoring for changes.if (mPackageObserver ! null) {getContext().unregisterReceiver(mPackageObserver);mPackageObserver null;}}/*** Helper function to take care of releasing resources associated* with an actively loaded data set.*/protected void onReleaseResources(ListAppEntry apps) {// For a simple List there is nothing to do. For something// like a Cursor, we would close it here.}
} 上面是官方的代码。 构造方法传入context。 loadInBackground是后台真正获取数据的代码。 deliverResult提交数据给客户端可以直接返回。 onStartLoading处理要开始的请求官方在这里进行了更新的监听。 onStopLoading要求停止官方直接使用cancelLoad()。 onCanceled()取消的操作官方建议对资源进行释放。 onReset重置详细看代码。 这样的话就能从头到尾自定义和使用一个Loader了。转载于:https://www.cnblogs.com/yutoulck/p/3619264.html
