您好我有一个从网站数据库中获取用户的功能 我的功能
private void get_users() {
try {
url = "my address";
dbGetData3 = new DbGetData();
new Thread(new Runnable() {
public void run() {
data = dbGetData3.getDataFromDB(url);
runOnUiThread(new Runnable() {
@Override
public void run() {
userha = parseJSON3(data);
}
});
}
}).start();
Toast.makeText(context, "please wait ", Toast.LENGTH_LONG)
.show();
} catch (Exception e) {
toast(9);
}
现在我想在获取数据完成时添加加载进度条。
我像这样使用AsyncTask：
private class LongOperation extends AsyncTask<String, Void, String> {
protected void onPreExecute() {
progressDialog = new ProgressDialog(Login.this);
progressDialog.setTitle("Processing...");
progressDialog.setMessage("Please wait...");
progressDialog.setCancelable(true);
progressDialog.show();
}
protected String doInBackground(String... params) {
try {
get_users();
} catch (Exception e) {
}
return null;
}
protected void onPostExecute(String result) {
progressDialog.dismiss();
}
}
我将此代码用于执行
mytask = new LongOperation();
if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.HONEYCOMB)
mytask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
else
mytask.execute();
imageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
onCreate(savedInstanceState);
}
});
但是我没有显示进度对话框（让用户工作）
我改变了我的代码：
if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.HONEYCOMB){
mytask.onPreExecute();
mytask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
}
else
{
mytask.onPreExecute();
mytask.execute();
}
然后我的进度对话框总是显示
我在stackoverflow中测试其他代码，如
AsyncTask doInBackground does not run
AsyncTask called from Handler will not execute doInBackground
Android SDK AsyncTask doInBackground not running (subclass)
但这对我不起作用 请帮帮我坦克
答案 0 :(得分：0)
Consdier使用LoaderManager和an AsyncTaskLoader来表达这类内容。
AsyncTasks是一个痛苦的屁股，因为你必须通过屏幕旋转来管理他们的生命周期等。使用LoaderManager，所有这些都是过去的。
以下是加载“项目”列表的加载程序示例。
public class ItemsLoader extends AsyncTaskLoader<List<Item>> {
private static final String TAG = "ItemsLoader";
private List<Item> mItems;
private ItemUpdatedReceiver mObserver;
private int mSomeParam;
public static class ItemUpdatedReceiver extends BroadcastReceiver {
private static final String TAG = "ItemLoader";
final ItemsLoader mLoader;
public ItemUpdatedReceiver(ItemsLoader mLoader) {
this.mLoader = mLoader;
// listen for changes to the account we're using
IntentFilter filter = new IntentFilter(GlobalConstants.ACTION_ITEMS_UPDATED);
LocalBroadcastManager.getInstance(mLoader.getContext()).registerReceiver(this, filter);
}
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (GlobalConstants.ACTION_ITEMS_UPDATED.equals(action)) {
mLoader.onContentChanged();
}
}
}
public void setSomeParam(int someParam){
mSomeParam = someParam;
onContentChanged();
}
public ItemsLoader(Context context, int someParam) {
super(context);
mSomeParam = someParam;
onContentChanged();
}
@Override
public List<Item> loadInBackground() {
// do whatever you need to do here
ArrayList<Item> Items = new ArrayList<>();
return Items;
}
/**
* Called when there is new data to deliever to the client.
*
* @param data
*/
@Override
public void deliverResult(List<Item> data) {
if (isReset()) {
// an async query came in while the loader is stopped, we don't need the result
//release resources if needed
onReleaseResources(data);
}
List<Item> oldItems = mItems;
mItems = data;
if (isStarted()) {
// If the Loader is currently started, we can immediately
// deliver its results.
super.deliverResult(mItems);
}
// 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 (oldItems != null) {
onReleaseResources(oldItems);
}
}
@Override
protected void onStartLoading() {
super.onStartLoading();
if (mItems != null) {
// If we currently have a result available, deliver it
// immediately.
deliverResult(mItems);
}
// start listening for changes
if (mObserver == null) {
mObserver = new ItemUpdatedReceiver(this);
}
if (takeContentChanged() || mItems == null) {
// 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(List<Item> items) {
super.onCanceled(items);
// At this point we can release the resources associated with 'profile'
// if needed.
onReleaseResources(items);
}
@Override
protected void onReset() {
super.onReset();
// Ensure the laoder is stopped
onStopLoading();
// At this point we can release the resources if needed.
if (mItems != null) {
onReleaseResources(mItems);
mItems = null;
}
// Stop monitoring for changes.
if (mObserver != null) {
LocalBroadcastManager.getInstance(getContext()).unregisterReceiver(mObserver);
mObserver = null;
}
}
/**
* Helper function to take care of releasing resources associated
* with an actively loaded data set.
*/
private void onReleaseResources(List<Item> data) {
// For a simple List<> there is nothing to do. For something
// like a Cursor, we would close it here.
}
}
要使用此类，您必须在活动中扩展LoaderManager.LoaderCallbacks＆gt;并覆盖方法：
public Loader<List<Item>> onCreateLoader(int id, Bundle args) {
// This is called when a new Loader needs to be created. This
// sample only has one Loader, so we don't care about the ID.
// start the loading dialog here
return new ItemsLoader(context);
}
public void onLoadFinished(Loader<List<Item>> loader, List<Item>data) {
// do something with your data, hide the progress dialog
}
public void onLoaderReset(Loader<Cursor> loader) {
// set the old data to null
}
实际开始加载：
getLoaderManager().initLoader(LOADER_ID, null, this);