在更改屏幕方向时，重新创建活动，进度对话框和异步任务时出现问题。我在这里看到了一些解决方案，我决定使用onRetainCustomNonConfigurationInstance（）来保存AsyncTask的实例。好吧，在onCreate中我检查是否有AsyncTask的实例，如果存在，我会显示一个新的进度对话框。但是这个对话框在无限循环中阻塞UI（在onPostExecute中有dialog.dismiss（）），并且活动当然没有显示结果。
的onCreate
getDirection = (GetDirection) getLastCustomNonConfigurationInstance();
if(getDirection != null) {
dialog = new ProgressDialog(RouteActivity.this);
dialog.setMessage(getResources().getString(R.string.loading_data));
dialog.setIndeterminate(false);
dialog.setCancelable(false);
dialog.show();
} else {
getDirection = new GetDirection();
getDirection.execute();
}
onRetainCustomNonConfigurationInstance
@Override
public Object onRetainCustomNonConfigurationInstance() {
return getDirection;
}
@Override
protected void onDestroy() {
super.onDestroy();
if (dialog.isShowing()) {
dialog.dismiss();
}
}
编辑＃1 ： 我采用了具有Fragment和Retained Fragment的Kingfisher解决方案，但是当我在AsyncTask的doInBackground期间更改方向时，在Expandable Listview上有一个NPE。
08-14 12:50:40.866: E/AndroidRuntime(22739): FATAL EXCEPTION: main
08-14 12:50:40.866: E/AndroidRuntime(22739): java.lang.NullPointerException
08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.adapter.ListRouteExpandableAdapter.getGroupCount(ListRouteExpandableAdapter.java:78)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.widget.ExpandableListConnector.getCount(ExpandableListConnector.java:399)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.widget.ListView.setAdapter(ListView.java:460)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.widget.ExpandableListView.setAdapter(ExpandableListView.java:470)
08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.activity.RouteActivity.onPostExecute(RouteActivity.java:792)
08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:244)
08-14 12:50:40.866: E/AndroidRuntime(22739): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:1)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.AsyncTask.finish(AsyncTask.java:631)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.AsyncTask.access$600(AsyncTask.java:177)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.Handler.dispatchMessage(Handler.java:99)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.os.Looper.loop(Looper.java:137)
08-14 12:50:40.866: E/AndroidRuntime(22739): at android.app.ActivityThread.main(ActivityThread.java:4895)
08-14 12:50:40.866: E/AndroidRuntime(22739): at java.lang.reflect.Method.invokeNative(Native Method)
08-14 12:50:40.866: E/AndroidRuntime(22739): at java.lang.reflect.Method.invoke(Method.java:511)
08-14 12:50:40.866: E/AndroidRuntime(22739): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
08-14 12:50:40.866: E/AndroidRuntime(22739): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
08-14 12:50:40.866: E/AndroidRuntime(22739): at dalvik.system.NativeStart.main(Native Method).
这里是片段中的代码：
public class GetDirectionFragment extends Fragment {
private Map<Leg, List<Step>> legsCollection;
private ArrayList<Object> legsAndSteps;
private List<Leg> legs;
private List<Poi> pois;
private List<LatLng> polyz;
/**
* Callback interface through which the fragment will report the
* task's progress and results back to the Activity.
*/
public static interface TaskCallbacks {
void onPreExecute();
void onPostExecute();
List<Poi> getListPoiByRoute();
void setLegs(List<Leg> legs, Map<Leg, List<Step>> legsCollection);
void setPolyline(List<LatLng> polyz);
}
private TaskCallbacks callbacks;
private GetDirectionTask getDirectionTask;
/**
* Hold a reference to the parent Activity so we can report the
* task's current progress and results. The Android framework
* will pass us a reference to the newly created Activity after
* each configuration change.
*/
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
callbacks = (TaskCallbacks) activity;
} catch(ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement TaskCallbacks");
}
pois = callbacks.getListPoiByRoute();
}
/**
* This method will only be called once when the retained
* Fragment is first created.
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Retain this fragment across configuration changes.
setRetainInstance(true);
// Create and execute the background task.
getDirectionTask = new GetDirectionTask();
getDirectionTask.execute();
}
/**
* Set the callback to null so we don't accidentally leak the
* Activity instance.
*/
@Override
public void onDetach() {
super.onDetach();
callbacks = null;
}
private class GetDirectionTask extends AsyncTask<Void, Integer, Void> {
@Override
protected void onPreExecute() {
if (callbacks != null) {
callbacks.onPreExecute();
}
}
/**
* Note that we do NOT call the callback object's methods
* directly from the background thread, as this could result
* in a race condition.
*/
@Override
protected Void doInBackground(Void... ignore) {
List<String> lats = new ArrayList<String>();
List<String> longs = new ArrayList<String>();
for(Poi poi: pois) {
lats.add(poi.getCoordinates().getLatitude());
longs.add(poi.getCoordinates().getLongitude());
}
String stringUrl = "http://maps.googleapis.com/maps/api/directions/" +
"json?";
//if(actualLanguage.equals("en")) {
// stringUrl += "language=en_EN";
//} else {
stringUrl += "language=it";
//}
stringUrl+="&mode=walking&units=metric&origin=" +
lats.get(0) + "," +
longs.get(0);
stringUrl += "&destination=" +
lats.get(pois.size()-1) + "," +
longs.get(pois.size()-1) + "&" +
"waypoints=";
for(int i = 1; i<=lats.size()-2 && i<=longs.size()-2; i++) {
stringUrl += lats.get(i)+","+longs.get(i);
if(i==(lats.size()-2) && i==(longs.size()-2)) {
stringUrl += "&sensor=false";
} else {
stringUrl +="|";
}
}
Log.i("urlgoogle", stringUrl);
StringBuilder response = new StringBuilder();
try {
URL url = new URL(stringUrl);
HttpURLConnection httpconn = (HttpURLConnection) url
.openConnection();
if (httpconn.getResponseCode() == HttpURLConnection.HTTP_OK) {
BufferedReader input = new BufferedReader(
new InputStreamReader(httpconn.getInputStream()),
8192);
String strLine = null;
while ((strLine = input.readLine()) != null) {
response.append(strLine);
}
input.close();
}
String jsonOutput = response.toString();
JSONObject jsonObject = new JSONObject(jsonOutput);
// routesArray contains ALL routes
JSONArray routesArray = jsonObject.getJSONArray("routes");
// Grab the first route
JSONObject route = routesArray.getJSONObject(0);
JSONArray legsArray = route.getJSONArray("legs");
legs = new ArrayList<Leg>();
legsAndSteps = new ArrayList<Object>();
String htmlInstructions;
legsCollection = new LinkedHashMap<Leg, List<Step>>();
for(int i=0; i<legsArray.length(); i++) {
List<Step> steps = new ArrayList<Step>();
Leg leg = new Leg();
//int idLeg = 0;
JSONObject legJson = legsArray.getJSONObject(i);
leg.setDistance(legJson.getJSONObject("distance").getString("text"));
leg.setDuration(legJson.getJSONObject("duration").getString("text"));
leg.setEndAddress(legJson.getString("end_address"));
leg.setStartAddress(legJson.getString("start_address"));
leg.setIdLeg(pois.get(i).getId());
leg.setStartPoiName(pois.get(i).getName());
leg.setEndPoiName(pois.get(i+1).getName());
legsAndSteps.add(leg);
JSONArray stepsArray = legJson.getJSONArray("steps");
for(int j=0; j<stepsArray.length(); j++) {
Step step = new Step();
JSONObject stepJson = stepsArray.getJSONObject(j);
step.setDistance(stepJson.getJSONObject("distance").getString("text"));
step.setDuration(stepJson.getJSONObject("duration").getString("text"));
htmlInstructions = android.text.Html.fromHtml(stepJson.getString("html_instructions")).toString();
step.setInstructions(htmlInstructions);
//step.setIdLeg(idLeg);
//Aggiunto per Exp
steps.add(step);
legsAndSteps.add(step);
}
legsCollection.put(leg, steps);
legs.add(leg);
}
JSONObject poly = route.getJSONObject("overview_polyline");
String polyline = poly.getString("points");
polyz = decodePoly(polyline);
callbacks.setLegs(legs, legsCollection);
callbacks.setPolyline(polyz);
} catch (Exception e) {
}
return null;
}
@Override
protected void onPostExecute(Void ignore) {
if (callbacks != null) {
callbacks.onPostExecute();
}
}
}
/* Method to decode polyline points */
private List<LatLng> decodePoly(String encoded) {
[code...]
}
}
此处为活动中的代码：
@Override
public void onPostExecute() {
expListView = (ExpandableListView) findViewById(R.id.lv_routepoi);
ListRouteExpandableAdapter expListAdapter = new ListRouteExpandableAdapter(
getApplicationContext(), legs, legsCollection);
expListView.setAdapter(expListAdapter);
setGroupIndicatorToRight();
expListView.setChildDivider(getResources().getDrawable(R.drawable.divider_route));
[code...]
dialog.dismiss();
}
@Override
public void setLegs(List<Leg> legs, Map<Leg, List<Step>> legsCollection) {
this.legs = legs;
this.legsCollection = legsCollection;
}
@Override
public void setPolyline(List<LatLng> polyz) {
this.polyz = polyz;
}
编辑＃2 ：我尝试了Kingfisher的新解决方案，但在doInBackground方法中总是有一个NPE。如果我在加载过程中没有更改屏幕的方向，应用程序不会崩溃并在列表视图上显示数据。
08-14 17:27:44.897: I/AsyncTask(30604): java.lang.NullPointerException
08-14 17:27:44.897: E/AndroidRuntime(30604): FATAL EXCEPTION: main
08-14 17:27:44.897: E/AndroidRuntime(30604): java.lang.NullPointerException
08-14 17:27:44.897: E/AndroidRuntime(30604): at com.pasquini.activity.RouteActivity.onPostExecute(RouteActivity.java:847)
08-14 17:27:44.897: E/AndroidRuntime(30604): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:253)
08-14 17:27:44.897: E/AndroidRuntime(30604): at com.pasquini.fragment.GetDirectionFragment$GetDirectionTask.onPostExecute(GetDirectionFragment.java:1)
08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.AsyncTask.finish(AsyncTask.java:631)
08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.AsyncTask.access$600(AsyncTask.java:177)
08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.Handler.dispatchMessage(Handler.java:99)
08-14 17:27:44.897: E/AndroidRuntime(30604): at android.os.Looper.loop(Looper.java:137)
08-14 17:27:44.897: E/AndroidRuntime(30604): at android.app.ActivityThread.main(ActivityThread.java:4895)
08-14 17:27:44.897: E/AndroidRuntime(30604): at java.lang.reflect.Method.invokeNative(Native Method)
08-14 17:27:44.897: E/AndroidRuntime(30604): at java.lang.reflect.Method.invoke(Method.java:511)
08-14 17:27:44.897: E/AndroidRuntime(30604): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
08-14 17:27:44.897: E/AndroidRuntime(30604): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
08-14 17:27:44.897: E/AndroidRuntime(30604): at dalvik.system.NativeStart.main(Native Method)
这里是片段中的代码：
public class GetDirectionFragment extends Fragment {
private Map<Leg, List<Step>> legsCollection;
private ArrayList<Object> legsAndSteps;
private List<Leg> legs;
private List<Poi> pois;
private List<LatLng> polyz;
/**
* Callback interface through which the fragment will report the
* task's progress and results back to the Activity.
*/
public static interface TaskCallbacks {
void onPreExecute();
void onPostExecute();
List<Poi> getListPoiByRoute();
void setLegs(List<Leg> legs, Map<Leg, List<Step>> legsCollection);
void setPolyline(List<LatLng> polyz);
}
private TaskCallbacks callbacks;
private GetDirectionTask getDirectionTask;
/**
* Hold a reference to the parent Activity so we can report the
* task's current progress and results. The Android framework
* will pass us a reference to the newly created Activity after
* each configuration change.
*/
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
callbacks = (TaskCallbacks) activity;
} catch(ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement TaskCallbacks");
}
pois = callbacks.getListPoiByRoute();
}
/**
* This method will only be called once when the retained
* Fragment is first created.
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Retain this fragment across configuration changes.
setRetainInstance(true);
// Create and execute the background task.
getDirectionTask = new GetDirectionTask();
getDirectionTask.execute();
}
/**
* Set the callback to null so we don't accidentally leak the
* Activity instance.
*/
@Override
public void onDetach() {
super.onDetach();
callbacks = null;
}
private class GetDirectionTask extends AsyncTask<Void, Integer, Void> {
@Override
protected void onPreExecute() {
if (callbacks != null) {
callbacks.onPreExecute();
}
}
/**
* Note that we do NOT call the callback object's methods
* directly from the background thread, as this could result
* in a race condition.
*/
@Override
protected Void doInBackground(Void... ignore) {
List<String> lats = new ArrayList<String>();
List<String> longs = new ArrayList<String>();
for(Poi poi: pois) {
lats.add(poi.getCoordinates().getLatitude());
longs.add(poi.getCoordinates().getLongitude());
}
String stringUrl = "http://maps.googleapis.com/maps/api/directions/" +
"json?";
//if(actualLanguage.equals("en")) {
// stringUrl += "language=en_EN";
//} else {
stringUrl += "language=it";
//}
stringUrl+="&mode=walking&units=metric&origin=" +
lats.get(0) + "," +
longs.get(0);
stringUrl += "&destination=" +
lats.get(pois.size()-1) + "," +
longs.get(pois.size()-1) + "&" +
"waypoints=";
for(int i = 1; i<=lats.size()-2 && i<=longs.size()-2; i++) {
stringUrl += lats.get(i)+","+longs.get(i);
if(i==(lats.size()-2) && i==(longs.size()-2)) {
stringUrl += "&sensor=false";
} else {
stringUrl +="|";
}
}
Log.i("urlgoogle", stringUrl);
StringBuilder response = new StringBuilder();
try {
URL url = new URL(stringUrl);
HttpURLConnection httpconn = (HttpURLConnection) url
.openConnection();
if (httpconn.getResponseCode() == HttpURLConnection.HTTP_OK) {
BufferedReader input = new BufferedReader(
new InputStreamReader(httpconn.getInputStream()),
8192);
String strLine = null;
while ((strLine = input.readLine()) != null) {
response.append(strLine);
}
input.close();
}
String jsonOutput = response.toString();
JSONObject jsonObject = new JSONObject(jsonOutput);
// routesArray contains ALL routes
JSONArray routesArray = jsonObject.getJSONArray("routes");
// Grab the first route
JSONObject route = routesArray.getJSONObject(0);
JSONArray legsArray = route.getJSONArray("legs");
legs = new ArrayList<Leg>();
legsAndSteps = new ArrayList<Object>();
String htmlInstructions;
legsCollection = new LinkedHashMap<Leg, List<Step>>();
for(int i=0; i<legsArray.length(); i++) {
List<Step> steps = new ArrayList<Step>();
Leg leg = new Leg();
//int idLeg = 0;
JSONObject legJson = legsArray.getJSONObject(i);
leg.setDistance(legJson.getJSONObject("distance").getString("text"));
leg.setDuration(legJson.getJSONObject("duration").getString("text"));
leg.setEndAddress(legJson.getString("end_address"));
leg.setStartAddress(legJson.getString("start_address"));
leg.setIdLeg(pois.get(i).getId());
leg.setStartPoiName(pois.get(i).getName());
leg.setEndPoiName(pois.get(i+1).getName());
legsAndSteps.add(leg);
JSONArray stepsArray = legJson.getJSONArray("steps");
for(int j=0; j<stepsArray.length(); j++) {
Step step = new Step();
JSONObject stepJson = stepsArray.getJSONObject(j);
step.setDistance(stepJson.getJSONObject("distance").getString("text"));
step.setDuration(stepJson.getJSONObject("duration").getString("text"));
htmlInstructions = android.text.Html.fromHtml(stepJson.getString("html_instructions")).toString();
step.setInstructions(htmlInstructions);
//step.setIdLeg(idLeg);
steps.add(step);
legsAndSteps.add(step);
}
legsCollection.put(leg, steps);
legs.add(leg);
}
JSONObject poly = route.getJSONObject("overview_polyline");
String polyline = poly.getString("points");
polyz = decodePoly(polyline);
setLegs(legs, legsCollection);
setPolyline(polyz);
} catch (Exception e) {
Log.i(TAG, e.toString());
}
return null;
}
@Override
protected void onPostExecute(Void ignore) {
if (callbacks != null) {
callbacks.onPostExecute();
}
}
}
/* Method to decode polyline points */
private List<LatLng> decodePoly(String encoded) {
[code...]
}
public void setLegs(List<Leg> legs, Map<Leg, List<Step>> legsCollection) {
this.legs = legs;
this.legsCollection = legsCollection;
}
public void setPolyline(List<LatLng> polyz) {
this.polyz = polyz;
}
public List<Leg> getLegs() {
return this.legs;
}
public Map<Leg, List<Step>> getMap() {
return this.legsCollection;
}
public List<LatLng> getPolyline() {
return this.polyz;
}
}
此处为活动中的代码：
@Override
protected void onCreate(Bundle savedInstanceState) {
[code...]
FragmentManager fm = getSupportFragmentManager();
getDirectionFragment = (GetDirectionFragment) fm.findFragmentByTag(TASK_FRAGMENT_TAG);
// If the Fragment is non-null, then it is currently being
// retained across a configuration change.
if (getDirectionFragment == null) {
getDirectionFragment = new GetDirectionFragment();
fm.beginTransaction().add(getDirectionFragment, TASK_FRAGMENT_TAG).commit();
[code...]
}
@Override
public void onPostExecute() {
legs = getDirectionFragment.getLegs();
legsCollection = getDirectionFragment.getMap();
polyz = getDirectionFragment.getPolyline();
expListView = (ExpandableListView) findViewById(R.id.lv_routepoi);
ListRouteExpandableAdapter expListAdapter = new ListRouteExpandableAdapter(
getApplicationContext(), legs, legsCollection);
expListView.setAdapter(expListAdapter);
setGroupIndicatorToRight();
expListView.setChildDivider(getResources().getDrawable(R.drawable.divider_route));
[code...]
}
答案 0 :(得分：2)
点击此链接：Handling Configuration Changes with Fragments或您可以使用AsyncTaskLoader。我建议使用Retained Fragment来处理配置更改。仔细阅读文章。
已编辑：请勿在{{1}}中致电callback.set。您应该在重新创建活动时找到doInBackground，并在Retained Fragment尝试使用onPost function {1}}获取获取列表结果的函数。
Retained Fragment希望得到这个帮助。
答案 1 :(得分：0)
在清单文件中的标记活动中使用android:configChanges="keyboardHidden|orientation|screenSize"。这导致活动不会再次更改方向而运行，您不需要保存任何数据
答案 2 :(得分：0)
你永远不会更新异步任务中的对话框，以便它会解除新的对话框（因此看似无限循环，但实际上只是阻止了UI，没有循环）。
当您保存状态并重新加载时，您需要将该对话框更新为新对话框，以便dismiss（）将忽略正确的状态。
只需在您的任务中添加setDialog（）方法，然后在onCreate（）中使用新对话框调用它。
还有一件事，您可能需要考虑添加一个检查以查看AsyncTask是否在您将新对话框设置为它之前完成并显示它。在你的方向改变之后但是在onCreate（）之前它可能已经完成，在这种情况下你会有一个被阻止的UI。这在onCreate中是安全的，因为onPostExecute和onCreate都在同一个线程（UI线程）上运行。
答案 3 :(得分：0)
我想出了一个相对简单的解决方案来解决这个问题。您可以使用持有者，该持有者可以参考您正在运行的AsyncTask。
活动：
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.add(R.id.container, new MainFragment());
transaction.commit();
}
}
}
碎片：
public class MainFragment extends Fragment implements View.OnClickListener, SampleAsyncTask.Callback {
private Button mExecuteButton;
private ProgressDialog mProgressDialog;
@Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_main, container, false);
mExecuteButton = (Button) view.findViewById(R.id.execute_button);
mExecuteButton.setOnClickListener(this);
SampleAsyncTask asyncTask = SampleAsyncTask.Holder.Instance.get();
asyncTask.setCallback(this);
if (asyncTask.isRunning()) {
showProgressDialog(asyncTask.getProgress());
}
return view;
}
@Override
public void onDetach () {
SampleAsyncTask asyncTask = SampleAsyncTask.Holder.Instance.get();
if (asyncTask.isRunning()) {
asyncTask.setCallback(null);
}
if (mProgressDialog != null) {
mProgressDialog.dismiss();
mProgressDialog = null;
}
super.onDetach();
}
private void showProgressDialog (int progress) {
mProgressDialog = new ProgressDialog(getActivity());
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setButton(ProgressDialog.BUTTON_NEGATIVE, "Cancel", makeNegativeButtonListener());
mProgressDialog.setCancelable(false);
mProgressDialog.setProgress(progress);
mProgressDialog.setMax(100);
mProgressDialog.show();
}
private DialogInterface.OnClickListener makeNegativeButtonListener () {
DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
@Override
public void onClick (DialogInterface dialog, int which) {
SampleAsyncTask asyncTask = SampleAsyncTask.Holder.Instance.get();
if (asyncTask.isRunning()) {
asyncTask.cancel(true);
mProgressDialog.dismiss();
}
}
};
return listener;
}
@Override
public void onClick (View v) {
SampleAsyncTask asyncTask = SampleAsyncTask.Holder.Instance.get();
asyncTask.setCallback(this);
if (!asyncTask.isRunning()) {
showProgressDialog(0);
asyncTask.execute(100, 200);
}
}
// SampleAsyncTask.Callback implementation
@Override
public void onPostExecute (boolean success) {
String message = (success) ? "SUCCESS" : "FAIL";
Toast.makeText(getActivity(), message, Toast.LENGTH_SHORT).show();
mProgressDialog.dismiss();
}
@Override
public void onProgressUpdate (int progressValue) {
if (mProgressDialog != null) {
mProgressDialog.setProgress(progressValue);
}
}
}
AsyncTask：
public class SampleAsyncTask extends AsyncTask<Integer, Integer, Boolean> {
public static final String LOG_TAG = SampleAsyncTask.class.getSimpleName();
private static final Callback LOG_CALLBACK = new Callback() {
@Override
public void onPostExecute (boolean success) {
Log.i(LOG_TAG, "#onPostExecute (" + success + ")");
}
@Override
public void onProgressUpdate (int progressValue) {
Log.i(LOG_TAG, "#onProgressUpdate(" + progressValue + ")");
}
};
private boolean mRunning = false;
private int mProgress = -1;
private Callback mCallback = LOG_CALLBACK;
public void setCallback (Callback callback) {
if (callback == null) {
mCallback = LOG_CALLBACK;
}
else {
mCallback = callback;
}
}
public boolean isRunning () {
return mRunning;
}
public int getProgress () {
return mProgress;
}
@Override
protected Boolean doInBackground (Integer... params) {
mRunning = true;
for (int i = 0; i < params[0]; i++) {
if (isCancelled()) {
return false;
}
try {
Thread.sleep(params[1]);
mProgress = i;
publishProgress(i);
}
catch (InterruptedException e) {
return false;
}
}
return true;
}
@Override
protected void onPostExecute (Boolean success) {
mRunning = false;
Holder.Instance.reset();
mCallback.onPostExecute(success);
}
@Override
protected void onProgressUpdate (Integer... values) {
mCallback.onProgressUpdate(values[0]);
}
@Override
protected void onCancelled (Boolean aBoolean) {
mRunning = false;
Holder.Instance.reset();
}
@Override
protected void onCancelled () {
mRunning = false;
Holder.Instance.reset();
}
public enum Holder {
Instance;
private SampleAsyncTask mSampleAsyncTask;
public SampleAsyncTask get () {
if (mSampleAsyncTask == null) {
mSampleAsyncTask = new SampleAsyncTask();
}
return mSampleAsyncTask;
}
private void reset () {
mSampleAsyncTask = null;
}
}
public interface Callback {
public void onPostExecute (boolean success);
public void onProgressUpdate (int progressValue);
}
}
答案 4 :(得分：0)
我编写了相同的代码来解决这个问题
第一步是制作应用类：
public class TheApp extends Application {
private static TheApp sTheApp;
private HashMap<String, AsyncTask<?,?,?>> tasks = new HashMap<String, AsyncTask<?,?,?>>();
@Override
public void onCreate() {
super.onCreate();
sTheApp = this;
}
public static TheApp get() {
return sTheApp;
}
public void registerTask(String tag, AsyncTask<?,?,?> task) {
tasks.put(tag, task);
}
public void unregisterTask(String tag) {
tasks.remove(tag);
}
public AsyncTask<?,?,?> getTask(String tag) {
return tasks.get(tag);
}
}
在AndroidManifest.xml中
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme"
android:name="com.example.tasktest.TheApp">
活动代码：
public class MainActivity extends Activity {
private Task1 mTask1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTask1 = (Task1)TheApp.get().getTask("task1");
}
/*
* start task is not running jet
*/
public void handletask1(View v) {
if (mTask1 == null) {
mTask1 = new Task1();
TheApp.get().registerTask("task1", mTask1);
mTask1.execute();
} else
Toast.makeText(this, "Task is running...", Toast.LENGTH_SHORT).show();
}
/*
* cancel task if is not finished
*/
public void handelCancel(View v) {
if (mTask1 != null)
mTask1.cancel(false);
}
public class Task1 extends AsyncTask<Void, Void, Void>{
@Override
protected Void doInBackground(Void... params) {
try {
for(int i=0; i<120; i++) {
Thread.sleep(1000);
Log.i("tests", "loop=" + i);
if (this.isCancelled()) {
Log.e("tests", "tssk cancelled");
break;
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onCancelled(Void result) {
TheApp.get().unregisterTask("task1");
mTask1 = null;
}
@Override
protected void onPostExecute(Void result) {
TheApp.get().unregisterTask("task1");
mTask1 = null;
}
}
}
当活动方向更改变量时，mTask将从应用程序上下文中获取。当任务完成时，变量设置为null并从内存中删除。
对我来说足够了。
答案 5 :(得分：0)