I've 10 apps which uses AsyncTasks. As you know i show progressdialog in asynctasks to show progress of the task. But there is a problem that i couldn't solve so far about progressdialog.
Here is one of my AsyncTask class (which is not in a other class);
public class GetBalanceAsyncTask extends AsyncTask<Void, Void, String> {
Context context;
ProgressDialog pd;
public GetBakiyeAsyncTask(Context context) {
this.context = context;
}
#Override
protected String doInBackground(Void... arg0) {
String userAgent = HttpHelper.getRandomUserAgent(context);
return HttpHelper.post(PreferenceHelper.getBalanceQueryAPI(context), userAgent);
}
#Override
protected void onPreExecute() {
super.onPreExecute();
pd = ProgressDialog.show(context, "","Please wait...",true);
}
#Override
protected void onPostExecute(String result) {
try {
if (pd != null & pd.isShowing()) {
pd.dismiss();
pd = null;
}
} catch (IllegalArgumentException e) {
pd = null;
e.printStackTrace();
}
if (result != null & result.length() > 0) {
Utils.doTask(result);
} else {
Utils.ShowToast(context,
"An error has occurred, please try again.",
STYLE_CONFIRM, LENGTH_LONG);
}
super.onPostExecute(result);
}
}
and the execption is
java.lang.IllegalArgumentException: View not attached to window manager
at android.view.WindowManagerImpl.findViewLocked(WindowManagerImpl.java:381)
at android.view.WindowManagerImpl.removeView(WindowManagerImpl.java:226)
at android.view.Window$LocalWindowManager.removeView(Window.java:432)
at android.app.Dialog.dismissDialog(Dialog.java:278)
at android.app.Dialog.access$000(Dialog.java:71)
at android.app.Dialog$1.run(Dialog.java:111)
at android.app.Dialog.dismiss(Dialog.java:268)
at fragments.RuyalarFragment$getRuyalarAsyncTask.onPostExecute(GetBalanceAsyncTask.java:27)
at fragments.RuyalarFragment$getRuyalarAsyncTask.onPostExecute(GetBalanceAsyncTask.java:1)
at android.os.AsyncTask.finish(AsyncTask.java:417)
at android.os.AsyncTask.access$300(AsyncTask.java:127)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3691)
at java.lang.reflect.Method.invokeNative(Method.java)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
at dalvik.system.NativeStart.main(NativeStart.java)
I've searched the solution almost everywhere but there is no working results. Most of answers contain use isFinishing, onDestroy or something like this but no body is sure which is working.
Thanks for advice.
How to reproduce the bug:
Enable this option on your device: Settings -> Developer Options -> Don't keep Activities.
Press Home button while the 'AsyncTask' is executing and the ProgressDialog is showing.
The Android OS will destroy an activity as soon as it is hidden. When onPostExecute is called the Activity will be in "finishing" state and the ProgressDialog will be not attached to Activity.
How to fix it:
Check for the activity state in your onPostExecute method.
Dismiss the ProgressDialog in onDestroy method. Otherwise, android.view.WindowLeaked exception will be thrown. This exception usually comes from dialogs that are still active when the activity is finishing.
try this code :
public class YourActivity extends Activity {
<...>
private void showProgressDialog() {
if (pDialog == null) {
pDialog = new ProgressDialog(StartActivity.this);
pDialog.setMessage("Loading. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
}
pDialog.show();
}
private void dismissProgressDialog() {
if (pDialog != null && pDialog.isShowing()) {
pDialog.dismiss();
}
}
#Override
protected void onDestroy() {
dismissProgressDialog();
super.onDestroy();
}
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
#Override
protected void onPreExecute() {
showProgressDialog();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args)
{
doMoreStuff("internet");
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url)
{
if (YourActivity.this.isDestroyed()) {
return;
}
dismissProgressDialog();
something(note);
}
}
}
Late to the party, but really this question has many duplicates on SO.
The most comprehensive summary of solutions I've found is here.
Basically use a retained Fragment to connect your AsyncTask to the new Activity.
Related
I am having the Xamarin.Forms application. I want to implement the local push notification for Android platform, through which an application can receive the notification whenever the app is minimized or phone is locked. I also want to wake-up the phone and display the notification on the lock screen whenever the phone is locked.
As I am new in this kindly help me.
Thanks in advance.
Vivek
I think you should consider two things.
1.Listen for the screen lock：
create a ScreenListener.cs :
public class ScreenListener
{
private Context mContext;
private ScreenBroadcastReceiver mScreenReceiver;
private static ScreenStateListener mScreenStateListener;
public ScreenListener(Context context)
{
mContext = context;
mScreenReceiver = new ScreenBroadcastReceiver();
}
/**
* screen BroadcastReceiver
*/
private class ScreenBroadcastReceiver : BroadcastReceiver
{
private String action = null;
public override void OnReceive(Context context, Intent intent)
{
action = intent.Action;
if (Intent.ActionScreenOn == action)
{ // screen on
mScreenStateListener.onScreenOn();
}
else if (Intent.ActionScreenOff == action)
{ // screen off
mScreenStateListener.onScreenOff();
}
else if (Intent.ActionUserPresent == action)
{ // unlock
mScreenStateListener.onUserPresent();
}
}
}
/**
* begin to listen screen state
*
* #param listener
*/
public void begin(ScreenStateListener listener)
{
mScreenStateListener = listener;
registerListener();
getScreenState();
}
/**
* get screen state
*/
private void getScreenState()
{
PowerManager manager = (PowerManager)mContext
.GetSystemService(Context.PowerService);
if (manager.IsScreenOn)
{
if (mScreenStateListener != null)
{
mScreenStateListener.onScreenOn();
}
}
else
{
if (mScreenStateListener != null)
{
mScreenStateListener.onScreenOff();
}
}
}
/**
* stop listen screen state
*/
public void unregisterListener()
{
mContext.UnregisterReceiver(mScreenReceiver);
}
/**
* regist screen state broadcast
*/
private void registerListener()
{
IntentFilter filter = new IntentFilter();
filter.AddAction(Intent.ActionScreenOn);
filter.AddAction(Intent.ActionScreenOff);
filter.AddAction(Intent.ActionUserPresent);
mContext.RegisterReceiver(mScreenReceiver, filter);
}
public interface ScreenStateListener
{// Returns screen status information to the caller
void onScreenOn();
void onScreenOff();
void onUserPresent();
}
}
then in the MainActivity.cs:
public class MainActivity : AppCompatActivity,ScreenStateListener
{
ScreenListener mScreenListener;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.activity_main);
mScreenListener = new ScreenListener(this);
}
protected override void OnDestroy()
{
base.OnDestroy();
mScreenListener.unregisterListener();
}
protected override void OnResume()
{
base.OnResume();
mScreenListener.begin(this);
}
public void onScreenOn()
{
Console.WriteLine("onScreenOn");
}
public void onScreenOff()
{
Console.WriteLine("onScreenOff");
}
public void onUserPresent()
{
Console.WriteLine("onUserPresent");
}
}
2.creat loacal Notification：
finally you just push the notification in the onScreenOff() method.
What you need is push notifications not local notifications. Local notifications only work if your app is running. Push notifications are handled by OS (Android in this case). Xamarin is recommending using Firebase service to handle it. Procedure is pretty straight forward all what you have to do is follow Tutorial from official Xamarin site.
Remote Notifications with Firebase Cloud Messaging
I have to schedule a work to fetch user current location and update to server in a given interval (Even the app is not running).
I am trying to WorkManagerAPI to implement the functionality.
Is it possible to fetch the current location of the user from the doWork() method ?
locationManager.requestLocationUpdates(
provider, timeInterval, travelDistance, locationListener
);
When I request Location updates from the doWork() it throws below error.
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
As per my understanding, when implementing LocationManager.requestLocationUpdates() on a Worker thread, the call is being made on a non-UI, background thread created by WorkManager. LocationManager.requestLocationUpdates() is an asynchronous call possibly on another background thread. To handle the callbacks defined by the LocationListener, the calling thread must stay alive. Thats why the exception says,
Can't create handler inside thread that has not called Looper.prepare()
Check the code snippet below. Please consider this as pseudocode, I haven't tested this piece of code.
public class LocationWorker extends Worker {
String LOG_TAG = "LocationWorker";
private Context mContext;
private MyHandlerThread mHandlerThread;
public LocationWorker(#NonNull Context context, #NonNull WorkerParameters workerParams) {
super(context, workerParams);
mContext = context;
}
#NonNull
#Override
public Result doWork() {
Log.d(LOG_TAG, "doWork");
mHandlerThread = new MyHandlerThread("MY_THREAD");
mHandlerThread.start();
Runnable runnable = new Runnable() {
#Override
public void run() {
LocationManager locationManager = (LocationManager) mContext.getSystemService(Context.LOCATION_SERVICE);
String bestProvider = locationManager.getBestProvider(new Criteria(), true);
boolean permission = false;
if (PermissionChecker.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED &&
PermissionChecker.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
Log.e(LOG_TAG, "This app requires ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION permissions.");
permission = true;
}
Log.d(LOG_TAG, "permission: "+permission);
Log.d(LOG_TAG, "bestProvider: "+bestProvider);
if (permission && bestProvider != null) {
MyLocationListener locListener = new MyLocationListener();
locationManager.requestLocationUpdates(bestProvider, 500, 1, locListener, mHandlerThread.getLooper());
}
}
};
mHandlerThread.post(runnable);
return Result.success();
}
class MyHandlerThread extends HandlerThread {
Handler mHandler;
MyHandlerThread(String name) {
super(name);
}
#Override
protected void onLooperPrepared() {
Looper looper = getLooper();
if (looper != null)
mHandler = new Handler(looper);
}
void post(Runnable runnable) {
if (mHandler != null)
mHandler.post(runnable);
}
}
class MyLocationListener implements LocationListener
{
#Override
public void onLocationChanged(final Location loc)
{
Log.d(LOG_TAG, "Location changed: " + loc.getLatitude() +","+ loc.getLongitude());
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras)
{
Log.d(LOG_TAG, "onStatusChanged");
}
#Override
public void onProviderDisabled(String provider)
{
Log.d(LOG_TAG, "onProviderDisabled");
}
#Override
public void onProviderEnabled(String provider)
{
Log.d(LOG_TAG, "onProviderEnabled");
}
}
}
I am trying to use AsyncTask and the activity is working perfectly but I am facing a problem. The problem comes after I have pressed back button, because pressing this button my app crashes. I have seen other posts saying that I must cancel the task in onStop() and onDestroy() but still crashes. Does anyone have any idea how can I solve that?
private class MyAsyncTask extends AsyncTask<Void, Integer, Boolean> {
#Override
protected Boolean doInBackground(Void... args0) {
for(int i=1; i<=10; i++) {
try{
if(isCancelled())
break;
publishProgress(i*10);
Thread.sleep(1000);
}catch (InterruptedException e){}
}
return null;
}
/*
* it will update the publishProgress method and it will
* update the interface (if it's necessary)
*/
#Override
protected void onProgressUpdate(Integer... values) {
int progreso = values[0].intValue();
pbarProgreso.setProgress(progreso); // showing progress
pbarProgreso.setSecondaryProgress(progreso + 5);
}
/*
* Initializing progressBar
*/
#Override
protected void onPreExecute() {
pbarProgreso.setMax(100); // maximum value for process bar
pbarProgreso.setProgress(0); // minimum value to start
}
#Override
protected void onPostExecute(Boolean result) {
if(!this.isCancelled())
Toast.makeText(getApplicationContext(), "Task finished!",
Toast.LENGTH_SHORT).show();
}
#Override
protected void onCancelled() {
Toast.makeText(getApplicationContext(), "Task cancelled!",
Toast.LENGTH_SHORT).show();
}
}
#Override
protected void onStop() {
super.onStop();
if(task != null && task.getStatus() == Status.RUNNING){
task.cancel(true);
}
}
#Override
protected void onDestroy() {
super.onDestroy();
if(task != null && task.getStatus() == Status.RUNNING) {
task.cancel(true);
}
}
It's because when you press back button, AsyncTask continues to work, and when it do context related work, that context no longer exists, and a crash happens, it's better to use a "isResumed" boolean indicator variable inside an activity, and set it to false in onPause and set to true inside onResume, and inside an AsyncTask do context related things, inside an if condition.
Or if this code is inside a fragment, can use isAdded() method, to check if fragment is active or not. Cancel is also important, but there may be a delay, between an Activity pause and AsyncTask cancel, so keeping that variable is important.
I'm developing an android app that requires to make UI changes according to a background thread processing results, I tried the following code at first:
Thread run_time = new Thread (){
public void run(){
ConnectToServer connect = new ConnectToServer(null);
while(true){
String server_response = connect.getServerResponse();
if(!server_response.equals(null)){
setResponse(server_response);
response_received();
}
}
}
};
run_time.start();
but my App crashes because i tried to make a UI changes from that background thread, then I tried that way:
runOnUiThread(new Runnable() {
public void run(){
ConnectToServer connect = new ConnectToServer(null);
while(true){
String server_response = connect.getServerResponse();
if(!server_response.equals(null)){
setResponse(server_response);
response_received();
}
}
}
});
but i got that exception:
01-29 16:42:17.045: ERROR/AndroidRuntime(605): android.os.NetworkOnMainThreadException
01-29 16:42:17.045: ERROR/AndroidRuntime(605): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1084)
01-29 16:42:17.045: ERROR/AndroidRuntime(605): at libcore.io.BlockGuardOs.recvfrom(BlockGuardOs.java:151)
01-29 16:42:17.045: ERROR/AndroidRuntime(605): at libcore.io.IoBridge.recvfrom(IoBridge.java:503)
01-29 16:42:17.045: ERROR/AndroidRuntime(605): at java.net.PlainSocketImpl.read(PlainSocketImpl.java:488)
01-29 16:42:17.045: ERROR/AndroidRuntime(605): at java.net.PlainSocketImpl.access$000(PlainSocketImpl.java:46)
and after search i found that I must run the code as AsyncTask to avoid these problems, but when attempting to use it i found that it's must be used with small tasks only not like a thread that runs in the background all the run_time.
So, what's the best day to run a thread or a task in the background in whole the run_time and also reflect it's changes to the UI.
EDIT:
For Long running network work you have a few options.
First and formost check the android docs on this topic:
http://developer.android.com/training/basics/network-ops/index.html
Next, I generally use Services for this type of thing:
https://developer.android.com/guide/components/services.html
I will point you at the vogella tutorial for this as well:
http://www.vogella.com/tutorials/AndroidServices/article.html
For communication from threads/asynctasks/services to the UI use Handlers:
Use Handlers:
static public class MyThread extends Thread {
#Override
public void run() {
try {
// Simulate a slow network
try {
new Thread().sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
downloadBitmap = downloadBitmap("http://www.devoxx.com/download/attachments/4751369/DV11");
// Updates the user interface
handler.sendEmptyMessage(0);
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
}
handler = new Handler() {
#Override
public void handleMessage(Message msg) {
// cal uiMethods here...
imageView.setImageBitmap(downloadBitmap);
// dialog.dismiss();
}
};
Taken from this tutorial:
http://www.vogella.com/tutorials/AndroidBackgroundProcessing/article.html
You can make this more interesting by defining constant_codes which corespond to the desired action:
private int DO_THIS = 0x0;
private int DO_THAT = 0x1;
// in your UI:
public void handleMessage(Message msg) {
// cal uiMethods here...
switch(msg.what()){
case(DO_THIS):
// do stuff
break;
case(DO_THAT):
// do other stuff
break;
}
}
// in your thread:
Message m = handler.obtainMessage(DO_THIS);
handler.sendMessage(m);
If the thread code (asynch task, service etc...) is separate from the UI you can use Broadcasts to pass the data between the two and then use Handlers from there to act on the UI thread.
you need to use handlers
here is documntation: https://developer.android.com/training/multiple-threads/communicate-ui.html
Use this code - it may contain compile time error you have to do it correct
public class MainActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Connect connect = new Connect();
connect.execute();
}
class Connect extends AsyncTask<Void, String, Void>
{
#Override
protected Void doInBackground(Void... params)
{
ConnectToServer connect = new ConnectToServer(null);
while(true)
{
String server_response = connect.getServerResponse();
if(!server_response.equals(null))
{
publishProgress(server_response);
//setResponse(server_response);
response_received();
}
}
return null;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
setResponse(values[0]);
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
}
}
}
You need "handlers" along with "loopers" for optimization
Example:
public void myMethod(){
Thread background = new Thread(new Runnable(){
#Override
public void run(){
Looper.prepare();
//Do your server process here
Runnable r=new Runnable() {
#Override
public void run() {
//update your UI from here
}
};
handler.post(r);
Looper.loop();
}
});
background.start();
}
And of course this is without using AsyncTask
I have the following code:
try {
res = new Utils(ubc_context).new DownloadCalendarTask().execute().get();
} catch (InterruptedException e) {
Log.v("downloadcalendar", "interruptedexecution : " + e.getLocalizedMessage());
res = false;
} catch (ExecutionException e) {
Log.v("downloadcalendar", "executionexception : " + e.getLocalizedMessage());
res = false;
}
Log.v("displaymenu", "A");
public class Utils {
private Context context;
public Utils(Context context) {
this.context = context;
}
public class DownloadCalendarTask extends AsyncTask<Void, Void, Boolean> {
private ProgressDialog dialog;
public DownloadCalendarTask() {
dialog = new ProgressDialog(context);
}
protected void onPreExecute() {
Log.v("preexecute", "A");
dialog.setMessage("Loading calendar, please wait...");
Log.v("preexecute", "B");
dialog.show();
Log.v("preexecute", "C");
}
protected Boolean doInBackground(Void... arg0) {
// do some work here...
return (Boolean) false;
}
protected void onPostExecute() {
Log.d("utils", "entered onpostexecute");
dialog.dismiss();
}
}
}
The first part of code is attached to an onClick listener for a button. When I click the button the button flashes (as it does to show it has been clicked), and then after about 8 seconds the Loading dialog appears but never finishes.
According to logcat, as soon as I click the button onPreExecute is executed as is Dialog.show(), so my first problem is why is there this 8 second delay? During these 8 seconds, logcat shows that doInBackground is being executed. However, according to logcat (this is the second problem) onPostExecute is never called (and so Dialog.dismiss()) is never run.
Logcat shows that everything following DownloadCalendarTask().execute().get() is being executed, so it's as if onPostExecute has just been skipped.
Many thanks for your help!
You are calling AsyncTask.get() which causes the UI thread to be blocked while the AsyncTask is executing.
new DownloadCalendarTask().execute().get();
If you remove the call to get() it will perform asynchronously and give the expected result.
new DownloadCalendarTask().execute();
Edit:
You will also need to update the parameters to your onPostExecute method, they need to include the result. e.g.
protected void onPostExecute(Boolean result) {