So I'm just trying to create an Alert Dialog that is just a message (no buttons or titles). I want to display an alert dialog when a background task is running. The alert dialog will run on the UI thread.
Here's what I have done so far:
protected void onPreExecute() {
super.onPreExecute();
AlertDialog altDlg;
altDlg = new AlertDialog.Builder(AlertDialogActivity.this).create();
altDlg.setMessage("Retrieving Information. Please Wait");
altDlg.show();
}
I also tried doing this:
AlertDialog.Builder builder = new AlertDialog.Builder(this)
.setMessage("Retrieve Info. Please Wait").show();
The error I am getting with the first one is:
cannot find symbol 'AlertDialogActivity'
symbol: class AlertDialogActivity
location: class com.example.Device.Activity
The second attempt error says:
incompatible types: com.example.Device.Activity cannot be converted to android.content.Context
I'm not sure what I am doing wrong in either scenario. I just want to display a basic message when a background task is running and I was hoping the closest thing I can use is AlertDialog.
EDIT for how to set up AsyncTask properly:
Small background of what I want to do. I just want to read in a file, deserialize it and save it's contents to a db.
Right now I'm assuming I only need two activities.
One is my main activity:
public class MainActivity extends Activity {
/**
* Called when the activity is first created.
*/
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.setup);
final Button setup_button = (Button) findViewById(R.id.setup_button);
setup_button.setOnClickListener (new View.OnClickListener() {
public void onClick(View view){
setContentView(R.layout.retrieve_info);
}
});
}
}
Now the onClick event just moves to the new view that is supposed to display the message or alert dialog that says retrieving information. Please Wait. It displays the message while reading a file and saving to db. Once the file is read and saved, The message should disappear and say something like setup complete.
My second activity so far is:
public class RetrieveInfoActivity extends AsyncTask<Void,Void,Void> {
private ProgressDialog progressBar;
private void retrieveInfo(String fileName) {
try {
File file = new File(fileName);
Scanner scanner = new Scanner(file);
//Read all the lines until there are no more lines
while (scanner.hasNextLine()) {
scanner.nextLine();
//TODO: deserialize and save to db
}
scanner.close();
}
catch (FileNotFoundException e) { e.printStackTrace(); }
}
#Override
protected Void doInBackground(Void... params) {
retrieveInfo("test.txt");
return null;
}
protected void onPreExecute() {
super.onPreExecute();
progressBar.setIndeterminate(true);
progressBar.setCancelable(false);
progressBar.setMessage("Retrieve Information.Please wait");
progressBar.show();
}
#Override
protected void onPostExecute() {
progressBar.dismiss();
}
}
That's all I really have so far. I just need to understand how to set up this in Android conceptually.
Hope this makes sense.
Try this:
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
Instead of using an AlertDialog use a ProgressBar, it will do the trick for you.
private ProgressDialog progressBar;
#Override
protected void onPreExecute() {
super.onPreExecute();
progressBar.setIndeterminate(true);
progressBar.setCancelable(false);
progressBar.setMessage("Your message");
progressBar.show();
}
#Override
protected void onPostExecute(final String error_code) {
progressBar.dismiss();
}
Looks like you are extending AsyncTask and trying to use it as a context. That won't work as AsyncTask itself is nothing but an abstract class.
You need to create a custom constructor for your AsyncTask to fetch the Context:
public class MyTask extends AsyncTask<Void, Void, Void> {
private Context mCtx;
public MyTask(Context context) {
mCtx = context;
}
...
Then when starting your AsyncTask, pass the context:
new MyTask(this).execute();
Another way would be to make the AsyncTask an inner class and use YourActivity.this when creating the dialog. Example:
public class YourActivity extends Activity {
...
private class MyTask extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
AlertDialog dialog = new AlertDialog.Builder(YourActivity.this).create();
}
#Override
protected Void doInBackground(Void... params) {
...
}
}
}
Related
I'am trying to implement an AsyncTask in Android that will load all my data from the database. Therefore I used the onPreExecute method to start a ProgressDialog
public class DataLoader extends AsyncTask<Void, Void, Void> {
private LoginActivity activity;
private ProgressDialog nDialog;
public DataLoader (LoginActivity act){
this.activity = act;
nDialog = new ProgressDialog(activity);
}
protected void onPreExecute() {
System.out.print("Start AsyncTask");
nDialog.setMessage("Loading data..");
nDialog.setTitle("Starting the application");
nDialog.setIndeterminate(false);
nDialog.setCancelable(true);
nDialog.show();
}
#Override
protected Void doInBackground(Void ... params) {
System.out.println("Starting doInBackground");
loadDashboardData();
return null;
}
protected void onPostExecute() {
nDialog.dismiss();
Intent i = new Intent();
i.setClass(activity.getApplicationContext(), DashboardActivity.class);
activity.startActivity(i);
}
The I use the doInBackground method to load call a function to load the data. This method is called from an visible activity. The task is called with:
public class LoginActivity extends Activity {
public void onClick(View v) {
DataLoader dl = new DataLoader(this);
dl.execute();
}
}
And the code for the doInBackground is:
protected Void doInBackground(Void ... params) {
System.out.println("Starting doInBackground");
loadDashboardData();
return null;
}
Now the problem is that my doInBackground method will not finish. I tried to implement the loadDashboardData() call in the onPreExecute method. This will not show my dialog box but it will load the data correctly. In this case the UI Thread is not responding and will response after all the data has been loaded.
What can hinder the doInBackground method to execute correctly and load the data properly? The called method works (because I can call it and get the correct data). Also I'am not seeing the println in my run console.
In the frontend I can see the progressbar spinning, but in the backend I can see that no data is loaded.
Your problem is that you are overriding the wrong method name : )
It should be
#Override
protected void onPostExecute(Void result) {
// your code
}
as in your case the variable which doInBackground return is Void.
You can check the documentation about AsyncTask .
I have an activity with a listview. When I call this activity the activity takes about 3-5 seconds to appear and display the listview. It looks as if the button has not been pressed to load the activity, i would like to display a progressdialog while this loads but can't figure it out.
ProgressDialog progress;
progress = ProgressDialog.show(this, "Loading maps!",
"Please wait...", true);
// sort out track array
getTracks();
progress.dismiss();
I did the above on the oncreate() of the activity with the listview but the dialog never shows?
What I would like is to show the progress dialog on Activity A when the button is pressed and then dismiss once Activity B is loaded and displayed?
Thanks
You need to implement AsyncTask or simple JAVA threading. Go with AsyncTask right now.
onPreExecute() - display dialog here
doInBackground() - call getTracks()
onPostExecute() - display tracks in ListView and dismiss dialog
For example:
private static class LoadTracksTask extends AsyncTask<Void, Void, Void> {
ProgressDialog progress;
#Override
protected void onPreExecute() {
progress = new ProgressDialog(yourActivity.this);
progress .setMessage("loading");
progress .show();
}
#Override
protected Void doInBackground(Void... params) {
// do tracks loading process here, don't update UI directly here because there is different mechanism for it
return null;
}
#Override
protected void onPostExecute(Void result) {
// write display tracks logic here
progress.dismiss(); // dismiss dialog
}
}
Once you are done with defining your AsyncTask class, just execute the task inside onCreate() by calling execute() method of your AsyncTask.
For example:
new LoadTracksTask().execute();
You can make progress Dialog like this :
onPreExecute(){
progressdialog = new ProgressDialog(MainActivity.this);
progressdialog.setMessage("Please wait while downloading application from the web.....");
progressdialog.setIndeterminate(false);
progressdialog.setMax(100);
progressdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressdialog.setCancelable(false);
progressdialog.show();
}
doInBackground(String... strings){
// here you code for downloading
}
onProgressUpdate(String... progress)
{
// here set progress update
progressdialog.setProgress(Integer.parseInt(progress[0]));
}
onPostExecute(String result)
{
progressdialog.dismiss();
}
Use something like this:
private static class MapLoader extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
progress.setVisibility(View.VISIBLE);
// make your element GONE
}
#Override
protected Void doInBackground(Void... params) {
// Load map processing
return null;
}
#Override
protected void onPostExecute(List<Document> result) {
progress.setVisibility(View.GONE);
adapter.setNewData(new_data);
adapter.notifyDataSetChanged();
}
}
In your onCreate() use:
listView.setAdapter(adapter);
new MapLoader.execute();
My app loads a lot of stuff on startup and after testing it delays too long at the beginning to not have a splash screen. So, I want to display a splash screen until my app is done loading. I do NOT want to display a screen with a timer for X seconds. I found an example here:
Android SplashScreen
I tried implementing the code in the SO topic above but I just don't understand the code. After integrating it in my code I come up with one error that I commented into the code below. But I don't understand a lot of the code and I have commented in the code below the parts I am confused by.
public class MainMenu extends Activity {
private ProgressDialog pd = null;
private Object data = null; //What is this?
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.mainmenu);
// show the ProgressDialog on this thread
this.pd = ProgressDialog.show(this, "Working...", "Downloading data...", true, false);
// start a new thread that will download all the data
new DownloadTask().execute("Any parameters to download."); //What is DownloadTask()?
}
private class DownloadTask extends AsyncTask<String, Void, Object> {
protected Object doInBackground(String... args) { //Are these parameters correct?
return "replace this with your object"; //What is this?
}
protected void onPostExecute(Object results) {
// pass the resulting data to the main activity
MainMenu.this.data = result; //Error: "result cannot be resolved to a variable"
if(MainMenu.this.pd != null) {
MainMenu.this.pd.dismiss();
}
}
}
}
Let's start with the error:
MainMenu.this.data = result;
Notice the typo? It should be result*s*:
MainMenu.this.data = results;
Addressing the rest of your questions below:
private class DownloadTask extends AsyncTask<String, Void, Object>
The declaration is for an inline class called DownloadTask, and it states that you'll be taking Strings (via String...) as parameters to your doInBackground(String... params).
The second parameter (Void in your case) indicates the datatype used to "publish" the progress via publishProgress(DATATYPE)/onProgressUpdate(DATATYPE... progress). This method is suitable for notifying the user of changes, for example when you've finished downloading a file but still have a few to go.
The last parameter (Object), indicates what type of data you'll be passing on to onPostExecute(DATATYPE), in this example Object. This could either be to update a ListAdapter somewhere, or trigger any other UI change based on the outcome of the actions done in doInBackground.
Show ProgressDialog in onPreexecute and dismiss it in onPostExcute methods
something like this
private class DownloadTask extends AsyncTask<String, Void, Object> {
#Override
protected void onPreExecute() {
mProgressDialog = new ProgressDialog(activity);
mProgressDialog =ProgressDialog.show(activity, "", "Please Wait",true,false);
super.onPreExecute();
}
protected Object doInBackground(String... args) { //Are these parameters correct?
return "replace this with your object"; //What is this?
}
protected void onPostExecute(Object results) {
// pass the resulting data to the main activity
MainMenu.this.data = results; //it should be results
if (mProgressDialog != null || mProgressDialog.isShowing()){
mProgressDialog.dismiss();
}
if(MainMenu.this.pd != null) {
MainMenu.this.pd.dismiss();
}
}
I would like to enable a few buttons from my main activity once the stuffs from doInBackground() is finished! Can someone please let me know how to do that?
I can't use findViewByID() for making he button visible from the AsyncTask class as it's not an activity class! :/
Do Like this...
Define a method which enables the Buttons.
Then on PostExecute() on AsyncTask, call that method
there is one callback onPostExecution(...) { } of AsynTask class use this method to UI stuff,for enable,disable button just write this way in onPostExcustion(...)
runOnUiThread(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
}
});
also make sure this method only available in activity class
thank you
Follow this way:
[1] Create your AsyncTask :
public class performBackgroundTask extends AsyncTask<Void, Void, Void> {
ProgressDialog Dialog = new ProgressDialog(HotUsers.this);
protected void onPreExecute() {
Dialog.setMessage("Loading Hot Users...");
Dialog.show();
}
protected void onPostExecute(Void unused) {
if(Dialog.isShowing())
Dialog.dismiss();
set_details_on_screen();
}
#Override
protected Void doInBackground(Void... params) {
get_details_from_server(); // get data like userid,username,userdesc etc...
return null;
}
}
[2] That will call function to proceed for UI changes.
public void set_details_on_screen()
{
if(userid > 0 )
handler_default.sendEmptyMessage(0);
else
handler_default.sendEmptyMessage(1);
}
[3] At last your UI changes will be reflected on screen with this Handler.
private Handler handler_default = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case 0: {
textuserid = (TextView) findViewById(R.id.userid);
textusername = (TextView) findViewById(R.id.username);
textuserdesc = (TextView) findViewById(R.id.userdesc);
textuserid.setText(userid);
textusername.setText(username);
textuserdesc.setText(userdesc);
break;
}
case 1: {
Toast.makeText(getApplicationContext(),"Error",Toast.LENGTH_LONG).show();
break;
}
}
}
};
Thanks.
your class which extends AsyncTask you can push your context into it, when calling the execute().
private class RegisterUser extends AsyncTask<String,String,String> {
private ListActivity activity;
public RegisterUser(ListActivity activity) {
this.activity = activity;
}
protected void onPostExecute(JSONObject json) {
activity.editText = (EditText)activity.findViewById(R.id.editText1);
//or
activity.enableButton();
}
}
and call the execute from the Activity like this:
new RegisterUser(this).execute(new String[] {"param"});
or you can define the AsyncTask class inside your Activity class - where you can reach everything.
more info Lars Vogel - Android Threads, Handlers and AsyncTask
I've got a quite interesting issue when I try to display a ProgressDialog (the simple, spinner type) within a onPreferenceChange listener.
public class SettingsActivity extends PreferenceActivity {
private ProgressDialog dialog;
public void onCreate(Bundle savedInstanceState) {
ListPreference pref= (ListPreference) findPreference("myPreference");
pref.setOnPreferenceChangeListener(new OnPreferenceChangeListener() {
#Override
public boolean onPreferenceChange(Preference preference, Object newValue) {
dialog = ProgressDialog.show(SettingsActivity.this, "", "Doing stuff...", true);
SystemClock.sleep(2000);
}
return true;
}
}
The ProgressDialog shows up, but not until the method (sleep in this case) has finished. What am I doing wrong?
You're sleeping on the main UI thread, which stops the operating system from handling your application's events. This will stop your app from redrawing and as you discovered, can prevent new windows from actually appearing.
Instead of sleeping, try this:
final ProgressDialog dialog = ProgressDialog.show(
SettingsActivity.this, "", "Doing stuff...", true);
new Handler().postDelayed(new Runnable() {
public void run() {
dialog.hide();
}
}, 2000);
You can use AsyncTask to run the function in a separate thread (see http://developer.android.com/resources/articles/painless-threading.html)
This is probably a bit unnecessary if you just want to invoke a sleep method, but should work even for other methods that otherwise would block the UI thread.
You could do something like this:
private class BackgroundTask extends AsyncTask<Integer, Integer, void> {
private ProgressDialog dialog;
#Override
protected void onPreExecute() {
dialog = ProgressDialog.show(SettingsActivity.this, "", "Doing stuff...", true);
}
#Override
protected void doInBackground(Integer... params) {
sleep(params[0]);
}
#Override
protected void onPostExecute(Boolean result) {
dialog.dismiss();
}
}
And than call it using the code below:
new BackgroundTask().execute(2000);