So I have a music application. I am trying to update the UI with the progress of the media player (like current time, current song, album cover) everytime the song changes. I found that using interfaces was a awesome magical way of communication between activity and fragments so I implemented an interface in my MusicManger class. My code will show what and how did it.
Two problems
1) Commented look below, ExecutorService seems to stop after one loop. No Errors in catch block (this is why I tagged with java)
2) Commented please look, All the System.out methods print but the UI doesn't update. I do believe I called the method from mainThread so it should update.
I'll show code in logical order will add titles in bold before code segment to tell you basic idea of code.
Passing UI references from fragment to MusicManager class, code below in Fragment class
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_item_songlist, container, false);
// Set the adapter
TextView musicManagerSongName, musicManagerCurrent, musicManagerTotal;
ProgressBar musicManagerProgress;
ImageView musicManagerImageView;
mListView = (AbsListView) view.findViewById(R.id.slist);
musicManagerSongName = (TextView)view.findViewById(R.id.textView12);
musicManagerCurrent = (TextView)view.findViewById(R.id.textView10);
musicManagerTotal = (TextView)view.findViewById(R.id.textView11);
musicManagerProgress = (ProgressBar)view.findViewById(R.id.progressBar);
musicManagerImageView = (ImageView)view.findViewById(R.id.imageView2);
MainActivity.mediaPlayer.passUIReferences(musicManagerSongName, musicManagerCurrent, musicManagerTotal, musicManagerProgress, musicManagerImageView, view);
// line above is a method within MusicManager that takes the references will show code next!
ImageButton playbutton = (ImageButton)view.findViewById(R.id.playbuttonbar);
ImageButton nextButton = (ImageButton)view.findViewById(R.id.nextbuttonbar);
ImageButton backButton = (ImageButton)view.findViewById(R.id.backbuttonbar);
ImageButton toggleButton = (ImageButton)view.findViewById(R.id.shufflebuttonbar);
ImageButton pausebutton = (ImageButton)view.findViewById(R.id.pausebuttonbar);
playbutton.setBackgroundResource(R.drawable.playbuttonbar);
playbutton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
MainActivity.mediaPlayer.stateChange(1);
}catch(Exception e) {
}
}
});
backButton.setBackgroundResource(R.drawable.backbutton1);
nextButton.setBackgroundResource(R.drawable.nextbutton1);
toggleButton.setBackgroundResource(R.drawable.shufflebuttonselected);
pausebutton.setBackgroundResource(R.drawable.pausebutton1);
pausebutton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
try {
MainActivity.mediaPlayer.stateChange(0);
} catch (Exception e){
}
}
});
mListView.setAdapter(mAdapter);
((MainActivity) mListener).restoreActionBar();
return view;
}
As Commended above the code that is located in MusicManager class that takes references and stores them. Also shows interface implementation with MusicManager class. And the Executor service
public void passUIReferences(View... views) {
this.uiElements = views;
}
private ExecutorService executorService = Executors.newSingleThreadExecutor();
private MediaplayerUpdateInterface uiUpdateInterface;
public MediaPlayerManager(MediaplayerUpdateInterface inter) {
this.player = new MediaPlayer();
this.uiUpdateInterface = inter;
// The below line starts the single thread while loop for excutorservice and only loops and prints "this" once after I start one song then it never loops again
executorService.submit(new Runnable() {
#Override
public void run() {
while(true) {
if (player.isPlaying() && uiElements != null) {
System.out.println("this");
uiUpdateInterface.updateUI(uiElements, 0);
}
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
}
}
});
}
public interface MediaplayerUpdateInterface {
public void updateUI(View[] views, int type);
}
Finally some code from MainActivity class that actually is suppose to update the UI note that both println's work as expected but only once as stated above because of the executorservice issue
public static MediaPlayerManager mediaPlayer = new MediaPlayerManager(new MediaPlayerManager.MediaplayerUpdateInterface() {
#Override
public void updateUI(View[] views, int type) {
System.out.println("check1 " + type);
updateMediaplayerViews(views, type);
}
});
private static void updateMediaplayerViews(View[] views, int type)
{
switch(type) {
case 0:
System.out.println("that?");
((TextView)views[0]).setText(mediaPlayer.getCurrentSongInfo().getName().length() > 22? mediaPlayer.getCurrentSongInfo().getName().substring(0, 19)+"..." : mediaPlayer.getCurrentSongInfo().getName());
break;
}
views[views.length - 1].invalidate();
}
The view array is shown perviously! Also the last view in the array is shown as the main view for songlist fragment.
I am sorry for all the code I've tried to debug it as you can see from my println's there is just something I am unaware of going on here.
Ok so there was an error that I needed to catch to see within the following code:
private static void updateMediaplayerViews(View[] views, int type)
{
switch(type) {
case 0:
System.out.println("that?");
((TextView)views[0]).setText(mediaPlayer.getCurrentSongInfo().getName().length() > 22? mediaPlayer.getCurrentSongInfo().getName().substring(0, 19)+"..." : mediaPlayer.getCurrentSongInfo().getName());
break;
}
views[views.length - 1].invalidate();
}
The issue is I was trying to change the view from a different thread then the one which created it. Solving it was pretty long and painful but basically I made it nonstactic used more interfaces then used the famous
Mainactivity.runOnUiThread(new Runnable(....));
Related
I programmed a Vocabulary Trainer with Vocabulary Cards. The Vocabulary Cards are Entries in a Room Database created from an asset. I am displaying these Vocabulary Cards with ViewPager2 in an Activity. I have a 'correct' and a 'false' button and when the user clicks on either, I want to update the Vocabulary Card (-> The entry in the sqlite database) and automatically swipe to the next item of the ViewPager2.
If I implement the buttons in the ViewPager2Adapter, I can't find a way to change the position of the ViewPager2. If I implement the buttons in the activity the sqlite entry does not update properly (After it updates the entry, the activity is constantly refreshed, it seems like it never the leaves the OnClick methode of the button).
So is it possible to change the position of ViewPager2 from inside the ViewPager2Adpater?
Thanks for your help!
That is the relevant code if I have the buttons in my ViewPager2Adapter. Here I don't know how to change the position of the ViewPager2
public void onBindViewHolder(#NonNull #NotNull ViewHolder holder, int position) {
VocabularyCard vocabularyCard = currentCards.get(position);
holder.btn_correct.setOnClickListener(view -> {
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
holder.btn_false.setOnClickListener(v15 -> {
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
That is the relevant code if I have the buttons in the Activity. Here the update function triggers an infinite updating of the Activity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
btn_correct_2.setOnClickListener(view -> {
int currentPos = viewpager2.getCurrentItem();
vocabularyViewModel.getCurrentCards().observe(this, vocabularyCards -> {
if (vocabularyCards.size() == currentPos){
Intent intent = new Intent(TestActivity.this, MainActivity.class);
startActivity(intent);
}else {
viewpager2.setCurrentItem(currentPos + 1);
}
VocabularyCard vocabularyCard = vocabularyCards.get(currentPos);
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
});
btn_false_2.setOnClickListener(view -> {
int currentPos = viewpager2.getCurrentItem();
vocabularyViewModel.getCurrentCards().observe(this, vocabularyCards -> {
if (vocabularyCards.size() == currentPos){
Intent intent = new Intent(TestActivity.this, MainActivity.class);
startActivity(intent);
}else {
viewpager2.setCurrentItem(currentPos + 1);
}
VocabularyCard vocabularyCard = vocabularyCards.get(currentPos);
vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard);
});
});
Objects.requireNonNull(getSupportActionBar()).setTitle(getResources().getString(R.string.learn_new_words));
LiveData<List<VocabularyCard>> allNewCards = vocabularyViewModel.getAllNewCards(goal);
allNewCards.observe(this, vocabularyCards -> vocabularyViewModel.setCurrentCards(vocabularyCards));
vocabularyViewModel.getCurrentCards().observe(this, vocabularyCards -> {
viewPager2Adapter.setCurrentCards(vocabularyCards);
viewpager2.setAdapter(viewPager2Adapter);
viewpager2.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
super.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
#Override
public void onPageSelected(int position) {
super.onPageSelected(position);
}
#Override
public void onPageScrollStateChanged(int state) {
super.onPageScrollStateChanged(state);
}
});
});
The update function in the Room DAO is straightforward:
#Update
void updateSingleVocabularyCard(VocabularyCard vocabularyCard);
I left out all the code that is not relevant.
There are several ways to propagate an event from the adapter to the activity where you manage your cards using ViewPager2. Let's have a look how it can be done either using an interface or using the same view model. But in any case I strongly recommend you to update your database in a background thread to prevent any possible UI lags.
1. Using an interface
This option is more flexible since you can propagate events as well as pass data as parameters. You can also reuse this interface for other cases. As far as I See you have a holder that has 2 buttons for the users to make choices. So our event here would be something like ChoiceEventListener, let's call this interface like so. Then you'd have to add a method to handle this event from within anywhere you wanna hear this event, and let's call its handle method onChoice(). Finally we would need a variable to indicate what the choice is. Now that ready to implement, let's write the new interface...
ChoiceEventListener.java
public interface ChoiceEventListener {
void onChoice(VocabularyCard vocabularyCard, boolean choice);
}
The next thing to do is to implement this interface where you want to listen to this event. In this case it is in your activity. There are 2 ways to do this:
You make your activity to inherit its methods using the implements keyword
YourActivity.java
public class YourActivity extends AppCompatActivity implements ChoiceEventListener {
// Use a background thread for database operations
private Executor executor = Executors.newSingleThreadExecutor();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
// You must construct your adapter class with the listener
ViewPager2Adapter adapter = new ViewPager2Adapter(/* Other params... */, this);
}
#Override
public void onChoice(VocabularyCard vocabularyCard, boolean choice) {
if(choice) {
// User pressed the correct button
}
else {
// User pressed the false button
}
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
}
}
You can implement it as an anonymous function
YourActivity.java
public class YourActivity extends AppCompatActivity {
// Use a background thread for database operations
private Executor executor = Executors.newSingleThreadExecutor();
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
// You must construct your adapter class with the listener
ViewPager2Adapter adapter = new ViewPager2Adapter(/* Other params... */, (vocabularyCard, choice) -> {
if(choice) {
// User pressed the correct button
}
else {
// User pressed the false button
}
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
});
}
}
Finally the ViewPager2Adapter class implementation would be something like this:
ViewPager2Adapter.java
public class ViewPager2Adapter extends RecyclerView.Adapter<ViewPager2ViewHolder> {
// Here is your listener to deliver the choice event to it
private final ChoiceEventListener listener;
// Constructor
public ViewPager2Adapter(/* Other params... */, ChoiceEventListener listener) {
/* Other inits */
this.listener = listener;
}
public void onBindViewHolder(#NonNull #NotNull ViewHolder holder, int position) {
VocabularyCard vocabularyCard = currentCards.get(position);
holder.btn_correct.setOnClickListener(view -> {
listener.onChoice(vocabularyCard, true); // true for correct
});
holder.btn_false.setOnClickListener(v15 -> {
listener.onChoice(vocabularyCard, false); // false for false :)
});
}
}
2. Use the ViewModel for inter-communication
In this option we use a LiveData object to make page switching. The only thing you need to know in your activity is the current position which you get it from the adapter class. Once you update it in the adapter, set the current position value in live data so that you can switch the page in your activity.
VocabularyViewModel.java
public class VocabularyViewModel extends ViewModel {
public MutableLiveData<Integer> mldCurrentPosition = new MutableLiveData<>(0);
}
YourActivity.java
public class YourActivity extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
initAll();
vocabularyViewModel.mldCurrentPosition().observe(this, currentPosition -> {
if(currenPosition == null) return; // ignore when null
viewpager2.setCurrentItem(currentPosition + 1);
}
}
}
Finally the ViewPager2Adapter class implementation would be something like this:
ViewPager2Adapter.java
public class ViewPager2Adapter extends RecyclerView.Adapter<ViewPager2ViewHolder> {
// Use a background thread for database operations
private Executor executor = Executors.newSingleThreadExecutor();
public void onBindViewHolder(#NonNull #NotNull ViewHolder holder, int position) {
VocabularyCard vocabularyCard = currentCards.get(position);
holder.btn_correct.setOnClickListener(view -> {
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
// Then invoke switching to the next card
vocabularyViewModel.mldCurrentPosition.setValue(position + 1);
});
holder.btn_false.setOnClickListener(v15 -> {
// Update card in the background
executor.execute(()-> vocabularyViewModel.updateSingleVocabularyCard(vocabularyCard));
// Then invoke switching to the next card
vocabularyViewModel.mldCurrentPosition.setValue(position + 1);
});
}
}
this is my first question on stack (great community, thanks!)
So, I have this problem:
I'm developing an android application with a tab layout. Whenever I navigate to the "Status" tab, I'd like to show a circular ProgressBar that is updated according to the value of a variable. Let's call this variable prog. Moreover, I'd like to display in the center of the ProgressBar a TextView that displays the same value of prog.
I have came up with this part of code:
public class StatusFragment extends Fragment
{
private ProgressBar torqueRefProgressBar;
private TextView torqueRefTextView;
RunningThreadExample r;
private Thread t1;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
//Inflate the layout for this fragment
return ...;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState)
{
// Initializations and other parts not relevant for the question...
this.torqueRefProgressBar = getView().findViewById(R.id.torqueRefProgressBar);
this.torqueRefTextView = getView().findViewById(R.id.torqueRefTextView);
t1 = new Thread( this.torqueRefProgressBar, this.torqueRefTextView)); // passing arguments by value but values are references to the objects, therefore I'm passing by ref
t1.start();
}
}
In this Fragment I create the ProgressBar and the TextView and then pass them to the Runnable as you can see below
public class RunningThreadExample implements Runnable
{
ProgressBar torqueRefProgBar_thread;
TextView torqueRefTextView_thread;
public RunningThreadExample(ProgressBar progressBar, TextView textView)
{
this.torqueRefProgBar_thread = progressBar;
this.torqueRefTextView_thread = textView;
this.endScale = this.torqueRefProgBar_thread.getMax();
}
#Override
public void run()
{
android.os.Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
float i = 0;
double temp = 0;
while(Running)
{
try
{
Thread.sleep(1000/60); // update freq 60Hz
}
catch (InterruptedException e)
{
e.printStackTrace();
}
temp = getCurrentVariableValue(); // Not shown here (returns a double)
this.torqueRefProgBar_thread.setProgress((int) temp);
this.torqueRefTextView_thread.setText(String.valueOf(temp));
}
Log.i(INFO_TAG,"Finishing thread!!!!!");
}
}
I'd like this update to run all the time the app is working (for this reason I've neglected AsyncTask). After a while, it happens that the ProgressBar stops updating, while the TextView continues to work without any problem.
I've been reading that a possible cause could be that the calling setProgress(temp) might stuck the UI. However I can't understand while the TextView is still working.
Can you suggest a better way to make the progressBar update?
Thank you!
See this thread:
Android basics: running code in the UI thread
So to summarize, Android requires certain types and sections of code to run in a specific context. Many tools such as Handlers are available to help with these tasks but it was difficult to learn to begin with.
You cannot affect View from any Thread other than Main Thread. Do the following in run() method
runOnUiThread(new Runnable() {
//
run(){
this.torqueRefProgBar_thread.setProgress((int) temp);
} this.torqueRefTextView_thread.setText(String.valueOf(temp));
);
I have a tab fragment inside of a container activity.
I would like to download some data to display in the tab. In the tab, I have made an asynctask that I execute just after inflating the fragment layout in onCreateView. When I do it this way, the AsyncTask's doInBackground... work occurs on the main thread and the view does not load until it is done. All of my progress... logs show up at the same time as soon as the task is done.
However, if I put a button in the fragment layout and start the asynctask work as a response to the button click, it works as expected, I get my normally spaced progress updates.
So, why does AsyncTask run on the main thread if it is the first thing to happen when my fragment starts? And, how can I prevent this? My ultimate goal is to show a progress wheel while the data is downloading.
Edit. Here is where I call my AsyncTask.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View rootView = inflater.inflate(R.layout.temp_my_moments, container, false);
getMyClips(getActivity(), rootView, p_session, p_person,progressBar);
//If I use this button, it works fine:
// test = (Button) rootView.findViewById(R.id.testbutton);
// test.setOnClickListener(new View.OnClickListener() {
// #Override
// public void onClick(View v) {
// progressBar =(ProgressBar) rootView.findViewById(R.id.myMomentsProgress);
// getMyClips(getActivity(), rootView, p_session, p_person, progressBar);
// }
// });
return rootView;
}
And here is getMyClips():
public void getMyClips(Context context,View view,String thisSession,String thisPerson,ProgressBar progressBar) {
Log.d("Currently running", "getMyClips");
JSONObject params = new JSONObject();
try {
params.put("Function", clipsMine_apiCall);
params.put("p_session", thisSession);
params.put("p_person", thisPerson);
} catch (JSONException e1) {
e1.printStackTrace();
}
ApiClipCaller webServiceTask = new ApiClipCaller(context,view,progressBar);
if (webServiceTask.hasConnection()) {
webServiceTask.execute(params);
} else {
//TODO no internet connection
}
}
Edit Here is my AsyncTask. This is inside the Fragment:
public class ApiClipCaller extends AsyncTask<JSONObject, Integer, ApiResponse> {
public Context context;
public String clipID;
public String sessionID;
public String personID;
public String functionName;
public View view;
public ProgressBar progressBar;
public final String apiURL = "...."; //need to keep private
LinearLayout loading;
public ApiClipCaller(Context c, View v,ProgressBar progressBar) {
this.context = c;
this.view = v;
this.progressBar = progressBar;
loading = (LinearLayout) view.findViewById(R.id.loadingMyMoments);
}
#Override
protected ApiResponse doInBackground(JSONObject... params) {
JSONObject realParams = params[0];
try {
functionName = realParams.getString("Function");
} catch (JSONException e) {
e.printStackTrace();
}
ApiResponse responseObject = masterFunction(realParams);
//making some work to see if it is running correctly
for (int i=10;i<=100;i += 10)
{
try {
Thread.sleep(1000);
publishProgress(i);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return responseObject;
}
#Override
protected void onProgressUpdate(Integer... progress) {
loading.setVisibility(View.VISIBLE);
progressBar.setProgress(progress[0]);
Log.d("progress",Integer.toString(progress[0]));
}
#Override
protected void onPostExecute(ApiResponse responseObject) {
loading.setVisibility(View.GONE);
if (functionName.equals(clipsMine_apiCall)) {
JSONObject clipObject = responseObject.getResponseJSONObject();
//just testing here to see if I can get data back in the fragment view when it is done.
///This works as expected.
String responseString = responseObject.getResponseString();
TextView showAsyncResults = (TextView) view.findViewById(R.id.testAsyncTask);
showAsyncResults.setText(responseString);
}
super.onPostExecute(responseObject);
}
}
So, it seems like the answer is that I was going about this all wrong. It it is not possible to launch asynctask when the first activity or fragment loads, because the onCreate etc. methods are not actually on the UI thread. So, AsyncTask cannot be executed directly from there, as Ordous pointed out.
Instead, it seems like the solution is to load information when the application first starts by creating a class which extends Application and doing the loading work from there, because this will necessarily be on the main thread. The methods in there can be called from the activity to access the layouts and make a progress bar or similar.
Reference: http://developer.android.com/reference/android/app/Application.html
A good example: http://www.intertech.com/Blog/androids-application-class/
I am having a problem updating the view in android every x seconds.
To get to know how android works I am writing a small game.
It has a GameController which holds the game loop. Inside the loop, the logic is executed and afterwards the gui will be informed about the changes.
The problem is that the changes cannot be seen in the view. The view stays the same until the game loop finishes and updates then only once.
Here is my code (the important parts):
GameController.java:
IGui gui;
public void play() {
while (playing) {
getAndProcessInput();
updateGui();
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
}
}
}
private void updateGui() {
gui.setPlayer(x, y);
// ...
}
GameActivity.java:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
GridView gridview = (GridView) findViewById(R.id.GridView1);
TextAdapter = new TextAdapter(this);
gridview.setAdapter(textAdapter);
GameController c = new GameController();
// here, the game loop shoud start.
// what i tried:
// new Thread(c).start(); <-- causes crash
// c.play(); <-- causes view to frease until game loop is done
this.runOnUiThread(c); <-- causes view to frease until game loop is done
}
TextAdapter.java:
public class TextAdapter extends BaseAdapter implements IGui {
private final Context context;
private final String[] texts;
public TextAdapter(Context context) {
this.context = context;
texts = new String[height * width];
for (int i = 0; i < texts.length; i++) {
texts[i] = " ";
}
}
public int getCount() {
return height * width;
}
public Object getItem(int position) {
return null;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
TextView tv;
if (convertView == null) {
tv = new TextView(context);
tv.setLayoutParams(new GridView.LayoutParams(25, 25));
} else {
tv = (TextView) convertView;
}
tv.setText(texts[position]);
return tv; // <-- this happens only when game loop is done, not everytime something changed
}
#Override
public void setPlayer(int x, int y) {
texts[width * y + x] = "X";
// this.notifyDataSetChanged(); <-- this does not help (view still freases)
// gridview.invalidateViews(); does not help either
}
}
I googled a lot and tried a lot as well (and I do know that similar questions where asked here already, but they did not help me either), but somehow it just does not work.
I cannot get it do work that the view and logic run on different theads in android, and if they run on the same thread the logic blocks the view.
Any help would be greatly appreciated.
// edit:
If I try new Thread(c).start(); LogCat sais:
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
And if I add Looper.prepare(); :
java.lang.RuntimeException: Unable to start activity ComponentInfo{GameActivity}: java.lang.RuntimeException: Only one Looper may be created per thread
If I try this.runOnUiThread(c); there are no errors.
First, this doesn't seems like the way to crate a game, you will need to use SurfaceView, or GLSurfaceView to better do what you want.
You can also look for Cocos2d for android, it's a 2D platform (that was ported from iPhone) that makes you life easier:
http://code.google.com/p/cocos2d-android/
I muse warn you though, I tried it a couple months back, and it was not production grade yet, it did crash from time to time.
Anyway, if you still want to continue heading your way I'll try answering your question:
I think you are messing too much with the way these stuff should work. try understanding first how handlers work with threads.
Do anything you want on your thread:
new Thread(new Runnable()
{
#Override
public void run()
{
try
{
calculateGameChangesHere();
handler.sendEmptyMessage(SUCCESS);
}
catch (Exception e)
{
handler.sendEmptyMessage(FAILURE);
}
}
}).start();
When your data is ready, tell the handler to put it in a view and show it:
protected Handler handler = new Handler()
{
#Override
public void handleMessage(Message msg)
{
if (msg.what == SUCCESS)
{
setCalculatedDataToaView(); // the data you calculated from your thread can now be shown in one of your views.
}
else if (msg.what == FAILURE)
{
errorHandlerHere();//could be your toasts or any other error handling...
}
}
};
This goes to everything that requires heavy processing/networking that shouldn't block your UI thread.
Hope this helps.
Not sure what you are trying to achieve by refreshing a listView every few seconds. Anyways if you are writing some 2d games, you have to use SurfaceView , which is especially meant for continuous refreshing.
Had the same problem and solved it using a pretty simple code.
Tips:
GridView must be refreshed by the UI thread
To display every change you must keep the loop and the Sleep method away from the UI thread
Solution:
Method to update the grid (put on your Activity that you build your GridView at the first place or wherever)
public void UpdateGrid(){
//your logic
//your way to change grid values (there are tones of other ways)
CustomGridAdapter cga = new CustomGridAdapter(this, values);
gridView.setAdapter(cga);
gridView.invalidateViews();
}
Build the non UI Thread that does the work
public class DataReceiver implements Runnable {
private MainActivity mainActivity;
public DataReceiver(MainActivity ma) {
mainActivity = ma;
}
#Override
public void run() {
for (int i = 0; i < 100; i++) {
mainActivity.runOnUiThread(new Runnable() {
public void run() {
//update the grid here
mainActivity.UpdateGrid();
}
});
//sleep here
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
I have an android app I am just experimenting things on and I cannot seem to figure out why my app force closes when I update a TextView via a while loop. When I comment out the updateText method it runs fine.
public class GameThread extends Thread {
Thread t;
private int i;
private boolean running;
private long sleepTime;
GameView gv;
public GameThread() {
t = new Thread(this);
t.start();
i = 0;
sleepTime = 1000;
}
public void initView(GameView v) {
this.gv = v;
}
public void setRunning(boolean b) {
this.running = b;
}
public boolean getRunning() {
return running;
}
public void run() {
while(running) {
i++;
update();
try {
t.sleep(sleepTime);
} catch(InterruptedException e) {
}
}
}
public void update() {
gv.setText(i); // when this is uncommented, it causes force close
Log.v("Semajhan", "i = " + i);
}
public class GameView extends LinearLayout {
public TextView tv;
public GameView(Context c) {
super(c);
this.setBackgroundColor(Color.WHITE);
tv = new TextView(c);
tv.setTextColor(Color.BLACK);
tv.setTextSize(20);
this.addView(tv);
}
public void setText(int i) {
tv.setText("i count: " + i);
}
public class Exp extends Activity {
GameThread t;
GameView v;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
v = new GameView(this);
setContentView(v);
t = new GameThread();
t.setRunning(true);
t.initView(v);
}
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
if (t.getRunning() == true) {
t.setRunning(false);
Log.v("Semajhan", "STOPPED");
} else {
t.setRunning(true);
Log.v("Semajhan", "RESTART");
}
}
return true;
}
protected void onDestroy() {
Log.v("Semajhan", "DESTROYING");
super.onDestroy();
}
protected void onStop() {
Log.v("Semajhan", "Stopping");
super.onStop();
}
I though i'd post the whole app since it is relatively small and so that I could get some help without confusion.
First, when you get a Force Close dialog, use adb logcat, DDMS, or the DDMS perspective in Eclipse to examine LogCat and look at the stack trace associated with your crash.
In this case, your exception will be something to the effect of "Cannot modify the user interface from a non-UI thread". You are attempting to call setText() from a background thread, which is not supported.
Using a GameThread makes sense if you are using 2D/3D graphics. It is not an appropriate pattern for widget-based applications. There are many, many, many, many examples that demonstrate how to create widget-based applications without the use of a GameThread.
You have to call it from the UI thread.
For more info check: Painless Threading .
If you decide to use a Handler, the easiest solution for you will be to:
Extend a View, override it's onDraw , in it draw the game objects, after you have calculated the game data for them first of course
The Handler: (in your Activity)
private Handler playHandler = new Handler() {
public void handleMessage(Message msg) {
gameView.postInvalidate(); // gameView is the View that you extended
}
};
The game thread has a simple
Message.obtain(playHandler).sendToTarget();
In 2 words, the View is responsible for the drawing (you can move the calculations in a separate class, and call it before the onDraw), the thread is responsible only for scheduled calls to the Handler, and the Handler is responsible only to tell the View to redraw itself.
You cannot update the UI of your app outside of the UI Thread, which is the 'main' thread you start in. In onCreate(Context) of you app, you are creating the game thread object, which is what is doing the updating of your UI.
You should use a Handler:
http://developer.android.com/reference/android/os/Handler.html