I need execute a method when the fragment is visible (to the user).
Example:
I have 2 buttons (button 1 and button 2) ,
2 fragments(fragment 1 and fragment 2)
and the method loadImages() inside the class fragment 2.
when I press "button2" I want to replace fragment 1 by fragment 2
and then after the fragment 2 is visible (to the user) call loadImages().
I tried to use onResume() in the fragment class but it calls the method before the fragment is visible and it makes some delay to the transition.
I tried setUserVisibleHint() too and did not work.
A good example is the Instagram app. when you click on profile it loads the profile activity first and then import all the images.
I hope someone can help me. I will appreciate your help so much. Thank you.
Use the ViewTreeObserver callbacks:
#Override
public void onViewCreated(View v, Bundle savedInstanceState) {
super.onViewCreated(v, savedInstanceState);
final View view = v;
// Add a callback to be invoked when the view is drawn
view.getViewTreeObserver().addOnDrawListener(new ViewTreeObserver.OnDrawListener() {
#Override
public void onDraw() {
// Immediately detach the listener so it only is called once
view.getViewTreeObserver().removeOnDrawListener(this);
// You're visible! Do your stuff.
loadImages();
}
});
}
I'm a little confused by what you are trying to do. It sounds like the images are loading too fast for you... so does that mean that you have the images ready to display? And that is a bad thing?
My guess (and this is just a guess) is that Instagram does not have the profile pictures in memory, so they have to make an API call to retrieve them, which is why they show up on a delay. If the same is the case for you, consider starting an AsyncTask in the onResume method of the fragment. Do whatever loading you need to do for the images in the background, and then make the images appear in the onPostExecute callback on the main thread. Make sure you only start the task if the images are not already loaded.
However, if you already have the images loaded in memory, and you just want a delay before they appear to the user, then you can do a postDelayed method on Handler. Something like this:
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
loadImages();
}
}, 1000);
Edit
As kcoppock points out, the handler code is pretty bad. I meant it to be a quick example, but it is so wrong I should not have included it in the first place. A more complete answer would be:
private Handler handler;
public void onResume(){
super.onResume();
if(handler == null){
handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
loadImages();
}
}, 1000);
}
}
public void onDestroyView(){
super.onDestroyView();
handler.removeCallbacksAndMessages(null);
handler = null;
}
Use the onActivityCreated() callBck
Related
Several times I've had problems writing code on onCreate(). Mostly because the UI has not been sized and laid out on the screen yet (even if I place my code at the end of the function). I've looked over the activity life-cycle to see if there's anything that runs after onCreate(). There is onStart(), but the problem is that onRestart() recalls onStart(), I don't want that. So is there a way to write code between onCreate() and onStart()? OR where should I write code that runs after the UI is placed and only runs once during its process?
Not sure what exactly you need but you can "cheat" and simply store whether you have run code or not:
private boolean mInit = false;
void onStart() {
if (!mInit) {
mInit = true;
// do one time init
}
// remaining regular onStart code
}
The other way of running code when UI is placed is to use the global layout listener:
public class FooActivity extends Activity implements ViewTreeObserver.OnGlobalLayoutListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list_content);
View content = findViewById(android.R.id.content);
content.getViewTreeObserver().addOnGlobalLayoutListener(this);
}
#Override
public void onGlobalLayout() {
// unregister directly, just interested once.
View content = findViewById(android.R.id.content);
content.getViewTreeObserver().removeOnGlobalLayoutListener(this);
// do things here.
}
}
I am building the app, which generates and adds view dynamically. I don't know in advance what views I need to create, these can be nested layouts or simple labels, etc, depending what comes back from web services.
Everything has been well so far until I started building really complex nested layouts .I have one case where I need to add about 11 levels of Layouts dynamically. When activity starts I display ProgressDialog(ring), while views are being generated. My problem is that with this complex structure ProgressDialog freezes while views are added. This is the code, which creates the view:
private class ViewCreator implements Runnable {
public BackgroundTaskViewCreatedResponse delegate;
private View mCreatedView;
private ComponentDefinition mComponent;
private ViewCreator(ComponentDefinition component){
this.mComponent = component;
}
#Override
public void run() {
try {
if (mComponent != null){
mComponent.setLinkedData(model.getLinkedData());
mCreatedView = componentCreator.createComponent(mComponent);
}
} finally {
if (mCreatedView != null)
delegate.processFinishTask(mCreatedView);
}
}
}
Layout, which has other views in it implements BackgroundTaskViewCreatedResponse, so, when view is ready, it will be added:
#Override
public void processFinishTask(final View createdView) {
//((Activity)view.getContext()).runOnUiThread(new Runnable(){
mView.post(new Runnable(){
#Override
public void run() {
mView.addView(createdView);
}
});
}
As you can see above, I have tried to call runOnUiThread call, but this blocks the UI thread completely while view hierarchy is being generated. At the same time view.post doesn't get called out of the box, so I have made some changes to views as suggested in this SO answer. So, now my views are added, but my ProgressDialog is not running smoothly. It stops in a few occasions and then resumes. I've also tried using Android AsyncTask, but that gives the same effect as runOnUiThread
I am not very experienced with Threads, have been trying to fix this for a few days now. Please help.
You can use AsyncTask to do this/ Here is an example:
private class GenerateViews extends AsyncTask<Void,Void,Void>{
#Override
protected void onPreExecute() {
// SHOW THE SPINNER WHILE GENERATING VIEWS
spinner.setVisibility(View.VISIBLE);
}
#Override
protected Void doInBackground(Void... params) {
//CALL YOUR VIEW GENERATING METHOD HERE
return null;
}
#Override
protected void onPostExecute(Void result){
spinner.setVisibility(View.INVISIBLE);
}
}
You can make this class inside your class, if you want to. And then, you just call
new GenerateCalls.execute();
I am new to Android development and I want to link a button with the animation. I am getting error near runOnUiThread() and getApplication(). When I add this in as an activity it is fine, but when declared in MainFragment it gives error. However when I fix the errors, it creates a method and returns false.
public class MainFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_main, container, false);
ImageButton btnFacebook = (ImageButton)rootView.findViewById(R.id.facebook2);
final Animation alpha = AnimationUtils.loadAnimation(getActivity(), R.anim.anim_alpha);
btnFacebook.setOnClickListener(new Button.OnClickListener(){
#Override
public void onClick(View arg0) {
arg0.startAnimation(alpha);
Thread thread = new Thread()
{
#Override
public void run()
{
try
{
Thread.sleep(1000);
}catch(InterruptedException e){
}
runOnUiThread(new Runnable() {
#Override
public void run() {
startActivity(new Intent(getApplication(),FacebookActivity.class));
}
});
}
};
thread.start();
}});
return rootView;
}}
In the XML file I only have the facebook imagebutton. When I click that, it has to trigger the animation and then onclick event has to happen, but I don't know why this error is popping up:
The method runOnUiThread(new Runnable(){}) is undefined for the type new Thread(){}
And near getapplication() method
The method getApplication() is undefined for the type new Runnable(){}
If I create the two methods the error goes away, but then when I click onto the button it will not go to the facebookActivity.java file.
Can anyone tell/help what should I add to solve this issue. Thanks.
runOnUIThread(...) is a method of Activity.
Therefore, use this:
getActivity().runOnUIThread(...);
But, beware. You're dealing with asynchronous threads, so your Fragment might be detached from its Activity, resulting in getActivity() returning null. You might want to add a check if(isAdded()) or if(getActivity() != null) before executing.
Alternatively, use an AsyncTask, which handles this running on the ui thread by itself.
runOnUiThread(new Runnable(){}) is method in Activity not in the Fragment.
so you need to change
runOnUiThread(new Runnable(){})
into
getActivity().runOnUiThread(new Runnable(){})
For your requrement it is better to use Handler instead of Thread for waiting 1000 milli seconds..
Please use getActivity() instead of using getApplication() .
which returns the activity associated with a fragment.
The activity is a context.
I have a long running method that is called during onCreate, this method populates textviews so interacts with the UI, and updates maybe 70 labels (about 3-20 seconds depending on device).
I want to display a progressdialog as this method executes.
Ideally I want to fire my method on the UI thread once the Activity has been displayed and the progress is displayed, this I cannot do, the Activity won't paint until the method has finished.
I hoped to find an event which was fired after the activity was displayed, and I found the one below, but it still leaves the screen black until the method has finished.
#Override
public void onPostCreate(Bundle savedInstanceState)
I am normally a WP7 developer, and in .NET you add an event handler for onLoadComplete which is fired after the ui is displayed, but before the user has a chance to interact withthe UI, how do I do this in Android JAVA?
Thanks
Put a ProgressBar in the View.
Then in the onCreate() or onResume() method do this:
new Thread() {
public void run() {
yourLargeMethod();
}
}.start();
Now you can do this inside your method to update the progressBar
public void yourLargeMethod() {
// doSomething
...
runOnUiThread(new Runnable() {
public void run() {
// update the progress from the thread
progressBar.setProgress(x); // x is your progress, 0 <= x <= progressBar.getMax()
}
});
}
I have an android app which is already handling changes for orientation, i.e. there is a android:configChanges="orientation" in the manifest and an onConfigurationChange() handler in the activity that switches to the appropriate layout and preps it. I have a landscape / portrait version of the layout.
The problem I face is that the activity has a dialog which could be open when the user rotates the device orientation. I also have a landscape / portrait version of the dialog.
Should I go about changing the layout of the dialog on the fly or perhaps locking the activity's rotation until the user dismisses the dialog.
The latter option of locking the app appeals to me since it saves having to do anything special in the dialog. I am supposing that I might disable the orientation when a dialog opens, such as
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_NOSENSOR);
and then when it dismisses
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR);
Would that be a sensible thing to do? If the screen orientation did change while it was locked, would it immediately sense the orientation change when it was unlocked?
Are there alternatives?
I would recommend not turning off the screen rotation, instead of this handle the configuration changes for the Dialog. You could use one of these two approach for this:
The first one is using a flag variable in onSaveInstanceState(outState) method, and restore the dialog onCreate(bundle) method:
in this example my flag variable is called 'isShowing Dialog', when the onCreate method is called by the android System for first time, the bundle argument will be null and nothing happens. However when the activity it's recreated by a configuration change (screen rotation), the bundle will have the boolean value isShowing Dialog, previously saved by the inSaveInstanceState(...) method, so if the variable gets true the dialog is created again, the trick here is set the flag in true when the dialog get showing, and false when it's not, is a little but simple trick.
Class MyClass extends Activity {
Boolean isShowingDialog = false;
AlertDialog myDialog;
#Override
protected void onCreate(Bundle savedInstanceState) {
if(savedInstanceState!=null){
isShowingDialog = savedInstanceState.getBoolean("IS_SHOWING_DIALOG", false);
if(isShowingDialog){
createDialog();
}
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
outState.putBoolean("IS_SHOWING_DIALOG", isShowingDialog);
super.onSaveInstanceState(outState);
}
#Override
protected void onPause() {
if(myDialog!=null && myDialog.isShowing()) {
myDialog.dismiss();
}
}
private void createDialog() {
AlertDialog.Builder dialog_builder = new AlertDialog.Builder(this);
dialog_builder.setTitle("Some Title"):
... more dialog settings ...
myDialog = dialog_builder.create();
myDialog.show();
isShowingDialog = true;
}
private void hideDialog(){
myDialog.dismiss();
isShowingDialog = false;
}
}
The second approach is to use the ability of the fragments components to retain its states, the main idea is create the dialog inside a fragment, there is the problem about detach and reattach the fragment during the configuration changes (because you need dismiss and show the dialog correctly), but the solution is very similar to the first approach. The advantage of this approach is that if you have an AlertDialog with a couple of configurations, when the fragment is recreated there is not needed to create and setting up the dialog again, only make it show() and the AlertDialog state is maintained by the fragment.
I hope this helps.
I suggest your Dialog should override onSaveInstanceState() and onRestoreInstanceState(Bundle) to save its state into a Bundle.
You then override those methods in your Activity, checking if the Dialog is shown and if so - calling the dialog's methods to save and restore it's state.
If you are displaying this dialog from a fragment, you will want to override OnActivityCreated(Bundle) instead of OnRestoreInstanceState.
For a source example see the built-in clock app provided with Android, where the SetAlarm Activity handles the TimePickerDialog this way.
If you are handling orientation changes yourself, then here is an approach.
I won't claim that this is an elegant solution, but it works:
You can keep track of whether the dialog has an active instance inside the dialog class itself, by using a static variable activeInstance, and overriding onStart() to set activeInstance = this and onCancel() to set activeInstance = null.
Provide a static method updateConfigurationForAnyCurrentInstance() that tests that activeInstance variable and, if non-null, invokes a method activeInstance.reInitializeDialog(), which is a method that you will write to contain the setContentView() call plus the code that wires the handlers for the dialog controls (button onClick handlers, etc. - this is code that would normally appear in onCreate()). Following that, you would restore any displayed data to those controls (from member variables in your dialog object). So, for example, if you had a list of items to be viewed, and the user were viewing item three of that list before the orientation change, you would re-display that same item three at the end of updateConfigurationForAnyCurrentInstance(), right after re-loading the controls from the dialog resource and re-wiring the control handlers.
You would then call that same reInitializeDialog() method from onCreate(), right after super.onCreate(), and place your onCreate()-specific initialization code (e.g., setting up the list of items from which the user could choose, as described above) after that call.
This will cause the appropriate resource (portrait or landscape) for the dialog's new orientation to be loaded (provided that you have two resources defined having the same name, one in the layout folder and the other in the layout-land folder, as usual).
Here's some code that would be in a class called YourDialog:
ArrayList<String> listOfPossibleChoices = null;
int currentUserChoice = 0;
static private YourDialog activeInstance = null;
#Override
protected void onStart() {
super.onStart();
activeInstance = this;
}
#Override
public void cancel() {
super.cancel();
activeInstance = null;
}
static public void updateConfigurationForAnyCurrentInstance() {
if(activeInstance != null) {
activeInstance.reInitializeDialog();
displayCurrentUserChoice();
}
}
private void reInitializeDialog() {
setContentView(R.layout.your_dialog);
btnClose = (Button) findViewById(R.id.btnClose);
btnClose.setOnClickListener(this);
btnNextChoice = (Button) findViewById(R.id.btnNextChoice);
btnNextChoice.setOnClickListener(this);
btnPriorChoice = (Button) findViewById(R.id.btnPriorChoice);
btnPriorChoice.setOnClickListener(this);
tvCurrentChoice = (TextView) findViewById(R.id.tvCurrentChoice);
}
private void displayCurrentUserChoice() {
tvCurrentChoice.setText(listOfPossibleChoices.get(currentUserChoice));
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
reInitializeDialog();
listOfPossibleChoices = new ArrayList<String>();
listOfPossibleChoices.add("One");
listOfPossibleChoices.add("Two");
listOfPossibleChoices.add("Three");
currentUserChoice = 0;
displayCurrentUserChoice();
}
#Override
public void onClick(View v) {
int viewID = v.getId();
if(viewID == R.id.btnNextChoice) {
if(currentUserChoice < (listOfPossibleChoices.size() - 1))
currentUserChoice++;
displayCurrentUserChoice();
}
}
else if(viewID == R.id.btnPriorChoice) {
if(currentUserChoice > 0) {
currentUserChoice--;
displayCurrentUserChoice();
}
}
Etc.
Then, in your main activity's onConfigurationChanged() method, you would just invoke YourDialog.updateConfigurationForAnyCurrentInstance() whenever onConfigurationChanged() is called by the OS.
Doesn't seem the title was ever resolved (Google Necro Direct).
Here is the solution, matching the request.
When your activity is created, log the screen orientation value.
when onConfiguration change is called on your activity, compare the orientation values. if the values don't match, fire off all of your orientation change listeners, THEN record the new orientation value.
Here is some constructive code to put in your activity (or any object that can handle configuration change events)
int orientation; // TODO: record orientation here in your on create using Activity.this.getRequestedOrientation() to initialize!
public int getOrientation(){return orientation;}
public interface OrientationChangeListener {
void onOrientationChange();
}
Stack<OrientationChangeListener> orientationChangeListeners = new Stack<>();
public void addOrientationChangeListener(OrientationChangeListener ocl){ ... }
public void removeOrientationChangeListener(OrientationChangeListener ocl){ ... }
That's the basic environment. Here's your executive:
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
if (orientation != newConfig.orientation)
for (OrientationChangeListener ocl:orientationChangeListeners) ocl.onOrientationChange();
orientation = newConfig.orientation;
}
In YOUR code model, you may need to send the new configuration, with the event, or the two orientation values with the event. However, Activity.this.getOrientation() != Activity.this.getRequestedOrientation() during event handling (because we are in a logical state of change between two logical values).
In review of my post, i have determined that there could be some synchronization issues, with multiple events! This is not a fault of this code, but a fault of "Android Platform" for not having defacto orientation sense handlers on every window, thusly trashing the polymorphic benefits of using java in the first place..
See the answer from Viktor Valencia above. That will work perfectly with the slight adjustment that you move the createDialog() to onResume.
#Override
protected void onResume() {
super.onResume();
if(isShowingDialog){
createDialog();
}
}
Fetch the boolean isShowingDialog value at onCreate, as suggested, but wait for onResume to display the dialog.