My code below is based on this: http://web.archive.org/web/20100816175634/http://blog.henriklarsentoft.com/2010/07/android-tabactivity-nested-activities/
My issue is with the history ArrayList that is supposed to store the activities so I can properly utilize the back button, however my app crashes when I hit back. I think it's because history isn't exactly storing Views.
I added:
View view = getLocalActivityManager().startActivity("ViewPagerActivity", new
Intent(this,ViewPagerActivity.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP))
.getDecorView();
to my back method to see if it would load it and it works.
public class FeaturedTabGroup extends ActivityGroup {
// Keep this in a static variable to make it accessible for all the nesten activities, lets them manipulate the view
public static FeaturedTabGroup group;
// Need to keep track of the history if you want the back-button to work properly, don't use this if your activities requires a lot of memory.
private ArrayList history;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.history = new ArrayList();
group = this;
// Start the root activity withing the group and get its view
View view = getLocalActivityManager().startActivity("ViewPagerActivity", new
Intent(this,ViewPagerActivity.class)
.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP))
.getDecorView();
// Replace the view of this ActivityGroup
replaceView(view);
}
public void replaceView(View v) {
// Adds the old one to history
history.add(v);
// Changes this Groups View to the new View.
setContentView(v);
System.out.println("view set successful");
}
public void back() {
if(history.size() > 0) {
history.remove(history.size()-1);
setContentView((Integer) history.get(history.size()-1));
}else {
finish();
}
}
#Override
public void onBackPressed() {
FeaturedTabGroup.group.back();
return;
}
}
EDIT:
For brevity, I'll approach this problem with another question: why does setContentView(v) work, but not when the Views are store in an ArrayList? What happens to the view when it is stored in an arraylist?
Can't you work around this issue with ViewSwitcher (http://developer.android.com/reference/android/widget/ViewSwitcher.html)? It provides a cleaner solution and you could always call showPrevious() and showNext() when needed.
setContentView(int) expects a layout resource ID. In your example, can you try to save the view object itself (i.e. without type cast to integer)? As jcXavier says - viewswitcher is a better way to handle this.
Maybe it's late , but here: (history.size() > 0), change 0 to 1, when size is 1, it should just finish.
Adam,
I know it must be late... but perhaps I can help somebody else.
Here is how I solved the problem:
public void back() {
View v;
if(history.size() > 1) {
history.remove(history.size()-1);
v = (View) history.get(history.size()-1);
FirstGroup.group.setContentView(v);
}else {
finish();
}
}
Related
I have the following Activity definition:
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/inspectionMainLayout"
xmlns:android="http://schemas.android.com/apk/res/android">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:singleLine="false"
android:id="#+id/breadCrumb"
android:visibility="gone">
</LinearLayout>
<ExpandableListView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="#+id/expandableListView" />
</LinearLayout>
Now in my code I do add buttons dynamically in breadCrumb LinearLayout:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_inspection);
LinearLayout mainLayout = (LinearLayout) findViewById(R.id.inspectionMainLayout);
if (mainLayout != null) {
ExpandableListView list = (ExpandableListView) findViewById(R.id.expandableListView);
list.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
#Override
public boolean onChildClick(ExpandableListView expandableListView, View view, int i, int i2, long l) {
LinearLayout breadCrumb = (LinearLayout) findViewById(R.id.breadCrumb);
Button filterButton = new Button(InspectionActivity.this);
filterButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
onFilterButtonClick((Button) view);
}
});
filterButton.setText(item.getFormattedFilter());
breadCrumb.addView(filterButton);
}
}
}
...
}
This code works well, until I do not change the device orientation and my Activity is recreated. Although all the code is executing correctly, screen seems not being updated. Once I restore the previous orientation, all the items suddenly appear. Any idea why and how to fix it?
Thanks
EDIT:
I do think that I'm running into the same problem as describe in this post:
Android: findViewById gives me wrong pointer?
Any idea on how to solve this?
As requested my onRestoreInstanceState:
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
baseCategories = savedInstanceState.getParcelable(BASE_CATEGORIES_STATE);
currentFilter = savedInstanceState.getParcelable(FILTERS_STATE);
}
and on onSaveInstanceState:
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putParcelable(BASE_CATEGORIES_STATE, baseCategories);
outState.putParcelable(FILTERS_STATE, currentFilter);
}
now both of my classes do implement Parcelable interface.
They are persisted and restored correctly.
Still for some resaon the call to the findViewById get's me pointed to the wrong object (not the one that is recreated).
You add views dynamically (on user click event).
By default, android does not "remember" to keep these dynamic views when re-creating the activity on configuration changes, you have to handle this process yourself.
Some possibilities :
Avoid recreating activity on screen rotation by declaring android:configChanges="keyboardHidden|orientation|screenSize" for your activity in AndroidManifest.xml - This is highly not recommended
"Remember" what views were dynamically added when re-creating activity after rotation (for example using extra flags to detect that new filter button was added and pass it via bundle in onSaveInstanceState, and check in onCreate whether you need to re-create the button), or retain the whole view object as explained here
One extra note : you perhaps want to specify "vertical" orientation for your breadCrumb layout, it is horizontal by default.
I found out why this is happening.
onSave/onRestoreInstanceState I was persisting the currentFilter class which has some custom listeners on it.
As onResume method I was doing the following:
#Override
protected void onResume() {
if (currentFilter == null) {
currentFilter = new FilterItemList();
currentFilter.addListener(new FilterItemListListener() {
#Override
public void filterChanged(FilterChangedEvent e) {
filterCategories(categoryRepository);
}
#Override
public void filterAdded(FilterAddedEvent e) {
FilterItem addedItem = e.getAddedItem();
baseCategories.remove(new BaseCategory("", addedItem.getSectionName()));
}
#Override
public void filterRemoved(FilterRemovedEvent e) {
FilterItem removedItem = e.getRemovedItem();
baseCategories.add(new BaseCategory("", removedItem.getSectionName()));
}
});
}
}
The pointer to the previous instance was persisted. That's why my interface was not behaving correctly.
Now I do re-register listeners even when currentFilter is not null (it is restored) so they can point to the right instance.
Is there any pattern in handling this situations?
Thanks
I have a layout with a ListView and ImageView. Initially, ImageView is invisible. I have a list, when an Item is clicked, it shows the Image of that item by setting ImageView and making it visible and listView is invisible, so far everything is ok. From there, onBackPressed() I want to see my listview again, I override onBackPressed(), to make my image view invisible and listview visible. However, when I select an item and see the image of it then press back, a blank activity comes, not my listView. I don't want to call the activity again, what should I do? What is wrong about listView? I tried to call invalidate() and invalidateViews(), setting adapter again, but they aren't woring.
Actually I'm filing adapter in the onResume of the activity, here is the code:
public class MyViewActivity extends Activity{
ListView imageList;
CustomImageListAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_list_view);
//initialization of image array list etc
}
#Override
public void onResume(){
super.onResume();
imageList = (ListView) findViewById(R.id.listView);
adapter = new CustomImageListAdapter(this,R.layout.image_item, imageNames);
imageList.setAdapter(adapter);
imageList.setOnItemClickListener(new OnItemClickListener()
{
public void onItemClick(AdapterView<?> adapter, View view, int i,
long l) {
// TODO Auto-generated method stub
if(imageNames.get(i) != null) {
onImageSelected(i);
}
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.image_list_view, menu);
return true;
}
public void onImageSelected(int position) {
...
}
#Override
public void onBackPressed() {
if (img.getVisibility() == ImageView.VISIBLE){
// img.setVisibility(ImageView.INVISIBLE);
// imageList.invalidateViews();
// imageList.setVisibility(ListView.VISIBLE);
// Here actually I want to use the upper part that I commented, but it didn't work, I have to call the same activity again to see my listview
Intent i = new Intent(MyViewActivity.this, MyViewActivity.class);
startActivity(i);
finish();
}
else {
....
}
return;
}
private class CustomImageListAdapter extends ArrayAdapter<String>{
...
}
As long as I can guess, the problem is caused by
img.setVisibility(ImageView.INVISIBLE);
You can try to use View.GONE instead.
The difference is clearly stated in android api's doc and I quoted:
/**
* This view is invisible, but it still takes up space for layout purposes.
*/
public static final int INVISIBLE = 0x00000004;
/**
* This view is invisible, and it doesn't take any space for layout
*/
public static final int GONE = 0x00000008;
By the way, I will recommend to use fragments to do your job. Specifically, a fragment A to present the listview, and when an item is clicked, switch to fragment B which contains the content. When Back is pressed, just let the backstack do its job.
Intent i = new Intent(MyViewActivity.this, MyViewActivity.class);
i.putExtra("currentObjectID",objectID);
startActivity(i);
finish();
Why are you traversing within the same activity? You should understand the use of intents ,If you want to stay within the same activity , Just set a flag for currentObjectID instead of put Extra..
DogActivity is using a custom View. The custom view handles some logic and so has fields. When a particular field reaches a certain value, I want to start a fragment whose parent is DogActivity. How would I do that?
Is it advisable to put a callback inside a custom view so that it calls its parent activity? Or is there a simpler way?
When programming you should always look for consistency, i.e. look around you and see how similar stuff to what you want to do is done. The Android SDK makes heavy use of callback listeners, so they are the way to go here.
In fact we don't even need to know what kind of View your CustomView really is, we can build a general purpose solution. Don't forget to adapt/optimize according to your specific surroundings however. And think about abstraction and generalisation once you get to a point where all your Views are spammed with listeners!
You will need 3 things:
A listener interface
public interface OnCountReachedListener {
public void onCountReached();
}
A place to accept the listener and a place to alert the listener in your CustomView
public class CustomView extends View {
private int theCount;
private OnCountReachedListener mListener;
public void setOnCountReachedListener(OnCountReachedListener listener) {
mListener = listener;
}
private void doSomething() {
while (theCount < 100) {
theCount++;
}
// The count is where we want it, alert the listener!
if (mListener != null) {
mListener.onCountReached();
}
}
An implementation of the interface in your Activity
public class DogActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
View myView = new CustomView();
myView.setOnCountReachedListener(new OnCountReachedListener() {
#Override
public void onCountReached() {
Log.w("tag", "COUNT REACHED!");
// START YOUR FRAGMENT TRANSACTION HERE
}
});
}
}
For further information look at the source code of the View class and all the On**XY**Listener interfaces in the Android SDK. They should give you plenty to think about
What is the type of the field? Is it an EditText? SeekBar? Depending on the View, you'll be able to specify different listeners/callbacks to determine when they have changed and if they've reached a certain threshold. I would attach these listeners within onCreate of DogActivity. When the threshold is reached, use a FragmentTransaction to add your Fragment as the child of a container View in DogActivity.
I'm creating an Android app with an activity comprised of a mixture of static views and dynamically created views. The activity contains UI elements held in an XML file and UI elements which are created dynamically based on the content of a model class. (as in, there is an array in my model class and an EditText will be created for every element in the array.. and a Spinner will be created containing every element in a different array)
What's the usual method for saving and restoring the state of the application when dynamically created UI elements are involved? Because I won't always know which UI elements will exist at any one time! Currently, my binding code simply reloads the data from the database when the device orientation changes, losing any changes that the user made.
I've had a good look around on Google/SO for this and I've not found anything related to this problem.
Thanks all
Edit:
For anyone that comes across this in the future, I did a slightly modified version of Yakiv's approach and wound up with this:
for (int i = 0; i < views.size(); i++) {
View currentView = views.get(i);
if (currentView instanceof CheckBox) {
outState.putBoolean("VIEW"+i, (((CheckBox) currentView).isChecked()));
} else if (currentView instanceof EditText) {
outState.putString("VIEW"+i, ((EditText) currentView).getText().toString());
} else if (currentView instanceof Spinner) {
//.....etc. etc.
}
}
Thanks again Yakiv for the awesome idea.
To restore dynamic views state you need to make them as class fields and initialize them in onCreate. Then just use this article to save and restore their state.
private List<View> mViews= new ArrayList<View>();
#Override
public void onCreate(..)
{
LinearLayout parent = ....//initialize it here
initializeViews();
}
public void initializeViews()
{
// create and add 10 (or what ever you need) views to the list here
mViews.add(new View(this));
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
int mViewsCount = 0;
for(View view : mViews)
{
savedInstanceState.putInt("mViewId_" + mViewsCount, view.getId());
mViewsCount++;
}
savedInstanceState.putInt("mViewsCount", mViewsCount);
}
#Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
int mViewsCount = savedInstanceState.getInt("mViewsCount");;
for(i = 0; i <= mViewsCount)
{
View view = mViews.get(i);
int viewId = savedInstanceState.getInt("mViewId_" + i);
view.setId(viewId);
mViewsCount++;
}
}
Best wishes.
I'm using a ViewPager for a multiple-choice exam app, which chooses out randomly thirty questions out of a bigger set. I do this in the PageAdapter that is supplying the pages to the ViewPager.
The problem is that when an orientation change occurs, not only the pager but also the adapter gets reloaded - I know how to save the current pager position but when the adapter gets reset, it also chooses new questions from the set. What would be the proper way to handle this?
Also, side question - what would be the best way to register the choices on the RadioGroups? Directly by click or in a different way?
I'm fairly new to the Android app developement.
Activity:
public class MyActivity extends SherlockActivity {
ActionBar actionBar;
ViewPager pager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
pager = new ViewPager(this);
setContentView(pager);
QuestionsAdapter adapter = new QuestionsAdapter(this);
pager.setAdapter(adapter);
int position = 0;
if (savedInstanceState != null) {
position = savedInstanceState.getInt("Q_NUMBER");
}
pager.setCurrentItem(position);
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
int position = pager.getCurrentItem();
savedInstanceState.putInt("Q_NUMBER", position);
}
}
Adapter:
class QuestionsAdapter extends PagerAdapter {
Context context;
QuestionsHelper dbQuestions;
boolean exam;
List<HashMap<String,Object>> examQuestions;
public QuestionsAdapter(Context context, boolean exam) {
this.context = context;
this.examQuestions = GetQuestionsFromDB(30);
}
public Object instantiateItem(View collection, int position) {
LayoutInflater inflater = (LayoutInflater) collection.getContext()
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view;
HashMap<String,Object> q;
view = inflater.inflate(R.layout.exam_question_layout, null);
q = getQuestion(position+1);
((TextView)view.findViewById(R.id.q_number)).setText(Integer.toString(position+1)+".");
((TextView)view.findViewById(R.id.q_question)).setText(q.get("question").toString());
((RadioButton)view.findViewById(R.id.q_answer_a)).setText(q.get("answer_a").toString());
((RadioButton)view.findViewById(R.id.q_answer_b)).setText(q.get("answer_b").toString());
((RadioButton)view.findViewById(R.id.q_answer_c)).setText(q.get("answer_c").toString());
((ViewPager)collection).addView(view, 0);
return view;
}
}
Screen Rotation will redraw the entire screen in the new orientation, we can prevent it with overriding configuration changes.
add android:configChanges="orientation|screenSize" under your screen declaration in Android Manifest
android:configChanges="orientation|screenSize"
And Override onConfigurationChanged(Configuration) in your activity like
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
}
I know how to save the current pager position but when the adapter
gets reset, it also chooses new questions from the set. What would be
the proper way to handle this?
Your questions should really have an id to uniquely identify them. I'm not sure how you get them from the database but when that would happen you would need to store their ids. Also:
Your adapter should have a long array(or integer) holding 30 values representing the ids of the current selected batch of questions
You'll need to implement the following logic in the adapter: if the long array from the previous point is null then assume it's a clean start and get a new set of 30 questions.
If the long array is non null then we are facing a restore from a configuration change and you'll need to use those ids to get the proper questions from the database instead of a random batch
In the Activity you'll save the long array of the adapter in the onSaveInstanceState() method(savedInstanceState.putLongArray)
In the onCreate method of the Activity, when you create the adapter, you'll check the savedInstanceState Bundle to see if it is non-null and it has the long array and set that on the adapter(so it will know which questions to get)
what would be the best way to register the choices on the RadioGroups?
Directly by click or in a different way?
You could use the above method, or create a custom class with Parcelable like it has already been recommended to you in the comments.