I am developing an Android app for tablets and not using the compatibility library.
There is just one Activity and it uses the ActionBar with 3 tabs.
In the TabListener I use setContentView to load the layout specific to that tab, and then add the relevant fragments to their frames.
This almost works exactly like I want, except when you switch between the tabs fast enough the app will crash.
I am using a Samsung Galaxy Tab as my debugging device and switching tabs is really fast. At a normal pace I can tap back and forth between them and the pages are loaded instantly. The problem is when I hyper switch between the tabs.
At first I got an
IllegalStateException: Fragment not added
as seen here:
http://code.google.com/p/android/issues/detail?id=17029
Following the suggestion to use try/catch blocks in onTabUnselected, I made the app a little more robust, but that lead to the issue at hand:
IllegalArgumentException: No view found for id 0x... for fragment ...
I have not found any other case on the web of anyone else having the same issue, so I am concerned that I may be doing something that’s not supported. Again, what I am trying to do is use 3 different layouts in one Activity – when you click on a tab, the listener will call setContentView to change the layout, and then add the fragments. It works beautifully unless you start aggressively switching between tabs.
I got the idea for this from: http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/app/FragmentTabs.html
and instead of the TabListener keeping a reference to one fragment, I have an array of them. Also, I am not using attach/detach since those were just added in API 13.
My theory is that either setContentView hasn’t finished creating the views, and that’s why FragmentTransaction can’t add them, OR the fragments are being added for one tab when another tab is selected and setContentView is called, destroying the other set of views.
I tried to hack something in to slow down tab switching but didn’t get anywhere.
Here is the code for my TabListener:
private class BTabListener<T extends Fragment> implements ActionBar.TabListener{
private int mLayout;
private Fragment[] mFrags;
private TabData mTabData;
private Activity mAct;
private boolean mNoNewFrags;
public BTabListener(Activity act, int layout, TabData td, boolean frags){
mLayout = layout;
mTabData = td;
mAct = act;
mNoNewFrags = frags;
mFrags = new Fragment[mTabData.fragTags.length];
for(int i=0; i<mFrags.length; i++){
//on an orientation change, this will find the fragments that were recreated by the system
mFrags[i] = mAct.getFragmentManager().findFragmentByTag(mTabData.fragTags[i]);
}
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
//this gets called _after_ unselected
//note: unselected wont have been called after an orientation change!
//we also need to watch out because tab 0 always gets selected when adding the tabs
//set the view for this tab
mAct.setContentView(mLayout);
for(int i=0; i<mFrags.length; i++){
//this will be null when the tab is first selected
if(mFrags[i]==null ){
mFrags[i] = Fragment.instantiate(GUITablet.this, mTabData.classes[i].getName());
}
//if there was an orientation change when we were on this page, the fragment is already added
if(!mNoNewFrags || mDefaultTab!=tab.getPosition()){
ft.add(mTabData.containterIDs[i], mFrags[i], mTabData.fragTags[i]);
}
}
mNoNewFrags = false;
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// this gets called when another tab is selected, before it's onSelected method
for(Fragment f : mFrags){
try{ //extra safety measure
ft.remove(f);
}catch(Exception e){
e.printStackTrace();
System.out.println("unselect couldnt remove");
}
}
}
}
And finally, the stack trace:
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): java.lang.IllegalArgumentException: No view found for id 0x7f0b0078 for fragment Fraggle{40ab2230 #2 id=0x7f0b0078 dummy2}
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:729)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:926)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.app.BackStackRecord.run(BackStackRecord.java:578)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1226)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:374)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.os.Handler.handleCallback(Handler.java:587)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.os.Handler.dispatchMessage(Handler.java:92)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.os.Looper.loop(Looper.java:132)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at android.app.ActivityThread.main(ActivityThread.java:4028)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at java.lang.reflect.Method.invokeNative(Native Method)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at java.lang.reflect.Method.invoke(Method.java:491)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
09-29 01:53:08.200: ERROR/AndroidRuntime(4611): at dalvik.system.NativeStart.main(Native Method)
THANK YOU!!
Okay, found a way around this:
Put the references to the fragments in the layout files, and surrounded the setContentView call in onTabSelected in a try/catch block.
The exception handling took care of it!