Develop Reference

Is there any way to track what fragment/s are visible right now?

I work on a very large project. It has a lot of modules and views - activities and fragments. I need to understand what fragment and what activity are running at the moment. Then I need to move to this class of activity and fragment in the project. Is there any way to find the class name? maybe by logs or smth else?

You can use Android Profiler for this. You will also get a lot of details from this tool. Just hover the mouse over the graph, it will show the fragment currently showing.

You can try Layout Inspector, a feature of android studio. When the app is running on a device that is connected to Android Studio, you can click on any item to see the view id, you can use these ids to find out which activity/fragment they belong to (through xml file)

Use UserVisibleHint for that:
boolean isVisible;
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
isVisible = isVisibleToUser;
}
When you want to check the visibility of the fragment, simply check it.
if (isVisible) {
//Fragment is visible
} else {
//Fragment is not visible
}

Android QR Scanner: How to quit ZXingScannerView.ResultHandler to get back to where I came from

In my first steps in exploring Android I now start with QR scanning.
Works all pretty well. But I am not able to come back from the ResultHandler after read the QR successfully to my MainActivity.
public class MainActivity extends AppCompatActivity implements
ZXingScannerView.ResultHandler
{
private ZXingScannerView mScannerView
....
#Override
public void handleResult(Result rawResult)
{
// my results are ok in rawResult
// the scanner does not scan anymore but it is still there
// how to go back to my main activity???
}
public void ClickButton (View view)
{
mScannerView = new ZXingScannerView(this);
setContentView(mScannerView);
mScannerView.setResultHandler(this);
mScannerView.startCamera();
}
}
}
I tried
mScannerview.stopCameraPreview
mScannerView.stopCamera
this.finish
setContentView(R.layout.activity_main); // shows my activity_main
// but I can not click anything
Thanks!!
EDIT
I added some code to describe it a bit better. The idea is from
https://www.numetriclabz.com/android-qr-code-scanner-using-zxingscanner-library-tutorial/

Your question isn't clear but I'm assuming you want to restart the scan process. Normally, you'd have to restart the SurfaceHolder to be in preview mode. Luckily for you the ZXingScannerView already has a method to do that. Call mScannerView.resumeCameraPreview(this) to restart the scan process.
Otherwise can you clarify? You say you want to go back but you're already in MainActivity

If you want to go back into activities/fragments stack you can try Activity.onBackPressed()
if you are in a fragment you must call this method against attached Activity
What do you want is not going back to your activity. You want to restore activity's layout.
I think the better choice is to add ScannerView to your activity's layout file with android:visibility="gone". Then in on click you can get this view and change it's visibility to VISIBILE.
Then when you have handled scanning result, you can reset yuoir ScannerView to visibility = GONE

I too was stuck with this problem for an hour, just like you. And later realised..
To solve this problem DON NOT implementing the ZXingScannerView in the same activity or fragment. Instead start a new activity when you click the button and this activity is just for the ZXingScannerView
Once the Scan is done finish and pass the data back to your activity or fragment

Just restart your MainActivity before this.finish()
the code below will start your main activity through intent...
worked fine for me
startActivity(new Intent(this,MainActivity.class));
this.finish();

remove from onCreate method this line setContentView(your layout) and when you finish scan write it after you stoped the camera then you can use your layout after scan

I had a bit of a look into android concepts and activities.
I put the QR handling in a 2nd activity and it worked well with the finish ().
Thanks for help anyway!!

I think it's too late, but I came with the same problem and I had so find a solution by myself.
You were on the right way, you need two steps more.
I called the methods where I link and set the listener of any buttons
There are the methods
Basically you were right where you set the content view, but you need to give the buttons their functionality back.
(I know its late, but better late than never). Good luck!

Are Activity/Fragment Transitions compatible with pre-Lollipop devices?

I'm trying to make an Activity Transition using Shared Elements on a pre-Lollipop device (4.x). Is it possible? So far, I'm trying this:
public class RewardDetail extends ActionBarActivity {
#Override
public void onCreate(final Bundle savedInstanceState) {
...
ViewCompat.setTransitionName(imageView, TRANSITION_NAME);
}
...
public static void launch(ActionBarActivity activity, View transitionView, WelcomeReward detailData) {
ActivityOptionsCompat options = ActivityOptionsCompat.makeSceneTransitionAnimation(activity, transitionView, TRANSITION_NAME);
Intent intent = new Intent(activity, RewardDetail.class);
intent.putExtra(PARAM_DATA, detailData);
ActivityCompat.startActivity(activity, intent, options.toBundle());
}
}
called by:
#Override
public void onClick(final View v) {
int position = recyclerView.getChildPosition(v);
WelcomeReward welcomeReward = data.get(position);
RewardDetail.launch(WelcomeRewardActivity.this, v.findViewById(R.id.reward_view), welcomeReward);
}
But it results in a "regular" transition (no shared element). Any ideas?
EDIT
According to this video, it could be done:
https://www.youtube.com/watch?v=RhiPJByIMrM&index=8&list=WL
Is there a library already implementing this for pre Lollipop ?

No, Activity/Fragment Transitions are not possible on pre-Lollipop devices. According to the documentation:
Start an activity with additional launch information, if able.
In Android 4.1+ additional options were introduced to allow for more control on activity launch animations. Applications can use this method along with ActivityOptionsCompat to use these animations when available. When run on versions of the platform where this feature does not exist the activity will be launched normally.
See also George Mount's answer to this StackOverflow question.

You can check out this library for activity and fragment transitions for pre lollipop devices
dependencies {
compile 'com.albinmathew:PreLollipopTransition:1.1.2'
}
https://github.com/albinmathew/PreLollipopTransition

Although the fancy Lollipop Activity/Fragment transitions are not available pre-Lollipop (without the use of a 3rd party library), you can still override the animation used to transition between activities.
Just before/after you start invoke startActivity() you can make a call to [Activity.overridePendingTransition](http://developer.android.com/reference/android/app/Activity.html#overridePendingTransition(int, int)). When you leave your activity, call the same method.
Similarly you can use ActivityOptionsCompat to define a custom animation to use during a transition.
ActivityOptionsCompat opts =
ActivityOptionsCompat.makeCustomAnimation(getActivity(), R.anim.in, R.anim.out);
startActivity(intent, opts.toBundle());

There is a support library, but it does not support (all) transitions on Android versions below 5.0. There are however some alternatives:
Unofficial Compatibility libraries https://github.com/andkulikov/transitions-everywhere
https://github.com/takahirom/PreLollipopTransition
https://github.com/lgvalle/Material-Animations
Android KitKat http://www.doubleencore.com/2013/11/new-transitions-framework/ and a
sample found in your SDK samples folder.
Posted earlier to a duplicate of this question here: https://stackoverflow.com/a/27344471/1683141

Android: Adding accessibility to a custom view

I'm attempting to implement accessibility on a few custom views for an Android app.
I've condensed what is done in the Google Authenticator app with no luck:
public class CardView extends RelativeLayout {
// ...
#Override
public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
event.setClassName(this.getClass().getName());
event.setPackageName(this.getContext().getPackageName());
event.getText().add("Card Test");
return true;
}
}
All TalkBack reports back is "Double-tap to select" when it's inside a ListView or ViewPager.
Does ViewPager override accessibility events?
What do I need to do in order to have TalkBack say "Card Test" inside ViewPagers and ListViews like I expect it to?

For current versions of Android, you need to set the content description of the view.
myView.setContentDescription("Card Test");

ListView and associated classes expect you to use the onItemSelectedListener instead of assigning an onClickListener to each View (and rightfully so).

If incorporating alanv's suggestion, try to convince android system to read out the content description
by either
If(accessibilityModeIsEnabled())//custom method that checks context.getSystemService(Context.ACCESSIBILITY_SERVICE).isEnabled()
myView.sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_HOVER_ENTER);
or AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED.
or requestFocus
Above should done when myView is visible. May be during onMesasure when width and height are both positive
If list view is still unable to do so, then try doing the above tricks on the first element of list view. Accessibility in Android varies devices to device and not one strategy fits all

Creating buttons in java

I'm pretty new to learning about java and android development; so please help me out. In the next line of code I am trying to create a button but I am having trouble understanding why the 'id' is underlined. When I fix it in the R folder the .blue_yes gets underlined and I am confused what I should do next? Any help would be helpful.
Thanks
Button yes = (Button) findViewById(R.id.blue_yes);
yes.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
mBtAdapter.enable();
setResult(CheckBluetoothEnabledActivity.RESULT_SUCCESS);
finish();
}
});
Button cancel = (Button) findViewById(R.id.blue_cancel);
cancel.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
setResult(CheckBluetoothEnabledActivity.RESULT_CANCEL);
finish();
}

you should have a button in the layout xml file with id blue_yes and blue_cancel before accessing that control in your in your code. probably you have not declared the control in your xml file correctly.
Once you specify a control in Layout file entry in R.Java is automatically made by eclipse android plugin. you don't need to mess with R folder and its file as R.java in automatically generated file and you should not change anything in that.
if even after declaring your control in layout file you are not able to get your control using findViewById method then please post your layout file as well to help you further.

Given the data, one of gazillion possible explanations is that you don't have R imported (and then fix it by creating a new class, and the new class lacks the id attribute).