Develop Reference

How can I change the title of an android activity based on the Fragment in ViewPager2/TabView

I am working on an app and when I slide to the next tab I would like to change the title of the screen to match the Tab!

You can use registerOnPageChangeCallback in ViewPager2 to detect page swipes. In ViewPager2s host(for example host Activity) implement this event and when onPageSelected is called change the title of host Activity. In onPageSelected method you can get current position of ViewPager2 and based on position set your title.
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);
// Set title of Activity based on the position of Fragment
}
#Override
public void onPageScrollStateChanged(int state) {
super.onPageScrollStateChanged(state);
}
});

Display spinner only on the last page of Viewpager

I have 3 fragments in my viewpager and I want to show a spinner item on my toolbar's menu on the last page. So if I am going from 2 -> 3 the spinner should become visible but if I go from 3 -> 2, it should become invisible. I know I have to add an onPageChangeListener to the viewpager but I am not sure how to determine which was the last page. How can I do it?

In MainActivity where you have used ViewPager use below method
//visible spinner when 3rd fragment is visible
viewPagerFloor.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
if(position==2){
spinner.setVisibility(View.VISIBLE);
}else{
spinner.setVisibility(View.GONE);
}
}
#Override
public void onPageScrollStateChanged(int state) {
}
});

Android show simple Toast on each calling Fragment on ViewPager

you suppose i have two fragment on viewpager which i can switch between them by swipe, for example Fragment1 and Fragment2,
what i want to that when i swipe? i want to show toast between switch on them, for example when i swipe to switch on Fragment1, application show toast, or when i swipe to switch on Fragment2 application show toast, and again, show toast each showing and switching between fragments,
how can i do that? i can't find any documentation about this solution

viewPager.setOnPageChangeListener(new OnPageChangeListener() {
public void onPageScrollStateChanged(int state) {}
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}
public void onPageSelected(int position) {
// Show your Toast Here like
Toast.makeText(app.getBaseContext(),"Some string",
Toast.LENGTH_SHORT).show();
}
});
and if you want some method's inside your Fragments use this in every fragment whereever you want to show toast
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
}

try this
viewpagerEvent.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
//toast message here
}
#Override
public void onPageSelected(int position) {
}
#Override
public void onPageScrollStateChanged(int state) {
}
});

set OnPageChangeListener on ViewPager to get callback when page changed/scrolled or selected.
pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
// Show fragment change/switch toast
Toast.makeText(this,"Fragment1",
Toast.LENGTH_LONG).show();
}
#Override
public void onPageScrollStateChanged(int state) {
}
});

You have to make condition for Both Fragment while on page changed. try below code on your Activity Class.
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
if(position == 0)
// Toast For Fragment 1
if(position == 1)
// Toast For Fragment 2
}
#Override
public void onPageScrollStateChanged(int state) {
}
});

How to execute a block of code when a certain fragment is shown?

I've set up a pager with 3 fragments, I want to execute an specific block of code when fragment #2 is shown but problem is that onCreate/onResume methods from this fragment execute when fragment #1 is shown. I understand that the logic behind this is doing work ahead for when fragment#2 is actually needed, but how can I do if I need something to be done specifically when fragment#2 is shown?

You can implement an OnPageChangeListener, override OnPageSelected and set it on the ViewPager this way:
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
if (position == 1) { // Meaning the position of the 2nd Fragment
doSomeCode();
}
}
#Override
public void onPageScrollStateChanged(int state) {
}
});

Viewpager scrolling finish event

I have a viewpager that dislapys text views. I have header layout above it. What i want is to hide or display this header when the user click on the screen. but not when the scrolling is occur. I tried the ViewPager.onPageChangeListener. But with no success. What i need is how to know when the swapping between pages finishes. The onPageScrollStateChange didnt help i create an instance variable to hold the state and keep updating it when this method call so i can use it in my onclick listener to now if the page is scrolling or not but with no success

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected(int position) {
}
#Override
public void onPageScrollStateChanged(int state) {
if(ViewPager.SCROLL_STATE_IDLE == state){
//Scrolling finished. Do something.
}
}
});