I'm using a viewpager to swipe between fragments and would like the back button to navigate to the previously viewed fragment rather than ending the activity. Sorry if this is a duplicate of this question however I didn't find the answer very helpful. Obviously onBackPressed needs to be overridden, but I don't know how to get and display the correct fragment. I assume that I should use the fragmentmanager's backstack, but getSupportFragmentManager().getBackStackEntryCount()
always returns 0. Do I need to manually add fragments to the backstack using FragmentTransaction.addToBackStack()
? If so, where would I add this in my adapter?
Here is the code for my activity,
public class PagerActivity extends FragmentActivity {
ArrayList<Sale> sales;
MyAdapter mAdapter;
ViewPager mPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent it = getIntent();
this.sales = (ArrayList<Sale>) it.getExtras().get("sales");
int position = it.getExtras().getInt("position");
ActionBar actionBar = getActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
setContentView(R.layout.fragment_pager);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
mPager.setCurrentItem(position);
}
public class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
@Override
public int getCount() {
return sales.size();
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
super.destroyItem(container, position, object);
}
@Override
public Fragment getItem(int position) {
SalesThumbFragment frag = new SalesThumbFragment();
return frag.newInstance(sales.get(position));
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.sales_controller, menu);
return true;
}
@Override
public void onBackPressed() {
if(getSupportFragmentManager().getBackStackEntryCount() != 0) {
getSupportFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}
}
In new design support library, i use this
I have same issue and i follow this step
In the main activity where there are 3 fragment in viewpager i create stack and push and pop data.
//private Stack<Integer> stackkk; ==> As i get edit suggestion
private Stack<Integer> stackkk = new Stack<>(); // Edited
private ViewPager mPager;
private int tabPosition = 0;
mTabLayout.setupWithViewPager(mPager);
mPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(mTabLayout));
mTabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
tabPosition = tab.getPosition();
mPager.setCurrentItem(tab.getPosition());
if (stackkk.empty())
stackkk.push(0);
if (stackkk.contains(tabPosition)) {
stackkk.remove(stackkk.indexOf(tabPosition));
stackkk.push(tabPosition);
} else {
stackkk.push(tabPosition);
}
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
tabPositionUnselected = tab.getPosition();
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
}
and in the onBackPressed in activity,
@Override
public void onBackPressed() {
if (stackkk.size() > 1) {
stackkk.pop();
mPager.setCurrentItem(stackkk.lastElement());
} else {
}
}