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Android - Fragment for handling view after it has been created and visible to user for the first time.
package cc.cubone.turbo.core.app;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.View;
/**
* Fragment for handling view after it has been created and visible to user for the first time.
*
* <p>Specially in {@link android.support.v4.view.ViewPager}, the page will be created beforehand
* but not be visible to user.
*
* <p>Call {@link android.support.v4.view.ViewPager#setOffscreenPageLimit(int)} to set the number of
* pages that should be retained.
*
* Reference:
* <ul>
* <li><a href="http://stackoverflow.com/questions/10024739/how-to-determine-when-fragment-becomes-visible-in-viewpager">
* How to determine when Fragment becomes visible in ViewPager</a>
* </ul>
*/
public class SightFragment extends Fragment {
private boolean mUserSeen = false;
private boolean mViewCreated = false;
public SightFragment() {
}
/*public boolean isUserSeen() {
return mUserSeen;
}
public boolean isViewCreated() {
return mViewCreated;
}*/
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (!mUserSeen && isVisibleToUser) {
mUserSeen = true;
onUserFirstSight();
tryViewCreatedFirstSight();
}
onUserVisibleChanged(isVisibleToUser);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// Override this if you want to get savedInstanceState.
mViewCreated = true;
tryViewCreatedFirstSight();
}
@Override
public void onDestroyView() {
super.onDestroyView();
mViewCreated = false;
mUserSeen = false;
}
private void tryViewCreatedFirstSight() {
if (mUserSeen && mViewCreated) {
onViewCreatedFirstSight(getView());
}
}
/**
* Called when the new created view is visible to user for the first time.
*/
protected void onViewCreatedFirstSight(View view) {
// handling here
}
/**
* Called when the fragment's UI is visible to user for the first time.
*
* <p>However, the view may not be created currently if in {@link android.support.v4.view.ViewPager}.
*/
protected void onUserFirstSight() {
}
/**
* Called when the visible state to user has been changed.
*/
protected void onUserVisibleChanged(boolean visible) {
}
}
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