ViewPager optimized Lifecycle

viewpager_lifecycle_sample.java

package com.rakuishi.viewpager_lifecycle_sample;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class SampleFragment extends Fragment {

    private static final String TAG = SampleFragment.class.getSimpleName();
    private static final String ARG_FRAGMENT_NUMBER = "fragment_number";
    private static final String ARG_IS_ON_TAB = "is_on_tab";

    private boolean isOnActivityCreated = false;
    private boolean isOnTab = false;
    private boolean isVisibleToUser = false;
    private boolean isOnUserVisible = false;

    public SampleFragment() {
    }

    public static SampleFragment newInstance(int fragmentNumber, boolean isOnTab) {
        SampleFragment fragment = new SampleFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_FRAGMENT_NUMBER, fragmentNumber);
        args.putBoolean(ARG_IS_ON_TAB, isOnTab);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_sample, container, false);
        TextView textView = rootView.findViewById(R.id.text_view);
        textView.setText(getString(R.string.fragment_number_format, getArguments().getInt(ARG_FRAGMENT_NUMBER)));
        setOnTab(getArguments().getBoolean(ARG_IS_ON_TAB));
        return rootView;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        isOnActivityCreated = true;
        Log.d(TAG, this.toString() + ": onActivityCreated: ");
        performOnUserVisibleIfNeeded();
    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        this.isVisibleToUser = isVisibleToUser;
        Log.d(TAG, this.toString() + ": setUserVisibleHint: " + isVisibleToUser);
        performOnUserVisibleIfNeeded();
    }

    @Override
    public void onDestroyView() {
        isOnActivityCreated = false;
        isOnUserVisible = false;
        super.onDestroyView();
    }

    private void performOnUserVisibleIfNeeded() {
        if (isOnActivityCreated && !isOnUserVisible) {
            if (!isOnTab || isVisibleToUser) {
                onUserVisible();
                isOnUserVisible = true;
            }
        }
    }

    /**
     * Call this method in `onAttach()` or `onCreate`
     *
     * @param onTab This fragment is on tab or not
     */
    public void setOnTab(boolean onTab) {
        isOnTab = onTab;
    }

    public void onUserVisible() {
        Log.d(TAG, this.toString() + ": onUserVisible: ");
    }
}