Android：检查活动中的当前片段

Question

I tried to check current Fragment in my Activity, This is scheme of my Fragment in my Activity : When user open Fragment A in Activity, then they click button in Fragment A , it will open Fragment B , we can't directly open fragment B from Activity

I know I can check it using this code :

Fragment fragment = getFragmentManager().findFragmentByTag("MY FRAGMENT");
if (fragment !=null & fragment.isVisible()){
//do whatever we do
}

Or with this code :

Fragment fragment = getFragmentManager().findFragmentById(R.id.container_body);
    if (fragment !=null & fragment.isVisible()){
    //do whatever we do
    }

but I still confuse where I must to put this code in in activity? I have put this in OnCreate method, but nothing happen

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
        mToolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(mToolbar);
            getSupportActionBar().setDisplayShowHomeEnabled(true);

        if (Build.VERSION.SDK_INT >= 21) {
            mToolbar.setPadding(0, getStatusBarHeight(), 0, 0);
        }
        mToolbar.setOnMenuItemClickListener(new Toolbar.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                search.setMenuVisibility(View.VISIBLE);
                    openSearch();
                    return true;
                }
            });

        drawerFragment = (MethodFragmentDrawer)getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
            drawerFragment.setDrawerListener(this);
            drawerFragment.setUp(R.id.fragment_navigation_drawer, drawerLayout, mToolbar);


        search = (SearchBox) findViewById(R.id.searchbox);
        search.setPadding(10, getStatusBarHeight(), 10, 0);
            search.setLogoText("E-Sehat");
            search.setMenuListener(new SearchBox.MenuListener() {
                @Override
                public void onMenuClick() {
                    drawerFragment.setButtonHamburgerClick();
                }

            });
        //display first Fragment
        displayView(0);
   Fragment fragment = getFragmentManager().findFragmentByTag("MY FRAGMENT");
    if (fragment !=null & fragment.isVisible()){
    //do whatever we do
    }

    }

Well.. is there somebody can help me to solve my problem? thank you very much.

Answer 1

The best way to go from one fragment to another is through an Activity. Below is a code snippet that i use whenever i go from one fragment to another:

In YourActivity(which acts as a container for fragments) have a method like the one below:

public Fragment fragment;
public void navigateTo(Fragment newFragment,boolean addToBackStack) {
    this.fragment = newFragment;
    FragmentManager manager = getSupportFragmentManager();
    FragmentTransaction ft = manager.beginTransaction();
    ft.replace(R.id.fragment_container, newFragment);
    if(addToBackStack)
        ft.addToBackStack(fragment.getClass().getSimpleName());
    ft.commit();
}

Now, suppose you have to go from FragmentA to FragmentB. Write the below code in FragmentA:

((YourActivity) getActivity()).navigateTo(new FragmentB(),true);//if you do not want to add to back stack then make the 2nd argument as false.

Hope the above description helps. Thanks.