android.support.v4.app.Fragment#setRetainInstance ( )源码实例Demo

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.com_facebook_activity_layout);
    Intent intent = getIntent();
    if (PASS_THROUGH_CANCEL_ACTION.equals(intent.getAction())) {
        handlePassThroughError();
        return;
    }
    FragmentManager manager = getSupportFragmentManager();
    Fragment fragment = manager.findFragmentByTag(FRAGMENT_TAG);
    if (fragment == null) {
        if (FacebookDialogFragment.TAG.equals(intent.getAction())) {
            Fragment dialogFragment = new FacebookDialogFragment();
            dialogFragment.setRetainInstance(true);
            dialogFragment.show(manager, FRAGMENT_TAG);
            fragment = dialogFragment;
        } else {
            fragment = new LoginFragment();
            fragment.setRetainInstance(true);
            manager.beginTransaction().add(R.id.com_facebook_fragment_container, fragment, FRAGMENT_TAG).commit();
        }
    }
    this.singleFragment = fragment;
}
 

@Override
public void onFragmentCreated(FragmentManager fm, Fragment f, Bundle savedInstanceState) {
    Timber.i(f.toString() + " - onFragmentCreated");
    // 在配置变化的时候将这个 Fragment 保存下来,在 Activity 由于配置变化重建时重复利用已经创建的 Fragment。
    // https://developer.android.com/reference/android/app/Fragment.html?hl=zh-cn#setRetainInstance(boolean)
    // 如果在 XML 中使用 <Fragment/> 标签,的方式创建 Fragment 请务必在标签中加上 android:id 或者 android:tag 属性,否则 setRetainInstance(true) 无效
    // 在 Activity 中绑定少量的 Fragment 建议这样做,如果需要绑定较多的 Fragment 不建议设置此参数,如 ViewPager 需要展示较多 Fragment
    f.setRetainInstance(true);
}
 

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.com_facebook_activity_layout);

    Intent intent = getIntent();
    if (PASS_THROUGH_CANCEL_ACTION.equals(intent.getAction())) {
        handlePassThroughError();
        return;
    }

    FragmentManager manager = getSupportFragmentManager();
    Fragment fragment = manager.findFragmentByTag(FRAGMENT_TAG);

    if (fragment == null) {
        if (FacebookDialogFragment.TAG.equals(intent.getAction())) {
            FacebookDialogFragment dialogFragment = new FacebookDialogFragment();
            dialogFragment.setRetainInstance(true);
            dialogFragment.show(manager, FRAGMENT_TAG);

            fragment = dialogFragment;
        } else {
            fragment = new LoginFragment();
            fragment.setRetainInstance(true);
            manager.beginTransaction()
                    .add(R.id.com_facebook_fragment_container, fragment, FRAGMENT_TAG)
                    .commit();
        }
    }

    singleFragment = fragment;
}
 

public Fragment fetchFragment(String id) {
    // Save the previous fragment in case an error happens after.
    String prevFragmentId = mCurrentFragmentId;

    // Set the current fragment.
    setCurrentFragment(id);

    if(mFragments.containsKey(id) && mFragments.get(id) != null) {
        return mFragments.get(id);
    }

    Fragment f;
    if(id.equals(SidebarEntry.ID_AUDIO)) {
        f = new AudioBrowserFragment();
    } else if(id.equals(SidebarEntry.ID_VIDEO)) {
        f = new VideoGridFragment();
    } else if(id.endsWith(SidebarEntry.ID_DIRECTORIES)) {
        f = new FileBrowserFragment();
    } else if(id.equals(SidebarEntry.ID_HISTORY)) {
        f = new HistoryFragment();
    } else if(id.equals(SidebarEntry.ID_MRL)) {
        f = new MRLPanelFragment();
    } else if(id.equals(SidebarEntry.ID_NETWORK)) {
        f = new NetworkBrowserFragment();
    }
    else {
        mCurrentFragmentId = prevFragmentId; // Restore the current fragment id.
        throw new IllegalArgumentException("Wrong fragment id.");
    }
    f.setRetainInstance(true);
    mFragments.put(id, f);
    return f;
}