Question

我想知道在将切换方向转换为横向之前，我的片段（启动画面）已经显示出来了。我想在方向改变后活动被破坏了。

MainActivity

public class MainActivity extends AppCompatActivity {

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

        //toolbar ...

       showFragment(new SplashFragment());
    }

    public void showFragment(Fragment fragment) {
        getSupportFragmentManager().beginTransaction().replace(R.id.main_frame_layout, fragment).addToBackStack("").commit();
    }

    @Override
    //Menu item icons
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

片段（闪屏）

公共类SplashFragment扩展了Fragment {

public static SplashFragment newInstance() {

    Bundle args = new Bundle();

    SplashFragment fragment = new SplashFragment();
    fragment.setArguments(args);
    return fragment;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_splash, container, false);

    return view;
}

@Override
public void onViewCreated(View view, @Nullable final Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    ButterKnife.bind(this, view);

    ((MainActivity) getActivity()).getSupportActionBar().hide();


    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            ((MainActivity) getActivity()).showFragment(ContactListFragment.newInstance());
        }
    }, 1000);
}

Answer 1

引用我的评论

在为SplashFragment完成处理程序后，您可以在包中添加一个布尔值。因此，当调用SplashFragment时，savedInstanceState可以检查它是否为true，然后跳过并显示ContactListFragment。或者使用SharedPreferences并将boolean存储在那里并从MainActivity中检查它并对showFragment（new SplashFragment.newInstance（））或showFragment（newContactListFragment.newInstance（））执行if（）else {}

SharedPreferences示例：

MainActivity.java

在showFragment()之前的onCreate

 [...] // other activity stuff
 SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
 boolean hasShown = sharedPref.getBoolean("hasShown", false);
 if(hasShown)
 { showFragment(new ContactListFragment()); }
 else
 { showFragment(new SplashFragment()); }

SplashFragment.java

在new Handler()之前的onViewCreated

 SharedPreferences sharedPref = ((MainActivity) getActivity()).getPreferences(Context.MODE_PRIVATE);
 SharedPreferences.Editor editor = sharedPref.edit();
 editor.putBoolean("hasShown", true);
 editor.commit();

Answer 2

到了你打电话的地步

getSupportFragmentManager().beginTransaction().remove(fragment).commit();

您可以通过调用

从FragmentManager找到您的片段

getFragmentManager().findFragmentByTag(/* by id or tag */)

例如你可以快速告诉

显示的片段

getFragmentManager().findFragmentByTag(/*Id or TAG*/) != null ? fragment was added to FragmentManager : fragment is not in FragmentManager

如果您调用了remove（）方法，则无法知道是否显示了splash。您可以尝试创建一个布尔值系统来指示片段是否在FragmentManager中。

Android上的方向更改会杀死活动和碎片。通过正确保存您的活动和碎片状态

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState)
    //Save your stuff to bundle
}

并在

恢复它们

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if ( savedInstanceState == null) return;
    //get your stuff from savedInstanceState
    //Example
    boolean[] array = savedInstanceState.getBooleanArray("yourkey");
}

您可以将布尔指示符的示例保存到boolean []数组，并知道在此“全局”生命周期中发生了什么

片段 - 改变方向

2 个答案: