Question

我有一个Activity，其中包含许多基于导航抽屉中所选项目交换的片段。我试图通过调用Fragment上的setRetainInstance(true)来检查方向更改中的当前片段，然后检查onCreate(...)中是否存在该片段。但是，当我尝试在onCreate(...)上获取时，Fragment始终为null。我一直在我的桌子上撞了几个小时。有人能发现问题吗？

活动的相关部分

public class StartActivity {

    private static final String MAIN_FRAGMENT_TAG = "mainFragment";

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

        ...

        if(savedInstanceState != null) {
            Fragment f = getSupportFragmentManager().findFragmentByTag(MAIN_FRAGMENT_TAG);
            if(f == null) {
                // FRAGMENT IS ALWAYS NULL
                switchToModeForPosition(...);
            } else {
                setupActionBarForPosition(...);
            }
        } else {
            // Default to events view
            switchToModeForPosition(0);
        }
    }

    private void switchToModeForPosition(int position) {
        Fragment fragment;
        switch (position) {
            default:
            case 0: //events
                fragment = new EventsByWeekFragment();
                setupActionBarForEvents();
                break;
            case 1: //teams
                fragment = new AllTeamsListFragment();
                setupActionBarForTeams();
                break;
            case 2: //insights
                fragment = new InsightsFragment();
                setupActionBarForInsights();
                break;
            case 3:
                startActivity(new Intent(this, SettingsActivity.class));
                mDrawerLayout.closeDrawer(mDrawerList);
                return;
        }
        fragment.setRetainInstance(true);
        getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment, MAIN_FRAGMENT_TAG).commit();
    }
}

Answer 1

在每个setRetainInstance(true)课程中使用Fragment。

public void onCreated(Bundle savedInstanceState)
        {
            super.onCreated(savedInstanceState);
            setRetainInstance(true);
        }

或

public void onActivityCreated(Bundle savedInstanceState)
    {
        super.onActivityCreated(savedInstanceState);
        setRetainInstance(true);
    }

片段setRetainInstance（true）不起作用

1 个答案: