获取NullPointerExceptionat片段提交

Question

我在同一个容器中进行片段转换。但有时它会在片段提交时产生NullPointerException。下面是我的方法，它给出了一个错误。

public void goToMapFragment() {
    if (getSupportFragmentManager().findFragmentByTag(Const.Tag.MAP_FRAGMENT) == null) {
        MapFragment mapFragment = new MapFragment();
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction ft = manager.beginTransaction();
        ft.setCustomAnimations(R.anim.fade_in_out,
                    R.anim.slide_out_left, R.anim.fade_in_out,
                    R.anim.slide_out_right);
        ft.replace(R.id.contain_frame, mapFragment, Const.Tag.MAP_FRAGMENT);

        //Here gives NullPointerException.....
        ft.commitNowAllowingStateLoss();    
    }
}

请提供您的解决方案。

下面我附上它的堆栈跟踪。

java.lang.NullPointerException
at android.support.v4.app.FragmentManagerImpl.ensureExecReady(FragmentManager.java:1959)
at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1980)
at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:626)
at com.gogo.MainDrawerActivity.goToMapFragment(MainDrawerActivity.java:392)