Question

我有一个FrameLayout并通过单击按钮放置一些片段，下一次单击应该从FrameLayout中删除片段，我通过removeAllViews()执行此操作（FrameLayout在另一个片段中，因此translaction方法在Activity中）。我需要在removeAllViews()启动时执行一些操作，并且必须在Fragment类中执行此操作，但出现问题。

我试过了： OnDestroy() OnDestroyView() OnPause() 在Fragment类

中

但它的作用如下：

将Fragment放入FrameLayout（来自Activity）
使用removeAllViews()（来自活动）
FrameLayout中没有片段（很清楚）但没有其他事情发生且方法无法正常工作
将新片段放入FrameLayout（来自Activity） - 现在所有方法（来自Fragment类的OnDestroy()）都可以工作（可能是destroy旧片段的实时）

当用户不存在Fragment时，如何“获取时刻”？如果用户隐藏片段，我想向服务器发送一些信息。

@ EDIT3 来自Activity的方法中的代码，我想进行翻译

public void showProductsList(String productType,int containerID){

        List<String> prodNames = new ArrayList<String>();
        List<Long> prodIds = new ArrayList<Long>();

            DatabaseDAOProdProtein dao = new DatabaseDAOProdProtein(getApplicationContext());
            dao.open();
            List<DatabaseProduct> productList = dao.getAllProducts();
            for(int i=0;i<productList.size();i++){
                prodNames.add(productList.get(i).getName());
                prodIds.add(productList.get(i).getId());
            }
            dao.close();

        ProductsList productsList = new ProductsList(productType,prodNames,prodIds);

        productsList.setOnSystemUiVisibilityChangeListener
                (new View.OnSystemUiVisibilityChangeListener() {
                    @Override
                    public void onSystemUiVisibilityChange(int visibility) {
                        // Note that system bars will only be "visible" if none of the
                        // LOW_PROFILE, HIDE_NAVIGATION, or FULLSCREEN flags are set.
                        Toast.makeText(getApplicationContext(),"action1 " ,Toast.LENGTH_LONG).show();
                        if ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
                            // TODO: The system bars are visible. Make any desired
                            // adjustments to your UI, such as showing the action bar or
                            // other navigational controls.
                            Toast.makeText(getApplicationContext(),"action2 " ,Toast.LENGTH_LONG).show();
                        } else {
                            // TODO: The system bars are NOT visible. Make any desired
                            // adjustments to your UI, such as hiding the action bar or
                            // other navigational controls.
                            Toast.makeText(getApplicationContext(),"action3 " ,Toast.LENGTH_LONG).show();
                        }
                    }
                });

        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.replace(containerID, productsList).commit();
    }

我在另一个片段中使用此方法：

((MainActivity) getContext()).showProductsList("carb", carbContainer.getId());

出现错误：

Error:(560, 21) error: cannot find symbol method setOnSystemUiVisibilityChangeListener(<anonymous OnSystemUiVisibilityChangeListener>)

Answer 1

你说：

“当Fragment不存在时，怎么可能'得到时刻' 用户？如果用户隐藏，我想向服务器发送一些信息片段“。

我现在知道你并不是指“隐藏”，所以只需使用OnDestroy()方法。

尝试此操作以触发“隐藏”

View topLevelLayout = findViewById(R.id.top_layout);
topLevelLayout.setVisibility(View.INVISIBLE);

当片段（活动）可见时，您无法进入停止状态。 Android destroying activities, killing processes

确保某些内容通过视图运行的最佳方法是通过帖子运行它：

topLevelLayout.post(new Runnable()
{
@Override
public void run()
{
        topLevelLayout.removeAllViews();
    }
}

要获得有关系统UI可见性更改的通知，请在View.OnSystemUiVisibilityChangeListener（片段）中注册view。

https://developer.android.com/training/system-ui/visibility.html

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Toast.makeText(getContext(),"action0 " ,Toast.LENGTH_LONG).show();
    Fragment your_frag = new ProductsList(productType,prodNames,prodIds);
getSupportFragmentManager().beginTransaction().replace(containerID,your_frag).commit();
    getSupportFragmentManager().executePendingTransactions();//make sure onCreateView has executed
        your_frag.getRootView().setOnSystemUiVisibilityChangeListener
                (new View.OnSystemUiVisibilityChangeListener() {
                    @Override
                    public void onSystemUiVisibilityChange(int visibility) {
                        // Note that system bars will only be "visible" if none of the
                        // LOW_PROFILE, HIDE_NAVIGATION, or FULLSCREEN flags are set.
                        Toast.makeText(getContext(),"action1 " ,Toast.LENGTH_LONG).show();
                        if ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
                            // TODO: The system bars are visible. Make any desired
                            // adjustments to your UI, such as showing the action bar or
                            // other navigational controls.
                            Toast.makeText(getContext(),"action2 " ,Toast.LENGTH_LONG).show();
                        } else {
                            // TODO: The system bars are NOT visible. Make any desired
                            // adjustments to your UI, such as hiding the action bar or
                            // other navigational controls.
                            Toast.makeText(getContext(),"action3 " ,Toast.LENGTH_LONG).show();
                        }
                    }
                });
    }

典型的片段如下所示：

public class HomeFragment extends Fragment {
    View                        mRootView     = null;
    public HomeFragment(){}//null constructor

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        mRootView = inflater.inflate(R.layout.fragment_home, container, false);

        return mRootView ;
    }
public View getRootView ()
{
    return mRootView;
}
}

删除片段时的Android

1 个答案: