删除片段时的Android

Question

我有一个 FrameLayout 并通过单击按钮将一些片段放在那里，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，因此翻译方法在 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

但它的工作原理是：

1. 将 Fragment 放入 FrameLayout（来自 Activity）
2. 使用removeAllViews()（来自活动）
3. FrameLayout 中没有 Fragment（很清楚），但没有其他反应，方法也不起作用
4. 将新 Fragment 放入 FrameLayout（来自 Activity） - 现在所有方法（来自 Fragment 类的OnDestroy()）都可以正常工作（可能是实时到destroy 旧片段）

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

@Edit3 来自我要进行翻译的 Activity 方法的代码

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 Fragment 中使用了这个方法：

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

有一个错误：

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

Answer 1

你说：

“当 Fragment 不存在时，如何'获得时刻' 用户？如果用户隐藏，我想向服务器发送一些信息 片段。”

我现在知道您的意思不是“隐藏”，所以只需使用 OnDestroy() 方法。

试试这个来触发“隐藏”

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

片段（活动）可见时，您不能进入停止状态。 Android destroying activities, killing processes

确保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();
    }
}

要获得系统 UI 可见性更改的通知，请将 View.OnSystemUiVisibilityChangeListener 注册到您的 view（片段）。

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();
                        }
                    }
                });
    }    

一个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;
}
}