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在android中使用底部導航視圖時如何恢復片段狀態？

[英]How to restore fragment states while using bottom navigation view in android?

 原文  2019-07-24 12:36:24  9   3    android/ bottomnavigationview

問題描述

我正在嘗試從 android 底部導航視圖中的第二個片段返回時恢復片段視圖狀態值（文本視圖等）。

我的活動.java

public class LandingPage extends AppCompatActivity implements ProductFragment.AddToCart {

    Fragment fragment;
    TextView txtCart;
    Button btnCart;
    ItemData itemData;
    ArrayList<ItemData> itemDataList;

    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {

            switch (item.getItemId()) {
                case R.id.nav_home:
                    fragment = new ProductFragment();
                    loadFragment(fragment);
                    return true;
                case R.id.nav_profile:
                    fragment = new ReportsFragment();
                    loadFragment(fragment);
                    return true;
                case R.id.nav_logout:
                    LogOut();
                    return true;
            }
            return true;
        }
    };
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_landing_page);

        txtCart = findViewById(R.id.txt_cart);
        btnCart = findViewById(R.id.btn_cartImg);

        itemDataList = new ArrayList<>();

        BottomNavigationView bottomNavigationView = findViewById(R.id.navigation);
        bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
        loadFragment(new ProductFragment());
}
 private void loadFragment(Fragment fragment) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.fragment_container, fragment);
        transaction.commit();
    }
}

產品片段.java

public class ProductFragment extends Fragment {


    private OnFragmentInteractionListener mListener;

    Button btnCart1,btnCart2,btnCart3;
    AddToCart addToCart;
    TextView txtItem1Des,txtItem1Price,txtItem2Des,txtItem2Price,txtItem3Des,txtItem3Price;
    Button btnCart1Inc,btnCart1Dec,btnCart2Inc,btnCart2Dec,btnCart3Inc,btnCart3Dec;
    TextView cart1txt,cart2txt,cart3txt;
    String itemDes,itemPrice,itemImg,itemCount;
    int quantity1,quantity2,quantity3;

    public ProductFragment() {

    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_product, container, false);

        btnCart1 = view.findViewById(R.id.cart1);
        txtItem1Des = view.findViewById(R.id.cart1_desc);
        txtItem1Price = view.findViewById(R.id.cart1_price);
        btnCart1Inc = view.findViewById(R.id.cart1Inc);
        btnCart1Dec = view.findViewById(R.id.cart1Dec);
        cart1txt = view.findViewById(R.id.cart1txt);

        btnCart2 = view.findViewById(R.id.cart2);
        txtItem2Des = view.findViewById(R.id.cart2_desc);
        txtItem2Price = view.findViewById(R.id.cart2_price);
        btnCart2Inc = view.findViewById(R.id.cart2Inc);
        btnCart2Dec = view.findViewById(R.id.cart2Dec);
        cart2txt = view.findViewById(R.id.cart2txt);

        btnCart3 = view.findViewById(R.id.cart3);
        txtItem3Des = view.findViewById(R.id.cart3_desc);
        txtItem3Price = view.findViewById(R.id.cart3_price);
        btnCart3Inc = view.findViewById(R.id.cart3Inc);
        btnCart3Dec = view.findViewById(R.id.cart3Dec);
        cart3txt = view.findViewById(R.id.cart3txt);

        quantity1 = Integer.parseInt(cart1txt.getText().toString());
        quantity2 = Integer.parseInt(cart2txt.getText().toString());
        quantity3 = Integer.parseInt(cart3txt.getText().toString());

        buttonInitialization();
        addingToCart();

        return view;
    }

    private void addingToCart() {
        btnCart1Dec.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quantity1 <= 1){
                    btnCart1.setVisibility(View.VISIBLE);
                    btnCart1Dec.setVisibility(View.INVISIBLE);
                    btnCart1Inc.setVisibility(View.INVISIBLE);
                    cart1txt.setVisibility(View.INVISIBLE);
                    addToCart.removeItemFromCart(1);
                }else {
                    quantity1 = quantity1-1;
                    cart1txt.setText(String.valueOf(quantity1));
                    addToCart.itemCount(cart1txt.getText().toString(),"1");
                }

            }
        });
        btnCart1Inc.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                quantity1 = quantity1+1;
                cart1txt.setText(String.valueOf(quantity1));
                addToCart.itemCount(cart1txt.getText().toString(),"1");
            }
        });
        btnCart2Dec.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quantity2 <= 1){
                    btnCart2.setVisibility(View.VISIBLE);
                    btnCart2Dec.setVisibility(View.INVISIBLE);
                    btnCart2Inc.setVisibility(View.INVISIBLE);
                    cart2txt.setVisibility(View.INVISIBLE);
                    addToCart.removeItemFromCart(2);
                }else {
                    quantity2 = quantity2-1;
                    cart2txt.setText(String.valueOf(quantity2));
                    addToCart.itemCount(cart2txt.getText().toString(),"2");
                }

            }
        });
        btnCart2Inc.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                quantity2 = quantity2+1;
                cart2txt.setText(String.valueOf(quantity2));
                addToCart.itemCount(cart2txt.getText().toString(),"2");
            }
        });
        btnCart3Dec.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(quantity3 <= 1){
                    btnCart3.setVisibility(View.VISIBLE);
                    btnCart3Dec.setVisibility(View.INVISIBLE);
                    btnCart3Inc.setVisibility(View.INVISIBLE);
                    cart3txt.setVisibility(View.INVISIBLE);
                    addToCart.removeItemFromCart(3);
                }else {
                    quantity3 = quantity3-1;
                    cart3txt.setText(String.valueOf(quantity3));
                    addToCart.itemCount(cart3txt.getText().toString(),"3");
                }

            }
        });
        btnCart3Inc.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                quantity3 = quantity3+1;
                cart3txt.setText(String.valueOf(quantity3));
                addToCart.itemCount(cart3txt.getText().toString(),"3");
            }
        });
    }


    private void buttonInitialization() {
        btnCart1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                    itemImg = "";
                    itemPrice = txtItem1Price.getText().toString().trim();
                    itemDes = txtItem1Des.getText().toString().trim();
                    itemCount = cart1txt.getText().toString().trim();
                    addToCart.cartCount("",itemPrice,itemDes,itemCount,"1");
                    btnCart1.setVisibility(View.INVISIBLE);
                    btnCart1Dec.setVisibility(View.VISIBLE);
                    btnCart1Inc.setVisibility(View.VISIBLE);
                    cart1txt.setVisibility(View.VISIBLE);
            }
        });
        btnCart2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                itemImg = "";
                itemPrice = txtItem2Price.getText().toString().trim();
                itemDes = txtItem2Des.getText().toString().trim();
                itemCount = cart2txt.getText().toString().trim();
                addToCart.cartCount("",itemPrice,itemDes,itemCount,"2");
                btnCart2.setVisibility(View.INVISIBLE);
                btnCart2Dec.setVisibility(View.VISIBLE);
                btnCart2Inc.setVisibility(View.VISIBLE);
                cart2txt.setVisibility(View.VISIBLE);
            }
        });
        btnCart3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                itemImg = "";
                itemPrice = txtItem3Price.getText().toString().trim();
                itemDes = txtItem3Des.getText().toString().trim();
                itemCount = cart3txt.getText().toString().trim();
                addToCart.cartCount("",itemPrice,itemDes,itemCount,"3");
                btnCart3.setVisibility(View.INVISIBLE);
                btnCart3Dec.setVisibility(View.VISIBLE);
                btnCart3Inc.setVisibility(View.VISIBLE);
                cart3txt.setVisibility(View.VISIBLE);
            }
        });
    }

    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        addToCart = (AddToCart) context;
    }


    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }
    public interface OnFragmentInteractionListener {
        void onFragmentInteraction(Uri uri);
    }
   public interface AddToCart{
        void cartCount(String item_img,String item_price,String item_desc,String item_count,String item_pos);
        void removeItemFromCart(int removeItem);
        void itemCount(String itemCount,String position);
    }

}

在 ProductFragment 中，我將向文本視圖添加值。 當我來自 ReportFragment 時，將在 ProductFragment 中清除視圖值。

3 個解決方案

解決方案1
 2  2019-07-24 13:01:22

我會考慮分兩步做：

  1. 保存片段實例而不是每次都重新創建一個新的

    private ProductFragment productFragment; private ReportsFragment reportsFragment; private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() { @Override public boolean onNavigationItemSelected(@NonNull MenuItem item) { switch (item.getItemId()) { case R.id.nav_home: if(productFragment == null) productFragment = new ProductFragment(); loadFragment(productFragment); break; case R.id.nav_profile: if(reportsFragment == null) reportsFragment = new ReportsFragment(); loadFragment(reportsFragment); break; case R.id.nav_logout: LogOut(); return true; } return true; } };

  2. 參考這個問題/答案，你應該在你的片段中同時實現void onSaveInstanceState(final Bundle outState)和void onActivityCreated(Bundle savedInstanceState)

通過這種方式，您肯定會保留片段的實例，而不是每次都創建一個新的實例（ new MyFragment()將始終重新創建它）。 此外，在onSaveInstanceState保存您的視圖狀態並在您的onActivityCreate恢復它，將允許您保留您的視圖/值。

我在沒有編譯器的情況下手工編寫了它，所以它可能並不完美。

如果您需要更多信息，請告訴我。

祝你好運

解決方案2
 1  2019-07-24 13:00:16

我正在使用這個解決方案，它對我有用。

解決方案3
 0  2021-06-08 03:11:17

你應該看到我對類似問題的詳細回答。 我希望它能解決你的問題。

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