我试图从Android底部导航视图中的第二个片段返回时还原片段视图状态值（文本视图，.. etc）。
MyActivity.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();
}
}
ProductFragment.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，IAM将向文本视图添加值。 当我来自ReportFragment时，视图值将在ProductFragment中清除。
我会考虑分两步这样做：
保存片段实例，而不是每次都重新创建一个实例
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; } }; 参考此问题/答案 ，您应该在片段中同时实现void onSaveInstanceState(final Bundle outState)和void onActivityCreated(Bundle savedInstanceState)
这样，您一定会保留片段的实例，而不是每次都创建一个实例（ new MyFragment()总是会重新创建它）。 另外，将视图状态保存在onSaveInstanceState并将其还原到onActivityCreate ，将允许您保留视图/值。
我是在没有编译器的情况下手工编写的，因此可能并不完美。
让我知道您是否需要更多信息。
祝好运
我正在使用此解决方案 ，它对我有用。