Java 即使从服务器中删除数据，数据仍显示在房间数据库中

我从服务器获取数据并保存在房间数据库中，然后从房间中显示在回收器视图中。数据完美地保存在房间数据库中并显示在回收器视图中

问题：当我从服务器数据库中删除一些数据时，先前保存的旧副本仍然保留在文件室中

我想要什么：我不想在“回收器”视图中显示从服务器删除的数据。所以，我如何根据服务器响应更新房间数据库

这就是我到目前为止所做的：

UserDao.java

@Dao
public interface UserDao {

@Insert(onConflict = OnConflictStrategy.REPLACE)
void Insert(User... users);

@Query("SELECT * FROM Users")
LiveData<List<User>> getRoomUsers();
}

@Entity(tableName = "Users")
public class User {

@NonNull
@PrimaryKey
private String id;

@ColumnInfo(name = "name")
@SerializedName("name")
@Expose
private String name;

@ColumnInfo(name = "age")
@SerializedName("age")
@Expose
private String age;

public User(String id,String name, String age) {
   this.id = id;
   this.name = name;
   this.age = age;
}

public String getId() {
   return id;
}

public void setId(String id) {
   this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
   this.name = name;
}

public String getAge() {
   return age;
}

public void setAge(String age) {
   this.age = age;
}
}

public class UserRepository {

private Context context;
private UserDb userDb;
private LiveData<List<User>> listLiveData;

public UserRepository(Context context) {
   this.context = context;
   userDb = UserDb.getInstance(context);
   listLiveData = userDb.userDao().getRoomUsers();
}

public void getUserList(){

      Retrofit retrofit = RetrofitClient.getInstance();
      ApiService apiService = retrofit.create(ApiService.class);

      Call<List<User>> userList = apiService.getUser();

      userList.enqueue(new Callback<List<User>>() {
          @Override
          public void onResponse(Call<List<User>> call, final Response<List<User>> response) {

              Completable.fromAction(new Action() {
                      @Override
                      public void run() throws Exception {

                          if(response.body() != null) {

                              List<User> list = response.body();

                              for (int i = 0; i < list.size(); i++) {

                                  String id = list.get(i).getId();
                                  String names = list.get(i).getName();
                                  String age = list.get(i).getAge();

                                  User user = new User(id,names,age);

                                  userDb.userDao().Insert(user);


                              }

                          }

                      }
                  }).subscribeOn(Schedulers.io())
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(new CompletableObserver() {
                        @Override
                        public void onSubscribe(Disposable d) {

                        }

                        @Override
                        public void onComplete() {

                            Toast.makeText(context,"Data inserted",Toast.LENGTH_SHORT).show();
                        }

                        @Override
                        public void onError(Throwable e) {

                            Toast.makeText(context,e.getMessage(),Toast.LENGTH_SHORT).show();
                        }
                    });


          }

          @Override
          public void onFailure(Call<List<User>> call, Throwable t) {
              Toast.makeText(context,t.getMessage(),Toast.LENGTH_LONG).show();
          }
      });

 }

public LiveData<List<User>> getRoomUsers(){

   return listLiveData;
  }
}

public class MainActivity extends AppCompatActivity {

UserRepository userRepository;
RecyclerView recyclerView;
UserViewModel userModel;
List<User> userList;
UserAdapter adapter;
ProgressBar prg;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

prg = findViewById(R.id.prg);

userRepository = new UserRepository(this);
userModel = ViewModelProviders.of(this).get(UserViewModel.class);

recyclerView = findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));

userList = new ArrayList<>();

adapter = new UserAdapter(userList,this);
recyclerView.setAdapter(adapter);

userModel.getListLiveData().observe(this, new Observer<List<User>>() {

    @Override
    public void onChanged(List<User> users) {

        prg.setVisibility(View.INVISIBLE);
        adapter.setUserList(users);
    }
});

FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent i = new Intent(MainActivity.this,AddUser.class);
        startActivity(i);
    }
});



   userRepository.getUserList();
}

UserRepository.java

@Dao
public interface UserDao {

@Insert(onConflict = OnConflictStrategy.REPLACE)
void Insert(User... users);

@Query("SELECT * FROM Users")
LiveData<List<User>> getRoomUsers();
}

@Entity(tableName = "Users")
public class User {

@NonNull
@PrimaryKey
private String id;

@ColumnInfo(name = "name")
@SerializedName("name")
@Expose
private String name;

@ColumnInfo(name = "age")
@SerializedName("age")
@Expose
private String age;

public User(String id,String name, String age) {
   this.id = id;
   this.name = name;
   this.age = age;
}

public String getId() {
   return id;
}

public void setId(String id) {
   this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
   this.name = name;
}

public String getAge() {
   return age;
}

public void setAge(String age) {
   this.age = age;
}
}

public class UserRepository {

private Context context;
private UserDb userDb;
private LiveData<List<User>> listLiveData;

public UserRepository(Context context) {
   this.context = context;
   userDb = UserDb.getInstance(context);
   listLiveData = userDb.userDao().getRoomUsers();
}

public void getUserList(){

      Retrofit retrofit = RetrofitClient.getInstance();
      ApiService apiService = retrofit.create(ApiService.class);

      Call<List<User>> userList = apiService.getUser();

      userList.enqueue(new Callback<List<User>>() {
          @Override
          public void onResponse(Call<List<User>> call, final Response<List<User>> response) {

              Completable.fromAction(new Action() {
                      @Override
                      public void run() throws Exception {

                          if(response.body() != null) {

                              List<User> list = response.body();

                              for (int i = 0; i < list.size(); i++) {

                                  String id = list.get(i).getId();
                                  String names = list.get(i).getName();
                                  String age = list.get(i).getAge();

                                  User user = new User(id,names,age);

                                  userDb.userDao().Insert(user);


                              }

                          }

                      }
                  }).subscribeOn(Schedulers.io())
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(new CompletableObserver() {
                        @Override
                        public void onSubscribe(Disposable d) {

                        }

                        @Override
                        public void onComplete() {

                            Toast.makeText(context,"Data inserted",Toast.LENGTH_SHORT).show();
                        }

                        @Override
                        public void onError(Throwable e) {

                            Toast.makeText(context,e.getMessage(),Toast.LENGTH_SHORT).show();
                        }
                    });


          }

          @Override
          public void onFailure(Call<List<User>> call, Throwable t) {
              Toast.makeText(context,t.getMessage(),Toast.LENGTH_LONG).show();
          }
      });

 }

public LiveData<List<User>> getRoomUsers(){

   return listLiveData;
  }
}

public class MainActivity extends AppCompatActivity {

UserRepository userRepository;
RecyclerView recyclerView;
UserViewModel userModel;
List<User> userList;
UserAdapter adapter;
ProgressBar prg;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

prg = findViewById(R.id.prg);

userRepository = new UserRepository(this);
userModel = ViewModelProviders.of(this).get(UserViewModel.class);

recyclerView = findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));

userList = new ArrayList<>();

adapter = new UserAdapter(userList,this);
recyclerView.setAdapter(adapter);

userModel.getListLiveData().observe(this, new Observer<List<User>>() {

    @Override
    public void onChanged(List<User> users) {

        prg.setVisibility(View.INVISIBLE);
        adapter.setUserList(users);
    }
});

FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent i = new Intent(MainActivity.this,AddUser.class);
        startActivity(i);
    }
});



   userRepository.getUserList();
}

公共类用户存储库{
私人语境；
私有用户数据库；
私有LiveData列表LiveData；
公共用户存储库（上下文）{
this.context=上下文；
userDb=userDb.getInstance（上下文）；
listLiveData=userDb.userDao（）.getRoomUsers（）；
}
public void getUserList（）{
Refundation-Refundation=RefundationClient.getInstance（）；
ApiService ApiService=reformation.create（ApiService.class）；
调用userList=apiService.getUser（）；
enqueue（新回调（）{
@凌驾
公共void onResponse（呼叫、最终响应）{
Completable.fromAction（新操作（）{
@凌驾
public void run（）引发异常{
if（response.body（）！=null）{
List=response.body（）；
对于（int i=0；i

MainActivity.java

@Dao
public interface UserDao {

@Insert(onConflict = OnConflictStrategy.REPLACE)
void Insert(User... users);

@Query("SELECT * FROM Users")
LiveData<List<User>> getRoomUsers();
}

@Entity(tableName = "Users")
public class User {

@NonNull
@PrimaryKey
private String id;

@ColumnInfo(name = "name")
@SerializedName("name")
@Expose
private String name;

@ColumnInfo(name = "age")
@SerializedName("age")
@Expose
private String age;

public User(String id,String name, String age) {
   this.id = id;
   this.name = name;
   this.age = age;
}

public String getId() {
   return id;
}

public void setId(String id) {
   this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
   this.name = name;
}

public String getAge() {
   return age;
}

public void setAge(String age) {
   this.age = age;
}
}

public class UserRepository {

private Context context;
private UserDb userDb;
private LiveData<List<User>> listLiveData;

public UserRepository(Context context) {
   this.context = context;
   userDb = UserDb.getInstance(context);
   listLiveData = userDb.userDao().getRoomUsers();
}

public void getUserList(){

      Retrofit retrofit = RetrofitClient.getInstance();
      ApiService apiService = retrofit.create(ApiService.class);

      Call<List<User>> userList = apiService.getUser();

      userList.enqueue(new Callback<List<User>>() {
          @Override
          public void onResponse(Call<List<User>> call, final Response<List<User>> response) {

              Completable.fromAction(new Action() {
                      @Override
                      public void run() throws Exception {

                          if(response.body() != null) {

                              List<User> list = response.body();

                              for (int i = 0; i < list.size(); i++) {

                                  String id = list.get(i).getId();
                                  String names = list.get(i).getName();
                                  String age = list.get(i).getAge();

                                  User user = new User(id,names,age);

                                  userDb.userDao().Insert(user);


                              }

                          }

                      }
                  }).subscribeOn(Schedulers.io())
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(new CompletableObserver() {
                        @Override
                        public void onSubscribe(Disposable d) {

                        }

                        @Override
                        public void onComplete() {

                            Toast.makeText(context,"Data inserted",Toast.LENGTH_SHORT).show();
                        }

                        @Override
                        public void onError(Throwable e) {

                            Toast.makeText(context,e.getMessage(),Toast.LENGTH_SHORT).show();
                        }
                    });


          }

          @Override
          public void onFailure(Call<List<User>> call, Throwable t) {
              Toast.makeText(context,t.getMessage(),Toast.LENGTH_LONG).show();
          }
      });

 }

public LiveData<List<User>> getRoomUsers(){

   return listLiveData;
  }
}

public class MainActivity extends AppCompatActivity {

UserRepository userRepository;
RecyclerView recyclerView;
UserViewModel userModel;
List<User> userList;
UserAdapter adapter;
ProgressBar prg;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

prg = findViewById(R.id.prg);

userRepository = new UserRepository(this);
userModel = ViewModelProviders.of(this).get(UserViewModel.class);

recyclerView = findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));

userList = new ArrayList<>();

adapter = new UserAdapter(userList,this);
recyclerView.setAdapter(adapter);

userModel.getListLiveData().observe(this, new Observer<List<User>>() {

    @Override
    public void onChanged(List<User> users) {

        prg.setVisibility(View.INVISIBLE);
        adapter.setUserList(users);
    }
});

FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent i = new Intent(MainActivity.this,AddUser.class);
        startActivity(i);
    }
});



   userRepository.getUserList();
}

public类MainActivity扩展了AppCompatActivity{
用户存储库用户存储库；
回收视图回收视图；
用户视图模型用户模型；
列表用户列表；
用户适配器；
ProgressBar prg；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
Toolbar Toolbar=findviewbyd（R.id.Toolbar）；
设置支持操作栏（工具栏）；
prg=findViewById（R.id.prg）；
userRepository=新的userRepository（此）；
userModel=ViewModelProviders.of（this.get）（UserViewModel.class）；
recyclerView=findViewById（R.id.recyclerView）；
recyclerView.setHasFixedSize（true）；
recyclerView.setLayoutManager（新的LinearLayoutManager（本））；
userList=newarraylist（）；
adapter=newuseradapter（userList，this）；
recyclerView.setAdapter（适配器）；
userModel.getListLiveData（）.observe（这个，新的观察者（）{
@凌驾
更改后的公共void（列出用户）{
prg.setVisibility（视图不可见）；
adapter.setUserList（用户）；
}
});
FloatingActionButton fab=findViewById（R.id.fab）；
fab.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图）{
意图i=新意图（MainActivity.this，AddUser.class）；
星触觉（i）；
}
});
userRepository.getUserList（）；
}

有人请让我知道我如何才能得到想要的结果。任何帮助将不胜感激

---

谢谢

您可以在插入新数据之前删除表以实现此目的，请使用以下代码：

@Dao
public abstract UserDao {

 @Insert(onConflict = OnConflictStrategy.REPLACE)
 abstract void Insert(User... users);

 @Query("SELECT * FROM Users")
 abstract LiveData<List<User>> getRoomUsers();

 @Insert(onConflict = OnConflictStrategy.IGNORE)
 abstract void insert( List<Users> list);

 @Query("DELETE FROM Users")
 abstract void deleteAll();

 @Transaction
 void deleteAndInsert(List<Users> list){
   deleteAll();
   insert(list);
 }

}

@Dao
公共抽象用户道{
@插入（onConflict=OnConflictStrategy.REPLACE）
摘要无效插入（用户…用户）；
@查询（“从用户中选择*）
抽象LiveData getRoomUsers（）；
@插入（onConflict=OnConflictStrategy.IGNORE）
摘要无效插入（列表）；
@查询（“从用户中删除”）
抽象void deleteAll（）；
@交易
作废删除和插入（列表）{
deleteAll（）；
插入（清单）；
}
}

现在您可以在之后使用

userDb.deleteAndInsert（list）

方法

List List=response.body（）；

将数据与服务器同步