Android serializable只读取一个对象

Question

可序列化列表只读取一个对象。

班级部门

public class Department implements Serializable {

int Id;
String DepartmentName;
int Status;

public Department(){

}
public Department(String Name, int faculty){
    this.DepartmentName = Name;
    this.Status = faculty;
}

public Department(int id, String name, int faculty){
    this.Id = id;
    this.DepartmentName = name;
    this.Status = faculty;
}

public int getId() {
    return this.Id;
}

public void setId(int id) {
    Id = id;
}

public String getDepartmentName() {
    return this.DepartmentName;
}

public void setDepartmentName(String departmentName) {
    DepartmentName = departmentName;
}

public int getStatus() {
    return this.Status;
}

public void setFaculty(int faculty) {
    Status = faculty;
}

public String toString(){
    return DepartmentName;
}
}

主菜单活动

public class MainMenu extends AppCompatActivity {

DataBase dataBase = new DataBase(this);
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_menu);

    //create faculty
    Faculty Science = new Faculty("Science");
    long Science_id = dataBase.CreateFaculty(Science);

    // create department
    Department computer = new Department("Computer", 0);
    Department maths = new Department("Maths",0);
    Department EMT = new Department("Environmental Science",0);
    Department physics = new Department("Physics",0);

    long comp_id = dataBase.CreateDepartment(computer, new long[]{Science_id});
    long math_id = dataBase.CreateDepartment(maths, new long[]{Science_id});
    long emt_id = dataBase.CreateDepartment(EMT, new long[]{Science_id});
    long physics_id = dataBase.CreateDepartment(physics, new long[]{Science_id});

    Log.d("Sciences:", "Science Departments " + dataBase.GetDepartmentsBYFac("Science"));


    // list of science departments
    // final List<Department> sci_departments = dataBase.GetDepartmentsBYFac("Science");

    ImageButton imageButton = (ImageButton) findViewById(R.id.science);
    imageButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainMenu.this, DepartmentsActivity.class);
            List<Department> departments = new ArrayList<Department>();
            departments = dataBase.GetDepartmentsBYFac("Science");
            Bundle bundle = new Bundle();
            bundle.putSerializable("Sciences", (Serializable) departments);
            intent.putExtra("Bundle", bundle);
            startActivity(intent);
        }
    });


}

接收活动（listview）

public class DepartmentsActivity extends ListActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_departments);

    DataBase dataBase = new DataBase(this);
    Intent intent = getIntent();
    Bundle bundle = intent.getBundleExtra("Bundle");
    List<Department> departments = (ArrayList<Department>) bundle.getSerializable("Sciences");

    ArrayAdapter<Department> adapter = new ArrayAdapter<Department>(this, android.R.layout.simple_list_item_1, departments);
    setListAdapter(adapter);

}

}

listview结果显示

physics 
physics 
physics 
physics

这是CreateDeppartment的方法

public long CreateDepartment(Department department, long[] fac_ids){

    SQLiteDatabase database = this.getWritableDatabase();

    values = new ContentValues();

    values.put(KEY_DEPARTMENT, department. getDepartmentName());

    values.put(KEY_STATUS, department.getStatus()); 

    long dept_id =database.insert(TABLE_DEPARTMENT, null, values); 

           for (long fac_id: fac_ids) { 

              CreateDeptStatus(dept_id, fac_id);
           } 



   return  dept__id;
} 

这是警告

Unchecked cast: 'java.io.Serializable' to 'java.util.ArrayList<com.example.umar.album.Models.Department>' less... (Ctrl+F1) 
 Signals places where an unchecked warning is issued by the compiler, for example:
void f(HashMap map) {
  map.put("key", "value");
  }

Hint: Pass -Xlint:unchecked to javac to get more details.