java - Activity to Fragment 错误，无法获取共享首选项的值

Question

我目前正在为我的类项目开发一个卡路里应用程序。我已经开始使用 Activity 进行布局，但我的教授希望我改用 fragment 。在尝试将代码转换为 fragment 时，我遇到了一些难以将值保存到共享首选项 xml 的问题。我当前正在开发的页面从用户那里获取信息，并根据用户的选择确定他们的卡路里。然后，该值将保存在共享首选项中，并显示在主 Activity 中。

提前感谢您的帮助，我是 android studio 和开发应用程序的新手。

配置文件java文件

`public class Profile extends Fragment implements View.OnClickListener {

  //adaptors spinners

  ArrayAdapter<String> HeightFeetAdapter;
  ArrayAdapter<String> WeightLBSAdapter;


   //references UI elements
   Button SaveButton;

   Spinner weightSpinner;
   Spinner heightSpinner;
   Spinner goal;
   Spinner gender;
   Spinner activityLevel;

   EditText age;
   private Animation anim;

   @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment


        View myView = inflater.inflate(R.layout.fragment_profile, container,
       false);

       String username = 
       getActivity().getIntent().getStringExtra("Username");

      TextView userMain = (TextView) myView.findViewById(R.id.User);
      userMain.setText(username);

      age =(EditText)myView.findViewById(R.id.editText3);
      age.setInputType(InputType.TYPE_CLASS_NUMBER);

      heightSpinner = (Spinner) myView.findViewById(R.id.HeightSpin);

      weightSpinner = (Spinner) myView.findViewById(R.id.WeightSpin);

      activityLevel = (Spinner) myView.findViewById(R.id.activity_level);
       ArrayAdapter<CharSequence> adapter_activity =   
      ArrayAdapter.createFromResource(getActivity(),
            R.array.activity_level, android.R.layout.simple_spinner_item);
          adapter_activity.setDropDownViewResource
        (android.R.layout.simple_spinner_dropdow
    n_item);
    activityLevel.setAdapter(adapter_activity);

     goal = (Spinner) myView.findViewById(R.id.goal);
    ArrayAdapter<CharSequence> adapter_goal = 
     ArrayAdapter.createFromResource(getActivity(),
            R.array.goal, android.R.layout.simple_spinner_item);
      adapter_goal.setDropDownViewResource
      (android.R.layout.simple_spinner_dropdown_item);
      goal.setAdapter(adapter_goal);

     gender = (Spinner) myView.findViewById(R.id.gender);
      ArrayAdapter<CharSequence> adapter_gender = 
     ArrayAdapter.createFromResource(getActivity(),
            R.array.gender, android.R.layout.simple_spinner_item);

      adapter_gender.setDropDownViewResource
     (android.R.layout.simple_list_item_activated_1);
    gender.setAdapter(adapter_gender);


    SaveButton = (Button) myView.findViewById(R.id.savebutton);
    SaveButton.setOnClickListener(this);


    initializeSpinnerAdapters();
    loadLBVal();
    loadFTVal();

    anim = AnimationUtils.loadAnimation(getActivity(), R.anim.fading);
    heightSpinner.startAnimation(anim);

    anim = AnimationUtils.loadAnimation(getActivity(), R.anim.fading);
    weightSpinner.startAnimation(anim);


    anim = AnimationUtils.loadAnimation(getActivity(), R.anim.fading);
    SaveButton.startAnimation(anim);

    SharedPreferences userInfo = 
   PreferenceManager.getDefaultSharedPreferences(getActivity());
    PreferenceManager.setDefaultValues(getActivity(), 
    R.xml.activity_preference, false);



    return myView;
}






    public void loadLBVal() {
    weightSpinner.setAdapter(WeightLBSAdapter);
    // set the default lib value
    weightSpinner.setSelection(WeightLBSAdapter.getPosition("170"));
   }


// load the feets value range to the height spinner
public void loadFTVal() {
    heightSpinner.setAdapter(HeightFeetAdapter);
    // set the default value to feets
    heightSpinner.setSelection(HeightFeetAdapter.getPosition("5\"05'"));
  }


   public void initializeSpinnerAdapters() {

    String[] weightLibs = new String[300];
    // loading spinner values for weight
    int k = 299;
    for (int i = 1; i <= 300; i++) {
        weightLibs[k--] = String.format("%3d", i);
    }
    // initialize the weightLibsAdapter with the weightLibs values
    WeightLBSAdapter = new ArrayAdapter<String>(getContext(), 
    R.layout.activity_spinner_item, weightLibs);

    WeightLBSAdapter.setDropDownViewResource
    (android.R.layout.simple_spinner_dropdown_item);


    String[] heightFeets = new String[60];
    // loading values  3"0' to 7"11' to the height in feet/inch
    k = 59;
    for (int i = 3; i < 8; i++) {
        for (int j = 0; j < 12; j++) {
            heightFeets[k--] = i + "\"" + String.format("%02d", j) + "'";
        }
    }
    // initialize the heightFeetAdapter with the heightFeets values

    HeightFeetAdapter = new ArrayAdapter<String>(getContext(),  

     R.layout.activity_spinner_item, heightFeets);

    HeightFeetAdapter.setDropDownViewResource
     (android.R.layout.simple_spinner_dropdown_item);


  }



    @Override
   public void onClick(View v) {

    switch (v.getId()) {

        case R.id.savebutton:


            int   activityLevel, goal, gender, age;
            // Get preferences
            float height = getSelectedHeight();
            float weight =  getSelectedWeight();


            activityLevel = 
     ((Spinner)getActivity().findViewById
     (R.id.activity_level)).getSelectedItemPosition();


            goal = ((Spinner)getActivity().
      findViewById(R.id.goal)).getSelectedItemPosition();

           gender= ((Spinner)getActivity().
      findViewById(R.id.gender)).getSelectedItemPosition();


            age = Integer.parseInt(((EditText).
           getActivity().findViewById(R.id.editText3)));




            int tdee = calculateTDEE(height,weight,activityLevel,age,gender, 
            goal);

            // Save preferences in XML
            SharedPreferences userInfo = getSharedPreferences("userInfo", 
            0);
            SharedPreferences.Editor editor = userInfo.edit();
            editor.putInt("tdee", tdee);
            editor.commit();


            break;
    }
  }


public float getSelectedWeight() {
    String selectedWeightValue = (String)weightSpinner.getSelectedItem();

    return (float) (Float.parseFloat(selectedWeightValue) * 0.45359237);


}



public float getSelectedHeight() {
    String selectedHeightValue = (String)heightSpinner.getSelectedItem();

    // the position is feets and inches, so convert to meters and return
    String feets = selectedHeightValue.substring(0, 1);
    String inches = selectedHeightValue.substring(2, 4);
    return (float) (Float.parseFloat(feets) * 0.3048) +
            (float) (Float.parseFloat(inches) * 0.0254);

}



  public int calculateTDEE(float height, float weight, int activityLevel,
  int 
 age, int gender, int goal) {

    double bmr = (10 * weight) + (6.25 * height) - (5 * age) + 5;
    if(gender == 1) {
        bmr = (10* weight) + (6.25 * height) - (5*age) - 161;
    }
    double activity = 1.25;
    switch(activityLevel) {
        case 1:
            activity = 1.375;
            break;
        case 2:
            activity = 1.55;
            break;
        case 3:
            activity = 1.725;
            break;
        case 4:
            activity = 1.9;
            break;
    }
    double tdee = bmr * activity;
    switch(goal) {
        case 0:
            tdee -=500;
            break;
        case 2:
            tdee +=500;
            break;
    }
    tdee += .5;
    return (int) tdee;
  }
















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

  }


    @Override
     public void onDestroy() {
      super.onDestroy();

   }

    @Override
    public void onDetach() {
      super.onDetach();
  }

}

`

fragment_profile xml

`

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"

    android:orientation="vertical"

    android:background="@drawable/imgbackground2"
    android:weightSum="1">
    <TextView
        android:layout_width="180dp"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="@string/emptyString"
        android:id="@+id/User"
        android:layout_marginLeft="0dp"
        android:layout_marginRight="0dp"
        android:layout_alignParentTop="true"
        android:layout_alignEnd="@+id/tv_main_title" />
    <TextView
        android:layout_width="294dp"
        android:layout_height="65dp"
        android:text="Please Complete Information"
        android:textColor="@color/colorBackground"
        android:layout_gravity="center_horizontal"
        android:gravity="center"
        android:textSize="20dp" />
   <TableLayout
   android:layout_width="match_parent"
   android:layout_height="wrap_content">

   <TableRow
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="60dp"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Age"
        android:id="@+id/textView12"
        android:layout_above="@+id/gender"
        android:layout_alignLeft="@+id/textView5"
        android:layout_alignStart="@+id/textView5" />

    <EditText
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/editText3"
        android:imeOptions="actionDone"
        android:layout_alignTop="@+id/gender"
        android:layout_alignLeft="@+id/editText"
        android:layout_marginLeft="0dp"
         android:layout_column="1" />
 </TableRow>

 </TableLayout>


    <RelativeLayout
        android:layout_width="194dp"
        android:layout_height="26dp"></RelativeLayout>


    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Gender"
        android:id="@+id/textView11"
        />

    <Spinner
        android:layout_width="113dp"
        android:layout_height="40dp"
        android:id="@+id/gender"
        android:layout_above="@+id/textView5"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="10dp"
        android:layout_alignStart="@+id/textView4"
        android:layout_alignEnd="@+id/textView3"
        android:spinnerMode="dropdown"
        android:popupBackground="@color/colorBackground" />

    <TableLayout
        android:id="@+id/tableLayout1"
        android:layout_width="329dp"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TableRow
            android:id="@+id/tableRow1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_marginTop="15dp" >

            <TextView
                android:id="@+id/textView1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginRight="5dp"
                android:text="@string/weightLabel"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:textColor="@color/colorBackground"
                android:textSize="25dp"
                android:paddingRight="0dp"
                android:paddingLeft="-2dp" />

            <Spinner
                android:id="@+id/WeightSpin"
                android:layout_width="fill_parent"
                android:layout_height="match_parent"
                android:prompt="@string/weightLabel"
                android:spinnerMode="dropdown"
                android:layout_weight="2"
                android:textAlignment="center"
                android:popupBackground="@drawable/graybackground2"

                android:layout_span="2"
                android:layout_column="1" />

        </TableRow>

        <TableRow
            android:id="@+id/tableRow2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_marginTop="15dp" >

        </TableRow>



        <TableRow
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:id="@+id/textView2"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginRight="5dp"
                android:text="@string/heightLabel"
                android:textAppearance="?android:attr/textAppearanceMedium"
                android:textColor="@color/colorBackground"
                android:textSize="25dp"
                android:layout_column="0"
                android:layout_marginLeft="5dp" />

            <Spinner
                android:id="@+id/HeightSpin"
                android:layout_width="fill_parent"
                android:layout_height="match_parent"
                android:prompt="@string/heightLabel"
                android:layout_weight="2"
                android:popupBackground="@drawable/graybackground2"

                android:spinnerMode="dropdown"
                android:layout_marginTop="0dp"
                android:layout_margin="0dp"
                android:layout_marginBottom="0dp"
                android:layout_column="1"
                android:paddingTop="0dp"
                android:paddingBottom="0dp"
                android:textAlignment="center"
                android:paddingStart="5dp"
                android:layout_marginLeft="0dp"
                android:layout_span="0"
                android:layout_marginRight="0dp" />


        </TableRow>

        <TableRow>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:text="Activity Level"
                android:id="@+id/textView7"
                android:layout_below="@+id/editText"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="10dp" />

            <Spinner
                android:layout_width="200dp"
                android:layout_height="50dp"
                android:id="@+id/activity_level"
                android:layout_below="@+id/textView7"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="5dp" />

        </TableRow>

        <TableRow>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textAppearance="?android:attr/textAppearanceLarge"
                android:text="Goal"
                android:id="@+id/textView8"
                android:layout_below="@+id/activity_level"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="10dp" />

            <Spinner
                android:layout_width="200dp"
                android:layout_height="50dp"
                android:id="@+id/goal"
                android:layout_below="@+id/textView8"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="5dp"
                android:spinnerMode="dropdown" />
        </TableRow>
    </TableLayout>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save"
        android:id="@+id/savebutton"
        android:radius="10dp"
        android:textColor="@color/colorBackground"
        android:onClick="saveAction"
        android:layout_alignParentBottom="true"
        android:layout_toEndOf="@+id/editText3"
        android:layout_gravity="right" />


</LinearLayout>

`

Fragmenthome.java

   import java.util.ArrayList;



   public class FragmentHome extends   Fragment  implements  
   View.OnClickListener {


  private TextView caloriesTotal;

  private TextView caloriesRemain;

  private ListView listView;
  private LinearLayout mLayout;

   private Animation anim;

   ImageButton AddEntrybtn;
   ImageButton ResetEntry;
   Context context;

  int goalCalories;
   int totalCalorie;



    Button mButton;

    //Database
    private DatabaseHandler dba;

   private ArrayList<Food> dbFoods = new ArrayList<>();
   private CustomListViewAdapter foodAdapter;
   private Food myFood ;



    //fragment
   private android.support.v4.app.FragmentManager fragmentManager;
   private FragmentTransaction fragmentTransaction;

   public FragmentHome() {
      // Required empty public constructor
   }




   @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View myView = inflater.inflate(R.layout.fragment_home, container, 
   false);



    caloriesTotal = (TextView) myView.findViewById(R.id.tv_calorie_amount);

    caloriesRemain = (TextView) myView.findViewById(R.id.calorieRemain);

    listView = (ListView) myView.findViewById(R.id.ListId);




    SharedPreferences prefs = 
    PreferenceManager.getDefaultSharedPreferences(getActivity());
    PreferenceManager.setDefaultValues(getActivity(), 
    R.xml.activity_preference, false);

    goalCalories = 
     Integer.parseInt(prefs.getString("prefs_key_daily_calorie_amount", 
    "2000"));



    AddEntrybtn = (ImageButton) myView.findViewById(R.id.AddItems);




    AddEntrybtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View arg0) {


            ((appMain) getActivity()).loadSelection(4);


        }
    });



    ResetEntry = (ImageButton) myView.findViewById(R.id.ResetEntry);
    ResetEntry.setOnClickListener(this);







    refreshData();



    anim= AnimationUtils.loadAnimation(getActivity(), R.anim.fading);
    listView.startAnimation(anim);

    return myView;


  }




    public void reset ()  {

  //


    dbFoods.clear();

    dba = new DatabaseHandler(getActivity());

    ArrayList<Food> foodsFromDB = dba.getFoods();


    //Loop
    for (int i = 0; i < foodsFromDB.size(); i ++){

        String name = foodsFromDB.get(i).getFoodName();
        String date = foodsFromDB.get(i).getRecordDate();
        int cal = foodsFromDB.get(i).getCalories();
        int foodId = foodsFromDB.get(i).getFoodId();

        Log.v("Food Id", String.valueOf(foodId));

        myFood= new Food();
        myFood.setFoodId(foodId);
        myFood.setFoodName(name);
        myFood.setCalories(cal);
        myFood.setRecordDate(date);

        dbFoods.clear();

        dbFoods.remove(myFood);
        foodsFromDB.remove(myFood);
       dba.deleteFood(foodId);
    }
    dba.close();

    //setting food Adapter:
    foodAdapter = new CustomListViewAdapter(getActivity(), 
    R.layout.row_item,dbFoods);
    listView.setAdapter(foodAdapter);
    foodAdapter.notifyDataSetChanged();



    anim= AnimationUtils.loadAnimation(getActivity(), R.anim.fading);
    listView.startAnimation(anim);


    }



   public void refreshData (){




    dbFoods.clear();

    dba = new DatabaseHandler(getActivity());

    ArrayList<Food> foodsFromDB = dba.getFoods();

    totalCalorie = dba.totalCalories();




    String formattedCalories = Utils.formatNumber(totalCalorie);
    String formattedRemain = Utils.formatNumber(goalCalories - 
    totalCalorie);


    //setting the editTexts:


    caloriesTotal.setText("Total Calories: " + formattedCalories);

   caloriesRemain.setText(formattedRemain);




    SharedPreferences prefs = 
    PreferenceManager.getDefaultSharedPreferences(getContext());
    PreferenceManager.setDefaultValues(getActivity(), 
    R.xml.activity_preference, false);




    goalCalories = 
    Integer.parseInt(prefs.getString("prefs_key_daily_calorie_amount", 
     "2000"));




    //Loop
    for (int i = 0; i < foodsFromDB.size(); i ++){

        String name = foodsFromDB.get(i).getFoodName();
        String date = foodsFromDB.get(i).getRecordDate();
        int cal = foodsFromDB.get(i).getCalories();
        int foodId = foodsFromDB.get(i).getFoodId();

        Log.v("Food Id", String.valueOf(foodId));

        myFood= new Food();
        myFood.setFoodId(foodId);
        myFood.setFoodName(name);
        myFood.setCalories(cal);
        myFood.setRecordDate(date);

        dbFoods.add(myFood);
    }
    dba.close();

    //setting food Adapter:
    foodAdapter = new CustomListViewAdapter(getActivity(), 
   R.layout.row_item,dbFoods);
    listView.setAdapter(foodAdapter);
    foodAdapter.notifyDataSetChanged();

    anim= AnimationUtils.loadAnimation(getActivity(), R.anim.fading);
    listView.startAnimation(anim);

 }


    //save prefs
    public void savePrefs(String key, int value) {

    SharedPreferences sharedPreferences = 
    PreferenceManager.getDefaultSharedPreferences(getContext());
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.putInt(key, value);
    editor.apply();
   }
    //get prefs
   public int loadPrefs(String key, int value) {
    SharedPreferences sharedPreferences =
     PreferenceManager.getDefaultSharedPreferences(getContext());
    return sharedPreferences.getInt(key, value);
   }




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

    Bundle username = getActivity().getIntent().getExtras();



    String username1 = username.getString("Username");

    TextView userMain= (TextView) getView().findViewById(R.id.User);

    userMain.setText(username1);




   }


  @Override
    public void onResume() {
     super.onResume();



}

@Override
public void onDestroy() {
    super.onDestroy();

}

    @Override
   public void onDetach() {
    super.onDetach();

    startActivity( new Intent(getContext(),MainActivity.class));
   }


    @Override
    public void onClick(View v) {
      switch (v.getId()) {
        case R.id.AddItems:

            AddEntry addEntry    = new AddEntry();

            fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.replace(R.id.FragmentHolder,addEntry)

                    .commit();


            break;

        case R.id.action_settings:

            Intent preferenceScreenIntent = new Intent(getContext(), 
             PreferenceScreenActivity.class);
            startActivity(preferenceScreenIntent);



            break;


        case R.id.ResetEntry:


           reset();
            anim= AnimationUtils.loadAnimation(getActivity(), 
            R.anim.fading);
            listView.startAnimation(anim);
            break;


      }


    }
 }

偏好.xml

    <PreferenceScreen     
    xmlns:android="http://schemas.android.com/apk/res/android">

   <PreferenceCategory android:title="User Settings">
   <EditTextPreference
     android:title="Daily Calorie Amount"
    android:inputType="number"
   android:defaultValue="2000"
   android:key="@string/prefs_key_daily_calorie_amount"
  android:summary="@string/prefs_description_daily_calorie_amount" />




  </PreferenceCategory>



  </PreferenceScreen>

Answer 1

您可以在要调用的函数之前使用 getContext() 或 getActivity()。 getContext().getSharedPreferences()、getContext().getFilesDir() 等