1。我有一个ListView，其中包含图像，人物姓名，人物生日。当用户单击某个项目时，将启动一个新活动以显示该项目的详细信息。在此活动中，我创建了一个“评分”栏，用户可以在其中对每个项目进行评分。
2。我尝试使用SharedPreferences保存所计算的额定项目的平均值。我发现，当我保存费率并再次启动该应用程序时，这些值未存储在SharedPreferences中。
我的主要目标是计算每个额定项目的平均值并将其保存在SharedPreferences中。
3。人员类别：
public class PersonInfo {
private int image;
private String name;
private String birthday;
private float rating;
public PersonInfo(int image, String name, String birthday, float rating) {
this.image = image;
this.name = name;
this.birthday = birthday;
this.rating = rating;
}
public float getRating() {
return rating;
}
public void setRating(float rating) {
this.rating = rating;
}
public String getName(){
return name;
}
public int getImage() {
return image;
}
public void setName(String name) {
this.name = name;
}
public String getBirthday() {
return birthday;
}
public void setBirthday(String birthday) {
this.birthday = birthday;
}
}
人员适配器：
public class StudentsListAdapter extends ArrayAdapter<PersonInfo>{
private Context contxt;
private int rsrc;
private List<PersonInfo> persons;
private boolean isAdmin;
private TextView pName, pBirthday;
public StudentsListAdapter( Context context, int resource, List<PersonInfo> _persons, boolean _isAadmin) {
super(context, resource, _persons);
contxt = context;
rsrc = resource;
persons=_persons;
isAdmin = _isAadmin;
}
@NonNull
@Override
public View getView(final int position, @Nullable View convertView, @NonNull ViewGroup parent) {
LayoutInflater inflater = LayoutInflater.from(contxt);
View view = inflater.inflate(rsrc, null,false);
ImageView imageView = view.findViewById(R.id.imgP);
pName = view.findViewById(R.id.txtView2);
pBirthday = view.findViewById(R.id.txtView3);
PersonInfo p = persons.get(position);
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent1 = new Intent(contxt,ViewItems.class);
String name = persons.get(position).getName();
String birth = persons.get(position).getBirthday();
intent1.putExtra("name",name);
intent1.putExtra("birth",birth);
contxt.startActivity(intent1);
}
});
imageView.setImageDrawable(contxt.getResources().getDrawable(p.getImage()));
pBirthday.setText(p.getBirthday());
pName.setText(p.getName());
}
return view;
}
评价项目：
public class ViewItems extends AppCompatActivity {
EditText edName;
TextView edBirth;
float myRating = 0;
Button svRate;
RatingBar rtBar;
String position;
SharedPreferences.Editor editor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_items);
edName = findViewById(R.id.st_editName);
edBirth = findViewById(R.id.tv_editDate);
rtBar = findViewById(R.id.ratingBar);
Bundle extras = getIntent().getExtras();
String name = extras.getString("name");
edName.setText(name);
edName.setEnabled(false);
edName.setTextColor(Color.BLACK);
String birth = extras.getString("birth");
edBirth.setText(birth);
edBirth.setEnabled(false);
edBirth.setTextColor(Color.BLACK);
ImageView image = (ImageView) findViewById(R.id.user_img);
image.setBackgroundResource(android.R.drawable.btn_star);
position = getIntent().getStringExtra("position");
rtBar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
@Override
public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
int rating1 = (int) rating;
String message = null;
myRating = ratingBar.getRating();
switch (rating1){
case 1:
message = "Sorry to hear that!";
break;
case 2:
message = "You always accept suggestions!";
break;
case 3:
message = "Good enough!";
break;
case 4:
message = "Great! Thank you!";
break;
case 5:
message = "Awesome! You are the best!";
break;
}
Toast.makeText(ViewItems.this, message, Toast.LENGTH_SHORT).show();
}
});
svRate = findViewById(R.id.sv_item);
svRate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i4 = new Intent(ViewItems.this, MainActivity.class);
SharedPreferences sharedPreferences = getSharedPreferences("SaveRating",Context.MODE_PRIVATE);
myRating = sharedPreferences.getFloat("rating_float", 0f);
float total = 0;
total += rtBar.getRating();
float average = total / 2;
rtBar.setRating(average);
startActivity(i4);
Toast.makeText(ViewItems.this, "Your rating is:" + (myRating), Toast.LENGTH_SHORT).show();
}
});
}
}
主要活动：
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private TextView edName,edBirth;
String position;
String ed_name;
String ed_birth;
String username, password;
ArrayList<PersonInfo> students;
ArrayList<PersonInfo> students1;
ListView listView1;
SharedPreferences sharedPref;
SharedPreferences.Editor editor;
float rtBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
students = new ArrayList<>();
students1 = new ArrayList<>();
Intent intent = getIntent();
if(getIntent() != null){
username = intent.getStringExtra("Username");
password = intent.getStringExtra("Password");
edName = findViewById(R.id.txtView2);
edBirth = findViewById(R.id.txtView3);
listView1 = (ListView) findViewById(R.id.li_view);
students1.add(new PersonInfo(android.R.drawable.btn_star, "Test1", "03/27/1998", 3));
students1.add(new PersonInfo(android.R.drawable.btn_star, "Test2", "03/27/1998",2));
students1.add(new PersonInfo(android.R.drawable.btn_star, "Test3", "03/27/1998",1));
students1.add(new PersonInfo(android.R.drawable.btn_star, "Test4", "03/27/1998",5));
test1 = new StudentsListAdapter(
this, R.layout.adapter_view_layout, students1, true);
listView1.setAdapter(test1);
if(username!= null && username.equals("test") && password != null && password.equals("123")){
Log.d(TAG, "onCreate: Started.");
ListView listView = (ListView) findViewById(R.id.li_view);
students.add(new PersonInfo(android.R.drawable.btn_star, "Test1", "03/27/1998", 3));
students.add(new PersonInfo(android.R.drawable.btn_star, "Test2", "03/27/1998",2));
students.add(new PersonInfo(android.R.drawable.btn_star, "Test3", "03/27/1998",1));
students.add(new PersonInfo(android.R.drawable.btn_star, "Test4", "03/27/1998",5));
test1 = new StudentsListAdapter(
this, R.layout.adapter_view_layout, students, true);
listView1.setAdapter(test1);
}
else if (username != null && username.equals("test2") && password != null && password.equals("1234"))
{
ListView listView = (ListView) findViewById(R.id.li_view);
students.add(new PersonInfo(android.R.drawable.btn_star, "Test1", "03/27/1998", 3));
students.add(new PersonInfo(android.R.drawable.btn_star, "Test2", "03/27/1998",2));
students.add(new PersonInfo(android.R.drawable.btn_star, "Test3", "03/27/1998",1));
students.add(new PersonInfo(android.R.drawable.btn_star, "Test4", "03/27/1998",5));
test1 = new StudentsListAdapter(
this, R.layout.adapter_view_layout, students,false);
listView1.setAdapter(test1);
}
SharedPreferences sharedPreferences = getSharedPreferences("SaveRating",Context.MODE_PRIVATE);
editor = sharedPreferences.edit();
editor.putFloat("rating_float", rtBar);
editor.apply();
}
}
}
我在做什么错？
任何帮助将不胜感激。谢谢！
您甚至都不尝试保存任何东西。你只把rtBar
editor.putFloat("rating_float", rtBar);
即使尚未初始化，但如果它是数据float的原始类型，则其默认值为0
我认为您忘了初始化rtBar，就像@Eugene告诉您的那样。您可以通过获取所有学生的平均值来初始化它：
for (PersonInfo personInfo : students) {
rtBar += personInfo.getRating();
}
// now store it in sharedPrefs