I am trying to get the sharedpreferences values that are saved, and I want to get the saved value to pop up in a Toast message. All this happens in a class, but I get the error: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
我不确定错误在哪里，但是我可以在类中发布我的两个方法，其中一个保存到sharedPreferences中，另一个方法应该从sharedPreferences中加载值（错误在这里）：
public void saveDataForPreferences(Context context, String userId, String lol, String key){
SharedPreferences sharedPreferences = context.getSharedPreferences(lol, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, userId);
editor.putString(key, lol);
editor.commit();
editor.apply();
readSharedPreference(context, userId, lol);
}
public String readSharedPreference(Context context,String lol ,String key){
SharedPreferences sharedPreferences = context.getSharedPreferences(lol, Context.MODE_PRIVATE);
Toast.makeText(mActivity, lol, Toast.LENGTH_SHORT).show();
return sharedPreferences.getString(key,DEFAULT);
}
因为我不确定问题出在哪里，所以将我的整个代码发布在这里：
package com.example.vi_prover_selvfolgelig_igjen.normal_java_classes.Firebase;
public class FirebaseUserProfile extends FirebaseRegistration {
private String introMessageSeen = "False";
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener firebaseAuthListener;
public Activity mActivity;
public FirebaseUserProfile(){
}
public String getUid() {
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
String the_uid = user.getUid();
return the_uid;
}
protected final static String DEFAULT = "0";
public void saveDataForPreferences(Context context, String userId, String lol, String key){
SharedPreferences sharedPreferences = context.getSharedPreferences(lol, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(key, userId);
editor.putString(key, lol);
editor.commit();
editor.apply();
readSharedPreference(context, userId, lol);
}
public String readSharedPreference(Context context,String lol ,String key){
SharedPreferences sharedPreferences = context.getSharedPreferences(lol, Context.MODE_PRIVATE);
Toast.makeText(mActivity, lol, Toast.LENGTH_SHORT).show();
return sharedPreferences.getString(key,DEFAULT);
}
public void addPersonalInfoToDB(final Context howToDoThis){ // is this correct?
Query secretNotesQuery = FirebaseDatabase.getInstance().getReference().child("AdditionalUserInfo");
secretNotesQuery.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
final DatabaseReference current_notes_db = FirebaseDatabase.getInstance().getReference().child("AdditionalUserInfo").push();
Map extraUserInfo = new HashMap();
extraUserInfo.put("sex", sex);
extraUserInfo.put("user-age", age);
extraUserInfo.put("user-weight", weight);
extraUserInfo.put("intro-message-seen", introMessageSeen);
extraUserInfo.put("user_id", getUid());
saveDataForPreferences(howToDoThis,getUid(), introMessageSeen,"0");
current_notes_db.setValue(extraUserInfo);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
public void getUserProfile(final Context theContext) {
final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
final String the_uid = user.getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference additionalUserInfoRef = rootRef.child("UserRegistraion");
Query userQuery = additionalUserInfoRef.orderByKey().equalTo(the_uid);
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = new HashMap<>();
String userName = ds.child("username").getValue(String.class);
String nameOfUser = ds.child("name").getValue(String.class);
setUsername(userName);
setName(nameOfUser);
showUserWorkOutProfile();
saveDataForPreferences(theContext, the_uid, nameOfUser, "0");
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(mActivity, "Something went wrong..", Toast.LENGTH_SHORT).show();
}
};
userQuery.addListenerForSingleValueEvent(valueEventListener);
}
public void CHANGEIMPORTANTUSERINFO(){
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
String the_uid = user.getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference additionalUserInfoRef = rootRef.child("UserRegistraion");
Query userQuery = additionalUserInfoRef.orderByKey().equalTo(the_uid);
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = new HashMap<>();
map.put("name", getName());
ds.getRef().updateChildren(map);
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(mActivity, "Something went wrong..", Toast.LENGTH_SHORT).show();
}
};
userQuery.addListenerForSingleValueEvent(valueEventListener);
}
public void ChangeWorkOutProfileDetails() {
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
String the_uid = user.getUid();
DatabaseReference additionalUserInfoRef = rootRef.child("AdditionalUserInfo");
Query userQuery = additionalUserInfoRef.orderByChild("user_id").equalTo(the_uid);
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = new HashMap<>();
map.put("user-age", age);
map.put("user-weight", weight);
ds.getRef().updateChildren(map);
showUserWorkOutProfile();
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(mActivity, "Something went wrong..", Toast.LENGTH_SHORT).show();
}
};
userQuery.addListenerForSingleValueEvent(valueEventListener);
}
public void showUserWorkOutProfile() {
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
String the_uid = user.getUid();
DatabaseReference additionalUserInfoRef = rootRef.child("AdditionalUserInfo");
Query userQuery = additionalUserInfoRef.orderByChild("user_id").equalTo(the_uid);
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Map<String, Object> map = new HashMap<>();
String userAge = ds.child("user-age").getValue(String.class);
String userWeight = ds.child("user-weight").getValue(String.class);
setAge(userAge);
setWeight(userWeight);
if (mRegistrationListener != null)
mRegistrationListener.onRegistrationComplete(true); // Assumes success
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(mActivity, "Something went wrong..", Toast.LENGTH_SHORT).show();
}
};
userQuery.addListenerForSingleValueEvent(valueEventListener);
}
private OnRegistrationCompleteListener mRegistrationListener;
// Set listener ( callback ) that will be called on registration completion
public FirebaseUserProfile(OnRegistrationCompleteListener listener ) {
mRegistrationListener = listener;
}
// Interface that can be implemented by other classes
public interface OnRegistrationCompleteListener
{
void onRegistrationComplete( boolean success);
}}
有人可以帮我解决这个问题吗？谢谢。
