Develop Reference

Read and write Parcel when using ArrayList of ArrayList

I'm trying to read and write this ArrayList structured as well: ArrayList<ArrayList<Pair<Float,Float>>> points I've seen that the only way would by using the class inside the external ArrayList, but in this case I haven't it. This is my full class, how do I can implement it?
import android.os.Parcel;
import android.os.Parcelable;
import android.util.Pair;
import java.io.Serializable;
import java.util.ArrayList;
public class Cornice implements Serializable, Parcelable {
private String number;
private ArrayList<ArrayList<Pair<Float,Float>>> points;
public Cornice(String n, ArrayList<ArrayList<Pair<Float,Float>>> p) {
number = n;
if (p!=null) points = new ArrayList<>(p);
else points=new ArrayList<>();
}
protected Cornice(Parcel in) {
number = in.readString();
points = //MISSING
}
public String getNumber () {
return number;
}
public ArrayList<ArrayList<Pair<Float,Float>>> getPoints () {
return points;
}
public static final Creator<Cornice> CREATOR = new Creator<Cornice>() {
#Override
public Cornice createFromParcel(Parcel in) {
return new Cornice(in);
}
#Override
public Cornice[] newArray(int size) {
return new Cornice[size];
}
};
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(number);
//MISSING
}
}

Pair is neither Parcelable, nor Serializable, so what you are trying to do won't work. You will have to change the data structure you use to hold the points to something else. For example you can convert it something like this:
private ArrayList<ArrayList<Float[]>> points;
or even (if you do not want to support null values) to:
private ArrayList<ArrayList<float[]>> points;

How to fix: Unable to invoke no-args constructor for class X: Registering an InstanceCreator with Gson for this type may fix this problem

I am trying to make a list of objects that are all of an abstract class, but each are there own class. This list needs to persistent so I figured I implement parcelable since I have done so in the past. Only not with different classes all of an abstract class.
I tried just making the abstract class parcelable but that can't have a creator that I am used to because (of course) you can't create an instance of it (because it is abstract). Reading around I noticed that people said you dont need a constructor in the abstract class, just in the subclasses.
AbstractFocusPower class
public abstract class AbstractFocusPower implements Parcelable {
private transient AppExtension app;
private ImplementSchool school;
private String name;
private int duration;
private int cost;
private int altCost;
private int requiredLevel;
private boolean isSelected;
private boolean isResonant;
private int nofSpirtBonusUsed;
/**
* Constructor for Focus Power with no alternative cost
*/
public AbstractFocusPower(AppExtension app, ImplementSchool school, String name, int requiredLevel, int duration, int cost, boolean isSelected) {
this.app = app;
this.school = school;
this.name = name;
this.requiredLevel = requiredLevel;
this.duration = duration;
this.cost = cost;
this.altCost = -1;
this.isSelected = isSelected;
this.isResonant = false;
}
// I cut out the other constructors
public abstract AbstractFocusPower makeCopy();
public abstract String getDescription();
// I cut out the getters and setters
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(this.school == null ? -1 : this.school.ordinal());
dest.writeString(this.name);
dest.writeInt(this.duration);
dest.writeInt(this.cost);
dest.writeInt(this.altCost);
dest.writeInt(this.requiredLevel);
dest.writeByte(this.isSelected ? (byte) 1 : (byte) 0);
dest.writeByte(this.isResonant ? (byte) 1 : (byte) 0);
dest.writeInt(this.nofSpirtBonusUsed);
}
protected AbstractFocusPower(Parcel in) {
int tmpSchool = in.readInt();
this.school = tmpSchool == -1 ? null : ImplementSchool.values()[tmpSchool];
this.name = in.readString();
this.duration = in.readInt();
this.cost = in.readInt();
this.altCost = in.readInt();
this.requiredLevel = in.readInt();
this.isSelected = in.readByte() != 0;
this.isResonant = in.readByte() != 0;
this.nofSpirtBonusUsed = in.readInt();
}
Sample subclass
public class AegisFocusPower extends AbstractFocusPower {
public AegisFocusPower(AppExtension app) {
super(app, ImplementSchool.ABJURATION, app.getString(R.string.focus_power_name_aegis), 0, 1, 1, false);
}
#Override
public String getDescription() {
return getApp().getString(R.string.focus_power_desc_aegis, (1+((int) Math.floor(getApp().getCurrentCharacter().getOccultistLevel()/6.0))));
}
#Override
public AegisFocusPower makeCopy() {
return new AegisFocusPower(getApp());
}
public AegisFocusPower(Parcel in) {
super(in);
}
public static final Parcelable.Creator<AegisFocusPower> CREATOR = new Parcelable.Creator<AegisFocusPower>() {
public AegisFocusPower createFromParcel(Parcel in) {
return new AegisFocusPower (in);
}
public AegisFocusPower [] newArray(int size) {
return new AegisFocusPower[size];
}
};
}
Code where I use it
Gson gsonFocusPowers = new Gson();
String jsonFocusPowers = sharedPreferences.getString(FOCUS_POWERS_GSON, null);
Type typeFocusPower = new TypeToken<ArrayList<AbstractFocusPower>>() {
}.getType();
ArrayList<AbstractFocusPower> focusPowers;
focusPowers = gsonFocusPowers.fromJson(jsonFocusPowers, typeFocusPower);
if (focusPowers != null) {
this.focusPowers.addAll(checkForNewFocusPowers(focusPowers));
} else {
this.focusPowers = getNewFocusPowerList();
}
Unfortunately this gives me an error which I don't know how to fix.
java.lang.RuntimeException: Unable to create application nl.rekijan.occultistmentalfocushelper.AppExtension: java.lang.RuntimeException: Unable to invoke no-args constructor for class nl.rekijan.occultistmentalfocushelper.mvc.focuspowers.AbstractFocusPower. Registering an InstanceCreator with Gson for this type may fix this problem.
Edit: Not sure why that post is a duplicate. For starters it doesn't have an accepted answer. The answer requires a 3rd party library. The question isn't about multiple subclasses under a single abstract.

have you tried registering a type adapter, something like Using Gson and Abstract Classes ? I always add adapters both for specific formatting (for dates, big decimals, anything where you usually require a very specific format) but also for sub-classing.
In this case however, no adapter is needed, this is.. straight on?
public abstract class AbstractFocusPower implements Parcelable {
// just some property needed to be pushed through a constructor
protected final String myString;
protected AbstractFocusPower(String myString) {
this.myString = myString;
}
}
and then the impl (yeah added toString(), hashCode() and equals() the way I like them to be in domain objects..):
public class AegisFocusPower extends AbstractFocusPower {
boolean imParcelled;
public AegisFocusPower(String myString) {
super(myString);
}
#Override //yup the interface impl
public void parcelMe() {
imParcelled = true;
}
#Override
public String toString() {
return new StringBuilder("{ imParcelled : ").append(imParcelled).append(", myString : ").append(myString).append(" }").toString();
}
#Override
public int hashCode() {
return toString().hashCode();
}
#Override
public boolean equals(Object other) {
if (other == this) {
return true;
} else if (other == null || !(other instanceof AegisFocusPower)) {
return false;
} else {
return other.hashCode() == hashCode();
}
}
}
and then I can run the following junit :
#Test
public void AegisFocusPowerToJsonAndBack(){
// single instance
AegisFocusPower ea = new AegisFocusPower("apa");
String json = GSON.toJson(ea);
assertEquals("{\"imParcelled\":\"false\",\"myString\":\"apa\"}", json);
AegisFocusPower backAtYa = (AegisFocusPower) GSON.fromJson(json, AegisFocusPower.class);
assertEquals(backAtYa, ea);
// A list
AegisFocusPower ea2 = new AegisFocusPower("bepa");
AegisFocusPower ea3 = new AegisFocusPower("cepa");
List<AegisFocusPower> powerList = new ArrayList<>();
powerList.add(ea2);
powerList.add(ea3);
String jsonList = GSON.toJson(powerList);
assertEquals("[{\"imParcelled\":\"false\",\"myString\":\"bepa\"},{\"imParcelled\":\"false\",\"myString\":\"cepa\"}]", jsonList);
List<AegisFocusPower> backAtYaz = Arrays.asList(GSON.fromJson(jsonList,AegisFocusPower[].class));
assertEquals(backAtYaz.get(0), ea2);
assertEquals(backAtYaz.get(1), ea3);
}
whereas GSON is initialized simply like
private static final Gson GSON = (new GsonBuilder()).registerTypeAdapter(Boolean.class, new JsonBooleanDeAndSerializer()).create();
and the type adapter registered for booleans which I use is irrelevant for your problem.
This is.. simple enough and would work for you too?

Check your imports. You may have mistakenly imported wrong class in your pojo. i.e. I have imported android.net.TransportInfo instead of my own TransportInfo class

Java nested parcelable, can't initialize an array

Okay, I have read through nearly every single parcelable question on stack overflow and have tried a number of solutions in order to solve this problem. So overall I have an android project and I want to send 2 ArrayLists of Arrays from one class to another through Intent.
Note: this is not a duplicate of the nested parcelable thread here which does not deal with arrays. It is not a duplicate of this because I have made all nested classes parcelable. It is not a duplicate of this or this because I am not using an array list and also I recognize the error is a failure of initializing. It is not a duplicate of this because I do not need a parameter-less constructor in this situation (I have tested adding one and it doesn't change the error). It is also not a duplicate of this because it is not a parcel nested in a parcel.
I must be doing something obvious because the nullpointer error should only occur if my array has not been initialized. However, it is not possible for me to initialize my array length until I know how long I want it to be...
(as a side note perhaps someone could give me greater insight into the readTypedList class and what exactly XXX.Creator does because this undoubtedly could be part of the problem. Also for any future people with the same problem here is a link to the Parcel javadoc which was informative but did not solve my problem.)
So now I have a Display object. The Display object is solely used to store a String[] and allow it to be parceled. The line that breaks with the has been commented below, and should be obvious for anyone with parcel experience because it has clearly not been initialized:
class Display implements Parcelable {
String[] labels;
public Display(String[] labels) {
this.labels = labels;
}
protected Display(Parcel in) {
in.readStringArray(this.labels); // **** THIS LINE BREAKS
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeStringArray(this.labels);
}
#Override
public int describeContents() {
return 0;
}
public static final Creator<Display> CREATOR = new Creator<Display>() {
#Override
public Display createFromParcel(Parcel in) {
return new Display(in);
}
#Override
public Display[] newArray(int size) {
return new Display[size];
}
};
}
So now I ask myself what I can do to solve this problem and investigated many other threads with promising names but they did not solve my issue.
Here was an answer I would have though would have helped, similarly here they suggested using createTypedList() instead of readTypedList().
However, I tried the first answer and also this and they didn't work because I don't know in advance how long I want my String[] to be, which just ends up leading instead to a bad array length error. And the second answer doesn't help because clearly I don't want to create a new typed list but instead use the typed list I already have, so by creating a new list I end up with a blank list and lose my data.
The root of all of these issues is the fact that my parcel is nested within another parcel and called via:
in.readTypedList(allChartLabels, Display.CREATOR);
Because it is nested, the CREATOR is being called in a way that very much limits my options and has led me to be unable to solve the issue.
Throughout various tests I have encountered a number of errors but no solutions... (the current error my code is throwing is Attempt to get length of null array error).
I know someone has a solution to this issue and for more details here is the rest of my code:
public class SummaryEntry implements Parcelable {
private ArrayList<Calculation> allChartValues; // NOTE: this is another nested parcel class which is basically a duplicate of Display but with float[]
private ArrayList<Display> allChartLabels;
public SummaryEntry() {
// initialize
allChartValues = new ArrayList<>();
allChartLabels = new ArrayList<>();
}
protected SummaryEntry(Parcel in) {
this();
// order in which we do this matters:
in.readTypedList(allChartLabels, Display.CREATOR);
in.readTypedList(allChartValues, Calculation.CREATOR);
}
#Override
public void writeToParcel(Parcel out, int i) {
// order in which we do this matters, must be same as reading typed lists
out.writeTypedList(allChartLabels);
out.writeTypedList(allChartValues);
}
/// ... getters and setters excluded because of irrelevance ///
/// PARCELABLE METHODS
#Override
public int describeContents() {
return 0;
}
public static final Creator<SummaryEntry> CREATOR = new Creator<SummaryEntry>() {
#Override
public SummaryEntry createFromParcel(Parcel in) {
return new SummaryEntry(in);
}
#Override
public SummaryEntry[] newArray(int size) {
return new SummaryEntry[size];
}
};
}
I appreciate you taking the time to read all the way down this long post. Ideally I am looking for a solution to the String[] initialization problem, or if someone could post their working code for a nested parcel including a array, or lastly perhaps someone could point out an easier way to achieve passing these items without nesting two parcels.

You can do it like below code:
Use writeArray & readArray like this:
Try with below updated code:
package com.myapplication;
import android.os.Parcel;
import android.os.Parcelable;
public class User implements Parcelable {
String name;
int age;
String [] array;
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(this.name);
dest.writeInt(this.age);
dest.writeStringArray(this.array);
}
public User() {
}
protected User(Parcel in) {
this.name = in.readString();
this.age = in.readInt();
this.array = in.createStringArray();
}
public static final Parcelable.Creator<User> CREATOR = new Parcelable.Creator<User>() {
#Override
public User createFromParcel(Parcel source) {
return new User(source);
}
#Override
public User[] newArray(int size) {
return new User[size];
}
};
}

I am still unable to solve the second half of the original question (which was how to parcel arrays) but I was able to achieve a successful nested parcel implementation by redesigning my program slightly.
The new design breaks the implementation into 4 nested classes with a straight forward implementation. I also removed my arrays because I was unable to initialize them properly in the parcel.
EDIT: I did also stumble upon this website which automatically creates parcelables for you. Very useful and I wish I had known about it before!
Also note that apparently it is unnecessary to create parcel classes to parcel String and Float. You can instead call Float.class.getClassLoader() and String.class.getClassLoader() to use the parcel CREATORS for those classes.
Here is my code:
Parcelable class Q contains ArrayList of:
Parcelable class A which contains 2 Arraylists of Strings and Floats
By breaking down the parcel into smaller nested parcels I was able to incrementally test the parcel until I arrived at the finalized solution which was able to be passed through my Intent via this code:
ON THE SENDING END:
// create the parcel
Q parcel = new Q();
ArrayList<String> strings = new ArrayList<>();
ArrayList<Float> stats = new ArrayList<>();
// ... populate arraylists ... //
Intent I = new Intent(CURRENTACTIVITY.this, FUTUREACTIVITY.class);
// PUT THE THING
I.putExtra("Data", parcel);
startActivity(I);
ON THE RECIEVING END:
Q parcel = getIntent().getParcelableExtra("Data"); // get data
FULL CODE for the working parcel:
This code is very long and repetitive but the basic principle for setting up parcels is clear and easy to re-use if you want to create your own parcel.
// top level parcelable class Q
public class Q implements Parcelable {
private ArrayList<A> element;
public Q()
{
this.element = new ArrayList<A>();
}
public void addToA(A a)
{
element.add(a);
}
public ArrayList<A> getA() {
return element;
}
public void setA(ArrayList<A> a) {
this.element = a;
}
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeTypedList(this.element);
}
private Q (Parcel in){
element = new ArrayList<A>();
in.readTypedList(this.element, A.CREATOR);
}
public static final Parcelable.Creator<Q> CREATOR = new Parcelable.Creator<Q>() {
public Q createFromParcel(Parcel in) {
return new Q(in);
}
public Q[] newArray(int size) {
return new Q[size];
}
};
}
// nested parcel object A
public class A implements Parcelable {
private ArrayList<Float> f;
private ArrayList<String> s;
public A() {
f = new ArrayList<>();
s = new ArrayList<>();
}
public A(ArrayList<Float> f, ArrayList<String> s) {
this.f = f;
this.s = s;
}
public ArrayList<String> getS() {
return s;
}
public void setS(ArrayList<String> s) {
this.s = s;
}
public ArrayList<Float> getF() {
return f;
}
public void setF(ArrayList<Float> f) {
this.f = f;
}
protected A(Parcel in) {
if (in.readByte() == 0x01) {
f = new ArrayList<>();
in.readList(f, Float.class.getClassLoader());
} else {
f = null;
}
if (in.readByte() == 0x01) {
s = new ArrayList<>();
in.readList(s, String.class.getClassLoader());
} else {
s = null;
}
}
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
if (f == null) {
dest.writeByte((byte) (0x00));
} else {
dest.writeByte((byte) (0x01));
dest.writeList(f);
}
if (s == null) {
dest.writeByte((byte) (0x00));
} else {
dest.writeByte((byte) (0x01));
dest.writeList(s);
}
}
#SuppressWarnings("unused")
public static final Parcelable.Creator<A> CREATOR = new Parcelable.Creator<A>() {
#Override
public A createFromParcel(Parcel in) {
return new A(in);
}
#Override
public A[] newArray(int size) {
return new A[size];
}
};
}

Java Serialize with Inheritance?

Here is the Goals.java
public abstract class Goals {
private String score;
public Goals(String str) {
this.score = str;
}
String getGoals() {
return this.score;
}
void doSomething(score) {
}
}
Here is the Game.java
public class Game implements Serializable {
public String name;
public int game_num;
public int opp;
public int player;
public Goals goal;
public Game(int i, int i2, int i3) {
this.player = i;
this.game_num = i2;
this.opp = i3;
}
public Game(String str, Goals goal) {
this.name = str;
this.goal = goal;
}
}
Can we create a Serialized Object in a way that after it is deserialized and casted to Game , it will set score inside Goals.java ?
Also, can you manipulate / overwrite doSomething method if the serialized data comes from untrusted source?

In the way you are trying to manipulates your objects, I think you can do that Goals implements Serializable, and Game implements Goals:
public abstract class Goals implements Serializable{
private String score;
public Goals(String str) {
this.score = str;
}
String getGoals() {
return this.score;
}
void doSomething(score) {
}
}
for Game
public class Game extends Goals {
public String name;
public int game_num;
public int opp;
public int player;
public Game(int i, int i2, int i3) {
this.player = i;
this.game_num = i2;
this.opp = i3;
}
public Game(String str) {
//create constructor also including the properties of Goals
Super()...
}
}

As mentioned in comments, implement Goals and its implementation with Serializable and also implement default constructor in both the classes .
Working piece of code:
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
abstract class Goals implements Serializable{
private String score;
public Goals() {
this(null);
}
public Goals(String str) {
this.score = str;
}
String getGoals() {
return this.score;
}
void doSomething(int score) {
}
}
class Game implements Serializable {
public String name;
public int game_num;
public int opp;
public int player;
public Goals goal;
public Game(int i, int i2, int i3) {
this.player = i;
this.game_num = i2;
this.opp = i3;
}
public Game(String str, Goals goal) {
this.name = str;
this.goal = goal;
}
}
class GoalImpl extends Goals implements Serializable{
public GoalImpl() {
}
public GoalImpl(String str) {
super(str);
}
}
public class Main{
public static void main(String...s) {
Goals goal = new GoalImpl("20");
Game game = new Game("name",goal);
try
{
//Saving of object in a file
FileOutputStream file = new FileOutputStream("gamefile.ser");
ObjectOutputStream out = new ObjectOutputStream(file);
// Method for serialization of object
out.writeObject(game);
out.close();
file.close();
System.out.println("Object has been serialized");
}
catch(IOException ex)
{
ex.printStackTrace();
System.out.println("IOException is caught");
}
Game object1 = null;
// Deserialization
try
{
// Reading the object from a file
FileInputStream file = new FileInputStream("gamefile.ser");
ObjectInputStream in = new ObjectInputStream(file);
// Method for deserialization of object
object1 = (Game)in.readObject();
in.close();
file.close();
System.out.println("Object has been deserialized ");
System.out.println("score = " + object1.goal.getGoals());
}
catch(IOException ex)
{
ex.printStackTrace();
System.out.println("IOException is caught");
}
catch(ClassNotFoundException ex)
{
System.out.println("ClassNotFoundException is caught");
}
}
}
Output:
Object has been serialized
Object has been deserialized
score = 20
PS:
An advice to make score as integer as otherwise you will not be able to do basic operations like increase score or decrease score using inbuilt operators (+ , - )
Always place proper getter setter name like getScore() and setScore int this case.
Do try to make constructors in sync, for example in case of Game constructor with player id, game num and opposition is called, Game name and Goals will never be initialized, better to initialize them with default value or other good option is make another constructor accepting all parameters and then from individual constructos you can call master constructor and pass default values for those which are not passed by the calling method.

Java Game - Pick up Item and Look around Function

I have been creating a java text game but I am stuck trying to figure out on how to implement the last 2 methods. I want it to print out the items in the room and the name of the npc thats in the room (A sort of a Look function). I am not sure on how to go on about it. Any help would be appriciated.
Room[] place = new Room[]{station, UC, Ollies, lounge, palace, AT301};
Sword sword = new Sword();
Thing heal = new HealthPotion();
Thing armour = new Armour();
Thing trap = new Trap();
and for the NPC (Mike, Jake, Evil, Carl)
public abstract class Player{
//abstract attributes
private String name;
private int currentHealth;
private int maxHealth;
private int damage;
private Room currentRoom;
private int stack;
private int effect;
//Constructor for player
public Player(String name, int currentHealth, int maxHealth, int damage, int effect, int stack){
this.name = name;
this.currentHealth = currentHealth;
this.maxHealth = maxHealth;
this.damage = damage;
this.effect = effect;
this.stack = stack;
}
//getters
public String getName(){ return name;}
public int getCurrentHealth(){ return currentHealth;}
public int getMaxHealth(){ return maxHealth;}
public int getDamage(){ return damage;}
public Room getCurrentRoom(){ return currentRoom;}
public int getEffect(){ return effect;}
public int getStack(){ return stack;}
//setters
public void setCurrentHealth(int currentHealth){this.currentHealth = currentHealth;}
public void setMaxHealth(int maxHealth){this.maxHealth = maxHealth;}
public void setDamage(int damage){ this.damage = damage;}
public void setCurrentRoom(Room room){this.currentRoom = room;}
public void setEffect(int effect){ this.effect = effect;}
public void setStack(int stack){ this.stack = stack;}
public void enter(Room room){ this.currentRoom = room;}
//abstract method because each player has a different attack;
public void takeDamage(int damage){ setCurrentHealth(this.currentHealth-damage);}
public boolean isDead(){
if(this.currentHealth<=0){ return true;}
return false;
}
}
I was able to make everything functional except the Look function for the player. I can't figure out how to go on about it.

Room is a vector of items right ? If so you can do a function on the player class that when it is called it goes to the vector of the room you're in and simply print out the items that are in the vector, something like this:
String lookAround(){
ArrayList temp = (ArrayList)getCurrentRoom(); //returns the array containing the items in the current room
for(Thing i : temp){
i.getDescription(); //Method present in all classes that come from Thing that prints out the name of the item and/or its caracheteristics
}
}
In the array of the room you should try to include the name of all players in the room including yourself so that you can print out everyone present in the room
Hope this helps

I would recommend you first of all creating a class Npc with attribute name and add it to the room.