如何將對象中的 Arraylist 用於另一個類中的方法

Question

我的程序應該從用戶那里獲取單詞和定義，並像閃存卡一樣顯示它們。 我已經把所有的詞整理成類等等，現在我需要做的就是讓它在我的應用程序按下按鈕時，控制器類將執行一個方法，該方法將通過 Card 類的數組列表並顯示單詞並最終顯示定義。

我的問題是我有一個包含所有卡片的 reader 類的對象，我希望能夠在 getWordClick 方法中調用隨機卡片。 我不知道如何在另一個類中使用該對象。

public class Main extends Application{


@Override
public void start(Stage primaryStage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("Scene.fxml"));
    primaryStage.setTitle("FlashCards");

    Scene scene = new Scene(root, 600, 400, Color.GREY);
    primaryStage.setScene(scene);
    primaryStage.show();
}


public static void main (String[] args){

    Reader r = new Reader();

    //Initialises the Arraylist and reads the file adding them to arraylist
    ArrayList<String> wordList = r.getWordList();
    r.OpenFile();
    r.readFile(wordList);
    r.closeFile();

    //Initialises the Definitions Arraylist and reads the file adding them
    ArrayList<String> definitionList = r.getDefinitionsList();
    r.OpenFile();
    r.readFile(definitionList);
    r.closeFile();

    /* IGNORE IS FOR TESTING PURPOSES
    //Wordlist is printed
    for (String i : wordList){
        System.out.println(i);
    }

    //Definitions list is printed
    for (String i : definitionList){
        System.out.println(i);
    } */

    //Card for each word and def is made
    ArrayList<Card> c = r.getCardList();
    Main m = new Main();
    r.cardSetter(m.addTerms(c, wordList.size(), wordList, definitionList));


    //Loops through and displays the word and defs
    for (Card i : c){
        System.out.printf("%s : %s\n",i.dispWord(),i.dispDef());
    }

    //Displays the window
    launch(args);
}

public ArrayList<Card> addTerms(ArrayList<Card> c, int q, ArrayList<String> word, ArrayList<String> def){
    for (int i = 0; i<q; i++){
        c.add(new Card(word,def,i));
    }
    return c;
}

}

這是讀者類

public class Reader {

private Scanner x;
private Scanner sc;

//ArrayList to store the words
private ArrayList<String> wordList = new ArrayList<>();
//ArrayList to store the definitions
private ArrayList<String> definitionsList = new ArrayList<>();
//ArrayList to store the cards
private ArrayList<Card> cardList = new ArrayList<>();


//Simple scanner collects user input
public String getFileName(){
    sc = new Scanner(System.in);
    return sc.nextLine();
}

//Method to open the file and throw an exception if failed
public void OpenFile(){
    try{
        x = new Scanner(new File(getFileName()));
    }
    catch (Exception e){
        System.out.println("could not find file");
    }
}

//Assigns each line to a Array
public void readFile(ArrayList<String> e){
    while(x.hasNext()){
        e.add(x.nextLine());
    }
}

//Closes file
public void closeFile(){
    x.close();
}

//Returns the wordlist
public ArrayList<String> getWordList(){
    return wordList;
}

//Returns Definitionlist
public ArrayList<String> getDefinitionsList(){
    return definitionsList;
}

//Returns cardList
public ArrayList<Card> getCardList(){
    return cardList;
}

public void cardSetter(ArrayList<Card> c){
    c = cardList;
}
}

這是卡片類

public class Card {

private String word;
private String definition;

public Card(ArrayList<String> Word,ArrayList<String> Definition, int i){
    word = Word.get(i);
    definition = Definition.get(i);
}

public String dispWord(){
    return word;
}

public String dispDef(){
    return definition;
}

}

最后這里是控制器

public class Controller {

Random rand = new Random();
private int Random;
//Makes the rand instance variable int so that the def class can use it

public Button wordBox;
public Label defBox;

public void getWordClick(){

}

public void goExit(){

}

public void goRand(){

}

public void getDefClick(){


}

public void goNext(){

}

public void goPrev(){

}

}

抱歉，我知道它很長，但代碼僅供參考，我主要關心的是如何從Reader r獲取ArrayList<Card>以便我可以在getWordClick()方法的控制器中使用它。 從字面上看，任何幫助都值得贊賞，我只需要有人在我陷入困境時將我推向正確的方向。

更新：我現在編輯了控制器類，所以它看起來像這個公共類 Controller {

Random rand = new Random();
private int Random;
//Makes the rand instance variable int so that the def class can use it

public Button wordBox;
public Label defBox;


private Reader mReader = null;

public Controller(Reader reader){
    this.mReader = reader;
}

public Reader getReader(){
    return this.mReader;
}

public void getWordClick(){
    getReader();
}

public void goExit(){

}

public void goRand(){

}

public void getDefClick(){


}

public void goNext(){

}

public void goPrev(){

}

}

但現在的問題是，當 fxml 文件運行並查找控制器時，它將如何自己創建對象或使用我創建的對象，因為我創建了一個對象，在其中添加了讀取器作為構造函數。 但是我不知道 fxml 文件將如何使用它進行事件處理。

Answer 1

好吧，我看到了一個簡單的方法，雖然我不知道它的內存效率如何：

在您的控制器類中聲明

private Reader mReader = null;

並添加一個構造函數

public Controller(Reader reader)
{
     this.mReader = reader;
}
public Reader getReader()
{
     return this.mReader;
}

所以你聲明 Controller 類的不同之處在於你將讀取器對象的引用傳遞給該類的引用。 這是一個稱為封裝的概念。

編輯：

可以提供構造函數的類是強大的工具。 多態性等是深入研究的主題，在開發方面有很多實際應用。 我也打算推薦鏈接來查看，但我需要自己做更多的研究：p

一個多態性java的快速谷歌會給你足夠的surknowledge！

EDIT2 代碼重述：

讀者

public class Reader {

private Scanner x;
private Scanner sc;

//ArrayList to store the words
private ArrayList<String> readContent = new ArrayList<>();
private String filename = "";

public Reader()
{
    //if every time I want a new reader, I want to read user input
    //this.filename = readUserInput();
    //If I want to read indefinitely which I will do for now
    readIndefinitely();
}

//This will continuously read until the user enters a valid file name
public void readIndefinitely()
{
    while (!OpenFile())
    {
        filename = readUserInput();
    }
}
public Reader(String fileIWantToRead)
{
    this.filename = fileIWantToRead;
}

public String readUserInput()
{
    if (sc != null)
    {
       sc.close();
       sc = null;
    }
    sc = new Scanner(System.in);
    return sc.nextLine();
}
//Simple scanner collects user input
public String getFileName(){
    return filename;
}

//Method to open the file and throw an exception if failed
public boolean OpenFile(){
    try{
        //assume we already know the filename
        x = new Scanner(new File(filename));
    }
    catch (Exception e){
        System.out.println("could not find file");
        return false;
    }
    return true;
}

//Assigns each line to a Array
public ArrayList<String> readFile(){
OpenFile();
try
{
    readContent.clear();
    while(x.hasNext()){
        readContent.add(x.nextLine());
    }
}
catch(Exception e)
{
    e.printStackTrace();
}
closeFile();
return readContent;
}

//Closes file
public void closeFile(){
    x.close();
}
public String getReadContent()
{
   return readContent;
}
public void clearReadContent()
{
   readContent.clear();
}
} //end class

卡片類

public class Card {
    private String word;
    private String definition;

    public Card(String word, String definition){
        this.word = word;
        this.definition = definition
    }

    public String getWord(){
        return word;
    }

    public String getDefinition(){
    return definition;
    }

}

主類

public class Main extends Application{

    private ArrayList<Card> mCards = new ArrayList<>();
    public Main(ArrayList<Card> cards)
    {
        this.mCards = cards;
        //do what is required to get the cards to the controller either here or start
    }

    @Override
public void start(Stage primaryStage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("Scene.fxml"));
    primaryStage.setTitle("FlashCards");

    Scene scene = new Scene(root, 600, 400, Color.GREY);
    primaryStage.setScene(scene);
    primaryStage.show();
}

    public static void main (String[] args){

        Reader wordReader = new Reader();
        Reader definitionReader = new Reader();
        wordReader.readFile();
        definitionReader.readFile();

        /* IGNORE IS FOR TESTING PURPOSES
        //Wordlist is printed
        for (String i : wordList){
            System.out.println(i);
        }

        //Definitions list is printed
        for (String i : definitionList){
            System.out.println(i);
        } */

        //if we know that both the words and definitions are the same size, we can make cards
        ArrayList<Card> c = makeCards(wordReader.getReadContent(), definitionReader.getReadContent());
    //Loops through and displays the word and defs
        for (Card i : c){
            System.out.printf("%s : %s\n",i.dispWord(),i.dispDef());
        }

        Main m = new Main(c);
    //Displays the window
        //Not sure how FXMLLoader and this functions as I don't work too much with java but if you pass a reference to main in you'd be good to go
        launch(args);
    }

public ArrayList<Card> makeCards(ArrayList<String> word, ArrayList<String> def){
    ArrayList<Card> cards = new ArrayList<>();
    for (int i = 0; i<word.size(); i++){
        c.add(new Card(word.get(i),def.get(i)));
    }
    return c;
}
}

控制器：

public class Controller {
    Random rand = new Random();
    private int Random;
    //Makes the rand instance variable int so that the def class can use it
    private int position = 0;
    public Button wordBox;
    public Label defBox;
    //instead of passing in an entire reader we just pass in cards (oops!)
    private ArrayList<Card> mCards = new ArrayList<>();

    public Controller(ArrayList<Card> cards){
        this.mCards = cards;
    }

    public ArrayList<Card> getCards()
    {
        return this.mCards;
    }

    public void goExit(){
        //Exit program
    }

    public void goRand(){
        //nextInt in range is ((max - min) + 1) + min and we want a position that corresponds from 0 to the size of cards

        position = rand.nextInt(cards.size());
        wordBox.setText(cards.get(position).getWord());
        defBox.setText(cards.get(position).getDefinition());
    }

    public void getDefClick(){
        //Call to either cards.get(position).getDefinition() or defBox.getText().toString()

    }

    public void goNext(){
        //because retrieving from cards starts at index 0 the equivalent position will require a +1 and we are looking for the next
        if (cards.size() < position+2)
        {
            position++;
            wordBox.setText(cards.get(position).getWord();
            defBox.setText(cards.get(position).getDefinition();
        }
    }

    public void goPrev(){
        //same concept as above but assume that position is already an acceptable value
        if (position != 0 && !cards.isEmpty())
        {
            position--;
            wordBox.setText(cards.get(position).getWord());
            defBox.setText(cards.get(position).getDefinition());
        }
    }
}

Answer 2

在我看來，您只需要對面向對象的設計概念進行更多練習即可。

讓我們從邏輯上看這個問題。 您有一個Controller類，它用作控制Card列表視圖的一種方式。 這里明顯的問題是您的Controller實際上缺少要控制的Card列表，因此，您應該將其添加到類中。

public class Controller {
    // The list of Cards that are being controlled.
    private ArrayList<Card> cards;

    ...
}

現在這只是增加了Controller的抽象概念。 顯然，我們需要一種方法來指定Controller應該使用哪個Card列表。 因此，我們應該創建一個構造函數。

public class Controller {
    // The list of Cards that are being controlled.
    private ArrayList<Card> cards;

    ...

    // A list of cards must be specified when creating a Controller instance.
    public Controller(ArrayList<Card> cards) {
        this.cards = cards;
    }

    ...
}

另外，您也可以使用賦值函數方法（也就是一組之三法）來設置的使用被稱為半導體封裝的概念卡的列表，如KoalaKoalified提及。

public class Controller {
    // The list of Cards that are being controlled.
    private ArrayList<Card> cards;

    ...

    // Specify a list of cards.
    public void setCards(ArrayList<Card> cards) {
        this.cards = cards;
    }

    ...
}

所以現在，在 Main 中，或者在任何您創建Controller實例的地方，您可以這樣做：

Controller controller = new Controller(r.getCardList());

或者，如果您更喜歡使用 mutator 方法，請執行以下操作：

Controller controller = new Controller();
controller.setCards(r.getCardList());

現在，你的Controller類可以參考清單Card S IN每個方法，如果你有一些其他來源它可能重新使用該設備的清單Cards秒。

我強烈建議對面向對象設計 (OOD) 進行更多研究。 Java 在很大程度上依賴於這種類型的設計。 您的程序中似乎有一些零碎的東西，但您似乎對某些細節以及可能的大局感到有些困惑。