Android Parcelable 和继承

Question

我有一个类 Drills 和几个扩展它的类，例如 AddDrill。我希望能够在 Activity 之间传递这个 Drill 对象“系列”，所以我正在使用 Parcelable。我找到了 this回答和this例如，我创建了这个 Drill 和 AddDrill 类，我想我做错了什么，我的实现中的每件事都很好吗？钻:

package com.simplemathgame;

import android.os.Parcel;
import android.os.Parcelable;

public abstract class Drill implements Parcelable{
    protected int firstNumber;
    protected int secondNumber;
    protected int answer;
    protected int userAnswer;
    protected String userAnswerString;
    protected String symbol;
    protected int minBound, maxBound;
    protected int drillNumber;

    public String getUserAnswerString() {
        return userAnswerString;
    }

    public void setUserAnswerString(String userAnswerString) {
        this.userAnswerString = userAnswerString;
    }

    Drill(int min, int max){
        minBound = min;
        maxBound = max;
        answer = answerCalculatetion();
        userAnswerString = "";
    }

    public Drill(Parcel in) {
        readFromParcel(in);
    }

    public int getDrillNumber() {
        return drillNumber;
    }

    public void setDrillNumber(int drillNumber) {
        this.drillNumber = drillNumber;
    }

    public int getUserAnswer() {
        return userAnswer;
    }

    public void setUserAnswer(int userAnswer) {
        this.userAnswer = userAnswer;
    }

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }

    public int getMinBound() {
        return minBound;
    }

    public void setMinBound(int minBound) {
        this.minBound = minBound;
    }

    public int getMaxBound() {
        return maxBound;
    }

    public void setMaxBound(int maxBound) {
        this.maxBound = maxBound;
    }

    //getters and setters
    public int getFirstNumber() {
        return firstNumber;
    }
    public void setFirstNumber(int firstNumber) {
        this.firstNumber = firstNumber;
    }
    public int getSecondNumber() {
        return secondNumber;
    }
    public void setSecondNumber(int secondNumber) {
        this.secondNumber = secondNumber;
    }
    public int getAnswer() {
        return answer;
    }
    public void setAnswer(int answer) {
        this.answer = answer;
    }

    protected int getRandomNumber(int high, int low){
        return (int) ((Math.random( ) * (high - low + 1)) + low);  
    }

    protected abstract int answerCalculatetion();

    protected String printDrill(){
        String FirstNumberS;
        String SecondNumberS;

        if(this.getFirstNumber() < 0){
            FirstNumberS = "(" + this.getFirstNumber() + ")";
        }
        else{
            FirstNumberS = "" + this.getFirstNumber();
        }

        if(this.getSecondNumber() < 0){
            SecondNumberS = "(" + this.getSecondNumber() + ")";
        }
        else{
            SecondNumberS = "" + this.getSecondNumber();
        }

        return (FirstNumberS + " " + this.getSymbol() + " " + SecondNumberS + " " + "="); 
    }

    protected String printDrillAnswer(){
        String FirstNumberS;
        String SecondNumberS;
        String answerS;

        if(this.getAnswer() < 0){
            answerS = "(" + this.getAnswer() + ")";
        }
        else{
            answerS = "" + this.getAnswer();
        }

        if(this.getFirstNumber() < 0){
            FirstNumberS = "(" + this.getFirstNumber() + ")";
        }
        else{
            FirstNumberS = "" + this.getFirstNumber();
        }

        if(this.getSecondNumber() < 0){
            SecondNumberS = "(" + this.getSecondNumber() + ")";
        }
        else{
            SecondNumberS = "" + this.getSecondNumber();
        }

        return (FirstNumberS + " " + this.getSymbol() + " " + SecondNumberS + " " + "=" + " " + answerS); 
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {

        // We just need to write each field into the
        // parcel. When we read from parcel, they
        // will come back in the same order
        dest.writeInt(firstNumber);
        dest.writeInt(secondNumber);
        dest.writeInt(answer);
        dest.writeInt(userAnswer);
        dest.writeString(userAnswerString);
        dest.writeString(symbol);
        dest.writeInt(minBound);
        dest.writeInt(maxBound);
        dest.writeInt(drillNumber);
    }

    /**
     *
     * Called from the constructor to create this
     * object from a parcel.
     *
     * @param in parcel from which to re-create object
     */
    protected void readFromParcel(Parcel in) {

        // We just need to read back each
        // field in the order that it was
        // written to the parcel

        firstNumber = in.readInt();
        secondNumber = in.readInt();
        answer = in.readInt();
        userAnswer = in.readInt();
        userAnswerString = in.readString();
        symbol = in.readString();
        minBound = in.readInt();
        maxBound = in.readInt();
    }

}

添加钻头:

package com.simplemathgame;

import android.os.Parcel;
import android.os.Parcelable;

public class AddDrill extends Drill {

    AddDrill(int min, int max) {
        super(min, max);
        symbol = "+";
        firstNumber = getRandomNumber(min, max);
        secondNumber = getRandomNumber(min, max);
        answer = answerCalculatetion();
    }

    private AddDrill(Parcel in) {
        super(in);
    }

    protected int answerCalculatetion() {
        return (this.getFirstNumber() + this.getSecondNumber());
    }

    public static final Parcelable.Creator<AddDrill> CREATOR = new Parcelable.Creator<AddDrill>() {
        public AddDrill createFromParcel(Parcel in) {
            return new AddDrill(in);
        }

        public AddDrill[] newArray(int size) {
            return new AddDrill[size];
        }
    };

    @Override
    public int describeContents() {
        // TODO Auto-generated method stub
        return 0;
    }
}

谢谢

Answer 1

在您的 AddDrill 类中，您需要实现 writeToParcel() 方法以及来自 Parcel 的构造函数。您可能还需要对这两种方法都使用 @Override，但您需要进行试验以找出最终解决方案