我将如何在 Java/Android 中的对象哈希中正确实现 parcel/parcelable

Question

我有以下课程：实验和测量。我在 Android 活动之间传递一个包含 Experiment 对象的 HashMap 作为值，并将它们的 Experiment.getExperimentName 作为键。

这些 Experiment 对象又包含一个 Measurements 对象的 HashMap。这个 HashMap 有一个 Measurements 对象作为值，它们的 Measurements.getMeasurements 作为键。

这些 Measurements 对象随后包含一个双精度数的 ArrayList。

我尝试了许多使用捆绑包或直接放入包裹的变体，但是当我在新活动中读取 HashMap 时，我不断收到“解组时出现 ClassNotFoundException：nl.bioinf.thema12.labpal.objects.Measurements” .

如何正确实现 parcel/parcelable？

实验课：

package nl.bioinf.thema12.labpal.objects;
import java.util.HashMap;
//import java.util.Set;

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

/**
 * @author roy
 * a class which describes an experiment
 */
public class Experiment implements Parcelable{
    private String experimentName = "";
    private HashMap<String,Measurements> measurements = new HashMap<String,Measurements>();

    //every Experiment needs a name to make it unique
    public Experiment(String experimentName) {
        this.experimentName=experimentName;
    }

    /**
     * a method which adds values to a measurement
     * @param   measurementName the name of the measurement you want to write a value to
     * @param   measurement the value of the measurement you want to add
     * @return  the sequence from the fasta
     */
    public void addValueToMeasurements(String measurementName, double measurement){
        //try to add the measurement
        if(measurements.get(measurementName)== null){
            Measurements m = new Measurements(measurementName);
            m.addMeasurement(measurement);
            measurements.put(measurementName,m);
        }
        //if the measurement does not exist, create it
        else{
            measurements.get(measurementName).addMeasurement(measurement);  
        }
    }
    /**
     * a method which returns the experiment name
     * @return  the experiment name
     */ 
    public String getExperimentName(){
        return experimentName;
    }



    //This makes the object parselable, I don't understand why
    /**
     * a constructor for the parcelable variant of the object
     */     
    public Experiment(Parcel in){
        measurements = new HashMap<String,Measurements>();
        readFromParcel(in);
    }

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

    @Override
    /**
     * a method which writes the objects to a parcel
     */ 
    public void writeToParcel(Parcel dest, int flags) {
        //dest.writeString(experimentName);
        //for(String s: (Set<String>)measurements.keySet()){
            //dest.writeString(s);
            //dest.writeValue(measurements.get(s));
        //}
        Bundle b = new Bundle();
        b.putString("experimentName", experimentName);
        b.putSerializable("measurements", measurements);
        dest.writeBundle(b);
    }

    /**
     * a method which reads from a parcel
     */ 
    public void readFromParcel(Parcel in){
        //experimentName = in.readString();
        Bundle b = in.readBundle();
        experimentName = b.getString("experimentName");
        measurements = (HashMap<String, Measurements>)b.getSerializable("measurements");
    }

    /**
     * generic parcelable creator method
     */ 
    public static final Parcelable.Creator CREATOR =
        new Parcelable.Creator() {
            public Experiment createFromParcel(Parcel in) {
                return new Experiment(in);
            }

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


}

测量类

package nl.bioinf.thema12.labpal.objects;

import java.util.ArrayList;

import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
/**
 * @author roy
 * a class which describes a group of measurements
 */

public class Measurements implements Parcelable{
    private ArrayList<Double> measurements;
    private String measurementName;

    //each measurement has at least a name and an empty list of measurements
    public Measurements(String measurementName) {
        this.measurementName=measurementName;
        measurements = new ArrayList<Double>();
    }

    /**
     * a method which adds a measurement to an ArrayList of measurements
     * @param   measurement a measurement to add to the ArrayList
     */
    public void addMeasurement(double measurement){
        measurements.add(measurement);
        System.out.println("added a measurement");
    }

    /**
     * a method which returns the measurement name
     * @return  the measurement name
     */
    public String getMeasurementName(){
        return measurementName;
    }

    /**
     * a method which returns an ArrayList of the values in the measurement
     * @return  the values of the measurements in an ArrayList
     */
    public ArrayList<Double> getMeasurements(){
        return measurements;
    }

    //This makes the object parselable, I don't understand why
    /**
     * a constructor for the parcelable variant of the object
     */     
    public Measurements(Parcel in){
        measurements = new ArrayList<Double>();
        readFromParcel(in);

    }

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

    /**
     * a method which writes the objects to a parcel
     */ 
    @Override
    public void writeToParcel(Parcel dest, int flags) {
        //dest.writeString(measurementName);
        //dest.writeList(measurements);
        Bundle b = new Bundle();
        b.putString("measurementName", measurementName);
        b.putSerializable("measurements", measurements);
    }

    /**
     * a method which reads from a parcel
     */ 
    public void readFromParcel(Parcel in){
        //measurementName = in.readString();
        //measurements = in.readArrayList(Object.class.getClassLoader());
        Bundle b = in.readBundle();
        measurementName = b.getString("measurementName");
        measurements = (ArrayList<Double>)b.getSerializable("measurements");
    }

    /**
     * generic parcelable creator method
     */ 
    public static final Parcelable.Creator CREATOR =
        new Parcelable.Creator() {
            public Measurements createFromParcel(Parcel in) {
                return new Measurements(in);
            }

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

接收包的活动代码

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //get the intent passed by the other activity
    Bundle b = getIntent().getExtras();
    experiment = b.getParcelable("nl.bioinf.thema12.labpal.objects.Experiment");
    setContentView(R.layout.activity_show_table);
}

发送包的活动代码

//setup the table button
        table = (Button)findViewById(R.id.button_activityMain_table);
        table.setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View v){
                try{
                    Intent intentToPassToShowTable = new Intent(MainActivity.this, ShowTable.class);
                    Bundle b = new Bundle();
                    b.putParcelable("nl.bioinf.thema12.labpal.objects.Experiment", experiments.get(experimentName.getSelectedItem().toString()));
                    intentToPassToShowTable.putExtras(b);
                    startActivity(intentToPassToShowTable);
                }
                catch(Exception e){
                    e.printStackTrace();
                }
            }
        });

Answer 1

你好试试这个代码它工作正常

  package com.example.objectsharing;

import java.util.ArrayList;
 import java.util.HashMap;

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

public class Experiment implements Parcelable {
private String experimentName = "";
private HashMap<String, ArrayList<Double>> measurements = new HashMap<String, ArrayList<Double>>();

// every Experiment needs a name to make it unique
public Experiment(String experimentName) {
    this.experimentName = experimentName;
}

/**
 * a method which adds values to a measurement
 * 
 * @param measurementName
 *            the name of the measurement you want to write a value to
 * @param measurement
 *            the value of the measurement you want to add
 * @return the sequence from the fasta
 */
public void addValueToMeasurements(String measurementName,
        double measurement) {
    // try to add the measurement
    if (measurements.get(measurementName) == null) {
        // Measurements m = new Measurements(measurementName);
        ArrayList<Double> _data = new ArrayList<Double>();
        // m.addMeasurement(measurement);
        _data.add(measurement);
        measurements.put(measurementName, _data);
    }
    // if the measurement does not exist, create it
    else {
        measurements.get(measurementName).add(measurement);
    }
}

/**
 * a method which returns the experiment name
 * 
 * @return the experiment name
 */
public String getExperimentName() {
    return experimentName;
}

// This makes the object parselable, I don't understand why
/**
 * a constructor for the parcelable variant of the object
 */
public Experiment(Parcel in) {
    measurements = new HashMap<String, ArrayList<Double>>();
    readFromParcel(in);
}

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

@Override
/**
 * a method which writes the objects to a parcel
 */
public void writeToParcel(Parcel dest, int flags) {
    // dest.writeString(experimentName);
    // for(String s: (Set<String>)measurements.keySet()){
    // dest.writeString(s);
    // dest.writeValue(measurements.get(s));
    // }
    Bundle b = new Bundle();
    b.putString("experimentName", experimentName);
    b.putSerializable("measurements", measurements);
    dest.writeBundle(b);
}

/**
 * a method which reads from a parcel
 */
public void readFromParcel(Parcel in) {
    // experimentName = in.readString();
    Bundle b = in.readBundle();
    experimentName = b.getString("experimentName");
    measurements = (HashMap<String, ArrayList<Double>>) b
            .getSerializable("measurements");
}

/**
 * generic parcelable creator method
 */
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
    public Experiment createFromParcel(Parcel in) {
        return new Experiment(in);
    }

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

}