Question

我从这个链接获得了解析器的代码。

http://www.warriorpoint.com/blog/2009/07/19/android-simplified-source-code-for-parsing-and-working-with-xml-data-and-web-services-in-android/

我收到了java.lang.NullPointerException

java.util.Calendar.setTime(Calendar.java:1284)

java.text.SimpleDateFormat.formatImpl(SimpleDateFormat.java:730)

java.text.SimpleDateFormat.format(SimpleDateFormat.java:1011)

java.text.DateFormat.format(DateFormat.java:384)

org.example.reader.Message.getDate(Message.java:46) .... Line 46 is return FORMATTER.format(this.date);

org.example.reader.Message.toString(Message.java:77)... Line 77 is sb.append(this.getDate());

java.lang.StringBuilder.append(StringBuilder.java:203)

任何人都可以帮我解决这个问题......谢谢..

import java.net.MalformedURLException;
import java.net.URL;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class Message implements Comparable<Message>{
    static SimpleDateFormat FORMATTER = 
        new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss Z");
    private String title;
    private URL link;
    private String description;
    private Date date;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title.trim();
    }
    // getters and setters omitted for brevity 
    public URL getLink() {
        return link;
    }

    public void setLink(String link) {
        try {
            this.link = new URL(link);
        } catch (MalformedURLException e) {
            throw new RuntimeException(e);
        }
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description.trim();
    }

    public String getDate() {
        return FORMATTER.format(this.date);
    }

    public void setDate(String date) {
        // pad the date if necessary
        while (!date.endsWith("00")){
            date += "0";
        }
        try {
            this.date = FORMATTER.parse(date.trim());
        } catch (ParseException e) {
            throw new RuntimeException(e);
        }
    }

    public Message copy(){
        Message copy = new Message();
        copy.title = title;
        copy.link = link;
        copy.description = description;
        copy.date = date;
        return copy;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Title: ");
        sb.append(title);
        sb.append('\n');
        sb.append("Date: ");
        sb.append(this.getDate());
        sb.append('\n');
        sb.append("Link: ");
        sb.append(link);
        sb.append('\n');
        sb.append("Description: ");
        sb.append(description);
        return sb.toString();
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((date == null) ? 0 : date.hashCode());
        result = prime * result
                + ((description == null) ? 0 : description.hashCode());
        result = prime * result + ((link == null) ? 0 : link.hashCode());
        result = prime * result + ((title == null) ? 0 : title.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Message other = (Message) obj;
        if (date == null) {
            if (other.date != null)
                return false;
        } else if (!date.equals(other.date))
            return false;
        if (description == null) {
            if (other.description != null)
                return false;
        } else if (!description.equals(other.description))
            return false;
        if (link == null) {
            if (other.link != null)
                return false;
        } else if (!link.equals(other.link))
            return false;
        if (title == null) {
            if (other.title != null)
                return false;
        } else if (!title.equals(other.title))
            return false;
        return true;
    }

    public int compareTo(Message another) {
        if (another == null) return 1;
        // sort descending, most recent first
        return another.date.compareTo(date);
    }
}

Answer 1

尝试初始化日期。您将获得空指针异常，因为date的值为null。

任何正文都可以帮我修复空指针错误

1 个答案: