如何在Android或Java中实现比较器以对对象进行排序

Question

让我从以下示例开始：

public void loadList(ArrayList<Calls> list) {
    List<Calls> calls = new ArrayList<Calls>();
    calls.addAll(list);
}

其中Calls是一个简单的类：

public class Calls {
    public long ms;
    public name;     
} 

我想基于ms字段以升序或降序对上面的List<Calls>进行排序。 我遇到了一些Comparator示例，但仍不清楚。

Answer 1

我想这会有所帮助

public void loadList(ArrayList<Calls> list) {
    List<Calls> calls = new ArrayList<Calls>();
    calls.addAll( list );

    // Ascending Order
    Collections.sort(calls, new Comparator<Calls>() {

        @Override
        public int compare(Calls o1, Calls o2) {
            return (int)(o1.ms-o2.ms);
        }
    });
    // Descending Order
    Collections.sort(calls, new Comparator<Calls>() {

        @Override
        public int compare(Calls o1, Calls o2) {
            return (int)(o2.ms-o1.ms);
        }
    });
}

Answer 2

只需通过以下方式实现比较器：

private class CallsComparator implements Comparator<Calls> {

    @Override
    public int compare(Calls calls1, Calls calls2) {
      //Swap calls1 with 2
      return 1;
      //Spap 2 with 1
      return -1;
      // do nothing
      return 0;
    }

  }

当然，您必须使用if-condition替换我的评论：-)

并使用以下命令执行比较器：

  Collections.sort(calls, new CallsComparator());

Answer 3

请参阅以下示例

class CallsComp implements Comparator<Calls>{

    @Override
    public int compare(Calls c1, Calls c2) {
        if(c1.getMs() < c2.getMs()){
            return 1;
        } else {
            return -1;
        }
    }
}

Answer 4

class MSComaparator implements Comparator<Calls>{

        @Override
        public int compare(Calls lhs, Calls rhs) {
            // TODO Auto-generated method stub
            return lhs.ms-rhs.ms;
        }

    }

    class NameComaparator implements Comparator<Calls>{

        @Override
        public int compare(Calls lhs, Calls rhs) {
            // TODO Auto-generated method stub
            return lhs.name.comapreTo(rhs.name);
        }

    }

并致电：

public void loadList(ArrayList<Calls> list) {
    List<Calls> calls = new ArrayList<Calls>();
    calls.addAll(list);
    Collections.sort(calls,new MSComaparator())
}

如果您只想基于ns进行排序，则可以简单地实现Comparable：

public class Calls implements Comparable<Calls>{
    public long ms;
    public name;     
    @Override
        public int compareTo(Calls  another) {
            // TODO Auto-generated method stub
            return this.ms>another.ms;
        }
} 

并致电：

public void loadList(ArrayList<Calls> list) {
    List<Calls> calls = new ArrayList<Calls>();
    calls.addAll(list);
    Collections.sort(calls)
}

Answer 5

Calls类需要实现Comparable接口并实现compareTo方法：

public class Calls implements Comparable<Calls> {
   public long ms;
   public name;

   @Override
   public int compareTo(Calls call) {
       // Prepend a -1 for inverse order
       return Long.compare(this.ms,call.ms);
   }
} 

然后，只需调用Collections.sort(calls)对列表进行排序即可。

Answer 6

@ARP

我知道回答这个问题为时已晚，但是我最近在我的项目中实现了同样的事情，所以我想与你分享

所以在添加列表后在function内部您可以做的是

public void loadList(ArrayList<Calls> list) {
    List<Calls> calls = new ArrayList<Calls>();
    calls.addAll(list);
    Collections.sort(calls, new Comparator<Calls>() {
                @Override
                public int compare(Calls o, Calls t1) {
                    return (int) (o.getMS() - t1.getMS());
                }
            });
}

这将根据ms存在的值为您排序ArrayList<Calls>调用。