我正在为安卓制作一个应用程序。我试图猜测用户刚刚在木琴上播放的歌曲。我有:private List<String> mDespacito = new ArrayList<String>(Arrays.asList("f", "a","d","d"));
和private List<String> mPlayed = new ArrayList<String>();
当用户按下木琴上的一个键时,我将他按下的键添加到 mPlay 数组列表中,如下所示:
public void playD(View v){
Log.d("Xylophone", "Played D!");
mSoundPool.play(mDSoundId,LEFT_VOLUME,RIGHT_VOLUME,PRIORITY,NO_LOOP,NORMAL_PLAY_RATE);
mPlayed.add("d");
CheckForSong();
}
现在,CheckForSong包含:
public void CheckForSong(){
if (mPlayed.containsAll(mDespacito)){
Log.d("Xylophone","You just played despacito");
mPlayed.removeAll(mDespacito);
}
}
所以,它应该做:
played F
played A
played D
played D
You just played despacito
但它确实:
played F
played A
played D
You just played despacito
played D
您甚至可以做到:
played F
played G
played A
played G
played D
You just played despacito
我知道为什么:因为if (mPlayed.containsAll(mDespacito))
只是检查mDespacito的元素是否在mPlayed中。但是我需要检查是否有mDespacito的所有元素(包括那些存在两次的元素)以及它们是否顺序正确。有没有我可以使用的命令?谢谢
Collections.indexOfSubList
就是答案。我是这样使用它的:
public void CheckForSong(){
int contains = Collections.indexOfSubList(mPlayed, mDespacito);
if (contains != -1){
Log.d("Xylophone","You just played despacito");
mPlayed.removeAll(mDespacito);
}
}
关于Collections.indexOfSubList
的更多信息:https://www.tutorialspoint.com/java/util/collections_indexofsublist.htm
使用
mPlayed.equals(mDespacito);
相反,将按顺序和元素检查元素。
重要说明:如果您没有按照代码演示使用字符串,则需要在添加到列表中的类中实现 hashCode 和 equals。
以下代码片段导致显示 true 两次,然后显示 false
import java.util.ArrayList;
public class MyClass {
public static void main(String args[]) {
ArrayList<String> a = new ArrayList();
a.add("f");
a.add("a");
a.add("d");
a.add("d");
ArrayList<String> b = new ArrayList();
b.add("f");
b.add("a");
b.add("d");
b.add("d");
System.out.println(a.equals(b));
System.out.println(b.equals(a));
b.add("c");
System.out.println(a.equals(b));
}
}
否则:您可以自己比较列表:
public boolean equals(List f, List s) {
if(f.size() != s.size())
return false;
for(int i = 0; i < f.size(); i++)
if(!f.get(i).equals(s.get(i))
return false;
}
但请记住提示,如果您不使用原语或字符串,则需要在对象上实现哈希代码和等于。
list1.equals(list2)
下面的链接给出了一个非常好的解释。请找到。
https://stackoverflow.com/a/1075699/4994582