Question

我是Android新手编码的新手。我被投入到一个项目中并且下面的代码有效，但我并不理解它，这实际上并不能帮助我学习。有人会用每个阶段的做法评论代码吗？

SharedPreferences myPrefs = this.getSharedPreferences("FileName", MODE_PRIVATE);
        TreeMap<String, ?> keys = new TreeMap<String, Object>(myPrefs.getAll());
        for (Map.Entry<String, ?> entry : keys.entrySet()) {
            Log.i("map values", entry.getKey());

        }


      List<Pair<Object, String>> sortedByValue = new LinkedList<Pair<Object,String>>();
        for (Map.Entry<String, ?> entry : keys.entrySet()) {
            Pair<Object, String> e = new Pair<Object, String>(entry.getValue(), entry.getKey());
            sortedByValue.add(e);
        }


     // Pair doesn't have a comparator, so you're going to need to write one.
        Collections.sort(sortedByValue, new Comparator<Pair<Object, String>>() {
            public int compare(Pair<Object, String> lhs, Pair<Object, String> rhs) {

                String sls = String.valueOf(lhs.first);
                String srs = String.valueOf(rhs.first);
                int res = sls.compareTo(srs);
                // Sort on value first, key second
                return res == 0 ? lhs.second.compareTo(rhs.second) : res;
            }
        });

        for (Pair<Object, String> pair : sortedByValue) {
            Log.i("map values", pair.first + "/" + pair.second);
        }


      Collection<?> stringArrayList = keys.values();
      final CharSequence[] prefsCharSequence = stringArrayList.toArray(new CharSequence[stringArrayList.size()]);

Answer 1

SharedPreferences myPrefs = this.getSharedPreferences("FileName", MODE_PRIVATE);
    TreeMap<String, ?> keys = new TreeMap<String, Object>(myPrefs.getAll());
    for (Map.Entry<String, ?> entry : keys.entrySet()) {
        Log.i("map values", entry.getKey());

    }

记录共享首选项文件中的所有键值对。

List<Pair<Object, String>> sortedByValue = new LinkedList<Pair<Object,String>>();
    for (Map.Entry<String, ?> entry : keys.entrySet()) {
        Pair<Object, String> e = new Pair<Object, String>(entry.getValue(), entry.getKey());
        sortedByValue.add(e);
    }

将包含所有设置的地图转换为用于排序的列表

Collections.sort(sortedByValue, new Comparator<Pair<Object, String>>() {
        public int compare(Pair<Object, String> lhs, Pair<Object, String> rhs) {

            String sls = String.valueOf(lhs.first);
            String srs = String.valueOf(rhs.first);
            int res = sls.compareTo(srs);
            // Sort on value first, key second
            return res == 0 ? lhs.second.compareTo(rhs.second) : res;
        }
    });

自定义比较器，用于对Pairs列表进行排序。它比较了这些值。如果它们相等，则比较第二个值。

for (Pair<Object, String> pair : sortedByValue) {
        Log.i("map values", pair.first + "/" + pair.second);
    }

打印已排序的偏好设置。

  Collection<?> stringArrayList = keys.values();
  final CharSequence[] prefsCharSequence = stringArrayList.toArray(new CharSequence[stringArrayList.size()]);

将来自SharedPreferences文件的密钥转换为Collection，然后将其转换为字符串列表。

这个Android / Java代码有什么作用？

1 个答案: