如何在数组列表上打印 10 个第一个项目答案

【问题标题】：How do I print a 10 first items on a Array List如何在数组列表上打印 10 个第一个项目
【发布时间】：2017-10-04 23:37:24
【问题描述】：

我的 ArrayList 有 100 行，但我只想显示前 10 个条目。也许有人会知道怎么做？

try {
                JSONObject jsonObj = new JSONObject(jsonStr);

                JSONArray devices = jsonObj.getJSONArray("list");

                for (int i = 0; i < devices.length(); i++) {
                    JSONObject c = devices.getJSONObject(i);
                    String id = c.getString("id");
                    String name = c.getString("name");
                    String known = c.getString("known");
                    String description = c.getString("description");
                    String controllerId = c.getString("controllerId");


                    JSONObject frequencySurvey = c.getJSONObject("frequencySurvey");
                    if (frequencySurvey.has("5000")) {
                        JSONObject fivezero = frequencySurvey.getJSONObject("5000");

                        String timestamp = fivezero.getString("timestamp");
                        String clients = fivezero.getString("clients");
                        String enabled = fivezero.getString("enabled");

                        HashMap<String, String> device = new HashMap<>();

                        device.put("id", id);
                        device.put("name", name);
                        device.put("enabled", enabled);
                        device.put("clients", clients);

                        DevicesList.add(device);

                    }
                }
            }

ListAdapter adapter = new SimpleAdapter(Devices_5_0.this, DevicesList,
                R.layout.list_item, new String[]{ "name","clients","enabled"},
                new int[]{R.id.name,R.id.clients, enabled});

        lv.setAdapter(adapter);

创建时：

DevicesList = new ArrayList<>();

全局声明：

    ArrayList<HashMap<String, String>> DevicesList;

我绝对不能提前限制我的清单

【问题讨论】：

标签： android sorting arraylist hashmap

【解决方案1】：

如果您的devices JSONArray 大小大于10，则仅针对first 10 条目解析JSONObject。

试试这个：

       try {
            JSONObject jsonObj = new JSONObject(jsonStr);

            JSONArray devices = jsonObj.getJSONArray("list");

            int limit = devices.length();
            if (limit > 10) 
                limit = 10;

            for (int i = 0; i < limit; i++) {
                JSONObject c = devices.getJSONObject(i);
                String id = c.getString("id");
                String name = c.getString("name");
                String known = c.getString("known");
                String description = c.getString("description");
                String controllerId = c.getString("controllerId");


                JSONObject frequencySurvey = c.getJSONObject("frequencySurvey");
                if (frequencySurvey.has("5000")) {
                    JSONObject fivezero = frequencySurvey.getJSONObject("5000");

                    String timestamp = fivezero.getString("timestamp");
                    String clients = fivezero.getString("clients");
                    String enabled = fivezero.getString("enabled");

                    HashMap<String, String> device = new HashMap<>();

                    device.put("id", id);
                    device.put("name", name);
                    device.put("enabled", enabled);
                    device.put("clients", clients);

                    DevicesList.add(device);

                }
            }
        }

希望对你有帮助~

【讨论】：

【解决方案2】：

你像这样添加一个for循环：

for(int i = 0; i < (yourArray.size() <= 10 ? yourArray.size() : 10); i++){
    //Add to another list, or do something to store these entries
}

//Display them, print them, whatever you need

它最多打印 10 个第一个条目。如果数组的大小

【讨论】：

我建议Math.min(10, yourArray.size()) 稍微提高可读性。