Java ArrayList Contains()方法不起作用

Question

我毫不怀疑 contains() 方法工作正常，但显然我做错了什么。我正在开发一个 android 应用程序，我正在检测 WiFi 并将 WiFi 列在 listView 中。我试图过滤掉重复出现的同一接入点，因此我创建了一个数组来跟踪重复项。这是我的代码:

public void getWifi(){

    ListView wifiList = (ListView)findViewById(R.id.listView);

    WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
    List<ScanResult> apList = wifiManager.getScanResults();
    wifiManager.startScan();

    List<String> wifees = new ArrayList<>();

    //split info into arrays
    for(int i=0; i < apList.size(); i++){

        String[] daList = String.valueOf(apList.get(i)).split(",");

        String info = "";
        List<String> SSIDs = new ArrayList<>();

        for (String listItem : daList) {
            String topic = String.valueOf(listItem.split(":")[0]);
            String val = listItem.split(":")[1];
            Log.d(TAG, topic);
            if (Objects.equals(topic, "SSID")) {
                if(SSIDs.contains(val)){
                    Log.d(TAG, "CONTAINS");
                    break;
                } else {
                    SSIDs.add(val);
                    info = val;
                }
            } else if (Objects.equals(topic, " level")){
                String strength = "";
                if (Integer.parseInt(val.substring(1)) >= -35) {
                    strength = "100%";
                } else if (Integer.parseInt(val.substring(1)) <= -35 && Integer.parseInt(val.substring(1)) >= -65) {
                    strength = "50%";
                } else {
                    strength = "1%";
                }
                info += "   " + strength;
            }
        }
        wifees.add(info);
    }

    assert wifiList != null;
    ArrayAdapter apter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, wifees);
    wifiList.setAdapter(apter);
}

这是 apList 项的内容，或者我调用 apList.get(i) 时得到的内容:

SSID: SCHOOL-GUEST, BSSID: 04:04:04:04:04:04, capabilities: [ESS], level: -91, frequency: 2412, timestamp: 72500687089, distance: ?(cm), distanceSd: ?(cm), passpoint: no, ChannelBandwidth: 0, centerFreq0: 0, centerFreq1: 0, 80211mcResponder: is not supported

这是该代码的输出(大致是因为它在手机上，出于安全原因我不想包含 AP 名称):

SCHOOL-WIRELESS        100%
SCHOOL-SECURE        50%
SCHOOL-GUEST        50%
SCHOOL WIRELESS        1%
SCHOOL_WIRELESS        1%
SCHOOL-SECURE        1%
SCHOOL-GUEST        1%
bxz1872         50%
...
...
...
(so on and so forth)

如果我能得到第二个意见就好了。我觉得我错过了一些明显的东西。谢谢!

Answer 1

.contains不起作用，因为你调用List<String> SSIDs = new ArrayList<>();在 for(int i=0; i < apList.size(); i++){ 内.您基本上为每个循环迭代创建新的空列表。您应该在外部 for 循环之前调用它一次:

List<String> SSIDs = new ArrayList<>();
for(int i=0; i < apList.size(); i++){
    ...
}