字符串数组列表成一个逗号分隔的字符串 [英] Arraylist of strings into one comma separated string

问题描述

尝试将字符串数组列表转换为一个用逗号分隔的大字符串.

Trying to convert a Arraylist of strings into one big comma separated string.

但是，当我使用

String joined = TextUtils.join(", ", participants);

调试器显示参与者的大小为4，但是连接的值为"，因此为空

Debugger shows me size of 4 for participants however the joined value as "" therefore empty

private ArrayList<String> participants;

不确定出什么问题了吗

更新:

List<String> list = new ArrayList<>();
list.add("Philip");
list.add("Paul Smith");
list.add("Raja");
list.add("Ez");

String s = TextUtils.join(", ", list);

当我有一个手动填充的列表时，此方法有效，但是下面是代码现在的工作方式.

This works when I have a list that I manually populate however below is how the code is working right now.

在onCreate()

In the onCreate()

callApi(type);
String s = TextUtils.join(", ", participants);
getSupportActionBar().setTitle(s);

在callAPI()中:

In callAPI():

JSONArray participantsR = sub.getJSONArray("referralParticipants");

Log.e("Participants length ", String.valueOf(participantsR.length()));

for (int i = 0; i < participantsR.length(); i++)
{
    JSONObject object = participantsR.getJSONObject(i);
    String firstname = (String) object.get("fullName");
    participants.add(firstname);
    Log.e("Times", String.valueOf(i));
}

推荐答案

我正在尝试重现您的错误，但无法执行.这是我的代码:

I'm trying to reproduce your error and am unable to. Here is my code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_temp);

    List<String> list = new ArrayList<>();
    list.add("Philip Johnson");
    list.add("Paul Smith");
    list.add("Raja P");
    list.add("Ezhu Malai");

    String s = TextUtils.join(", ", list);

    Log.d(LOGTAG, s);
}

我的输出是预期的Philip Johnson, Paul Smith, Raja P, Ezhu Malai.

您要导入正确的TextUtils类吗?

Are you importing the correct TextUtils class?

android.text.TextUtils;

鉴于新信息，这是我的方法:

Given the new information, here is my approach:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_temp);

    callApi(type, new OnResponseListener<List<String>>() {
        @Override public void onResponse(List<String> list) {
            getSupportActionBar().setTitle(TextUtils.join(", ", list));
        }
    });
}

我不知道您使用的是哪个网络库，但是您可能必须将OnResponseListener定义为接口.非常简单:

I don't know what networking library you're using, but you may have to define OnResponseListener as an interface. It's very easy:

public interface OnResponseListener<T> {
    public void onResponse(T response);
}

然后，您需要修改callApi函数以获取OnResponseListener的实例>，并在完成调用后调用它的onResponse方法.

You will then need to modify your callApi function to take an instance of OnResponseListener> and call it's onResponse method after completing the call.

我建议您查看 Volley库，然后阅读 Android文档.

I would recommend looking into the Volley library, and reading the Android documentation about simple network calls.

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