Volley：JsonObjectRequest 中的 onResponse 延迟请求

Question

我是 Volley 库的新手，我正在创建一个简单的 Android 应用程序，该应用程序从以 JSON 格式生成的 API 获取数据。经过调试，只有下面提到的这个特定功能fetchAccD在Android Volley上有延迟问题。此 Activity 中的其他功能和暗示 JsonObjectRequest 的其他 Activity 运行良好。

{
    "Account": {
        "remarks": "NIL"
        "uname": "admin"
        "pword": null // value not to be shown
        "key": 1316451
        "name": "msummons sudo"
    }
}

这是我当前的代码

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_dashboard);
    uName = getIntent().getStringExtra("username");
    // reset session
    authidCoDe = 0;

    // invoke session
    Account account = fetchAccD(uName);

    if (account != null) {
        authidCoDe = account.getKey();
        ...


// init user details before loading
private final Account fetchAccD (String userN) {
    final Account account = new Account();
    requestQueue = null;
    requestQueue = Volley.newRequestQueue(this);
    String urlConstruct = *json url*;

    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, urlConstruct,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    try {
                        JSONArray jsonArray = response.getJSONArray("Account");
                        JSONObject jsonObject = jsonArray.getJSONObject(0);
                        account.setUname(jsonObject.optString("uname"));
                     // account.setPword(jsonObject.optString("pword"));
                        account.setKey(jsonObject.optInt("key"));
                        account.setName(jsonObject.optString("name"));
                        account.setRemarks(jsonObject.optString("remarks"));
                        requestQueue.stop();
                    }
                    catch (JSONException e) {
                        Toast.makeText(getApplicationContext(), "Fetch failed!", Toast.LENGTH_SHORT).show();
                        requestQueue.stop();
                    }
                }
            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Toast.makeText(getApplicationContext(), "Fetch failed!", Toast.LENGTH_SHORT).show();
            requestQueue.stop();
        }
    });
    requestQueue.add(jsonObjectRequest);
    return account;
}

调用fetchAccD时，代码运行完美

JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, urlConstruct,
        new Response.Listener<JSONObject>()

然后它继续到onCreate，在fetchAccD方法之后运行

if (account != null) {
    authidCoDe = account.getKey();
    ...

在它返回到fetchAccD 方法中的其余部分onResponse 之前。

@Override
public void onResponse(JSONObject response) {
    try {
        JSONArray jsonArray = response.getJSONArray("Account");
        ...

我的大部分函数都使用JsonObjectRequest GET 来获取JSON，这个问题只发生在fetchAccD 函数中。谢谢！

Answer 1

onResponse是异步的，当服务器返回响应时会被调用。

所以你应该在这样做之前等待响应：

if (account != null) {
    authidCoDe = account.getKey();
    ...
}

---

onCreate 应该这样做：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_dashboard);
    uName = getIntent().getStringExtra("username");
    // reset session
    authidCoDe = 0;

    // invoke session
    fetchAccD(uName);
}

在onResponse 你可以这样做：

public void onResponse(JSONObject response) {

    try {
        JSONArray jsonArray = response.getJSONArray("Account");
        JSONObject jsonObject = jsonArray.getJSONObject(0);
        account.setUname(jsonObject.optString("uname"));
     // account.setPword(jsonObject.optString("pword"));
        account.setKey(jsonObject.optInt("key"));
        account.setName(jsonObject.optString("name"));
        account.setRemarks(jsonObject.optString("remarks"));
        useAccount(account);
        requestQueue.stop();
    }
    catch (JSONException e) {
        Toast.makeText(getApplicationContext(), "Fetch failed!", Toast.LENGTH_SHORT).show();
        requestQueue.stop();
    }
}

定义一个方法useAccount:

private void useAccount(Account account) {
    if (account != null) {
        authidCoDe = account.getKey();
        ...
    }
}

而fetchAccD不需要返回值，可以设为void。