Question

解决方案：我的问题在于上下文，以防其他人遇到同样的问题。

我试图在我的Android应用程序中使用JsonObjectRequest和RequestQueue与Volley lib发出请求，但我不断收到错误。

首先，我尝试使用JsonObjectRequest（没有RequestQueue），但我没有得到任何数据，所以我尝试使用RequestQueue。

这是我的代码：

   JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, urlMarket, null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray result = response.getJSONArray("result");
                //we loop the response
                for (int i = 0; i < result.length(); i++) {
                    coin.setHigh(Double.parseDouble(result.getJSONObject(i).getString("High")));
                    coin.setLow(Double.parseDouble(result.getJSONObject(i).getString("Low")));
                    coin.setLast(Double.parseDouble(result.getJSONObject(i).getString("Last")));
                    coin.setVolInBtc(Double.parseDouble(result.getJSONObject(i).getString("BaseVolume")));
                    coin.setBid(Double.parseDouble(result.getJSONObject(i).getString("Bid")));
                    coin.setAsk(Double.parseDouble(result.getJSONObject(i).getString("Ask")));
                    coin.setPrevDay(result.getJSONObject(i).getString("PrevDay"));


                }
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            error.printStackTrace();
        }
    });

    requestQueue.add(request);

这是我初始化requestQueue的方式：

   requestQueue=Volley.newRequestQueue(context);

这是我得到的错误：

     java.lang.RuntimeException: Unable to start activity ComponentInfo{space.bewa.bewa_v10/space.bewa.bewa_v10.activities.DashboardActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getCacheDir()' on a null object reference
                                                                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
                                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
                                                                 at android.app.ActivityThread.-wrap11(Unknown Source:0)
                                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
                                                                 at android.os.Handler.dispatchMessage(Handler.java:106)
                                                                 at android.os.Looper.loop(Looper.java:164)
                                                                 at android.app.ActivityThread.main(ActivityThread.java:6494)
                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                 at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
                                                              Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getCacheDir()' on a null object reference
                                                                 at com.android.volley.toolbox.Volley.newRequestQueue(Volley.java:43)
                                                                 at com.android.volley.toolbox.Volley.newRequestQueue(Volley.java:78)

非常感谢任何形式的帮助

Answer 1

as per my above comment

您context是null

初个化context这样的

Context context=YourActivity.this;

或

Context context=getApplicationContext();

JsonObjectRequest和RequestQueue错误

1 个答案: