我正在处理一个项目，并且一切正常，但是当我单击获取按钮时，它并没有获取pdf并在列表视图中显示它们。
它仅显示过程对话框，并且对话框在半秒后消失
我尝试了依赖关系，但是一切都好了，gradle构建没有错误
private void getPdfs() {
progressDialog.setMessage("Fetching Pdfs... Please Wait");
progressDialog.show();
StringRequest stringRequest;
stringRequest = new StringRequest(Request.Method.POST, PDF_FETCH_URL,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
progressDialog.dismiss();
try {
JSONObject obj = new JSONObject(response);
Toast.makeText(MCA.this,obj.getString("message"), Toast.LENGTH_SHORT).show();
JSONArray jsonArray = obj.getJSONArray("pdfs");
for(int i=0;i<jsonArray.length();i++){
//Declaring a json object corresponding to every pdf object in our json Array
JSONObject jsonObject = jsonArray.getJSONObject(i);
//Declaring a Pdf object to add it to the ArrayList pdfList
Pdf pdf = new Pdf();
String pdfName = jsonObject.getString("name");
String pdfUrl = jsonObject.getString("url");
pdf.setName(pdfName);
pdf.setUrl(pdfUrl);
pdfList.add(pdf);
}
pdfAdapter=new PdfAdapter(MCA.this,R.layout.list_layout, pdfList);
listView.setAdapter(pdfAdapter);
pdfAdapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}
);
RequestQueue request = Volley.newRequestQueue(this);
request.add(stringRequest);
}
}