Question

参数结果可以为null意味着我想显示Alert / Toast我怎么能这样做，因为我的应用程序将在响应为NULL时崩溃。这就是我有你的意思。我认为NULL值问题所以我想避免这件事（坠毁）

private class BackTask extends AsyncTask<Void,Void,Void> {
    ArrayList<String> list;
    protected void onPreExecute(){
        super.onPreExecute();
        list=new ArrayList<>();
    }
    protected Void doInBackground(Void...params){
        InputStream is=null;
        String result="";
        try{
            HttpClient httpclient=new DefaultHttpClient();
            HttpPost httppost= new HttpPost("http://IP/web/getOrderPendCusname.php");
            HttpResponse response=httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            // Get our response as a String.
            is = entity.getContent();
            System.out.println(is);
        }catch(IOException e){
            e.printStackTrace();
        }

        //convert response to string
        try{
            BufferedReader reader = new BufferedReader(new InputStreamReader(is,"utf-8"));
            String line = null;
            while ((line = reader.readLine()) != null) {
                result+=line;
            }
            is.close();
            //result=sb.toString();
        }catch(Exception e){
            e.printStackTrace();
        }
        // parse json data
        try{
            JSONObject object = new JSONObject(result);
            JSONArray jArray = object.getJSONArray("Cus_name");
            //JSONArray jArray =new JSONArray(result);
            for (int i = 0; i < jArray.length(); i++) {
                JSONObject jsonObject = jArray.getJSONObject(i);
                // add interviewee name to arraylist
                list.add(jsonObject.getString("Cus_name"));
            }
        }
        catch(JSONException e){
            e.printStackTrace();
        }
        return null;
    }
    protected void onPostExecute(Void result){
        listItems.addAll(list);
        adapter.notifyDataSetChanged();
    }
}

logcat的：

org.json.JSONException: Value null of type org.json.JSONObject$1 cannot be converted to JSONObject
07-21 17:01:16.057 17179-17289/com.example.vari.new_varri W/System.err:     at org.json.JSON.typeMismatch(JSON.java:111)
07-21 17:01:16.057 17179-17289/com.example.vari.new_varri W/System.err:     at org.json.JSONObject.<init>(JSONObject.java:160)
07-21 17:01:16.057 17179-17289/com.example.vari.new_varri W/System.err:     at org.json.JSONObject.<init>(JSONObject.java:173)
07-21 17:01:16.057 17179-17289/com.example.vari.new_varri W/System.err:     at com.example.vari.new_varri.Order_Pending$BackTask.doInBackground(Order_Pending.java:579)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at com.example.vari.new_varri.Order_Pending$BackTask.doInBackground(Order_Pending.java:538)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:295)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
07-21 17:01:16.058 17179-17289/com.example.vari.new_varri W/System.err:     at java.lang.Thread.run(Thread.java:818)

Answer 1

你真的可以在google上找到它。

if(IDontKnowWhatValue == null){
    Toast.makeText(context, "MyMessage", Toast.LENGTH_SHORT).show();
}

Answer 2

试试这个，

 if(ReceivedVal == null)
 {
   Toast.makeText(context, "Null value Received..", Toast.LENGTH_SHORT).show();
   Log.i("NULL" , "Null value received");
 }

编辑1：

 runOnUiThread(new Runnable() {

                    @Override
                    public void run() {
                        // TODO Auto-generated method stub
                        Toast.makeText(context, "Null value Received..", Toast.LENGTH_SHORT).show();
                    }
                });

编辑2

您的result变量是字符串，因此您可以将equals()视为

if(result.equals(""))
{
 // your toast is here
}
else
{
  // do your stuff here
}

如何在我的响应为NULL时显示警报/ Toast

2 个答案: