[英]Line -> JSONArray jArray=new JSONArray(result); giving nullpointer exception
package com.example.fyptrialapp;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
public class SearchByName extends Activity{
HttpPost httppost;
StringBuffer buffer;
HttpResponse response;
HttpClient httpclient;
InputStream inputStream=null;
Intent i;
//public static final String recipes[]=new String[]{"Almond-Sheera","Bhel","Bread-Pizzas","Carrot-Pickle","Carrot-Relish"};
String recipes[];
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.search_recipe);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
Button b2=(Button)findViewById(R.id.bSearchByName);
try{
httpclient = new DefaultHttpClient();
httppost = new HttpPost("http://10.0.2.2/fypTrial2/searchByName.php");
response = httpclient.execute(httppost); // Execute HTTP Post Request
inputStream = response.getEntity().getContent();
String result=null;
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line=null;
while((line=reader.readLine())!= null){
sb.append(line+"\n");
}
inputStream.close();
result=sb.toString();
JSONArray jArray=new JSONArray(result);// this statment gives error
for(int i=0;i<jArray.length();i++){
JSONObject json=jArray.getJSONObject(i);
recipes[i]=json.getString("name");
}
}
catch(Exception e){
Log.e("log_tag3", "Error convering result"+e.toString());
}
ArrayAdapter<String> ac=new ArrayAdapter<String>(this,android.R.layout.simple_dropdown_item_1line,recipes);
AutoCompleteTextView tv=(AutoCompleteTextView) findViewById(R.id.autoCompleteTextView2);
tv.setAdapter(ac);
b2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i=new Intent("com.example.practice.Search_Result");
startActivity(i);
}
});
}
}
錯誤
java.nullpointerexception。 錯誤轉換結果變量以及致命的主要錯誤
如果我想使用ASnk任務,應該如何編寫。
您確實應該將AsyncTask
用於網絡部分。 您的應用可能已經崩潰,並出現NetworkOnMainThread錯誤,請點擊此鏈接以使用AsyncTask。
除此之外,您還提供了很少的代碼來指出NullPointerException
的原因。 您應該始終檢查對象是否不為null(如果可能會出現)。
try{
//your code
}catch(NullPointerException ex){
ex.printStackTrace();
}
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