我在运行项目时遇到此错误。
java.lang.NullPointerException：尝试调用虚方法 空对象上的'boolean java.lang.String.equals（java.lang.Object）' 参考 在com.example.arhen.tugasrplii.Register $ InputData.onPostExecute（Register.java:100）
这是完整日志：
03-05 03:22:02.822 2575-2575/com.example.arhen.tugasrplii E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.arhen.tugasrplii, PID: 2575
**java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
at com.example.arhen.tugasrplii.Register$InputData.onPostExecute(Register.java:100)**
at com.example.arhen.tugasrplii.Register$InputData.onPostExecute(Register.java:54)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
这是我在Register.java上的完整代码：
/** * Created by arhen on 05/03/15. */
public class Register extends Activity{
ProgressDialog pDialog;
JSONParser jsonParser = new JSONParser();
EditText first_name,last_name,email,username,password;
private static String url = "http://127.0.0.1/login/register.php";
Button register;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.register);
register = (Button)findViewById(R.id.btn_register);
first_name = (EditText)findViewById(R.id.fld_first);
last_name = (EditText)findViewById(R.id.fld_last);
email = (EditText)findViewById(R.id.fld_email);
username = (EditText)findViewById(R.id.fld_username);
password = (EditText)findViewById(R.id.fld_pwd);
register.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
new InputData().execute();
}
});
}
public class InputData extends AsyncTask<String, String, String>{
String success;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Register.this);
pDialog.setMessage("Registering Account...");
pDialog.setIndeterminate(false);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
String strfirst_name = first_name.getText().toString();
String strlast_name = last_name.getText().toString();
String stremail = email.getText().toString();
String strusername = username.getText().toString();
String strpassword = password.getText().toString();
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("first_name",strfirst_name));
params.add(new BasicNameValuePair("last_name",strlast_name));
params.add(new BasicNameValuePair("email",stremail));
params.add(new BasicNameValuePair("username",strusername));
params.add(new BasicNameValuePair("password",strpassword));
JSONObject json =
jsonParser.makeHttpRequest(url,
"POST", params);
try {
success = json.getString("success");
} catch (Exception e) {
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_SHORT).show();
}
});
}
return null;
}
protected void onPostExecute(String file_url) {
// dismiss the dialog once done
pDialog.dismiss();
if (success.equals("1")) {
Toast.makeText(getApplicationContext(),"Registration Succesfully",Toast.LENGTH_LONG).show();
}else{
Toast.makeText(getApplicationContext(),"Registration Failed",Toast.LENGTH_LONG).show();
}
}
}
@Override
public void onBackPressed(){
Intent i = new Intent(getApplicationContext(),Login.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
finish();
} }
我认为来自JSONParser.java的错误，这个代码：
/**
* Created by arhen on 04/03/15.
*/
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
public JSONObject getJSONFromUrl(String url) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new
InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " +
e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new
DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new
UrlEncodedFormEntity(params));
HttpResponse httpResponse =
httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new
DefaultHttpClient();
String paramString =
URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse =
httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new
InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " +
e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
这是我的register.php代码：
<?php
$first_name = $_POST['first_name'];
$last_name = $_POST['last_name'];
$email = $_POST['email'];
$username = $_POST['username'];
$pwd = $_POST['password'];
include 'koneksi.php';
$namaTabel = "akun";
header('Content-Type:text/xml');
$query = "INSERT INTO $namaTabel VALUES('','$first_name','$last_name','$email','$username','$pwd')";
$hasil = mysql_query($query);
if($hasil)
{
$response["success"] = "1";
$response["message"] = "Data has Input";
echo json_encode($response);
}
else
{$response["success"] = "0";
$response["message"] = "Upss, Something Happens! Try again";
// echoing JSON response
echo json_encode($response);
}
?>
我看过这篇文章： What is a NullPointerException, and how do I fix it?
我试着给成功一个字符串：
String success ="";
但它没有工作..它给我的代码激活了这个语句错误：
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_SHORT).show();
}
});
我不知道。请帮助.. 非常感谢...
答案 0 :(得分：0)
如果String success = ""不起作用，则此行可能会返回null：
success = json.getString("success");
您是否检查了要解析的JSON并验证了“成功”字段是否符合预期并且格式正确？
答案 1 :(得分：-3)
try {
success = json.getString("success");
int successFlag = Integer.parseInt(success);
...
使用此successFlag来比较0 / 1，然后执行进一步操作。