Android引起：java.lang.NullPointerException

概述我现在编辑了…我检查布局和初始化但仍然是相同的错误..它可能是日食错误？publicclassActivityOwnerextendsActivityimplementsOnClickListener{EditTextownerUser,ownerPass;privateButtonbtnLogin;privateProgressDialogpDialog;

我现在编辑了…我检查布局和初始化但仍然是相同的错误..它可能是日食错误？

public class ActivityOwner extends Activity implements OnClickListener {        EditText ownerUser, ownerPass;        private button btnLogin;        private ProgressDialog pDialog;        JsONParser JsonParser = new JsONParser();        private static final String OWNER_LOGIN_URL = "http://192.168.2.5/IDot/owner_login.PHP";        // ---JsON element IDs from response of PHP script        private static final String TAG_SUCCESS = "success";        private static final String TAG_MESSAGE = "message";        @OverrIDe        protected voID onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentVIEw(R.layout.activity_owner);            ownerUser = (EditText) findVIEwByID(R.ID.owner_login_username);            ownerPass = (EditText) findVIEwByID(R.ID.owner_login_password);            TextVIEw tvlinkToRegister = (TextVIEw) findVIEwByID(R.ID.link_to_register);            tvlinkToRegister.setonClickListener(new VIEw.OnClickListener() {                @OverrIDe                public voID onClick(VIEw vIEw) {                    // Todo auto-generated method stub                    Intent registrationForm = new Intent(ActivityOwner.this,                            ActivityOwnerRegister.class);                    startActivity(registrationForm);                }            });            btnLogin = (button) findVIEwByID(R.ID.btNownerLogin);            btnLogin.setonClickListener(this);        }        @OverrIDe        public voID onClick(VIEw v) {            new AttemptLogin().execute();        }        class AttemptLogin extends AsyncTask<String, String, String> {            @OverrIDe            protected voID onPreExecute() {                super.onPreExecute();                pDialog = new ProgressDialog(ActivityOwner.this);                pDialog.setMessage("Attempting login...");                pDialog.setIndeterminate(false);                pDialog.setCancelable(true);                pDialog.show();            }            @OverrIDe            protected String doInBackground(String... args) {                // Check for success tag                int success;                String username = ownerUser.getText().toString();                String password = ownerPass.getText().toString();                try {                    // Building Parameters                    List<nameValuePair> params = new ArrayList<nameValuePair>();                    params.add(new BasicnameValuePair("owner_username", username));                    params.add(new BasicnameValuePair("owner_password", password));                    Log.d("request!", "starting");                    // getting product details by making http request                    JsONObject Json = JsonParser.makehttpRequest(OWNER_LOGIN_URL,                            "POST", params);                    // check your log for Json response                    Log.d("Login attempt", Json.toString());                    // Json success tag                    success = Json.getInt(TAG_SUCCESS);                    if (success == 1) {                        Log.d("Login Successful!", Json.toString());                        // save user data                        SharedPreferences sp = PreferenceManager                                .getDefaultSharedPreferences(ActivityOwner.this);                        Editor edit = sp.edit();                        edit.putString("owner_username", username);                        edit.commit();                        Intent i = new Intent(ActivityOwner.this,                                ActivityOwnerSuccessLogin.class);                        pDialog.dismiss();                        finish();                        startActivity(i);                        return Json.getString(TAG_MESSAGE);                    } else {                        Log.d("Login Failure!", Json.getString(TAG_MESSAGE));                        return Json.getString(TAG_MESSAGE);                    }                } catch (JsONException e) {                    e.printstacktrace();                }                return null;            }            @OverrIDe            protected voID onPostExecute(String result) {                // dismiss the dialog once product deleted                pDialog.dismiss();                if (result != null) {                    Toast.makeText(ActivityOwner.this, result, Toast.LENGTH_SHORT)                            .show();                }            }        }    }

—— logcat的——-

11-14 21:30:52.517: E/AndroIDRuntime(18929): Caused by: java.lang.NullPointerException11-14 21:30:52.517: E/AndroIDRuntime(18929):    at ph.IDot.owner.ActivityOwner$AttemptLogin.doInBackground(ActivityOwner.java:88)

解决方法:

A.B.C形式的行上的空指针异常意味着点左侧的某些内容为空.在这个例子中：

> A无效;
>或A.B为空.

没有其他原因.因此,由于textVIEw.getText()永远不会返回null,唯一的可能是用户为null.

总结

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