Question

我在行

处有一个Null Pointer Exception

** if（json.getString（KEY_SUCCESS）！= null）{

public class Register extends Activity {


/**
 *  JSON Response node names.
 **/

@Override
public void onBackPressed() {
    Intent bkr = new Intent(this,Login.class);
    startActivity(bkr);
    this.finish();
}


private static String KEY_SUCCESS = "success";
private static String KEY_UID = "uid";
private static String KEY_FIRSTNAME = "fname";
private static String KEY_LASTNAME = "lname";
private static String KEY_USERNAME = "uname";
private static String KEY_EMAIL = "email";
private static String KEY_CREATED_AT = "created_at";
private static String KEY_ERROR = "error";

/**
 * Defining layout items.
 **/

EditText inputFirstName;
EditText inputLastName;
EditText inputUsername;
EditText inputEmail;
EditText inputPassword;
EditText reinputPassword;
Button btnRegister;
TextView registerErrorMsg;


/**
 * Called when the activity is first created.
 */
@Override
public void onCreate(Bundle savedInstanceState) {
    Window window = this.getWindow();
    window.addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
    super.onCreate(savedInstanceState);
   setContentView(R.layout.register);

/**
 * Defining all layout items
 **/
    inputFirstName = (EditText) findViewById(R.id.fname);
    inputLastName = (EditText) findViewById(R.id.lname);
    inputUsername = (EditText) findViewById(R.id.uname);
    inputEmail = (EditText) findViewById(R.id.email);
    inputPassword = (EditText) findViewById(R.id.pword);
    reinputPassword = (EditText) findViewById(R.id.rpword);
    btnRegister = (Button) findViewById(R.id.register);
    registerErrorMsg = (TextView) findViewById(R.id.register_error);

/ ** *单击时切换回登录屏幕的按钮 ** /

    Button login = (Button) findViewById(R.id.bktologin);
    login.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Intent myIntent = new Intent(view.getContext(), Login.class);
            startActivityForResult(myIntent, 0);
            finish();
        }

    });

    /**
     * Register Button click event.
     * A Toast is set to alert when the fields are empty.
     * Another toast is set to alert Username must be 5 characters.
     **/

    btnRegister.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            if (  ( !inputUsername.getText().toString().equals("")) && ( !inputPassword.getText().toString().equals("")) && ( !inputFirstName.getText().toString().equals("")) && ( !inputLastName.getText().toString().equals("")) && ( !inputEmail.getText().toString().equals("")) )
            {
                if ( inputUsername.getText().toString().length() > 4 )
                {
                    if(inputPassword.getText().toString().equals(reinputPassword.getText().toString()))
                     NetAsync(view);
                    else
                    {
                        Toast.makeText(getApplicationContext(),
                                "Passwords Don't Match, Re-Enter Passwords Carefully", Toast.LENGTH_SHORT).show();
                    }


                }
                else
                {
                    Toast.makeText(getApplicationContext(),
                            "Username should be minimum 5 characters", Toast.LENGTH_SHORT).show();
                }
            }
            else
            {
                Toast.makeText(getApplicationContext(),
                        "One or more fields are empty", Toast.LENGTH_SHORT).show();
            }
        }
    });
   }
/**
 * Async Task to check whether internet connection is working
 **/

private class NetCheck extends AsyncTask<String,String,Boolean>
{
    private ProgressDialog nDialog;

    @Override
    protected void onPreExecute(){
        super.onPreExecute();
        nDialog = new ProgressDialog(Register.this);
        nDialog.setMessage("Loading..");
        nDialog.setTitle("Checking Network");
        nDialog.setIndeterminate(false);
        nDialog.setCancelable(true);
        nDialog.show();
    }

    @Override
    protected Boolean doInBackground(String... args){

/ ** *获取当前设备状态并通过尝试Google检查工作的互联网连接。 ** /

 ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnected()) {
            try {
                URL url = new URL("http://www.google.com");
                HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
                urlc.setConnectTimeout(3000);
                urlc.connect();
                if (urlc.getResponseCode() == 200) {
                    return true;
                }
            } catch (MalformedURLException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return false;

    }
    @Override
    protected void onPostExecute(Boolean th){

        if(th == true){
            nDialog.dismiss();
            new ProcessRegister().execute();
        }
        else{
            nDialog.dismiss();
            registerErrorMsg.setText("Error in Network Connection");
        }
    }
}





private class ProcessRegister extends AsyncTask<String,String,JSONObject> {

/ ** *定义流程对话框 ** / 私人ProgressDialog pDialog;

    String email,password,fname,lname,uname;
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        inputUsername = (EditText) findViewById(R.id.uname);
        inputPassword = (EditText) findViewById(R.id.pword);
           fname = inputFirstName.getText().toString();
           lname = inputLastName.getText().toString();
            email = inputEmail.getText().toString();
            uname= inputUsername.getText().toString();
            password = inputPassword.getText().toString();
        pDialog = new ProgressDialog(Register.this);
        pDialog.setTitle("Contacting Servers");
        pDialog.setMessage("Registering ...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    @Override
    protected JSONObject doInBackground(String... args) {


    UserFunctions userFunction = new UserFunctions();
    JSONObject json = userFunction.registerUser(fname, lname, email, uname, password);

        return json;


    }
   @Override
    protected void onPostExecute(JSONObject json) {
   /**
    * Checks for success message.
    **/
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    registerErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS);

                    String red = json.getString(KEY_ERROR);

                    if(Integer.parseInt(res) == 1){
                        pDialog.setTitle("Getting Data");
                        pDialog.setMessage("Loading Info");

                        registerErrorMsg.setText("Successfully Registered");


                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        /**
                         * Removes all the previous data in the SQlite database
                         **/

                        UserFunctions logout = new UserFunctions();
                        logout.logoutUser(getApplicationContext());
                        db.addUser(json_user.getString(KEY_FIRSTNAME),json_user.getString(KEY_LASTNAME),json_user.getString(KEY_EMAIL),json_user.getString(KEY_USERNAME),json_user.getString(KEY_UID),json_user.getString(KEY_CREATED_AT));
                        /**
                         * Stores registered data in SQlite Database
                         * Launch Registered screen
                         **/

                        Intent registered = new Intent(getApplicationContext(), Registered.class);

                        /**
                         * Close all views before launching Registered screen
                        **/
                        registered.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        pDialog.dismiss();
                        startActivity(registered);


                          finish();
                    }

                    else if (Integer.parseInt(red) ==2){
                        pDialog.dismiss();
                        registerErrorMsg.setText("User already exists");
                    }
                    else if (Integer.parseInt(red) ==3){
                        pDialog.dismiss();
                        registerErrorMsg.setText("Invalid Email id");
                    }

                }


                    else{
                    pDialog.dismiss();

                        registerErrorMsg.setText("Error occured in registration");
                    }

            } catch (JSONException e) {
                e.printStackTrace();


            }
        }}
    public void NetAsync(View view){
        new NetCheck().execute();
    }}

Answer 1

此行上的

NullPointerException表示您的json对象等于null。因此，在尝试从中获取某些值之前，您需要检查它是否等于null。

空指针异常android JSONobject

1 个答案: