Android Login button stops working

Question

Hi I am developing an android app, but my login button not working properly, as I am able to signup with web service but after in login page its stopped working, as I can navigate from signup to other page but login button does not let me login, please help me, below is my code for login functionality

thanks

public class Login extends ActionBarActivity {
Button btnLogin;
Button fbbutton;
Button gpbutton;
Button twbutton;
Button btnRegister;

EditText username, password;
String uname, pass;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.login);
    username = (EditText) findViewById(R.id.username);
    password = (EditText) findViewById(R.id.password);
    Button btnLogin = (Button) findViewById(R.id.btnLogin);

    //import button
    Button btnRegister = (Button) findViewById(R.id.btnRegister);

    btnRegister.setOnClickListener(new View.OnClickListener(){
        public void onClick(View view){
            Intent i = new Intent(getApplicationContext(),
                    Signup.class);
            startActivity(i);
            finish();
        }
    });


}

public void send(View v) {
    try {

        // CALL post method to make post method call
        post();
    } catch (Exception ex) {
        String error = ex.getMessage();
    }

}

//Method to get list value pair and form the query
private String getQuery(List<NameValuePair> params) throws UnsupportedEncodingException {
    StringBuilder result = new StringBuilder();
    boolean first = true;

    for (NameValuePair pair : params) {
        if (first)
            first = false;
        else
            result.append("&");

        result.append(URLEncoder.encode(pair.getName(), "UTF-8"));
        result.append("=");
        result.append(URLEncoder.encode(pair.getValue(), "UTF-8"));
    }

    return result.toString();
}


//Method to post data to webservice
public void post() throws UnsupportedEncodingException {
    try {
        // Calling async task to get json
        new DownloadOperation().execute();

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

//Handle popout messages
public void error(boolean flag, String etext) {
    if (flag == true) {
        Toast.makeText(getBaseContext(), etext, Toast.LENGTH_SHORT).show();
        //Code to handle failure
        username.setText("");
        password.setText("");

    } else {
        Toast.makeText(getBaseContext(), etext, Toast.LENGTH_SHORT).show();
        setContentView(R.layout.welcome);

    }
}

private class DownloadOperation extends AsyncTask<Void, Void, String> {
    String uname = "";
    String pass = "";


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Get user defined values
        uname = username.getText().toString();
        pass = password.getText().toString();

    }

    @Override
    protected String doInBackground(Void... params) {
        String response = "";
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost("http://rgbpallete.in/led/api/login");
        HttpEntity httpEntity = null;
        HttpResponse httpResponse = null;
        try {
            List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
            nameValuePairs.add(new BasicNameValuePair("uname", uname));
            nameValuePairs.add(new BasicNameValuePair("pass", pass));
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
            httpResponse = httpclient.execute(httppost);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            httpEntity = httpResponse.getEntity();
            response = EntityUtils.toString(httpEntity);
            return response;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(String jsonStr) {
        super.onPostExecute(jsonStr);
        Log.d("tag", "Result:\n" + jsonStr);
        if (jsonStr != null) {
            try {
                JSONObject jsonObj = new JSONObject(jsonStr);
                String message = jsonObj.getString("message");
                boolean error = jsonObj.getBoolean("error");

                error(error, message);

            } catch (JSONException e) {
                e.printStackTrace();
            }
        } else {
            Log.e("ServiceHandler", "Couldn't get any data from the url");
        }
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement


    return super.onOptionsItemSelected(item);
}

layout code of btnLogin Button

<Button 
   android:id="@+id/btnLogin" 
   style="@android:style/Widget.Material.Button.Borderless"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content" 
   android:layout_below="@+id/password" 
   android:layout_centerHorizontal="true" 
   android:layout_marginTop="20dp" 
   android:background="@drawable/button" 
   android:text="Login" 
   android:textColor="#ffffff" 
   android:textSize="20sp" 
   android:onClick="welcome" />

Answer 1

change this line to

Button btnLogin = (Button) findViewById(R.id.btnLogin);

to this

btnLogin = (Button) findViewById(R.id.btnLogin);

you are not initialize it properly.you are creating new variable.if you are getting null pointer exception that would be the reason

Answer 2

Your application is crashing because in xml you have set onClick as welcome (as per your comment). But you haven't implement it in Activity . So, when you click on that Button you are getting java.lang.NoSuchMethodException . In Activity welcome method is required add this in Activity

public void welcome(View v) {
   //do your action i.e call AsyncTask
}

Answer 3

1. make sure you have registered onclick listener to your login button, you haven't registered any click listener with btnLogin and also not set any action to be performed onClick to btnLogin!! just implemented those in btnRegister! I think you forgot it!!

2. if you are using onclick attribute of xml; then make sure these things are correct regarding your method:

a. your method is public and is the member of the Activity.

b. corresponding method should have one parameter, whose type should match the XML object. eg: View

Answer 4

You are missing

Button btnLogin = (Button) findViewById(R.id.btnLogin);

    btnLogin .setOnClickListener(new View.OnClickListener(){
        public void onClick(View view){
            //all your stuff here
        }
    });

Add and test.. Actually for each button you have to use OnClickListener