setOnClickListener crashs my android app

Question

I am facing a problem as I try to implement a login screen in my Android app. The user has to fill out the login and password field with the string \"user\". Whenever I run thi

Answer 1

Try this..

Because Button,EditText's all belongs to fragment_main.xml so you have to do that in PlaceholderFragment.java

public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }
    Button ok = null;
    EditText login = null;
    EditText pass = null;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        ok = (Button) rootView.findViewById(R.id.ok);  

login = (EditText) rootView.findViewById(R.id.login_text); 
pass = (EditText) rootView.findViewById(R.id.pass_text); 

ok.setOnClickListener(new View.OnClickListener() { 
        public void onClick(View view) { 
                String loginStr = login.getText().toString(); 
                String passStr = pass.getText().toString(); 
                if (loginStr != null && loginStr.equals("user")) { 
                        if (passStr != null && passStr.equals("user")) {
                            Toast.makeText(getActivity(), "Redirecting...", 
                            Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(getActivity(), "Wrong Credentials",
                            Toast.LENGTH_SHORT).show();
                        }
                }
        } 
}); 
        return rootView;
    }
}

Answer 2

add method

myMethod() {

//Code hear

}

To Activity and on your xml add

android:onClick="myMethod"

To your button

Answer 3

You are initializing views that is in fragment_main.xml in Activity. Instead you should initialize it in Fragment onCreateView using rootView.findViewById.

findViewById looks for a view in the current view hierarchy. You have set activity_main.xml to Activity. So if you initializing views in Activity fails leading to NUllPointerException.

public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }
    Button ok = null;
    EditText login = null;
    EditText pass = null;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        ok = (Button) rootView.findViewById(R.id.ok);  

        login = (EditText) rootView.findViewById(R.id.login_text); 
        pass = (EditText) rootView.findViewById(R.id.pass_text); 

        ok.setOnClickListener(new View.OnClickListener() { 
        public void onClick(View view) { 
                String loginStr = login.getText().toString(); 
                String passStr = pass.getText().toString(); 
                if (loginStr != null && loginStr.equals("user")) { 
                        if (passStr != null && passStr.equals("user")) {
                            Toast.makeText(getActivity(), "Redirecting...", 
                            Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(getActivity(), "Wrong Credentials",
                            Toast.LENGTH_SHORT).show();
                        }
                }
        } 
     }); 
        return rootView;
    }
}