android:onclick method doesn't work

Question

xml code:

 <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Invia"
            android:clickable="true"
            android:onClick="onClick1"
            android:id="@+id/invia" />

java code:

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

public class CreazioneSondaggio extends AppCompatActivity   {

    String URL;
    private EditText titolo;
    private EditText sceltaA;
    private EditText sceltaB;
    private EditText sceltaC;
   private Button invio;
    private EditText server;
    @Override
    protected void onCreate(Bundle savedInstanceState)  {
        titolo = (EditText) findViewById(R.id.titolo);
        sceltaA = (EditText) findViewById(R.id.A);
        sceltaB = (EditText) findViewById(R.id.B);
        sceltaC = (EditText) findViewById(R.id.C);
        server= (EditText) findViewById(R.id.server);
       invio = (Button) findViewById(R.id.invia);

       // invio.setOnClickListener(this);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_creazione_sondaggio);
    }

    private void inviodati() {
        ......
    }

    public void onClick1(View v) {
        Toast.makeText(CreazioneSondaggio.this, "ok", Toast.LENGTH_LONG).show();

           inviodati();



    }


}

Error:

Process: com.example.rober.registrazione, PID: 21261 java.lang.IllegalStateException: Could not execute method for android:onClick at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:275) at android.view.View.performClick(View.java:5210) at android.view.View$PerformClick.run(View.java:21288) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5527) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620) Caused by: java.lang.reflect.InvocationTargetException at java.lang.reflect.Method.invoke(Native Method) at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270) at android.view.View.per formClick(View.java:5210) at android.view.View$PerformClick.run(View.java:21288) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5527) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference at com.example.rober.registrazione.CreazioneSondaggio.inviodati(CreazioneSondaggio.java:48) at com.example.rober.registrazione.CreazioneSondaggio.onClick1(CreazioneSondaggio.java:87) at java.lang.reflect.Method.invoke(Native Method) at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.ja va:270) at android.view.View.performClick(View.java:5210) at android.view.View$PerformClick.run(View.java:21288) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5527) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

How can I fix it?

Answer 1

update your oncreate method

 protected void onCreate(Bundle savedInstanceState)  {
  super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_creazione_sondaggio);
        titolo = (EditText) findViewById(R.id.titolo);
        sceltaA = (EditText) findViewById(R.id.A);
        sceltaB = (EditText) findViewById(R.id.B);
        sceltaC = (EditText) findViewById(R.id.C);
        server= (EditText) findViewById(R.id.server);
       invio = (Button) findViewById(R.id.invia);

       // invio.setOnClickListener(this);


    }

Answer 2

Xml Layout:

 <Button
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:text="Invia"
     android:clickable="true"
     android:id="@+id/invia" />

Add following code to your activity:

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.your_layout);

        titolo = (EditText) findViewById(R.id.titolo);
        sceltaA = (EditText) findViewById(R.id.A);
        sceltaB = (EditText) findViewById(R.id.B);
        sceltaC = (EditText) findViewById(R.id.C);
        server= (EditText) findViewById(R.id.server);
        invio = (Button) findViewById(R.id.invia);

        invio.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(CreazioneSondaggio.this, "ok", Toast.LENGTH_LONG).show();
                // code
            }
        });

    }

Answer 3

Do like this...

super.onCreate(savedInstanceState);
        setContentView(R.layout.your_layout);
    InviaButton = (TextView) findViewById(R.id.invia);

     InviaButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
    //your_code
      }
    }

Answer 4

you need to find each view of activity once layout is inflated to activity as follows

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_creazione_sondaggio);

    titolo = (EditText) findViewById(R.id.titolo);
    sceltaA = (EditText) findViewById(R.id.A);
    sceltaB = (EditText) findViewById(R.id.B);
    sceltaC = (EditText) findViewById(R.id.C);
    server= (EditText) findViewById(R.id.server);

and since you have used attribute onClick no need to initiate Button reference you can do directly

 public void onClick1(View v) {

           if(v.getId() == R.id.invia)
           {

           }


        }

Answer 5

Read the full stack here it is saying java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' you have not initialized EditText but you are using in your onClick method. Try to figure it out.