Android application = Unfortunately project has stopped

Question

Android application = Unfortunately project has stopped

Navigation

#1 by (0 votes)
#2 by (0 votes)

1

I'm studying Android and I want to make a simple parameter pass for another Activity but the application is terminated in the emulator and the logCat shows a NullPointerException, can anyone help me?

Class:

public class MainActivity extends Activity {


    EditText num1 = (EditText) findViewById(R.id.txtNumber1);
    EditText num2 = (EditText) findViewById(R.id.txtNumber2);
    String n1= num1.getText().toString();
    int numero1 = Integer.parseInt(n1);
    String n2= num2.getText().toString();
    int numero2 = Integer.parseInt(n1);
    int soma=numero1+numero2;


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


        Button bt = (Button) findViewById(R.id.bt1);
        final Intent it = new Intent(this, Cadastros.class);
        bt.setOnClickListener(new Button.OnClickListener() {

            @Override
            public void onClick(View v) {
                it.putExtra("Total", soma);
                startActivity(it);
            }


        });
    }

XML:

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout
    android:id="@+id/widget0"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
<Button
    android:id="@+id/bt1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Click"
    android:gravity="center"
    android:layout_x="134dp"
    android:layout_y="102dp" />

<EditText
    android:id="@+id/txtNumber1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_x="56dp"
    android:layout_y="179dp"
    android:ems="10"
    android:inputType="number" >

    <requestFocus />
</EditText>

<EditText
    android:id="@+id/txtNumber2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_x="69dp"
    android:layout_y="222dp"
    android:ems="10"
    android:inputType="number" />

</AbsoluteLayout>

Log

06-16 08:09:48.240: D/AndroidRuntime(948): Shutting down VM
06-16 08:09:48.270: W/dalvikvm(948): threadid=1: thread exiting with uncaught exception (group=0x41465730)
06-16 08:09:48.330: E/AndroidRuntime(948): FATAL EXCEPTION: main
06-16 08:09:48.330: E/AndroidRuntime(948): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{br.com.passagemparam/br.com.passagemparam.MainActivity}: java.lang.NullPointerException
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.os.Looper.loop(Looper.java:137)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.ActivityThread.main(ActivityThread.java:5103)
06-16 08:09:48.330: E/AndroidRuntime(948):     at java.lang.reflect.Method.invokeNative(Native Method)
06-16 08:09:48.330: E/AndroidRuntime(948):     at java.lang.reflect.Method.invoke(Method.java:525)
06-16 08:09:48.330: E/AndroidRuntime(948):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
06-16 08:09:48.330: E/AndroidRuntime(948):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
06-16 08:09:48.330: E/AndroidRuntime(948):     at dalvik.system.NativeStart.main(Native Method)
06-16 08:09:48.330: E/AndroidRuntime(948): Caused by: java.lang.NullPointerException
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.Activity.findViewById(Activity.java:1853)
06-16 08:09:48.330: E/AndroidRuntime(948):     at br.com.passagemparam.MainActivity.<init>(MainActivity.java:14)
06-16 08:09:48.330: E/AndroidRuntime(948):     at java.lang.Class.newInstanceImpl(Native Method)
06-16 08:09:48.330: E/AndroidRuntime(948):     at java.lang.Class.newInstance(Class.java:1130)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
06-16 08:09:48.330: E/AndroidRuntime(948):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2128)
06-16 08:09:48.330: E/AndroidRuntime(948):     ... 11 more

java android nullpointerexception

asked by anonymous 16.06.2015 / 14:48

2 answers

AngularJS + RequireJS [Error Injection] How to configure the Java HttpClient to accept JavaScript and Cookies?

score 0 · Answer 1

The result in this way worked well:

insira o código aqui
  AlertDialog.Builder dialogo = new AlertDialog.Builder(Cadastros.this);
            // setando título
            dialogo.setTitle("Resultado");
            // setando mensagem
            dialogo.setMessage("Soma: " + total);
            // setando botão
            dialogo.setNeutralButton("OK", null);
            // chamando o AlertDialog
            dialogo.show();

score 0 · Answer 2

You should use findViewById() within onCreate() because if you execute the method before that it will not find view because it does not have any layout assigned to the Activity, since this is done in onCreate() .

So, the correct would be to use this:

public class MainActivity extends Activity {        

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

         EditText num1 = (EditText) findViewById(R.id.txtNumber1);
         EditText num2 = (EditText) findViewById(R.id.txtNumber2);
         String n1= num1.getText().toString();
         int numero1 = Integer.parseInt(n1);
         String n2= num2.getText().toString();
         int numero2 = Integer.parseInt(n1);
         int soma=numero1+numero2;

         Button bt = (Button) findViewById(R.id.bt1);
         final Intent it = new Intent(this, Cadastros.class);
         bt.setOnClickListener(new Button.OnClickListener() {

              @Override
              public void onClick(View v) {
                it.putExtra("Total", soma);
                startActivity(it);
              }
         });
}