Android Studio FATAL EXCEPTION: main

Question

I am newbie at developing android. And this is my first app I want to create. But I get some problem on this and don't know how to resolve it. Please help me. This error I got:

03-19 14:30:44.502 22661-22661/com.don.test E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.don.test, PID: 22661
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.don.test/com.don.test.MainActivity}: java.lang.NullPointerException
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2224)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2283)
  at android.app.ActivityThread.access$800(ActivityThread.java:144)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:136)
  at android.app.ActivityThread.main(ActivityThread.java:5158)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:515)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
  at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
  at com.don.test.MainActivity.onCreate(MainActivity.java:29)
  at android.app.Activity.performCreate(Activity.java:5998)
  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2181)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2283) 
  at android.app.ActivityThread.access$800(ActivityThread.java:144) 
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205) 
  at android.os.Handler.dispatchMessage(Handler.java:102) 
  at android.os.Looper.loop(Looper.java:136) 
  at android.app.ActivityThread.main(ActivityThread.java:5158) 
  at java.lang.reflect.Method.invokeNative(Native Method) 
  at java.lang.reflect.Method.invoke(Method.java:515) 
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566) 
  at dalvik.system.NativeStart.main(Native Method) 

This is my MainActivity.java

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

Button bLogout;
EditText etId, etNama, etUsername;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    etId = (EditText) findViewById(R.id.etId);
    etNama = (EditText) findViewById(R.id.etNama);
    etUsername = (EditText) findViewById(R.id.etUsername);
    bLogout = (Button) findViewById(R.id.bLogout);

    bLogout.setOnClickListener(this);

}

@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.bLogout:


            break;
    }
}
}

I use my Samsung Galaxy SIII Mini as emulator. Can you help me with this error, thanks before

Answer 1

You need to set the content view for your Activity before using it's views:

Add

setContentView(R.layout.activity_main); // activity_main is an example, here you need to put the name of your layout

Right after

super.onCreate(savedInstanceState);