Question

My app force closes as soon as I open it,
this is my first app, and I have tried to find errors, but I can’t
I have attached log cat since starting this app:

          12-03 16:04:54.040: W/dalvikvm(8798): threadid=1: thread exiting with uncaught exception (group=0x40018578)
          12-03 16:04:54.040: E/AndroidRuntime(8798): FATAL EXCEPTION: main
          12-03 16:04:54.040: E/AndroidRuntime(8798): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sditya.quadratic.equation/com.sditya.quadratic.equation.Quadratic}: java.lang.NullPointerException
          ...
          12-03 16:04:54.040: E/AndroidRuntime(8798): Caused by: java.lang.NullPointerException
          12-03 16:04:54.040: E/AndroidRuntime(8798):   at com.sditya.quadratic.equation.Quadratic.initialize(Quadratic.java:58)

The initialize method:

private void initialize() { 
// TODO Auto-generated method stub
tr = (TextView) findViewById(R.id.tvResults); 
xs = (EditText) findViewById(R.id.editText1);
x = (EditText) findViewById(R.id.editText2); 
c = (EditText) findViewById(R.id.editText3); 
b.setOnClickListener(this); 
} 

---

Edit: Resolved, I forgot to inflate button ‘b’.

Answer 1

In your initialize method, you need to set the button variable before setting the listener..

private void initialize() { 
// TODO Auto-generated method stub
tr = (TextView) findViewById(R.id.tvResults); 
xs = (EditText) findViewById(R.id.editText1);
x = (EditText) findViewById(R.id.editText2); 
c = (EditText) findViewById(R.id.editText3); 

b = (Button) findViewById(R.id.button1); 
b.setOnClickListener(this); 
}