Question

Hi I’m new to Android Programming and I’m trying to make a simple program that changes the text by clicking a button. Here’s my code:

public class HelloAndroidActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        final Button button_scan = (Button) findViewById(R.id.button_scan);

        button_scan.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                buttonBeenPressed();
        }
        });

       }

public void buttonBeenPressed(){

    final Button button_scan = (Button) findViewById(R.id.button_scan);
    TextView tv_barcode = (TextView)findViewById(R.id.textview_barcode);
    if (tv_barcode != null){
    tv_barcode.setText("been pressed.");
    } else {
        button_scan.setText("it's null dawg.");
    }
    }
}

And my XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <Button android:text="Scan" android:layout_height="wrap_content" android:layout_width="match_parent" android:id="@+id/button_scan"></Button>
    <TextView android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="TextView" android:textAppearance="?android:attr/textAppearanceLarge" android:id="@+id/textview_barcode"></TextView>
</LinearLayout>

However the TextView is returning NULL and i don’t know why. Any suggestions? Thanks.

Answer 1

Hmmm i got no problems with your code, runs without any error! Are you working with eclipse? Then try to clean your project.