Question

I used to have some experience with developing for android but I started up again after 6 months and forgot most of it. I am now using a macbook to do my developing on and had to set up Eclipse, the Android SDK and AVD all over again and I’m worried I messed something up.

When I start a new project with the default activity that displays “Hello World” on my screen the app runs fine. I then tried to put in two buttons that cause the text in a new TextView to change. But whenever I include the textView part I get a runtime error. When I comment it out, the app runs but obviously nothing happens. Based upon the tutorials I’ve been reading, this is the appropriate place and way to declare/create the textView but I can’t figure out what’s wrong. Any suggestions?

[Edit] I was messing around and found that I can make the mytext a field instead of a TextView and that worked. So in my onCreate(), I put

 mytext = (TextField)findViewById(R.id.TextView1);

but that doesn’t seem the right way to do things.

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class IntroActivity extends Activity {

     TextView myText = (TextView)findViewById(R.id.textView1);
   //i've tried this with final added on to it as well (recommended by eclipse)

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

       setButtonClickListener();
    }

    private void setButtonClickListener() {
         Button button1 = (Button)findViewById(R.id.button1);
         Button button2 = (Button)findViewById(R.id.button2);

        button1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                myText.setText("Hello");
            }
        });
        button2.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            //  myText.setText("Goodbye");
            }
        });
            }



    }

Answer 1

This:

TextView myText = (TextView)findViewById(R.id.textView1);

should be separated. The declaration should be at the same place:

private TextView myText;

But the assignment should come only after setContentView:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    myText = (TextView)findViewById(R.id.textView1);

This is done since before setContentView, Dalvik doesn’t know from which layout to take the view that matchs the id R.id.textView1