Android app force closes - setOnClickListener [simple app] [beginner]

Question 1

You have not set you content view for your activity class MyOwnOnClickListener. So method findViewById() cannot find the view you are passing as argument.

I think the MyOwnOnClickListener class shouldn't be an Activity class, but just a listener. You can pass a reference to the TextView to the listener to use it.

Or you can implement the listener in your MainActivity class and suppress the MyOwnOnClickListener class.

public class MainActivity extends Activity implements OnClickListener {
    Button mybutton;
    TextView tvView;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_main);
        mybutton = (Button) findViewById(R.id.myactualbutton);
        tvView = (TextView) findViewById(R.id.produceText1);
        mybutton.setOnClickListener(this);
    }

    public void onClick(View v) {
        addiTion(v);
    }

    public void addiTion(View v){
        tvView.setText("fgdsgdfhgdfh");
    }
}

EDIT: If you want to use a listener class, just keep your MainActivity as it is, change only the call to the MyOwnOnClickListener to pass the tvView reference, and change the MyOwnOnClickListener class like this:

public class MyOwnOnClickListener implements OnClickListener{
TextView id2;

    // MainActivity caller;
    public MyOwnOnClickListener(TextView id2) {
        this.id2 = id2;
    }

    public void onClick(View v) {
        switch(v.getId()) {
        case R.id.produceText1:
            id2.setText("fgdsgdfhgdfh");
            break;
        // Other cases here...
        default:
            // Whatever you want to manage the situation...
        }
    }
}

It should work...

Question 2

replace your

mybutton.setOnClickListener(new MyOwnOnClickListener());

by

mybutton.setOnClickListener(new OnClickListener(){
    public void onClick(View v) {
         tvView.setText("fgdsgdfhgdfh");
    }   
});

which is called anonymous class in Java.

Setting listener this way, you declare anonymous class that implements interface OnClickListener, implement its abstract method onClick , create an object of this anonymous class and pass this object onto button's setOnClickListener method to make your button proceed clicks on it in a way you want.

Question 3

Alternative Solution with onClick attribute:

Add this attribute to your Button in the xml:

android:onClick="buttonClicked"

and add this method to the MainActivity:

public void buttonClicked(View view) {
     tvView.setText("fgdsgdfhgdfh");
}

then also delete this line:

mybutton.setOnClickListener(new MyOwnOnClickListener());

then get rid of the whole MyOwnOnClickListener Activity at all