Android：将EditText添加到View错误

Question

bascially I want to have two views. One view is for the canvas, used for drawing rectangles and another view or adding of new editText boxes whenever a rectangle is drawn. When I run my program, an error occured "java.lang.NullPointerException". Is it possible to add the edittext boxes onto the canvas view so that I keep only one view?

My code are as follows:

public class MainActivity extends Activity {
        public static DrawRect DR;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        DR = new DrawRect(this);

        rectbutton = (Button) findViewById(R.id.rectbutton);

        RelativeLayout mainLayout = (RelativeLayout) findViewById(R.id.RelativeLayout);

        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.MATCH_PARENT,
                RelativeLayout.LayoutParams.MATCH_PARENT);


        lp.addRule(RelativeLayout.BELOW, R.id.rectbutton);

        DR.setLayoutParams(lp);

        mainLayout.addView(DR);


    rectbutton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {

                     addRect(); // in my DrawRect class i have this method to draw rect on canvas
              addEditText();

                     }// onclick

        });
}

    private void addEditText(){

        RelativeLayout editTextLayout = new RelativeLayout(this);
          EditText editText = new EditText(this);
          editTextLayout.addView(editText);
           mainLayout.addView(editTextLayout);

    }
}

Please Advice. Thank you.

Answer 1

Which line its giving error. if its giving error in

 mainLayout.addView(editTextLayout);

means mainLayout is null.you can add EditText in canvas. the problem is in

RelativeLayout mainLayout = (RelativeLayout) findViewById(R.id.RelativeLayout);

check the id in layout xml.