Android : Dynamically created views are overlapping after drag and drop

I'm working on a app in which dynamic views are being generated onClick. The code is working fine but the problem is,when I drag the button to the previously generated buttons,it overlaps other button(s),which is not my requirement. What am I doing wrong? Or what is missing?

MainActivity.java

public class MainActivity extends Activity {

    private Button btn;
    private RelativeLayout rl1;
    int i=0 ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rl1=(RelativeLayout)findViewById(R.id.relative_layout);
        btn=(Button)findViewById(R.id.btnAdd);
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                final Button btn = new Button(MainActivity.this);
                btn.setText(""+1+i);
                i++;
                RelativeLayout.LayoutParams rlparams = new RelativeLayout.LayoutParams(
                        LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
                rlparams.addRule(RelativeLayout.CENTER_IN_PARENT);
                rlparams.leftMargin = 280;


                btn.setOnTouchListener(new OnTouchListener() {                      

                    @Override
                    public boolean onTouch(View v, MotionEvent event) {                             



                        switch (event.getAction()) {

                        // when touching the img
                        case MotionEvent.ACTION_DOWN:
                            break;

                        // when moving
                        case MotionEvent.ACTION_MOVE:

                            btn.setX(btn.getX()+ event.getX()- btn.getWidth() / 2);
                            btn.setY(btn.getY()+ event.getY()- btn.getHeight() / 2);

                            break;

                        // when not touched
                        case MotionEvent.ACTION_UP:

                            if ((btn.getY() < rl1.getY())) {
                                btn.setY(event.getRawY());
                            } else if (btn.getX() < rl1.getX()) {
                                // btn.setY(event.getRawY());
                                btn.setX(event.getRawX());
                            } else if (btn.getX()+btn.getWidth()>rl1.getX()+rl1.getWidth()) {

                            btn.setX(event.getRawY());

                            }

                            break;

                        default:
                            break;
                        }
                        return true;
                    }
                });

                rl1.addView(btn);


            }
        });
    }
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relative_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/btnAdd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="AddButton"
        android:text="Button" />

</RelativeLayout>