onOptionsItemSelected方法问题

public boolean onOptionsItemSelected(MenuItem item) {

    if (item.getItemId() == R.id.action_settings) {
        Intent intent = new Intent(CanvasActivity.this, MainActivity.class);
        CanvasActivity.this.startActivity(intent);
        return true;
    }
    return super.onOptionsItemSelected(item);
}

    在actionbar的setting按钮上添加监听，希望跳转到mainactivity界面。但是点击之后自动退出了，请问是什么问题？

http://blog.csdn.net/u011918382/article/details/51565122