Android非XML形式动态生成、调用页面的方法

<activity android:name="com.example.stest.SignPage"/>

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Color;
import android.view.*;
import android.widget.*;
import android.widget.RelativeLayout.LayoutParams;
public class SignPageA extends Activity{
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  RelativeLayout main = new RelativeLayout(this);
  //添加这个可以随意摆放
  //控件位置
  main.setBackgroundColor(0xFFFFFFFF);
  setContentView(main);
  EditText emailEditText=new EditText(this);
  LayoutParams params = new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
  //这句一定要写，这样用来获取EditText对象，不写就会出错
  params.leftMargin=50;
  params.topMargin=50;
  emailEditText.setHint("Email");
  emailEditText.setTextColor(Color.BLACK);
  emailEditText.setGravity(Gravity.TOP);
  //emailEditText.setRawInputType(0x00000021);
  //0x00000081 PASSWORD
  main.addView(emailEditText, params);
 }
}

Intent intent=new Intent(MainActivity.this,SignPageA.class);
   startActivity(intent);
   finish();
//调用子页面