viewpager的layout_width="wrap_content"无效问题

package com.soulagou.ui;
  
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
/**
 * 
 * @author pangxg
 * @title 扩展viewPager
 * @description 和一般的ViewPager一样使用
 */
public class ViewPager extends android.support.v4.view.ViewPager{
    //private static final String tag=ViewPager.class.getSimpleName();
    protected ViewPager viewPager=null;
    protected final int wrap_content=-2;
    protected final int match_parent=-1;
    protected int w  =match_parent;
    protected int h   =match_parent;
    protected int ph =match_parent;
    protected int pw =match_parent;
      
    public ViewPager(Context context) {
        super(context);
        viewPager=this;
    }
    public ViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
        viewPager=this;
    }
    @Override
    protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) {
        super.onLayout(arg0, arg1, arg2, arg3, arg4);
         ViewGroup.LayoutParams params =null;
         ph=viewPager.getLayoutParams().height;
         pw=viewPager.getLayoutParams().width; 
          
         Drawable  bg=  viewPager.getBackground();
         if (bg!=null) {
                int h = bg.getIntrinsicHeight();
                int w= bg.getIntrinsicWidth();
                if (ph==wrap_content) {
                    this.h=h;
                }else if( ph==match_parent) {
                    this.h=ph;
                }
                  
                if (pw==wrap_content) {
                    this.w=w;
                }else if( pw==match_parent) {
                    this.w=pw;
                }
        }
        viewPager.setBackgroundColor(getResources().getColor(android.R.color.transparent));
        ViewParent pv=viewPager.getParent();
        if (pv instanceof LinearLayout) {
            params = new LinearLayout.LayoutParams(this.w, this.h);
        }else if (pv instanceof RelativeLayout) {
            params = new RelativeLayout.LayoutParams(this.w, this.h);
        }else if (pv instanceof FrameLayout) {
            params = new FrameLayout.LayoutParams(this.w, this.h);
        }
        viewPager.setLayoutParams(params); 
    }   
    @Override
    protected void onMeasure(int arg0, int arg1) {
        super.onMeasure(arg0, arg1);
    }
      
  
}

<FrameLayout android:layout_marginTop="13dp"    android:layout_gravity="center_horizontal"   android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="@drawable/bord_indexbg">
     <com.soulagou.ui.ViewPager
          android:id="@+id/myindex_guidePager"
          android:layout_gravity="center_horizontal"  
          android:layout_marginTop="5dp"
          android:background="@drawable/defa_advpic"
          android:layout_width="wrap_content" 
          android:layout_height="wrap_content">  
     </com.soulagou.ui.ViewPager> 
</FrameLayout>