利用HorizontalScrollView实现滑动页面时的缩放效果

<com.crazy.reduce.ReduceSideslip xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:id="@+id/reduce_lay"
 android:layout_width="wrap_content"
 android:layout_height="match_parent"
 android:background="@drawable/bg"
 android:scrollbars="none"
 tools:context="com.crazy.reduce.MainActivity"  
 
 <LinearLayout
  android:layout_width="wrap_content"
  android:layout_height="match_parent"
  android:orientation="horizontal"  
 
  <include layout="@layout/item" / 
 
  <LinearLayout
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:background="@drawable/bg_01"  
 
   <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="toggleMenu"
    android:text="点击" / 
  </LinearLayout 
 </LinearLayout 
 
</com.crazy.reduce.ReduceSideslip 

<?xml version="1.0" encoding="utf-8"? 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"  
 
 <LinearLayout
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_centerHorizontal="true"
  android:orientation="vertical"  
 
  <Button
   android:id="@+id/bt_b"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_marginTop="50dp"
   android:text="一个不同的按钮" / 
 
  <ImageView
   android:id="@+id/img"
   android:layout_width="wrap_content"
   android:layout_height="match_parent"
   android:scaleType="centerCrop"
   android:src="@drawable/bg_03" / 
 </LinearLayout 
 
 
</RelativeLayout 

package com.crazy.reduce;
 
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
 
public class MainActivity extends Activity {
 
 private ReduceSideslip rs;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 
 rs = (ReduceSideslip)findViewById(R.id.reduce_lay);
 }
 
 public void toggleMenu(View v) {
 rs.reduce();
 }
}

package com.crazy.reduce;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.HorizontalScrollView;
import android.widget.LinearLayout;
import com.nineoldandroids.view.ViewHelper;
public class ReduceSideslip extends HorizontalScrollView {
private int mScreenWidth;  // 屏幕宽度
private int mMnuRightPadding = 300;
private int mMenuWidth; // 视图宽度（左边的视图）
private int mHalfMenuWidth;
private boolean isOpen; // 标记菜单是否打开
private boolean once;  // 是否已经初始化回收菜单
private ViewGroup mMenu; // 左边的视图
private ViewGroup mContent; // 右边的视图
public ReduceSideslip(Context context, AttributeSet attrs) {
super(context, attrs);
mScreenWidth = context.getResources().getDisplayMetrics().widthPixels;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
if (!once) {
// 要与布局文件当中的一致
LinearLayout temp = (LinearLayout)getChildAt(0);
mMenu = (ViewGroup)temp.getChildAt(0);
mContent = (ViewGroup)temp.getChildAt(1);
mMenuWidth = mScreenWidth - mMnuRightPadding;
mHalfMenuWidth = mMenuWidth/2;
mMenu.getLayoutParams().width = mMenuWidth;
mContent.getLayoutParams().width = mScreenWidth;
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
// 在视图计算完自身及子视图的宽高后，重新排版
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if (changed) {
// 隐藏菜单
this.scrollTo(mMenuWidth, 0);
once = true;
}
}
public void reduce(){
if (isOpen) {
closeMenu();
} else {
openMenu();
}
}
private void openMenu() {
if (isOpen) {
return;
}
// 和 scrollTo() 相似，但是要缓和些，
// 不像 scrollTo() 直接移动过去
this.smoothScrollTo(0, 0);
isOpen = true;
}
private void closeMenu() {
if (isOpen) {
this.smoothScrollTo(mMenuWidth, 0);
isOpen = false;
}
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()){
case MotionEvent.ACTION_UP:  // 松开手
int scrollX = getScrollX();   // 水平滑动的距离
if (scrollX   mHalfMenuWidth) {
this.smoothScrollTo(mMenuWidth, 0);
isOpen = false;
} else {
this.smoothScrollTo(0, 0);
isOpen = true;
}
return true;
}
return super.onTouchEvent(ev);
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
// 左右视图切换时的渐变范围 (注意是 l 不是1(一))
float scale = l*1.0f/mMenuWidth;  // 范围值 (0, 1)
float leftScale = 1- 0.3f*scale;  // 范围值(0.7, 1)
float rightScale = 0.8f + 0.2f*scale; // 范围值 (0.8, 1)
ViewHelper.setScaleX(mMenu, leftScale);
ViewHelper.setScaleY(mMenu, leftScale);
// 往右滑动时，左边的视图逐渐变亮
ViewHelper.setAlpha(mMenu, 0.6f + 0.4f * (1 - scale)); // (0.6, 1)
// 往左滑动时，左边的视图不用移除屏幕左边界(可以不要) 
ViewHelper.setTranslationX(mMenu, mMenuWidth * scale * 0.7f);
ViewHelper.setScaleX(mContent, rightScale);
ViewHelper.setScaleY(mContent, rightScale);
}
}