Android项目实战（四）：ViewPager切换动画（3.0版本以上有效果）

学习内容来自“慕课网”

一般APP进去之后都会有几张图片来导航，这里就学习怎么在这张图片切换的时候添加切换动画效果

先看布局文件

activity_main.layout

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/frameLayout1"
    android:orientation="vertical">

</FrameLayout>

然后是java文件

mainactivity.java

 package com.example.viewpage;

 import java.util.ArrayList;
 import java.util.List;

 import android.os.Bundle;
 import android.app.Activity;
 import android.graphics.DashPathEffect;
 import android.support.v4.view.PagerAdapter;
 import android.support.v4.view.ViewPager;
 import android.text.style.SuperscriptSpan;
 import android.view.Menu;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.Window;
 import android.widget.ArrayAdapter;
 import android.widget.ImageView;
 import android.widget.ImageView.ScaleType;

 public class MainActivity extends Activity {

     private ViewPager mviewpager; //控件
     private int[] mImgIds = new int[]{R.drawable.guide_image1,R.drawable.guide_image2,R.drawable.guide_image3};//初始化图片
     private List<ImageView> mImages = new ArrayList<ImageView>();

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         requestWindowFeature(Window.FEATURE_NO_TITLE);
         setContentView(R.layout.activity_main);

         mviewpager = (ViewPager) findViewById(R.id.id_viewpager);
         //为ViewPage切换添加动画效果(3.0以上版本才可以有效果)
         mviewpager.setPageTransformer(true, new ZoomOutPageTransformer());

         mviewpager.setAdapter(new PagerAdapter() {

             @Override
             public Object instantiateItem(View container, int position) {
                 ImageView imageview = new ImageView(MainActivity.this);
                 imageview.setImageResource(mImgIds[position]);
                 imageview.setScaleType(ScaleType.CENTER_CROP); //设置图片不变形
                 ((ViewGroup) container).addView(imageview);
                 mImages.add(imageview);
                 return imageview;
             };
             @Override
             public void destroyItem(View container, int position, Object object) {
                 // TODO Auto-generated method stub

                 ((ViewPager) container).removeView(mImages.get(position));
             }
             public boolean isViewFromObject(View view, Object object) {
                 // TODO Auto-generated method stub
                 return view == object;
             }

             @Override
             public int getCount() {                   //返回图片个数
                 // TODO Auto-generated method stub
                 return mImgIds.length;
             }
         });
     }

 }

这里代码很简单，主要就是一行代码控制切换效果 第36行mviewpager.setPageTransformer(true, new ZoomOutPageTransformer());

第二个参数就是切换效果，当然不是随便的参数

这些参数可以在http://wear.techbrood.com/training/animation/screen-slide.html网上查阅到

代码是给定的，只要复制代码，点击包粘贴就生成了相应的java文件

这里展示下几种效果：

1、ZoomOutPageTransformer（）

 public class ZoomOutPageTransformer implements ViewPager.PageTransformer {
     private static final float MIN_SCALE = 0.85f;
     private static final float MIN_ALPHA = 0.5f;

     public void transformPage(View view, float position) {
         int pageWidth = view.getWidth();
         int pageHeight = view.getHeight();

         if (position < -) { // [-Infinity,-1)
             // This page is way off-screen to the left.
             view.setAlpha();

         } else if (position <= ) { // [-1,1]
             // Modify the default slide transition to shrink the page as well
             float scaleFactor = Math.max(MIN_SCALE,  - Math.abs(position));
             float vertMargin = pageHeight * ( - scaleFactor) / ;
             float horzMargin = pageWidth * ( - scaleFactor) / ;
             if (position < ) {
                 view.setTranslationX(horzMargin - vertMargin / );
             } else {
                 view.setTranslationX(-horzMargin + vertMargin / );
             }

             // Scale the page down (between MIN_SCALE and 1)
             view.setScaleX(scaleFactor);
             view.setScaleY(scaleFactor);

             // Fade the page relative to its size.
             view.setAlpha(MIN_ALPHA +
                     (scaleFactor - MIN_SCALE) /
                     ( - MIN_SCALE) * ( - MIN_ALPHA));

         } else { // (1,+Infinity]
             // This page is way off-screen to the right.
             view.setAlpha();
         }
     }
 }

效果图：

     

红色的为第一张，蓝色的为第二张，向左滑动显示蓝色。效果为两张图并行缩小滑动

2、DepthPageTransformer（）

 public class DepthPageTransformer implements ViewPager.PageTransformer {
     private static final float MIN_SCALE = 0.75f;

     public void transformPage(View view, float position) {
         int pageWidth = view.getWidth();

         if (position < -) { // [-Infinity,-1)
             // This page is way off-screen to the left.
             view.setAlpha();

         } else if (position <= ) { // [-1,0]
             // Use the default slide transition when moving to the left page
             view.setAlpha();
             view.setTranslationX();
             view.setScaleX();
             view.setScaleY();

         } else if (position <= ) { // (0,1]
             // Fade the page out.
             view.setAlpha( - position);

             // Counteract the default slide transition
             view.setTranslationX(pageWidth * -position);

             // Scale the page down (between MIN_SCALE and 1)
             float scaleFactor = MIN_SCALE
                     + ( - MIN_SCALE) * ( - Math.abs(position));
             view.setScaleX(scaleFactor);
             view.setScaleY(scaleFactor);

         } else { // (1,+Infinity]
             // This page is way off-screen to the right.
             view.setAlpha();
         }
     }
 }

效果图：

     

红色的为第一张，蓝色的为第二张，向左滑动显示蓝色。效果为红色无变化向左滑动，蓝色由淡到深，由小到大占据屏幕

注意：添加DepthPageTransformer（）和ZoomOutPageTransformer（）java文件的时候 有两个错误 很容易 ctrl+1都能解决

更多动画类：

下载地址:

http://yunpan.cn/cFyjVgaeIFZ4e （提取码：ff5f）