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 < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left.
            view.setAlpha(0);

        } else if (position <= 1) { // [-1,1]
            // Modify the default slide transition to shrink the page as well
            float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
            float vertMargin = pageHeight * (1 - scaleFactor) / 2;
            float horzMargin = pageWidth * (1 - scaleFactor) / 2;
            if (position < 0) {
                view.setTranslationX(horzMargin - vertMargin / 2);
            } else {
                view.setTranslationX(-horzMargin + vertMargin / 2);
            }

            // 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) /
                    (1 - MIN_SCALE) * (1 - MIN_ALPHA));

        } else { // (1,+Infinity]
            // This page is way off-screen to the right.
            view.setAlpha(0);
        }
    }
}

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 < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left.
            view.setAlpha(0);

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

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

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

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

        } else { // (1,+Infinity]
            // This page is way off-screen to the right.
            view.setAlpha(0);
        }
    }
}

 

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）