Android实现ViewPager滑屏动作并添加动画效果

1、整个文件是这样的：一个Activity主页，三个Fragment，两个谷歌官方的动画效果例子2

2、activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.sky.viewpage.MainActivity">

<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/viewPager_test">
</android.support.v4.view.ViewPager>
</RelativeLayout>

3、fragment_text_one.xml，另外的两个Fragment布局和这个是一样的，只是背景色和中间显示的文字不同

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.sky.viewpage.text_one">

<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#f9f0"
android:text="这个是第一个页面"
android:textSize="30dp"
android:gravity="center"/>

</FrameLayout>

4、布局文件写好了，现在主要是MainActivity里的代码，大概思路就是将三个Fragment存储到ArrayList中，然后弄一个适配器，这里我们用FragmentPagerAdapter，代码如下

package com.example.sky.viewpage;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;

import com.example.sky.viewpage.transform.ZoomOutPageTransformer;

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

public class MainActivity extends AppCompatActivity{
private static final float MIN_SCALE = 0.75f;
private ViewPager viewPager;
private List<Fragment> list;
private text_one one;
private text_two two;
private text_three three;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
viewPager = (ViewPager)this.findViewById(R.id.viewPager_test);
//调用滑动效果
//  viewPager.setPageTransformer(true,new DepthPageTransformer());
viewPager.setPageTransformer(true,new ZoomOutPageTransformer());

viewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {
@Override
public Fragment getItem(int position) {
return list.get(position);
}

@Override
public int getCount() {
return list.size();
}
});
}
//初始化数据
public void init()
{

list = new ArrayList<>();
one = new text_one();
two = new text_two();
three = new text_three();

list.add(one);
list.add(two);
list.add(three);
}
}

到这里一个简单传统的的左右滑屏就可以实现了。

5、接下来我们就实现两个动画效果，让滑屏看起来更舒服    

       1、ViewPager有个方法：setPageTransformer（boolean reverseDrawingOrder,PageTransformer transformer）可以用于设置切换时的动画效果，并且谷歌官方给了两个实例，一个是DepthPageTransformer  ，一个是ZoomOutPageTransformer，我们只需在上述代码中调用就可以实现动画效果了。

          （一）DepthPageTransformer  
   

package com.example.sky.viewpage.transform;

import android.support.v4.view.ViewPager;
import android.view.View;

/**
* Created by sky on 2017/4/2.
*/

public class DepthPageTransformer implements ViewPager.PageTransformer {
private static final float MIN_SCALE = 0.50f;
@Override
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);
}
}

}

 调用代码：

viewPager.setPageTransformer(true,new DepthPageTransformer());

（二）ZoomOutPageTransformer

package com.example.sky.viewpage.transform;

import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;

/**
* Created by sky on 2017/4/2.
*/

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {
private static final float MIN_SCALE = 0.85f;
private static final float MIN_ALPHA = 0.5f;
@Override
public void transformPage(View view, float position) {
int pageWidth = view.getWidth();
int pageHeight = view.getHeight();

Log.e("TAG", view + " , " + position + "");

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

} else if (position <= 1) //a页滑动至b页 ； a页从 0.0 -1 ；b页从1 ~ 0.0
{ // [-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);
}
}
}

  调用代码 

viewPager.setPageTransformer(true,new ZoomOutPageTransformer());

好了，到这里就结束了，截图如下