设计一个android引导页面的动画，最好是透明渐变动画效果，求大神帮忙！

Question

设计一个android引导页面的动画，最好是透明渐变动画效果，大概样式就像APP微信精选那个引导页面那种样式，求大神帮忙给个Demo！

Answer 1

之前回复的都回复不了，现在重新再给你回复一遍吧，首先创建三个Fragment，我现在给你举一个例子：

 public class WelcomeFragment1 extends Fragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater,
            @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_welcome1, null);
        return view;
    }
}

下面是fragment对应的布局文件：

 <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"
        android:src="@drawable/jpg_1" />

</LinearLayout>

同理，你自己新建另外两个Fragment和布局文件，下面是一个引导页GuideActivity:

 package com.example.splashdemo;

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

import com.nineoldandroids.view.ViewHelper;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.Log;
import android.view.View;

public class GuideActivity extends FragmentActivity {

    private WelcomeFragment1 fragment1;
    private WelcomeFragment2 fragment2;
    private WelcomeFragment3 fragment3;
    private FragAdapter adapter;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_guide);
        viewPager = (ViewPager) findViewById(R.id.viewpager);
        List<Fragment> fragments = new ArrayList<Fragment>();
        fragment1 = new WelcomeFragment1();
        fragment2 = new WelcomeFragment2();
        fragment3 = new WelcomeFragment3();
        fragments.add(fragment1);
        fragments.add(fragment2);
        fragments.add(fragment3);

        if (adapter == null) {
            adapter = new FragAdapter(getSupportFragmentManager(), fragments);
            viewPager.setAdapter(adapter);
            viewPager.setPageTransformer(true, new RotateDownPageTransformer());
        }else{
            adapter.notifyDataSetChanged();
        }

        viewPager.setOnPageChangeListener(new OnPageChangeListener() {

            @Override
            public void onPageSelected(int arg0) {

            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {

            }

            @Override
            public void onPageScrollStateChanged(int arg0) {

            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
    }

    public class FragAdapter extends FragmentPagerAdapter{
        private List<Fragment> mFragments;
        public FragAdapter(FragmentManager fm,List<Fragment> fragments) {
            super(fm);
            mFragments = fragments;
        }

        @Override
        public Fragment getItem(int arg0) {
            return mFragments.get(arg0);
        }

        @Override
        public int getCount() {
            return mFragments.size();
        }

    }

    public class RotateDownPageTransformer implements ViewPager.PageTransformer  
    {  

        private static final float ROT_MAX = 20.0f;  
        private float mRot;  



        public void transformPage(View view, float position)  
        {  

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

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

                    mRot = (ROT_MAX * position);  
                    ViewHelper.setPivotX(view, view.getMeasuredWidth() * 0.5f);  
                    ViewHelper.setPivotY(view, view.getMeasuredHeight());  
                    ViewHelper.setRotation(view, mRot);  
                } else  
                {  

                    mRot = (ROT_MAX * position);  
                    ViewHelper.setPivotX(view, view.getMeasuredWidth() * 0.5f);  
                    ViewHelper.setPivotY(view, view.getMeasuredHeight());  
                    ViewHelper.setRotation(view, mRot);  
                }  

                // Scale the page down (between MIN_SCALE and 1)  

                // Fade the page relative to its size.  

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

不过你这个时候还需要到网上下载一个jar包，nineoldAndroid.jar，这个jar包主要是兼容3.0以下的，还有上面使用的ViewHelper是依赖于这个包的，你可以用我给的代码试试，不懂的再问。