稍微巧妙的双模块联动-ViewPager

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上个月我们项目开启了新的版本,有一个双模块联动的效果印象很深,这次就记录下来供大家参考一下

预计效果

这个部分一开始是上面或者下面滑动到上一个或下一个时 另一个才会进行移动,苹果同学那边好像很简单的就搞定了,我们这边就需要特别改造一下Viewpager.

第一步就是先实现上面的画廊效果,这个倒是不难,下面是代码

activity.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clipChildren="false"
    tools:context=".viepager.ViewpagerActivity">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewpager1"
        android:layout_width="200dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_height="200dp"
        android:layout_marginTop="20dp"
        android:clipChildren="false"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.viewpager.widget.ViewPager
        android:layout_marginTop="30dp"
        android:id="@+id/viewpager2"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toBottomOf="@id/viewpager1" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity

public class ViewpagerActivity extends AppCompatActivity {

    private ViewPager mViewpager1;
    private ViewPager mViewpager2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_viewpager);
        initView();
    }

    private void initView() {
        mViewpager1 = findViewById(R.id.viewpager1);
        mViewpager2 = findViewById(R.id.viewpager2);
        zoomOutPageTransformer = new ZoomOutPageTransformer();
        mViewpager1.setPageMargin(ImageUtil.dp2px(this, 20));
        mViewpager1.setPageTransformer(true, zoomOutPageTransformer);
        mViewpager1.setAdapter(new TopViewPgaerAdapter(this));
        mViewpager2.setAdapter(new BottomViewPagerAdapter(this));
        //缓存一下,不然会出现位置错乱
        mViewpager1.setOffscreenPageLimit(5);
        mViewpager2.setOffscreenPageLimit(5);
    }
}

ZoomOutPageTransformer

//画廊
public class ZoomOutPageTransformer implements ViewPager.PageTransformer{
    //自由控制缩放比例
    private static final float MAX_SCALE = 1f;
    private static final float MIN_SCALE = 0.8f;//0.85f

    @Override
    public void transformPage(View page, float position) {

        if (position <= 1) {
            float scaleFactor = MIN_SCALE + (1 - Math.abs(position)) * (MAX_SCALE - MIN_SCALE);
            page.setScaleX(scaleFactor);
            if (position > 0) {
                page.setTranslationX(-scaleFactor * 2);
            } else if (position < 0) {
                page.setTranslationX(scaleFactor * 2);
            }
            page.setScaleY(scaleFactor);
        } else {
            page.setScaleX(MIN_SCALE);
            page.setScaleY(MIN_SCALE);
        }
    }
} 

这个用的是网络上某位兄弟的代码,这里我也找不到原作者了,复制百度一下一堆相同的,感谢那位兄弟提供的轮子代码.

TopViewPgaerAdapter

class TopViewPgaerAdapter(var context: Context) : PagerAdapter() {
    override fun getCount(): Int {
        return 5
    }

    override fun isViewFromObject(view: View, `object`: Any): Boolean {
        return view == `object`
    }
    override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
    }

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        val inflate = LayoutInflater.from(context).inflate(R.layout.item_top, container, false)
        container.addView(inflate)
        return inflate
    }
}

item_top

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.constraintlayout.utils.widget.ImageFilterButton
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@color/teal_200"/>
</androidx.constraintlayout.widget.ConstraintLayout>

BottomViewPagerAdapter

class BottomViewPagerAdapter(var context: Context) : PagerAdapter() {
    override fun getCount(): Int {
        return 5
    }

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        val inflate = LayoutInflater.from(context).inflate(R.layout.item_parent, container, false)
        container.addView(inflate)

        return inflate
    }

    override fun isViewFromObject(view: View, `object`: Any): Boolean {
        return view === `object`
    }

    override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
    }
}

item_parent

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginTop="20dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="撒打发建行卡沙发开讲啦啥大富科技阿斯顿
撒打发建行卡沙发开讲啦啥大富科技阿斯顿\n
撒打发建行卡沙发开讲啦啥大富科技阿斯顿\n
撒打发建行卡沙发开讲啦啥大富科技阿斯顿\n"
        android:textSize="20dp"
        android:textStyle="italic" />
</androidx.constraintlayout.widget.ConstraintLayout>

效果

效果还不错,雏形已经准备完毕,开始完善细节

首先在initView加这么几行代码

BaseLinkPageChangeListener baseLinkPageChangeListener = new BaseLinkPageChangeListener(mViewpager1, mViewpager2, this, true);
mViewpager1.addOnPageChangeListener( baseLinkPageChangeListener);

BaseLinkPageChangeListener baseLinkPageChangeListener1 = new BaseLinkPageChangeListener(mViewpager2, mViewpager1, this, false);
baseLinkPageChangeListener1.setZoomOutPageTransformer(zoomOutPageTransformer);
mViewpager2.addOnPageChangeListener(baseLinkPageChangeListener1);

BaseLinkPageChangeListener

public class BaseLinkPageChangeListener implements ViewPager.OnPageChangeListener {

    private final ViewPager linkViewPager;
    private final ViewPager selfViewPager;
    private final Activity activity;
    private ZoomOutPageTransformer zoomOutPageTransformer;
    private final boolean isTop;

    private int marginX = 0;

    public BaseLinkPageChangeListener(ViewPager selfViewPager, ViewPager linkViewPager, Activity activity, boolean isTop) {
        this.linkViewPager = linkViewPager;
        this.selfViewPager = selfViewPager;
        this.activity = activity;
        this.isTop = isTop;
    }

    public void setZoomOutPageTransformer(ZoomOutPageTransformer zoomOutPageTransformer) {
        this.zoomOutPageTransformer = zoomOutPageTransformer;
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        //计算移动值
        marginX = ((selfViewPager.getWidth() + selfViewPager.getPageMargin()) * position
                + positionOffsetPixels) * (linkViewPager.getWidth() + linkViewPager.getPageMargin()) / (
                selfViewPager.getWidth()
                        + selfViewPager.getPageMargin());

        if (linkViewPager.getScrollX() != marginX) {
            linkViewPager.scrollTo(marginX, 0);
        }

        //如果是底部viewpager,那么在滑动的时候也要响应的将动画给带动起来
        if (!isTop) {
            if (zoomOutPageTransformer != null) {
                final int scrollX = marginX;
                final int childCount = linkViewPager.getChildCount();
                for (int i = 0; i < childCount; i++) {
                    final View child = linkViewPager.getChildAt(i);
                    final ViewPager.LayoutParams lp = (ViewPager.LayoutParams) child.getLayoutParams();

                    if (lp.isDecor) continue;
                    final float transformPos = (float) (child.getLeft() - scrollX) / ImageUtil.dp2px(activity,200);
                    //重要!!!
                    zoomOutPageTransformer.transformPage(child, transformPos);
                }
            }
        }
    }

    @Override
    public void onPageSelected(int position) {

    }

    @Override
    public void onPageScrollStateChanged(int state) {
//        if (state == ViewPager.SCROLL_STATE_IDLE) {
//            linkViewPager.setCurrentItem(position);
//        }
    }
}

这个是最为重要的一个类了,主要涉及到滑动处理,self就是当前viewpager,link就是另一个viewpager

效果

我在实际项目的使用中是拿到数据后在setadapter加setOffscreenPageLimit,你也可以拿到数据后notifyDataSetChanged然后setOffscreenPageLimit设置缓存,缓存是必须的,不然会动画,数据错乱

Handler handler = new Handler(new Handler.Callback() {
    @Override
    public boolean handleMessage(@NonNull Message msg) {
        topViewPgaerAdapter.setPos(5);
        bottomViewPagerAdapter.setPos(5);

        topViewPgaerAdapter.notifyDataSetChanged();
        bottomViewPagerAdapter.notifyDataSetChanged();

        mViewpager1.setOffscreenPageLimit(5);
        mViewpager2.setOffscreenPageLimit(5);
        return true;
    }
});

简单用handler实现了一个伪环境,setPos就是getcount需要的值,这样也是可以的,其实不必要使用PagerAdapter也可以使用FragmentPagerAdapter,用Fragment实现更复杂丰富的页面,我这里只是提供一个思路

好了,摸鱼时间结束,开始优化项目啦!!!