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