Android自定义卡片切换效果

今天给大家实现一个自定义的卡片切换效果。

gallery

工程结构非常简单，就以下三个类：

        TestGalleryActivity

package com.openld.seniorui.testgallery

import android.os.Bundle
import android.os.Message
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import androidx.viewpager.widget.ViewPager
import com.openld.seniorui.R
import java.util.*


class TestGalleryActivity : AppCompatActivity() {
    private val TAG = "Gallery"

    private var mCurrentIndex = 0

    private lateinit var mGallery: ViewPager

    private val mFruitList = mutableListOf()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_test_gallery)

        initData()

        initWidgets()

        addListeners()
    }

    private fun initData() {
        mFruitList.add(R.drawable.fruit_image1)
        mFruitList.add(R.drawable.fruit_image2)
        mFruitList.add(R.drawable.fruit_image3)
        mFruitList.add(R.drawable.fruit_image4)
        mFruitList.add(R.drawable.fruit_image5)
        mFruitList.add(R.drawable.fruit_image6)
        mFruitList.add(R.drawable.fruit_image7)
        mFruitList.add(R.drawable.fruit_image8)
        mFruitList.add(R.drawable.fruit_image9)
        mFruitList.add(R.drawable.fruit_image10)
        mFruitList.add(R.drawable.fruit_image11)
        mFruitList.add(R.drawable.fruit_image12)
        mFruitList.add(R.drawable.fruit_image13)
        mFruitList.add(R.drawable.fruit_image14)
        mFruitList.add(R.drawable.fruit_image15)
        mFruitList.add(R.drawable.fruit_image16)
        mFruitList.add(R.drawable.fruit_image17)
    }

    private fun addListeners() {
        mGallery.addOnPageChangeListener(object : ViewPager.OnPageChangeListener {
            override fun onPageScrolled(
                position: Int,
                positionOffset: Float,
                positionOffsetPixels: Int
            ) {
                Log.d(TAG, ">>> $position")
                mCurrentIndex = position
            }

            override fun onPageSelected(position: Int) {
            }

            override fun onPageScrollStateChanged(state: Int) {
            }
        })
    }

    private fun initWidgets() {
        Message.obtain()
        mGallery = findViewById(R.id.gallery)
        val adapter = GalleryAdapter(this, mFruitList)
        mGallery.offscreenPageLimit = mFruitList.size
        mGallery.adapter = adapter
        mGallery.currentItem = mFruitList.size - 1
        mGallery.setPageTransformer(false, GalleryTransformer())

        // 滑到第一个
        scrollToFirst()

        // 训话滑动轮播
        loopScroll()
    }

    
    private fun loopScroll() {
        // 轮播
        mGallery.postDelayed({
            val timer = Timer()
            timer.schedule(object : TimerTask() {
                override fun run() {
                    if (mCurrentIndex == mFruitList.size) {
                        mCurrentIndex = 0
                    }
                    mGallery.currentItem = mCurrentIndex++
                }
            }, 0, 2000)
        }, 2200)
    }

    
    private fun scrollToFirst() {
        // 这鬼滑动速度不知道怎么控制
        mGallery.postDelayed({
            mGallery.setCurrentItem(0, true)
        }, 200)
    }
}

        页面布局activity_test_gallery.xml

        页面中的图片资源自己替换下好了

        GalleryAdapter

package com.openld.seniorui.testgallery

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.annotation.NonNull
import androidx.appcompat.widget.AppCompatImageView
import androidx.viewpager.widget.PagerAdapter
import com.openld.seniorui.R

class GalleryAdapter(@NonNull context: Context, @NonNull fruitList: List) :
    PagerAdapter() {
    private val mContext = context
    private var mFruitList: List = fruitList

    override fun getCount(): Int {
        return mFruitList.size
    }

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

    override fun instantiateItem(container: ViewGroup, position: Int): Any {
        return LayoutInflater.from(mContext).inflate(R.layout.item_gallery, container, false)
            .apply {
                val imgFruit: AppCompatImageView = findViewById(R.id.img_fruit)
                imgFruit.setImageResource(mFruitList[position])
                imgFruit.setOnClickListener {
                    Toast.makeText(mContext, "点击了第${position}个图片", Toast.LENGTH_SHORT).show()
                }

                tag = "gallery_item_$position"
                container.addView(this)
            }
    }

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

        适配器条目布局item_gallery.xml

用到的图片资源自己换一下好了

        GalleryTransformer

        控制滑动时候的各种属性变化，达到自定义滑动切换时候的炫酷效果。

package com.openld.seniorui.testgallery

import android.view.View
import androidx.viewpager.widget.ViewPager


class GalleryTransformer : ViewPager.PageTransformer {
    private val MIN_SCALE = 0.5F

    override fun transformPage(page: View, position: Float) {
        if (position < 0F) {
            page.scaleX = MIN_SCALE * position + 1.5F
            page.scaleY = MIN_SCALE * position + 1.5F
            page.alpha = MIN_SCALE * position + 1
//            page.rotationY = 30F * position
            page.rotation = 30 * position
        } else {
            page.scaleX = -MIN_SCALE * position + 1.5F
            page.scaleY = -MIN_SCALE * position + 1.5F
            page.alpha = -MIN_SCALE * position + 1
//            page.rotationY = 30F * position
            page.rotation = 30 * position
        }

        page.elevation = page.scaleX
    }
}

        这里效果的关键就是这个GalleryTransformer类，不明白原理的可以看下ViewPager.PageTransformer的相关源码或者解释。

        就是page滑到中间的时候position为0，page在左侧时position取值区间为(-1, 0)，page在右侧时position取值区间为(0, 1)，根据这个再结合一些诸如alpha、scaleX、scaleY、rotation等属性的设置就能实现你要的切换效果啦。