Modify:创建ViewPager2的基础adapter封装。Fragment，Activity的数据状态帮助类重写封装。

lib_common/src/main/java/com/quyunshuo/androidbaseframemvvm/common/ui/BaseFragmentStateAdapter.kt

@@ -0,0 +1,176 @@
+package com.quyunshuo.androidbaseframemvvm.common.ui
+
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.FragmentActivity
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.RecyclerView
+import androidx.viewpager2.adapter.FragmentStateAdapter
+import kotlin.random.Random
+
+/**
+ * @author DBoy 2021/8/5 <p>
+ * - 文件描述 : ViewPager2 FragmentAdapter封装
+ * - 对于元数据[mData]的增加删除操作只能通过内部提供的4种方式进行操作:
+ *     - [setNewData]
+ *     - [addNewData]
+ *     - [addData]
+ *     - [removeData]
+ * - 内部使用[DiffUtil]工具实现更新UI,不需调用[notifyDataSetChanged]等一系列方法。
+ */
+abstract class BaseFragmentStateAdapter<T> : FragmentStateAdapter {
+
+    private val TAG = "FragmentAdapter"
+
+    /**
+     * 记录生成的Fragment id列表
+     */
+    private var mFragmentIdMap = mutableMapOf<T, Long>()
+
+    /**
+     * 需要生成页面的数据
+     */
+    var mData: MutableList<T>
+        set(value) {
+            field = value
+            mFragmentIdMap.clear()
+            createFragmentsIds(field)
+        }
+
+    constructor(fragment: Fragment, data: MutableList<T> = mutableListOf()) : super(fragment) {
+        mData = data
+    }
+
+    constructor(activity: FragmentActivity, data: MutableList<T> = mutableListOf()) : super(
+        activity
+    ) {
+        mData = data
+    }
+
+    /**
+     * 获取需要创建几个Fragment
+     */
+    override fun getItemCount(): Int = mData.size
+
+    /**
+     * 创建Fragment
+     */
+    final override fun createFragment(position: Int): Fragment {
+        return createFragment(mData[position], position)
+    }
+
+    /**
+     * 创建fragment 传递数据
+     */
+    abstract fun createFragment(item: T, position: Int): Fragment
+
+    /**
+     * 获取fragment 对应 id
+     */
+    override fun getItemId(position: Int): Long {
+        if (position >= mData.size) return RecyclerView.NO_ID
+        return mFragmentIdMap[mData[position]] ?: return RecyclerView.NO_ID
+    }
+
+    /**
+     * 判断是否包含这个id的数
+     */
+    override fun containsItem(itemId: Long): Boolean {
+        return mFragmentIdMap.values.contains(itemId)
+    }
+
+    /**
+     * 设置新数据
+     */
+    fun setNewData(data: MutableList<T> = mutableListOf()) {
+        val oldData = copyData()
+        mData = data
+        diffNotifyDataSetChanged(oldData, mData)
+    }
+
+    /**
+     * 累加新数据
+     */
+    fun addNewData(data: MutableList<T> = mutableListOf()) {
+        val oldData = copyData()
+        mData.addAll(data)
+        //创建新的对应位置的id
+        createFragmentsIds(data)
+        diffNotifyDataSetChanged(oldData, mData)
+
+    }
+
+    /**
+     * 添加数据
+     */
+    fun addData(data: T) {
+        val oldData = copyData()
+        mData.add(data)
+        //随机一个id对应当前位置Fragment,两次随机确保同id率为最低概率
+        mFragmentIdMap[data] = Random.nextLong() - Random.nextInt()
+        diffNotifyDataSetChanged(oldData, mData)
+    }
+
+    /**
+     * 移除某个数据
+     */
+    fun removeData(data: T): Boolean {
+        val oldData = copyData()
+        if (mData.remove(data)) {
+            mFragmentIdMap.remove(data)
+            diffNotifyDataSetChanged(oldData, mData)
+            return true
+        }
+        return false
+    }
+
+    /**
+     * 移除某个位置的数据
+     */
+    fun removeData(position: Int): Boolean {
+        if (position < mData.size && position < mFragmentIdMap.size) {
+            val oldData = copyData()
+            val removeItem = mData.removeAt(position)
+            mFragmentIdMap.remove(removeItem)
+            diffNotifyDataSetChanged(oldData, mData)
+            return true
+        }
+        return false
+    }
+
+    /**
+     * 拷贝原数据
+     */
+    private fun copyData(): MutableList<T> {
+        val oldData = mutableListOf<T>()
+        oldData.addAll(mData)
+        return oldData
+    }
+
+    /**
+     * 使用diff工具更新UI,当前diff工具对比使用的方式是 [==] 所以如果需要精确对比不同item数据，可以重写[T]的[equals]方法.
+     */
+    private fun diffNotifyDataSetChanged(oldData: MutableList<T>, newData: MutableList<T>) {
+        DiffUtil.calculateDiff(object : DiffUtil.Callback() {
+
+            override fun getOldListSize(): Int = oldData.size
+
+            override fun getNewListSize(): Int = newData.size
+
+            override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean = oldData[oldItemPosition] == newData[newItemPosition]
+
+            override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean = oldData[oldItemPosition] == newData[newItemPosition]
+
+        }, true).dispatchUpdatesTo(this)
+    }
+
+
+    /**
+     * 创建[mData]对应Fragment的id
+     */
+    private fun createFragmentsIds(data: MutableList<T>) {
+        for (item in data) {
+            mFragmentIdMap[item] = Random.nextLong() - Random.nextInt()
+        }
+    }
+
+}