android mvvm+FragmentContainerView+BottomNavigationView搭建基础框架

技术小白菜
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背景

android的知识更新相对于后台来说稍微频繁一点，下面主要讲解用最新技术栈来搭建一个最基础的框架，顺便练练手，其中遇到了一点小小坑，特此记录一下。

一、搭建基础类 BaseActivity

abstract class BaseActivity<T : ViewDataBinding> : AppCompatActivity {

    constructor() : super()

    private lateinit var mLoadingDialog: LoadingDialog

    var mBinding: T? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        //getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_PAN);
        StatusBar().fitSystemBar(this)
        mLoadingDialog = LoadingDialog(this)
        mBinding = DataBindingUtil.setContentView(this, getLayoutId())
        initData(savedInstanceState)

    }

    override fun onDestroy() {
        super.onDestroy()
        mBinding?.unbind()
    }

    abstract fun initData(savedInstanceState: Bundle?)

    abstract fun getLayoutId(): Int


    /**
     * show 加载中
     */
    fun showLoading() {
        mLoadingDialog.showDialog(this, false)
    }

    /**
     * dismiss loading dialog
     */
    fun dismissLoading() {
        mLoadingDialog.dismissDialog()
    }


    /**
     * 设置toolbar名称
     */
    protected fun setToolbarTitle(view: TextView, title: String) {
        view.text = title
    }

    /**
     * 设置toolbar返回按键图片
     */
    protected fun setToolbarBackIcon(view: ImageView, id: Int) {
        view.setBackgroundResource(id)
    }
}

二、搭建基础类BaseFragment

package com.example.command.base

import android.content.Context
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.databinding.DataBindingUtil
import androidx.databinding.ViewDataBinding
import androidx.fragment.app.Fragment
import com.example.command.R
import com.example.command.databinding.BaseFragmentLayoutBinding
import com.example.command.widget.LoadingDialog

import com.kingja.loadsir.core.LoadService

private const val TAG = "BaseFragment"

abstract class BaseFragment<T : ViewDataBinding> : Fragment() {

    var mBinding: T? = null
    private lateinit var mContext: Context
    private lateinit var mLoadingDialog: LoadingDialog
    private lateinit var loadService: LoadService<Any>
    private lateinit var mBaseContainBinding: BaseFragmentLayoutBinding

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        mBaseContainBinding =
            DataBindingUtil.inflate(inflater, R.layout.base_fragment_layout, container, false)
        mBinding = DataBindingUtil.inflate(inflater, getLayoutId(), container, false)

        mBaseContainBinding.baseContainer.addView(mBinding?.root)
        return mBaseContainBinding.root
    }

    override fun onAttach(context: Context) {
        super.onAttach(context)
        mContext = context
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        mLoadingDialog = LoadingDialog(view.context)
        initData()
    }

    abstract fun initData()

    override fun onDestroy() {
        super.onDestroy()
        mBinding?.unbind()
    }

    abstract fun getLayoutId(): Int


    /**
     * show 加载中
     */
    private fun showLoading() {
        mLoadingDialog.showDialog(mContext, false)
    }

    /**
     * dismiss loading dialog
     */
    private fun dismissLoading() {
        mLoadingDialog.dismissDialog()
    }

    private var time: Long = 0
    private var oldMsg: String? = null

    /**
     * 相同msg 只显示一个。
     */
    fun showToast(msg: String) {
        if (msg != oldMsg) {
            Toast.makeText(mContext, msg, Toast.LENGTH_SHORT).show()
            time = System.currentTimeMillis()
        } else {
            if (System.currentTimeMillis() - time > 2000) {
                Toast.makeText(mContext, msg, Toast.LENGTH_SHORT).show()
                time = System.currentTimeMillis()
            }
        }
        oldMsg = msg
    }

三、编写MainActivity类

（1）activity.main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

    </data>

    <LinearLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:fitsSystemWindows="true"
        android:background="@color/color_ffffff">

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/nav_host_container"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            app:defaultNavHost="true"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            />

        <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/nav_view"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:menu="@menu/bottom_nav_view" />

    </LinearLayout>
</layout>

这里布局采用的FragmentContainerView+BottomNavigationView方式，而不再采用传统的FrameLayout+GroupBottom的这种方式。

(2)menu

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/navigation_home"
        android:icon="@drawable/ic_baseline_home_24"
        android:title="@string/title_home"/>

    <item
        android:id="@+id/navigation_dashboard"
        android:icon="@drawable/ic_baseline_call_split_24"
        android:title="@string/title_dashboard"/>

    <item
        android:id="@+id/navigation_personal"
        android:icon="@drawable/ic_baseline_person_outline_24"
        android:title="@string/title_notifications"/>
</menu>

（3） 创建Fragment文件

image.png

（1）naviation_home.xml

     
<?xml version="1.0" encoding="utf-8"?>
<navigation 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:id="@+id/navigation_home"
 app:startDestination="@id/fragment_home">
 <fragment
     android:id="@+id/fragment_home"
     android:name="com.example.home.HomeFragment"
     tools:layout="@layout/fragment_home"/>
</navigation>

这里需要注意一下，这个android:id="@+id/navigation_home"一定要和men资源下的item id一定是相同的，这样才能绑定Id，一个小坑。比如首页Id是"navigation_home"，那么给navigation id也要是"navigation_home"

（2）HomeFragement

class HomeFragment : BaseFragment<FragmentHomeBinding>() {
    override fun getLayoutId(): Int {
      return R.layout.fragment_home
    }

    override fun initData() {
    }


}

其他类似

（4）MainActivity

package com.example.study

import android.os.Bundle
import android.view.View
import androidx.lifecycle.LiveData
import androidx.lifecycle.Observer
import androidx.navigation.NavController
import com.alibaba.android.arouter.facade.annotation.Route
import com.example.command.base.BaseActivity
import com.example.command.ktx.setupWithNavController
import com.example.command.support.Constants
import com.example.study.databinding.ActivityMainBinding


private const val TAG = "MainActivity"

class MainActivity : BaseActivity<ActivityMainBinding>() {
    private var currentNavController: LiveData<NavController>? = null

    override fun getLayoutId(): Int {
        return R.layout.activity_main
    }

    override fun initData(savedInstanceState: Bundle?) {
        if (savedInstanceState == null) {
            setupBottomNavigationBar()
        }

    }

    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
        super.onRestoreInstanceState(savedInstanceState)
        setupBottomNavigationBar()
    }

    /**
     * navigation绑定BottomNavigationView
     */
    private fun setupBottomNavigationBar() {
        val navGraphIds =
            listOf(R.navigation.naviation_home, R.navigation.navigation_dashboard,R.navigation.navigation_personal)

        val controller = mBinding?.navView?.setupWithNavController(
            navGraphIds = navGraphIds,
            fragmentManager = supportFragmentManager,
            containerId = R.id.nav_host_container,
            intent = intent
        )
        controller?.observe(this, Observer { navController ->
            //setupActionBarWithNavController(navController)
            navController.addOnDestinationChangedListener { _, destination, _ ->
                run {
                    val id = destination.id
                     mBinding?.navView?.visibility = View.VISIBLE
                }
            }
        })
        currentNavController = controller
    }

    override fun onSupportNavigateUp(): Boolean {
        return currentNavController?.value?.navigateUp() ?: false
    }
}

（4）自定义BottomNavigationView.setupWithNavController方法

fun BottomNavigationView.setupWithNavController(
    navGraphIds: List<Int>,
    fragmentManager: FragmentManager,
    containerId: Int,
    intent: Intent
): LiveData<NavController> {

    // Map of tags
    val graphIdToTagMap = SparseArray<String>()
    // Result. Mutable live data with the selected controlled
    val selectedNavController = MutableLiveData<NavController>()

    var firstFragmentGraphId = 0

    // First create a NavHostFragment for each NavGraph ID
    navGraphIds.forEachIndexed { index, navGraphId ->
        val fragmentTag = getFragmentTag(index)

        // Find or create the Navigation host fragment
        val navHostFragment = obtainNavHostFragment(
            fragmentManager,
            fragmentTag,
            navGraphId,
            containerId
        )

        // Obtain its id
        val graphId = navHostFragment.navController.graph.id

        if (index == 0) {
            firstFragmentGraphId = graphId
        }

        // Save to the map
        graphIdToTagMap[graphId] = fragmentTag

        // Attach or detach nav host fragment depending on whether it's the selected item.
        Log.d(TAG, "setupWithNavController: $selectedItemId and $graphId")
        Log.d(TAG, "setupWithNavController: $fragmentTag and $graphId")
        if (this.selectedItemId == graphId) {
            // Update livedata with the selected graph
            selectedNavController.value = navHostFragment.navController
            attachNavHostFragment(fragmentManager, navHostFragment, index == 0)
        } else {
            detachNavHostFragment(fragmentManager, navHostFragment)
        }
    }

    // Now connect selecting an item with swapping Fragments
    var selectedItemTag = graphIdToTagMap[this.selectedItemId]
    val firstFragmentTag = graphIdToTagMap[firstFragmentGraphId]
    var isOnFirstFragment = selectedItemTag == firstFragmentTag

    // When a navigation item is selected
    setOnNavigationItemSelectedListener { item ->
        // Don't do anything if the state is state has already been saved.
        if (fragmentManager.isStateSaved) {
            Log.d(TAG, "setupWithNavController: isStateSaved ")
            false
        } else {
            val newlySelectedItemTag = graphIdToTagMap[item.itemId]
            if (selectedItemTag != newlySelectedItemTag) {
                // Pop everything above the first fragment (the "fixed start destination")
                fragmentManager.popBackStack(firstFragmentTag,
                    FragmentManager.POP_BACK_STACK_INCLUSIVE)
                val selectedFragment = fragmentManager.findFragmentByTag(newlySelectedItemTag)
                        as NavHostFragment

                Log.d(TAG, "setupWithNavController: $firstFragmentTag and $newlySelectedItemTag")
                // Exclude the first fragment tag because it's always in the back stack.
                if (firstFragmentTag != newlySelectedItemTag) {
                    // Commit a transaction that cleans the back stack and adds the first fragment
                    // to it, creating the fixed started destination.
                    fragmentManager.beginTransaction()
                        .setCustomAnimations(
                            R.anim.nav_default_enter_anim,
                            R.anim.nav_default_exit_anim,
                            R.anim.nav_default_pop_enter_anim,
                            R.anim.nav_default_pop_exit_anim)
                        .attach(selectedFragment)
                        .setPrimaryNavigationFragment(selectedFragment)
                        .apply {
                            // Detach all other Fragments
                            graphIdToTagMap.forEach { _, fragmentTagIter ->
                                if (fragmentTagIter != newlySelectedItemTag) {
                                    detach(fragmentManager.findFragmentByTag(firstFragmentTag)!!)
                                }
                            }
                        }
                        .addToBackStack(firstFragmentTag)
                        .setReorderingAllowed(true)
                        .commit()
                    Log.d(TAG, "setupWithNavController: $firstFragmentTag")
                }
                selectedItemTag = newlySelectedItemTag
                isOnFirstFragment = selectedItemTag == firstFragmentTag
                selectedNavController.value = selectedFragment.navController
                true
            } else {
                false
            }
        }
    }

    // Optional: on item reselected, pop back stack to the destination of the graph
    setupItemReselected(graphIdToTagMap, fragmentManager)

    // Handle deep link
    setupDeepLinks(navGraphIds, fragmentManager, containerId, intent)

    // Finally, ensure that we update our BottomNavigationView when the back stack changes
    fragmentManager.addOnBackStackChangedListener {
        if (!isOnFirstFragment && !fragmentManager.isOnBackStack(firstFragmentTag)) {
            this.selectedItemId = firstFragmentGraphId
        }

        // Reset the graph if the currentDestination is not valid (happens when the back
        // stack is popped after using the back button).
        selectedNavController.value?.let { controller ->
            if (controller.currentDestination == null) {
                controller.navigate(controller.graph.id)
            }
        }
    }
    return selectedNavController
}

private fun BottomNavigationView.setupDeepLinks(
    navGraphIds: List<Int>,
    fragmentManager: FragmentManager,
    containerId: Int,
    intent: Intent
) {
    navGraphIds.forEachIndexed { index, navGraphId ->
        val fragmentTag = getFragmentTag(index)

        // Find or create the Navigation host fragment
        val navHostFragment = obtainNavHostFragment(
            fragmentManager,
            fragmentTag,
            navGraphId,
            containerId
        )
        // Handle Intent
        if (navHostFragment.navController.handleDeepLink(intent)
            && selectedItemId != navHostFragment.navController.graph.id) {
            this.selectedItemId = navHostFragment.navController.graph.id
        }
    }
}

private fun BottomNavigationView.setupItemReselected(
    graphIdToTagMap: SparseArray<String>,
    fragmentManager: FragmentManager
) {
    setOnNavigationItemReselectedListener { item ->
        val newlySelectedItemTag = graphIdToTagMap[item.itemId]
        val selectedFragment = fragmentManager.findFragmentByTag(newlySelectedItemTag)
                as NavHostFragment
        val navController = selectedFragment.navController
        // Pop the back stack to the start destination of the current navController graph
        navController.popBackStack(
            navController.graph.startDestination, false
        )
    }
}

private fun detachNavHostFragment(
    fragmentManager: FragmentManager,
    navHostFragment: NavHostFragment
) {
    fragmentManager.beginTransaction()
        .detach(navHostFragment)
        .commitNow()
}

private fun attachNavHostFragment(
    fragmentManager: FragmentManager,
    navHostFragment: NavHostFragment,
    isPrimaryNavFragment: Boolean
) {
    Log.d(TAG, "attachNavHostFragment: ")
    fragmentManager.beginTransaction()
        .attach(navHostFragment)
        .apply {
            if (isPrimaryNavFragment) {
                setPrimaryNavigationFragment(navHostFragment)
            }
        }
        .commitNow()

}

private fun obtainNavHostFragment(
    fragmentManager: FragmentManager,
    fragmentTag: String,
    navGraphId: Int,
    containerId: Int
): NavHostFragment {
    // If the Nav Host fragment exists, return it
    val existingFragment = fragmentManager.findFragmentByTag(fragmentTag) as NavHostFragment?
    existingFragment?.let { return it }

    Log.d(TAG, "obtainNavHostFragment existingFragment : $existingFragment ")
    // Otherwise, create it and return it.
    val navHostFragment = NavHostFragment.create(navGraphId)
    fragmentManager.beginTransaction()
        .add(containerId, navHostFragment, fragmentTag)
        .commitNow()
    return navHostFragment
}

private fun FragmentManager.isOnBackStack(backStackName: String): Boolean {
    val backStackCount = backStackEntryCount
    for (index in 0 until backStackCount) {
        if (getBackStackEntryAt(index).name == backStackName) {
            return true
        }
    }
    return false
}

private fun getFragmentTag(index: Int) = "bottomNavigation#$index"

三、效果图

（1）

image.png

（2）

image.png

（3）

image.png

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