【Android Jetpack】使用Kotlin DSL配置Navigation Components

柔情只为你懂 2022-12-26 11:22 198阅读 0赞

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想要在APP中使用Jetpack的Navigation组件进行页面跳转，需要事先为其配置`NavGraph`

# 基于XML配置 #

--------------------

通常可以使用xml进行配置，例如官方`sunflower`例子中的`nav_garden.xml`

<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" app:startDestination="@id/view_pager_fragment">
    
        <fragment android:id="@+id/view_pager_fragment" android:name="com.google.samples.apps.sunflower.HomeViewPagerFragment" tools:layout="@layout/fragment_view_pager">
    
            <action android:id="@+id/action_view_pager_fragment_to_plant_detail_fragment" app:destination="@id/plant_detail_fragment" app:enterAnim="@anim/slide_in_right" app:exitAnim="@anim/slide_out_left" app:popEnterAnim="@anim/slide_in_left" app:popExitAnim="@anim/slide_out_right" />
        </fragment>
    
        <fragment android:id="@+id/plant_detail_fragment" android:name="com.google.samples.apps.sunflower.PlantDetailFragment" android:label="@string/plant_details_title" tools:layout="@layout/fragment_plant_detail">
    
            <action android:id="@+id/action_plant_detail_fragment_to_gallery_fragment" app:destination="@id/gallery_fragment" app:enterAnim="@anim/slide_in_right" app:exitAnim="@anim/slide_out_left" app:popEnterAnim="@anim/slide_in_left" app:popExitAnim="@anim/slide_out_right" />
            <argument android:name="plantId" app:argType="string" />
        </fragment>
    
        <fragment android:id="@+id/gallery_fragment" android:name="com.google.samples.apps.sunflower.GalleryFragment" android:label="@string/plant_details_title" tools:layout="@layout/fragment_gallery">
            <argument android:name="plantName" app:argType="string" />
        </fragment>
    
    </navigation>

然后在Layout的根Fragment（即`NavHostFragment`）配置此xml资源

# 基于DSL配置 #

--------------------

随着Kotlin在Android中的日益普及，使用Kotlin的dsl替代xml或许是一个更好的选择。谷歌官方顺势为Navigation推出了`KTX`扩展，支持使用dsl配置`NavGraph`

dependencies { 
        def nav_version = "2.3.1"
        implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
    }

使用dsl后，NavHostFragment无需再指定xml资源

<androidx.fragment.app.FragmentContainerView android:id="@+id/nav_host" android:name="androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" - app:defaultNavHost="true" - app:navGraph="@navigation/nav_garden" + app:defaultNavHost="true" />

然后我们直接在代码中通过dsl配置NavGraph。

//GardenActivity.kt
    class GardenActivity : AppCompatActivity() { 
        override fun onCreate(savedInstanceState: Bundle?) { 
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_garden)
    
            val navHostFragment = supportFragmentManager
                    .findFragmentById(R.id.nav_host) as NavHostFragment
    
            navHostFragment.navController.apply { 
                graph = createGraph(nav_graph.id, nav_graph.dest.home) {  // this: NavGraphBuilder
                    // 配置Fragment Destination
                    fragment<HomeViewPagerFragment>(nav_graph.dest.home) { 
                        label = getString(R.string.home_title)
                        action(nav_graph.action.to_plant_detail) { 
                            destinationId = nav_graph.dest.plant_detail
                        }
                    }
                    fragment<PlantDetailFragment>(nav_graph.dest.plant_detail) { 
                        label = getString(R.string.plant_detail_title)
                        argument(nav_graph.args.plant_id) { 
                            type = NavType.StringType
                        }
                    }
                }
            }
        }
    }

`createGraph()` 创建并返回NavGraph，`fragment<T>()` 用来在graph中配置Fragment Destination，通过泛型T可以更加TypeSafe的指定Fragment类型。`action`、`argument`等用来配置fragment相关信息。不输于XML的可读性，同时避免了解析XML的耗时。

`action`、`argument`等所需的`IdRes`，需要通过常量进行配置

//NavGraph.kt
    object nav_graph { 
    
        const val id = 1 // graph id
    
        object dest { 
            const val home = 2
            const val plant_detail = 3
        }
    
        object action { 
            const val to_plant_detail = 4
        }
    
        object args { 
            const val plant_id = "plantId"
        }
    }

# 使用效果 #

--------------------

使用dsl配置的Navigation进行页面跳转与传统的xml方式几乎没有区别，只是需要注意将`IdRes`替换为`Kt常量`即可：

//GardenPlantingAdapter.kt
    private fun navigateToPlant(plantId: String) { 
    
        val args = bundleOf(nav_graph.args.plant_id to plantId)
        findNavController().navigate(nav_graph.action.to_plant_detail, args)
    }

dsl也同样支持`Deeplinks`配置

//GardenActivity.kt
    fragment<PlantDetailFragment>(nav_graph.dest.plant_detail) { 
        label = getString(R.string.plant_details_title)
        argument(nav_graph.args.plant_id) { 
            type = NavType.StringType
        }
        deepLink("https://www.example.com/plants/{plantId}/") //deeplink配置
        // deepLink(getString(R.string.deep_link_plants)) 也可以使用StringRes配置
    }

需要特别注意的是，Deeplinks功能需要在`AndroidManifest.xml`中对Activity进行配置，传统的xml方式在`<Activity/>`下添加`<nav-graph>`即可:

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.myapplication">
    
        <application ... >
    
            <activity name=".MainActivity" ...>
                ...
    
                <nav-graph android:value="@navigation/nav_graph" />
    
                ...
    
            </activity>
        </application>
    </manifest>

dsl方式因为不依赖xml资源，所以需要针对`Intent`手动配置Deeplink所需的信息（即url等）：

<intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.BROWSABLE" />
        <category android:name="android.intent.category.DEFAULT" />
        <data android:host="www.example.com" android:pathPattern="/plants.*" android:scheme="https" />
    </intent-filter>

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