Android：Navigation使用safe args插件传递参数

1、 使用配置

afe args与传统传参方式相比，好处在于安全的参数类型，并且通过谷歌官方的支持，能很方便的进行参数传值。

1、在项目的根build.gradle下添加插件

buildscript {
    ext.kotlin_version = "1.3.72"
    repositories {
        google()
        jcenter()
    }
    dependencies {
         classpath "com.android.tools.build:gradle:7.0.4"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
       classpath "androidx.navigation:navigation-safe-args-gradle-plugin:2.5.0"
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}
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2、然后在app的build.gradle中引用 'androidx.navigation.safeargs.kotlin'

    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
    id 'androidx.navigation.safeargs.kotlin'
}
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3、添加完插件后，回到nav_graph，切到design模式，给目标页面添加需要接收的参数

这里需要在FragmentA跳转到FragmentB时传参数，所以给FragmentB设置参数，点击FragmentB，点击右侧面板的Arguments右侧的+，输入参数的key值，指定参数类型和默认值，即可快速添加参数
4、添加完后，rebuild一下工程，safeArgs会自动生成一些代码，在/build/generated/source/navigation-args目录下可以看到
safeArgs会根据nav_graph中的fragment标签生成对应的类，

• action标签会以“类名+Directions”命名，
• argument标签会以“类名+Args”命名。

使用safeArgs后，传递参数是这样的

 override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        tv.setOnClickListener {
            val navController = Navigation.findNavController(it)
            //通过safeArgs传递参数
            val navDestination = FragmentADirections.actionFragmentAToFragmentB2("test")
            navController.navigate(navDestination)
            
            // 普通方式传递参数
		   // val bundle = Bundle()
            // bundle.putString("key", "test")
            // navController.navigate(R.id.action_fragmentA_to_fragmentB2, bundle)
        }
    }

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接收参数是这样的

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        arguments?.let {
            val value = FragmentBArgs.fromBundle(it).key
            .......
        }
        .......
    }
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2、举例说明

nav_main.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/nav_main"
    app:startDestination="@id/avalFragment">

    <fragment
        android:id="@+id/avalFragment"
        android:name="ir.MrMohamadHosein.navigationcomponent.AvalFragment"
        android:label="fragment_aval"
        tools:layout="@layout/fragment_aval" >

        <action
            android:id="@+id/action_avalFragment_to_dovomFragment"
            app:destination="@id/dovomFragment" />

    </fragment>

    <fragment
        android:id="@+id/dovomFragment"
        android:name="ir.MrMohamadHosein.navigationcomponent.DovomFragment"
        android:label="fragment_dovom"
        tools:layout="@layout/fragment_dovom" >
        <argument
            android:name="MyName"
            app:argType="string"
            android:defaultValue="no-name" />
    </fragment>

</navigation>
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注意：在目标Fragment中定义你要传递的参数，不是在一开始的Fragment中定义你的传递参数

1、MainActivity

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
}
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activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragment_container_view"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_main" />

</androidx.constraintlayout.widget.ConstraintLayout>
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2、AvalFragment, DovomFragment

2.1、AvalFragment

AvalFragment

class AvalFragment : Fragment() {
    lateinit var binding: FragmentAvalBinding

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentAvalBinding.inflate(layoutInflater)
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        binding.btnGoToSecondFragment.setOnClickListener {
            findNavController().navigate(
                AvalFragmentDirections.actionAvalFragmentToDovomFragment().setMyName("amir")
            )
        }

    }

}
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fragment_aval.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".AvalFragment">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="fragment aval"
        android:textSize="36sp" />

    <Button
        android:id="@+id/btnGoToSecondFragment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="80dp"
        android:text="go to second fragment" />


</FrameLayout>
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2.2、DovomFragment

DovomFragment

class DovomFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_dovom, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val data = DovomFragmentArgs.fromBundle(requireArguments()).myName
        Toast.makeText(context, data, Toast.LENGTH_SHORT).show()

    }

}
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fragment_dovom.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".DovomFragment">

    <TextView
        android:textSize="36sp"
        android:layout_gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="fragment dovom" />

</FrameLayout>
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参考