Jetpack初尝试 NavController，LiveData,DataBing,ViewModel,Paging-阿里云开发者社区

插件配置

classpath “androidx.navigation:navigation-safe-args-gradle-plugin:2.2.0”
apply plugin: ‘androidx.navigation.safeargs.kotlin’
dataBinding { enabled = true}
implementation ‘android.arch.paging:rxjava2:1.0.1’
implementation ‘android.arch.paging:runtime:1.0.1’
…

NavController 使用

1. 创建xml

<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <fragment
            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"/>

    </FrameLayout>

</layout>

2. 创建Activity

class MainActivity2 : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView<ActivityMain2Binding>(this, R.layout.activity_main2)
    }

}

3. res 创建navigation/nav_garden和说明

<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.gctech.androidstudydemo.jetpack.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.gctech.androidstudydemo.jetpack.EmptyFragment"
     android:label="详情标题">
     <argument
         android:name="id"
         app:argType="string" />
 </fragment>

</navigation>

startDestination

destination

action

通过id指向目标

传参数 argument name

获取参数如果传入的有参数就会生成对应的Args 然后获取到

private val args: EmptyFragmentArgs by navArgs()

流程

nav_garden->startDestination->id->name

action->destination->id->name

ViewModel 负责页面的数据

包含 LiveData和ObservableField 和其他数据

LiveData onChanged

观察者模式->订阅数据的变化

Observable addOnPropertyChangedCallback

数据和view双向绑定

创建viewmodle

ViewModelProvider.Factory

创建viewmodle 可以用SavedStateHandle存储和读取数据

AbstractSavedStateViewModelFactory(@NonNull SavedStateRegistryOwner owner, @Nullable Bundle defaultArgs)

DataBinding

页面用viewmodel item用实体类

<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>

        <variable
            name="hasPlantings"
            type="boolean" />

        <import type="android.view.View"/>

        <variable
            name="vm"
            type="com.gctech.androidstudydemo.jetpack.viewmodels.EmptyDataViewModel" />
    </data>

    <FrameLayout
        android:id="@+id/fl_content"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/tv_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{vm.datas.title}"
            android:visibility="@{vm.datas.isGone() ? View.VISIBLE : View.INVISIBLE}" />

    </FrameLayout>

</layout>


 class EmptyFragment : Fragment() {
    private val args: EmptyFragmentArgs by navArgs()

    private lateinit var binding: FragmentEmptyBinding

    private val viewModel: EmptyDataViewModel by viewModels {
        InjectorUtils.provideCommonViewModelFactory("")
    }


    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentEmptyBinding.inflate(inflater, container, false)

        binding.tvContent.setOnClickListener {
            ToastUtils.showShort("========")
            viewModel.datas.get()?.title ="6666"
            viewModel.datas.notifyChange()
        }


        viewModel.datas.set(A("1", true, "434"))
        binding.vm = viewModel
        binding.lifecycleOwner = viewLifecycleOwner
        binding.hasPlantings = true
        return binding.root
    }

}

API接口使用

定义接口

interface ApiService {

    /**
     * 1.测试第一个接口
     */
    @GET("xxx/testOne")
    suspend fun testOne(): HttpResult<List<Country>>

    /**
     * 1.测试第二 个接口
     */
    @GET("xxx/testTwo")
    suspend fun testTwo(@Query("list") countries: Int): HttpResult<List<Country>>

    /**
     * 1.测试分页接口
     */
    @GET("xxx/testPage")
    fun testPage(@Query("page") page: Int, @Query("pageSize") pageSize: Int= 20): Call<HttpResult<Tx>>
}

viewmodel中使用

class EmptyDataViewModel(
    private val params: Any?
) : ViewModel() {
    val datas = ObservableField<A>()
    val firstName = ObservableField<String>()
    val lastName = ObservableField<String>()
    val isShowDialog = MutableLiveData<Boolean>()
    val allName = object : ObservableField<String>(firstName, lastName) {
        override fun get(): String? {
            return "${firstName.get()} ${lastName.get()}"
        }
    }

    //调用一个接口
    fun country() = liveData(Dispatchers.IO) {
        isShowDialog.postValue(true)
        try {
            emit(
                Api.createService(ApiService::class.java)
                    .testOne()
            )
            isShowDialog.postValue(false)
        } catch (e: Exception) {
            isShowDialog.postValue(false)
        }
    }

    //顺序调用接口
    fun country2() = liveData(Dispatchers.IO) {
        isShowDialog.postValue(true)
        val d = Api.createService(ApiService::class.java)
            .testOne()
        val d2 = Api.createService(ApiService::class.java)
            .testTwo(d.data!!.size)
        try {
            emit(d2)
            isShowDialog.postValue(false)
        } catch (e: Exception) {
            isShowDialog.postValue(false)
        }
    }

    //合并多个接口
    fun country3() = liveData(Dispatchers.IO) {
        isShowDialog.postValue(true)
        val d = Api.createService(ApiService::class.java)
            .testOne()
        val d2 = Api.createService(ApiService::class.java)
            .testTwo(3)

        try {
            emit(Triple(d, d2, null))
            isShowDialog.postValue(false)
        } catch (e: Exception) {
            isShowDialog.postValue(false)
        }
    }

    val title = MutableLiveData<String>()

    fun addData() {
        viewModelScope.launch {
            //调用接口
        }

        datas.addOnPropertyChangedCallback(object : Observable.OnPropertyChangedCallback() {
            override fun onPropertyChanged(sender: Observable?, propertyId: Int) {

            }
        })

    }
}


 // fragment中使用
      binding.tvContent.setOnClickListener {
            ToastUtils.showShort("========")
            viewModel.country3().observe(viewLifecycleOwner) {
                viewModel.datas.get()?.title = "${it.first.data?.size}"
                viewModel.datas.notifyChange()
            }
        }
        viewModel.isShowDialog.observe(viewLifecycleOwner) {
            if (it) {
                LoadDialogUtil.showWaitDialog(activity as Context)
            } else {
                LoadDialogUtil.dismissWaitDialog()
            }
        }

Paging使用

自定义PageKeyedDataSource

class CustomPageDataSource() :
    PageKeyedDataSource<Int, A>() {
    override fun loadInitial(
        params: LoadInitialParams<Int>,
        callback: LoadInitialCallback<Int, A>
    ) {
        loge("loadInitial size : ${params.requestedLoadSize} ")
        fetchData(LoadParams(1, 10)) {
            callback.onResult(it.tx, null, 2)
        }


    }

    override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, A>) {
        loge("loadAfter size : ${params.requestedLoadSize}  page:${params.key}")
        fetchData(params) {
            if (params.key == 3) {
                callback.onResult(mutableListOf(), params.key + 1)
            } else {

                callback.onResult(it.tx, params.key + 1)
            }
        }

    }

    override fun loadBefore(params: LoadParams<Int>, callback: LoadCallback<Int, A>) {
        loge("loadBefore size : ${params.requestedLoadSize}  page:${params.key}")
        fetchData(params) {
            callback.onResult(it.tx, params.key - 1)
        }
    }


    private fun fetchData(params: LoadParams<Int>, pagingCallback: (Tx) -> Unit) {

        Api.createService(ApiService::class.java)
            .testPage(params.key, params.requestedLoadSize)
            .enqueue(object : Callback<HttpResult<Tx>> {
                override fun onFailure(call: Call<HttpResult<Tx>>, t: Throwable) {
                    t.printStackTrace()
                }

                override fun onResponse(
                    call: Call<HttpResult<Tx>>,
                    response: Response<HttpResult<Tx>>
                ) {
                    val data = response.body()
                    data?.let {
                        pagingCallback(it.data!!)
                    }
                }

            })
    }

}

自定义 DataSource.Factory

class CustomPageDataSourceFactory() : DataSource.Factory<Int, A>() {
    override fun create(): DataSource<Int, A> {
        return CustomPageDataSource()
    }
}

viewmodle中使用

class CommonListDataViewModel(
    private val params: Any?,
    private val savedStateHandle: SavedStateHandle
) : ViewModel() {

    val moreLoading = MutableLiveData<Boolean>()//上拉加载更多状态
    val liveDataMerger = MediatorLiveData<Any>()

    val data2 = LivePagedListBuilder(
        CustomPageDataSourceFactory(), PagedList.Config.Builder()
            .setPageSize(10)
            .setEnablePlaceholders(true)
            .setInitialLoadSizeHint(10)
            .build()
    ).build()


    val datas = MutableLiveData(MutableList(10) {
        A("@it", false, "标题$it")
    })

    fun refresh() {
        data2.value?.let {
            (it.dataSource as PageKeyedDataSource).invalidate()
        }

    }

    fun addData() {
//        liveDataMerger.addSource(refreshing, Observer {
//            liveDataMerger.value = it
//        })
//        liveDataMerger.addSource(moreLoading, Observer {
//            liveDataMerger.value = it
//        })
        viewModelScope.launch {
            //调用接口
        }
    }
}

// fragment中使用 
  private fun subscribeUi(adapter: CustomAdapter, binding: FragmentListLoadmoreBinding) {
        //观察多个liveData
        viewModel.data2.observe(viewLifecycleOwner) {
            adapter.submitList(it)
            Handler().postDelayed({
                binding.isLoading = false
            }, 2000)
        }
        binding.btnClick.setOnClickListener {
            viewModel.refresh()
        }

    }

自定义属性

自定义方法

    @BindingAdapter("visibleGone")
    fun showHide(view: View, show: Boolean) {
        view.visibility = if (show) View.VISIBLE else View.GONE
    }

xml中使用

<TextView
            android:id="@+id/tv_loading"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:text="isLoading..."
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:visibleGone="@{isLoading}" />

拼接字符串

<string name="person_number">Person:%1$s人</string>


android:text="@{@string/person_number(viewModel.field3)}"


android:text='@{String.format("%s - %s", viewModel.field4, viewModel.field5)}'

学习视频

Jetpack Playlist

Jetpack初尝试 NavController，LiveData,DataBing,ViewModel,Paging

NavController 使用

1. 创建xml

2. 创建Activity

3. res 创建navigation/nav_garden和说明

流程

ViewModel 负责页面的数据

LiveData onChanged

Observable addOnPropertyChangedCallback

创建viewmodle

DataBinding

API接口使用

定义接口

viewmodel中使用

Paging使用

自定义PageKeyedDataSource

自定义 DataSource.Factory

viewmodle中使用

自定义属性

自定义方法

xml中使用

拼接字符串

学习视频

热门文章

最新文章

相关电子书

Jetpack初尝试 NavController，LiveData,DataBing,ViewModel,Paging

NavController 使用

1. 创建xml

2. 创建Activity

3. res 创建navigation/nav_garden和说明

流程

ViewModel 负责页面的数据

LiveData onChanged

Observable addOnPropertyChangedCallback

创建viewmodle

DataBinding

API接口使用

定义 接口

viewmodel中使用

Paging使用

自定义PageKeyedDataSource

自定义 DataSource.Factory

viewmodle中使用

自定义属性

自定义方法

xml中使用

拼接字符串

学习视频

热门文章

最新文章

相关电子书

定义接口