如何让我的 retrofit 调用出现在 recyclerview 中？

Question

我在将来自 rest api 调用的数据显示在我的 recyclerview 上时遇到问题。 build 和 logcat 没有错误，可以在模拟器中正常打开而不会崩溃，并且可以显示其他功能。 只是这部分 recyclerview 没有显示来自 retrofit 调用的任何数据。 我正在尝试许多教程/解决方案，但没有一个有效。

这是我的 JSON 数据，我想获取库存的名称和数量：

13{
"body": [
    {
        "stock_ID": "1004",
        "stock_name": "kobis",
        "stock_quantity": "2"
    },
    {
        "stock_ID": "1005",
        "stock_name": "bawang",
        "stock_quantity": "2"
    },
    {
        "stock_ID": "2001",
        "stock_name": "ayam",
        "stock_quantity": "4"
    },
    {
        "stock_ID": "2003",
        "stock_name": "kambing",
        "stock_quantity": "1"
    },
    {
        "stock_ID": "3001",
        "stock_name": "kayu manis",
        "stock_quantity": "2"
    },
    {
        "stock_ID": "3002",
        "stock_name": "lada hitam",
        "stock_quantity": "3"
    },
    {
        "stock_ID": "4001",
        "stock_name": "minyak",
        "stock_quantity": "1"
    },
    {
        "stock_ID": "4002",
        "stock_name": "gula",
        "stock_quantity": "5"
    },
    {
        "stock_ID": "4003",
        "stock_name": "garam",
        "stock_quantity": "5"
    },
    {
        "stock_ID": "4004",
        "stock_name": "kicap",
        "stock_quantity": "4"
    },
    {
        "stock_ID": "4005",
        "stock_name": "beras",
        "stock_quantity": "3"
    },
    {
        "stock_ID": "5001",
        "stock_name": "cawan",
        "stock_quantity": "5"
    }
],
"inventoryCount": 13

}

我的数据 class (LowStockItem.kt)：

data class LowStockList(val items: ArrayList<LowStockItem>)
data class LowStockItem(
val stock_ID: String,
val stock_name: String,
val stock_quantity: String,)

RestApiService.kt：

@GET ("/inventory/read_lowstock.php")
fun getsLowStock(): Call<LowStockList>

RestApiInstance.kt

    companion object {

    var BASE_URL = "http://roslibiz.com/api/"

    fun getRestApiInstance() : Retrofit {

        return Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build()

    }
}

LowStockAdapter（回收站视图适配器）：

class LowStockAdapter: RecyclerView.Adapter<LowStockAdapter.MyViewHolder>() {

var items = ArrayList<LowStockItem>()

fun setListData(data: ArrayList<LowStockItem>) {
    this.items = data
notifyDataSetChanged()
}

override fun onCreateViewHolder(
    parent: ViewGroup,
    viewType: Int
): MyViewHolder {
    val inflater = LayoutInflater.from(parent.context).inflate(R.layout.low_stock_card, parent, false)

    return MyViewHolder(inflater)
}

override fun getItemCount(): Int {
    return items.size
}

override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
    holder.bind(items[position])
}



class MyViewHolder(view: View): RecyclerView.ViewHolder(view) {
    val nama = view.namaLSrv
    val id = view.idLSrv
    val kuantiti = view.kuantitiLSrv

    fun bind(data: LowStockItem){
        id.text = data.stock_ID
        if(!TextUtils.isEmpty(data.stock_name)){
            nama.text = data.stock_name
            kuantiti.text = data.stock_quantity
        }else{
            nama.text = "Nama tiada dalam rekod"
            kuantiti.text = "0"
        }
    }
}
}

主要活动：

lateinit var recyclerViewAdapter: LowStockAdapter
private fun setupRV(){
    lowStockRV.apply {
        layoutManager = LinearLayoutManager(this@MainActivity)
        recyclerViewAdapter = LowStockAdapter()
        adapter = recyclerViewAdapter

        val decoration = DividerItemDecoration(applicationContext, VERTICAL)
        addItemDecoration(decoration)
}
    private fun getLowStock(){

    val retroInstance = RestApiInstance.getRestApiInstance().create(RestApiService::class.java)
    val call = retroInstance.getsLowStock()

    call.enqueue(object: retrofit2.Callback<LowStockList>{
        override fun onResponse(call: Call<LowStockList>, response: Response<LowStockList>) {
            if (response.isSuccessful){
                recyclerViewAdapter.setListData(response.body()?.items!!)
            }
        }

        override fun onFailure(call: Call<LowStockList>, t: Throwable) {
            Toast.makeText(this@MainActivity, "Masalah untuk mendapatkan data", Toast.LENGTH_LONG).show()
        }
    })
}

我无能为力，需要其他角度的帮助。 先感谢您。

编辑。 这是我从调试中得到的，老实说我不知道该怎么做。

02/24 15:04:25: Launching 'app' on Pixel 2 XL API 30.
Install successfully finished in 688 ms.
$ adb shell am start -n "com.example.roslibusiness/com.example.roslibusiness.ui.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER -D
Waiting for application to come online: com.example.roslibusiness.test | com.example.roslibusiness
Waiting for application to come online: com.example.roslibusiness.test | com.example.roslibusiness
Waiting for application to come online: com.example.roslibusiness.test | com.example.roslibusiness
Connecting to com.example.roslibusiness
Connected to the target VM, address: 'localhost:63581', transport: 'socket'
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
I/e.roslibusines: Not late-enabling -Xcheck:jni (already on)
I/e.roslibusines: Unquickening 12 vdex files!
W/e.roslibusines: Unexpected CPU variant for X86 using defaults: x86
W/ActivityThread: Application com.example.roslibusiness is waiting for the debugger on port 8100...
I/System.out: Sending WAIT chunk
I/System.out: Debugger has connected
    waiting for debugger to settle...
I/System.out: waiting for debugger to settle...
I/chatty: uid=10153(com.example.roslibusiness) identical 5 lines
I/System.out: waiting for debugger to settle...
I/System.out: debugger has settled (1362)
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
I/MultiDex: VM with version 2.1.0 has multidex support
    Installing application
    VM has multidex support, MultiDex support library is disabled.
D/libEGL: loaded /vendor/lib/egl/libEGL_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv1_CM_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv2_emulation.so
W/e.roslibusines: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed)
    Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
W/e.roslibusines: Accessing hidden method Ljava/lang/invoke/MethodHandles$Lookup;-><init>(Ljava/lang/Class;I)V (greylist, reflection, allowed)
W/e.roslibusines: Accessing hidden method Ldalvik/system/CloseGuard;->get()Ldalvik/system/CloseGuard; (greylist,core-platform-api, reflection, allowed)
    Accessing hidden method Ldalvik/system/CloseGuard;->open(Ljava/lang/String;)V (greylist,core-platform-api, reflection, allowed)
    Accessing hidden method Ldalvik/system/CloseGuard;->warnIfOpen()V (greylist,core-platform-api, reflection, allowed)
D/CompatibilityChangeReporter: Compat change id reported: 147798919; UID 10153; state: ENABLED
D/HostConnection: HostConnection::get() New Host Connection established 0xea4a3c50, tid 7992
D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit GL_OES_EGL_image_external_essl3 GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_gles_max_version_3_0 
W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
D/EGL_emulation: eglCreateContext: 0xea483f10: maj 3 min 0 rcv 3
D/EGL_emulation: eglMakeCurrent: 0xea483f10: ver 3 0 (tinfo 0xbbc39170) (first time)
I/Gralloc4: mapper 4.x is not supported
D/HostConnection: createUnique: call
    HostConnection::get() New Host Connection established 0xea483d50, tid 7992
D/goldfish-address-space: allocate: Ask for block of size 0x100
    allocate: ioctl allocate returned offset 0x3fbc17000 size 0x2000
D/HostConnection: HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3 ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit GL_OES_EGL_image_external_essl3 GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_gles_max_version_3_0 
I/OpenGLRenderer: Davey! duration=1136ms; Flags=1, IntendedVsync=9582448914498, Vsync=9582548914494, OldestInputEvent=9223372036854775807, NewestInputEvent=0, HandleInputStart=9582554363800, AnimationStart=9582555337800, PerformTraversalsStart=9582555413300, DrawStart=9583238424100, SyncQueued=9583494447900, SyncStart=9583496712300, IssueDrawCommandsStart=9583496796500, SwapBuffers=9583584814100, FrameCompleted=9583588012900, DequeueBufferDuration=571700, QueueBufferDuration=1002300, GpuCompleted=8029250115450508212, 
I/Choreographer: Skipped 56 frames!  The application may be doing too much work on its main thread.

编辑：我应该怎么处理这个错误？

E/Retrofit Error: retrofit2.DefaultCallAdapterFactory$ExecutorCallbackCall@ccab847

Answer 1

您应该更改 function setListData的定义

目前是这个

fun setListData(data: ArrayList<LowStockItem>) {
    this.items = data
}

应该改为

fun setListData(data: ArrayList<LowStockItem>) {
    this.items = data
    notifyDataSetChanged()
}

这是从 class 内通知适配器的更好方法。

notifyDataSetChanged() 通知您的适配器数据已更改以供 RecyclerView 使用，因此适配器会查看新数据并相应地对其进行膨胀。

还要确保您在适配器中传递正确的数据。

您在上面发布的 retrofit 数据不包含您在 class 中声明的 ID 字段。 在这种情况下，它可能会引发一些错误。 As you are in Kotlin, you can use the Android Studio feature to directly convert your json data into an object class, this would help you to create exactly what needs to be used for the successful deserialization. 这个 Android Studio 功能被称为Kotlin data class file from JSON ，可以在 File->New 下找到。

Answer 2

问题是将List的新实例分配给项目，当适配器持有不同的引用时，将response添加到现有列表而不是重新分配实例

fun setListData(data: ArrayList<LowStockItem>) {
    this.items.clear()
    this.items.addAll(data) 
}