Kotlin实现Retrofit网络请求RecyclerView展示图片列表

1.新建一个项目   选中lnclude kotlin support

2.然后导包

    compile 'com.squareup.retrofit2:retrofit:2.3.0'
    compile 'com.squareup.retrofit2:converter-gson:2.3.0'
    compile 'com.squareup.retrofit2:converter-scalars:2.3.0'
    compile 'com.squareup.okhttp3:logging-interceptor:3.7.0'
    compile 'com.google.code.gson:gson:2.8.0'
    compile 'com.github.bumptech.glide:glide:4.2.0'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.2.0'
    compile 'com.android.support:recyclerview-v7:26.1.0'

3.创建一个接口  当然创建有些不一样

4.然后点击Kind这一行  选择Interface    

5. 接口地址：

http://route.showapi.com/197-1?showapi_appid=42684&showapi_sign=f6527e909abc4edea350ec8b9a9db0f5&num=10

接口代码 ：

interface PictureApi {
    @POST("197-1")
    @FormUrlEncoded
    fun getPicture(@Field("showapi_appid") showapi_appid: String,
                   @Field("showapi_sign") showapi_sign: String,
                   @Field("num") num: Int) : Call<ImageBean>
}

6.创建一个实体类       这里还要装一个工具

File --> Settings --> Plugins --> 搜索 JsonToKotlinClass  然后安装即可

按住alt+k键弹出一个框    第一个Class Name填写ImageBean就行了，这里可以随便写，JSON Text就可以放置接口里面的JSON数据

第一排有三个Property，Annotation，other         

Property—选择—>Val—选择—>lnit with default value（avoid null）

Annotation—选择—>Gson

然后点ok就会自动生成下面所示的代码

7.创建HttpManager网络请求类

class HttpManager {
    var retrofit = Retrofit.Builder()
            .baseUrl("http://route.showapi.com/")   //基地址
            .addConverterFactory(GsonConverterFactory.create())
            .build()
    fun getPicture(num: Int, success: (ImageBean) -> Unit, fail: (String) -> Unit) {
        var pictureApi: PictureApi = retrofit.create(PictureApi::class.java)
        var call: Call<ImageBean> = pictureApi.getPicture("42684", "f6527e909abc4edea350ec8b9a9db0f5", num)
        call.enqueue(object : Callback<ImageBean> {
            override fun onResponse(call: Call<ImageBean>?, response: Response<ImageBean>) {
                success(response.body()!!)
            }
            override fun onFailure(call: Call<ImageBean>?, t: Throwable?) {
                fail(t.toString())
            }
        })
    }
}

8.主布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="点击我吧" />

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

9.item_rcy_picture布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <TextView
        android:id="@+id/TextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <ImageView
        android:id="@+id/ImageView"
        android:layout_width="wrap_content"
        android:layout_height="180dp" />
</LinearLayout>

10.recyclerview适配器

class PictureAdapter(private var list: List<Newslist>) : RecyclerView.Adapter<PictureAdapter.MyViewHolder>() {

    fun notifyDataChange(list: List<Newslist>) {       //更新适配器数据
        this.list = list
        notifyDataSetChanged()
    }

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

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        var view = LayoutInflater.from(parent.context).inflate(R.layout.item_rcy_picture, parent, false)
        return MyViewHolder(view)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.textView.text = list[position].title //展示图片标题
        Glide.with(holder.imageView)                //ImageView中展示图片
                .load(list[position].picUrl)
                .into(holder.imageView)
        //这是图片点击事件
        holder.imageView.setOnClickListener {
            mListener?.invoke(position)
        }

    }

    class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var textView: TextView = itemView.findViewById(R.id.TextView)
        var imageView: ImageView = itemView.findViewById(R.id.ImageView)

    }

    var mListener: ((pos: Int) -> Unit)? = null
    fun setOnItemClickListener(listener: ((pos: Int) -> Unit)) {
        mListener = listener
    }

}

11.主函数

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
		var adapter = PictureAdapter(ArrayList()) //适配器，默认一个空的集合，等网络请求后更新数据
		recyclerView.layoutManager = LinearLayoutManager(this)
		recyclerView.adapter = adapter

		button.setOnClickListener {
			//按钮点击事件
			HttpManager().getPicture(
					10, //网络请求 5条数据 num表示网络请求返回的数据数量
					{ adapter.notifyDataChange(it.showapiResBody.newslist) }, //成功的回掉接口
					{ Toast.makeText(this, it, Toast.LENGTH_SHORT).show() } //失败的回掉接口
			)
		}
		adapter.setOnItemClickListener {
			Toast.makeText(this, it.toString(), Toast.LENGTH_SHORT).show()
		}
	}
}

12.最后别忘记加网络访问权限

<uses-permission android:name="android.permission.INTERNET" />