如何创建位图适配器并将其显示在ImageView中

Question

我是 Kotlin 和 Android Studio 的初学者，我想请求帮助来解决这个问题：

1. 从 URL 下载图像；
2. 创建Adapter模块来接收位图；
3. 通过ImageView对象显示图像

---

1. 我设法用这个更简单的方法解决了第一个项目。下一步是改进一些库，但它正在起作用。

` 私人乐趣 downloadImage(item: Item) = Thread {

    val imageConnection = URL(imageItem.url).openConnection() as HttpURLConnection

    try {
        if (photosConnection.responseCode == HTTP_OK) {
            runOnUiThread {
                val bitmap = BitmapFactory.decodeStream(photosConnection.inputStream)
                activityMainBinding.objImageView.apply {
                // Implementar o novo Adapter                    
                }
            }
        } else {
            runOnUiThread{
                Toast.makeText(this, " Deu erro !!!", Toast.LENGTH_SHORT).show()
            }
        }
    } catch ( e: Exception)  {
            e.printStackTrace()
    } finally {
        imageConnection.disconnect()
    }
}.start()`

2. 创建适配器模块

我尝试制作这个适配器，这是我作为参考。但是继承自ArrayAdapter我知道与Bitmap类型不兼容。我也不确定通常我使用的对象（android.R.layout）（android.R.layout.simple_list_item_1）当它们是字符串列表应用程序时。但在这种情况下，我没有找到类似的，例如（android.R.layout.image）。

` 类 ImageAdapter ( private val ActivityContext：上下文， 私有 val imageList：MutableList ): ArrayAdapter(activityContext, android.R.layout.simple_list_item_1, photosList) {

    private data class ImageHolder( val imageVw: ImageView )

    override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {

        val imageView = convertView ?: LayoutInflater.from(activityContext)
            .inflate(android.R.layout.simple_list_item_1,parent,false).apply {
                tag = ImageHolder(findViewById(android.R.id.text1))
            }

        (imageView.tag as ImageHolder)imageVw.setImageBitmap = imageList[position]

        return imageView
    }

}`

我感谢任何帮助

Answer 1

我会尽量保持简单

1. 使用库下载图像，例如glide，它非常简单，可以处理所有其他事情，例如 url 连接、线程和缓存图像。

2. 为此，您应该使用

   RecyclerView

   来创建

   RecyclerView.Adapter

   的子类。

3. 还可以使用 glide 库完成。

现在的代码，这是 Activity 布局，您必须将 recyclerView 放在某处以显示带有图像的列表，在我的示例中

activity_image_adapter.xml

：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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=".simpleimageAdapter.ImageAdapterActivity">


    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/recyclerView"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
        tools:itemCount="4"
        tools:listitem="@layout/item_image"/>

</FrameLayout>

还为图像项目创建布局，在我的示例中

item_image.xml

<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/itemImageView"
    android:layout_width="match_parent"
    android:layout_height="256dp"
    android:importantForAccessibility="no"
    android:scaleType="centerCrop"/>

下一步您需要为 recyclerView 创建自定义适配器：

class ImageAdapter : RecyclerView.Adapter<ImageAdapter.ImageViewHolder>() {

//Data list for the adapter, we will set data later
private var images: List<ImageItem> = emptyList()

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ImageViewHolder {
    //Creates view holder which holds view. Recycler is reusing views because of performance
    val inflater = LayoutInflater.from(parent.context)
    //Create view and attach it to the parent
    val view = inflater.inflate(R.layout.item_image, parent, false)
    return ImageViewHolder(view)
}

override fun onBindViewHolder(holder: ImageViewHolder, position: Int) {
    //Called to show data with holder
    holder.onBind(item = images[position])
}

override fun getItemCount(): Int {
    //Returns items count this adapter shows
    return images.size
}


fun setData(list: List<ImageItem>) {
    this.images = list
    //Set new dataset for adapter and notify it about change
    //notifyDataSetChanged isn't the best option but for now let's keep it simple
    notifyDataSetChanged()
}


inner class ImageViewHolder(contentView: View) : RecyclerView.ViewHolder(contentView) {
    
    private val imageView: ImageView = contentView.findViewById(R.id.itemImageView)
    
    fun onBind(item: ImageItem) {
        //Load image with glide library and show it with imageView
        Glide.with(imageView.context)
            .load(item.url)
            .centerCrop()
            .into(imageView)
    }
}
}

现在将它们全部放在活动代码中：

class ImageAdapterActivity : AppCompatActivity() {


override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_image_adapter)


    //Just simple data for the example
    val data = listOf(
        ImageItem(url = "https://static.vecteezy.com/system/resources/thumbnails/025/284/015/small_2x/close-up-growing-beautiful-forest-in-glass-ball-and-flying-butterflies-in-nature-outdoors-spring-season-concept-generative-ai-photo.jpg"),
        ImageItem(url = "https://i0.wp.com/picjumbo.com/wp-content/uploads/beautiful-nature-mountain-scenery-with-flowers-free-photo.jpg?w=600&quality=80"),
        ImageItem(url = "https://media.istockphoto.com/id/517188688/photo/mountain-landscape.jpg?s=612x612&w=0&k=20&c=A63koPKaCyIwQWOTFBRWXj_PwCrR4cEoOw2S9Q7yVl8=")
    )

    val recyclerView: RecyclerView = findViewById(R.id.recyclerView)
    val imageAdapter = ImageAdapter()
    //Set adapter to the recycler
    recyclerView.adapter = imageAdapter

    //Set data to adapter
    imageAdapter.setData(list = data)
}
}

完成所有部分后，您将能够显示图像，例如如图所示