Kotlin 图片的保存与读取

图片的保存

mPath = getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS).toString() + "/"

btn_save.setOnClickListener {
    val bitmap = ll_info.drawingCache
    val file_path = "$mPath${DateUtil.nowDateTime}.png"
    FileUtil.saveImage(file_path, bitmap)
}

override fun onStart() {
    super.onStart()
    ll_info.isDrawingCacheEnabled = true
}

override fun onStop() {
    super.onStop()
    ll_info.isDrawingCacheEnabled = false
}

object FileUtil {
    fun saveImage(path: String, bitmap: Bitmap) {
        try {
            val file = File(path)
            //outputStream获取文件的输出流对象
            val fos: OutputStream = file.outputStream()
            //压缩格式为JPEG图像，压缩质量为80%
            bitmap.compress(Bitmap.CompressFormat.JPEG, 80, fos)
            fos.flush()
            fos.close()
        } catch (e: Exception) {
            e.printStackTrace()
        }

    }
}

图片的读取

• 方式一

//readBytes读取字节数组形式的文件内容
val bytes = File(file_path).readBytes()
//decodeByteArray从字节数组解析图片
val bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.size)

• 方式二

//inputStream获取文件的输入流对象
val fis = File(file_path).inputStream()
//decodeStream从输入流解析图片
val bitmap = BitmapFactory.decodeStream(fis)
fis.close()

• 方式三

//decodeFile从指定路径解析图片
val bitmap = BitmapFactory.decodeFile(file_path)

文件遍历

遍历某个文件下的所有图片文件

var fileNames: MutableList<String> = mutableListOf()
val fileTree: FileTreeWalk = File(mPath).walk()
fileTree.maxDepth(1) //需遍历的目录层级为1，即无需检查子目录
    .filter { it.isFile } //只挑选文件，不处理文件夹
    .filter { it.extension in listOf("png", "jpg") } //选择扩展名为png和jpg的图片文件
    .forEach { fileNames.add(it.name) } //循环处理符合条件的文件