Ivan's questions

我正在尝试将图片写入手机的外部存储器（外部存储），但未创建文件夹和文件本身。在一台设备上一切正常，但在另一台设备上却没有，写入访问被拒绝。它可以在其上运行，有一个版本的 sdk 25，另一个版本是 29。

java.io.FileNotFoundException：/storage/emulated/0/1588875980977.jpg：打开失败：EACCES（权限被拒绝）

private fun checkPermission() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED || ContextCompat.checkSelfPermission(this, android.Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, arrayOf(android.Manifest.permission.WRITE_EXTERNAL_STORAGE, android.Manifest.permission.READ_EXTERNAL_STORAGE), 100)
        }
    }
}

override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    if (requestCode == 100) {
        if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED) {
            settings.edit().putBoolean("save", true).apply()
        } else {
            settings.edit().putBoolean("save", false).apply()
        }
    }
}

private fun getImageUriFromBitmap(bitmap: Bitmap?): Uri{
    val path = Environment.getExternalStorageDirectory().toString()
    val file = File(path,System.currentTimeMillis().toString() + ".jpg")
    val output = FileOutputStream(file)
    bitmap!!.compress(Bitmap.CompressFormat.JPEG, 100, output)
    output.flush()
    output.close()
    return Uri.fromFile(file)
}

我做了一个RecyclerView，如果里面有很多元素，那么它会混合这些元素。可能是什么问题呢 ？

inner class AboutUsAdapter: RecyclerView.Adapter<AboutUsAdapter.ViewHolder>() {

        inner class ViewHolder (view: View) : RecyclerView.ViewHolder(view){
            var imageView = view.findViewById<ImageView>(R.id.image_show)
            var name = view.findViewById<TextView>(R.id.name)
            var subtitle = view.findViewById<TextView>(R.id.sub_text)
            val ad = view.findViewById<TextView>(R.id.ad_text)
        }

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
            return ViewHolder(LayoutInflater.from(applicationContext).inflate(R.layout.about_us_element, parent, false))
        }

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

        override fun onBindViewHolder(holder: ViewHolder, position: Int) {
            holder.name.text = texts[position]
            holder.subtitle.text = subtitles[position]
            if(position == 0){
                holder.ad.text = ""
            }
            if (position == 0 || position == 1){
                holder.imageView.setImageBitmap(applicationContext.resources.getDrawable(R.mipmap.ic_launcher).toBitmap())
            } else {
                holder.imageView.setImageBitmap(getPicFromAsset(files[position - 2]))
            }
            holder.itemView.setOnClickListener {
                val sound: MediaPlayer = MediaPlayer.create(applicationContext, R.raw.simple_tap)
                sound.isLooping = false
                sound.setOnCompletionListener {
                    when (position) {
                        0 -> {
                            if (showAd) {
                                mInterstitialAd.adListener = object : AdListener() {
                                    val adIntent = Intent(applicationContext, ChooseImage::class.java)
                                    override fun onAdOpened() {
                                    }

                                    override fun onAdClosed() {
                                        adIntent.putExtra("bundle",extras)
                                        startActivity(adIntent)
                                        val ad = AdRequest.Builder()
                                                .addNetworkExtrasBundle(AdMobAdapter::class.java, extras)
                                                .build()
                                        mInterstitialAd.loadAd(ad)
                                    }
                                }
                                if (mInterstitialAd.isLoaded) {
                                    mInterstitialAd.show()
                                } else {
                                    val intent = Intent(applicationContext, ChooseImage::class.java)
                                    intent.putExtra("bundle",extras)
                                    startActivity(intent)
                                }
                            } else {
                                val intent = Intent(applicationContext, ChooseImage::class.java)
                                intent.putExtra("bundle",extras)
                                startActivity(intent)
                            }
                        }
                        else -> {
                            val intent = Intent(Intent.ACTION_VIEW, Uri.parse(array[position - 1]))
                            startActivity(intent)
                        }
                    }
                }
                sound.start()
            }
        }

如何加载广告，以免它们减慢应用程序的速度。我确信 loadAd 方法会减慢下载速度。我能做些什么来防止这种情况发生？

        object : AsyncTask<Void?, Void?, Void?>() {
            var adRequest: AdRequest? = null
            override fun onPostExecute(aVoid: Void?) {
                super.onPostExecute(aVoid)
                    mInterstitialAd = InterstitialAd(applicationContext)
                    mInterstitialAd.adUnitId = AD_ID
                    mInterstitialAd.loadAd(adRequest)
                    mAdView.loadAd(adRequest)
            }
            override fun doInBackground(vararg p0: Void?): Void? {
                adRequest = if (isPersonalized) {
                    AdRequest.Builder().build()
                } else {
                    extras.putString("npa", "1")
                    AdRequest.Builder()
                        .addNetworkExtrasBundle(AdMobAdapter::class.java, extras)
                        .build()
                }
                return null
            }
        }.execute()

我正在尝试实现一个显示资产照片的 GridView。一切正常，但滚动时，图片出现延迟。你会有什么建议和建议？

inner class ImageAdapter(private val mContext: Context) : BaseAdapter() {
        private val am: AssetManager = mContext.assets
        private val files: Array<String>? = am.list("img")

        override fun getCount(): Int {
            return files!!.size
        }

        override fun getItem(position: Int): Any? {
            return null
        }

        override fun getItemId(position: Int): Long {
            return 0
        }

        override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
            var convertView = convertView
            if (convertView == null) {
                val layoutInflater = LayoutInflater.from(mContext)
                convertView = layoutInflater.inflate(R.layout.choose_element, null)
            }
            val imageView = convertView!!.findViewById<ImageView>(R.id.gridImageview)
            imageView.post {
                object : AsyncTask<Void?, Void?, Void?>() {
                    private var bitmap: Bitmap? = null
                    override fun onPostExecute(aVoid: Void?) {
                        super.onPostExecute(aVoid)
                        imageView.setImageBitmap(bitmap)
                    }

                    override fun doInBackground(vararg p0: Void?): Void? {
                        if (!listId.contains(position)) {
                            bitmap = getPicFromAsset(imageView, files!![position])
                            list.add(bitmap!!)
                            listId.add(position)
                        } else {
                            bitmap = list[position]
                        }
                        return null
                    }
                }.execute()
            }
            return convertView
        }

        private fun getPicFromAsset(imageView: ImageView, assetName: String): Bitmap? {
            val targetW = imageView.width
            val targetH = imageView.height
            return if (targetW == 0 || targetH == 0) {
                null
            } else try {
                val `is` = am.open("img/$assetName")
                val bmOptions = BitmapFactory.Options()
                bmOptions.inJustDecodeBounds = true
                BitmapFactory.decodeStream(`is`, Rect(-1, -1, -1, -1), bmOptions)
                val photoW = bmOptions.outWidth
                val photoH = bmOptions.outHeight
                val scaleFactor = (photoW / targetW).coerceAtMost(photoH / targetH)
                `is`.reset()
                bmOptions.inJustDecodeBounds = false
                bmOptions.inSampleSize = scaleFactor
                bmOptions.inPurgeable = true
                BitmapFactory.decodeStream(`is`, Rect(-1, -1, -1, -1), bmOptions)
            } catch (e: IOException) {
                FirebaseCrash.report(e); // Generate report
                e.printStackTrace()
                null
            }
        }
    }