android - 在 AsyncTask 中使用 kotlin 初始化数据库

Question

在我的 doInBackground 中，我声明并初始化了 db，我收到一个错误，提示类型不匹配。我应该放什么而不是放 this？

var dbHelper: MyDBHelper? = null
dbHelper = MyDBHelper(this)

我应该放什么，那里说 Required: Context!

这是我的异步任务代码，dbHelper = MyDBHelper(this) 的问题。

private class UpgradeDB(textView: TextView?) : AsyncTask<String, String, String>() {
        var innerTextView: TextView? = textView

        override fun onPreExecute() {
            innerTextView!!.visibility = View.VISIBLE
        }

        override fun doInBackground(vararg params: String): String? {
            val filename = "eBOSSInv_Upgrade.sql"
            val sdcard = Environment.getExternalStorageDirectory()
            val file = File(sdcard, filename)

            if (!file.exists()) isCancelled

            try {
                var dbHelper: MyDBHelper? = null

                dbHelper = MyDBHelper(this)

                dbHelper!!.writableDatabase.use { db ->
                    var intTotalLine = 0
                    var intLine = 1
                    BufferedReader(FileReader(file)).useLines { _ -> intTotalLine++ }
                    BufferedReader(FileReader(file)).use { r ->
                        r.lineSequence().forEach {
                            if (it.isNotEmpty()) {
                                db!!.execSQL(it)
                                publishProgress(String.format("Updating %s/%s records", intLine, intTotalLine))
                                intLine++
                            }
                        }
                    }
                }
            } catch (e: Exception) {

            }
            return null
        }

        override fun onProgressUpdate(vararg text: String) {
            innerTextView!!.text = text[0]
        }

        override fun onPostExecute(result: String?) {
            innerTextView!!.text = ""
        }

        override fun onCancelled() {

        }
    }

Answer 1

您需要将 context 传递给 Async Task。

例子:

llUpdate.setOnClickListener { 
       UpgradeDB(txtUpdate!!, getApplication()).execute("", "", "") 
}

然后在UpgradeDB中，初始化上下文。

private class UpgradeDB(textView: TextView?, context: Context) : AsyncTask<String, String, String>() {
        var innerTextView: TextView? = textView
        var mContext:Context? = context // initialize context
    }

最后

dbHelper = MyDBHelper(mContext)