第一个完整项目有感而发

1.一些奇淫巧技的记录

1.assets里预置数据库

RgerRO

把预装好数据的db文件放在assets文件夹里，然后写到/data/data/packagename/databases里就能实现预装数据库

关键代码如下：

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val dbHelper = MyDatabaseHelper(this,"LearningData.db",1)

dbHelper.copyFileFromAssets(MyApplication.context,"LearningData.db","/data/data/com.lnm011223.learning_companion/databases","LearningData.db")

fun copyFileFromAssets(
    context: Context,
    assetName: String,
    savePath: String,
    saveName: String
) {
    // 若目标文件夹不存在，则创建
    //val dir = File(Environment.getExternalStorageDirectory().toString() + "/" + savePath)
    //if (!dir.exists()) {
    //    if (!dir.mkdir()) {
    //        Log.d("FileUtils", "mkdir error: $savePath")
    //        return
    //    }
    //}

    // 拷贝文件
    val filename = savePath + "/" + saveName
    val file = File(filename)
    if (!file.exists()) {
        try {
            val inStream: InputStream = context.assets.open(assetName)
            val fileOutputStream = FileOutputStream(filename)
            var byteread: Int
            val buffer = ByteArray(1024)
            while (inStream.read(buffer).also { byteread = it } != -1) {
                fileOutputStream.write(buffer, 0, byteread)
            }
            fileOutputStream.flush()
            inStream.close()
            fileOutputStream.close()
        } catch (e: IOException) {
            e.printStackTrace()
        }
        Log.d("FileUtils", "[copyFileFromAssets] copy asset file: $assetName to : $filename")
        Toast.makeText(context, "保存成功", Toast.LENGTH_SHORT).show()
    } else {
        Log.d("FileUtils", "[copyFileFromAssets] file is exist: $filename")
        //Toast.makeText(context, "已存在", Toast.LENGTH_SHORT).show()
    }
}

2.数据库数据填充

可以用Excel填充数据然后导入进db文件的表里

3.广播用法

可以通过触发发送一个自定义广播，然后再接收这个广播，从而达到recycleview里的操作可以通知到fragment

关键代码如下：

viewHolder.deleteerror_btn.setOnClickListener {
    val position = viewHolder.adapterPosition
    val errorBookQuestion = errorlist[position]
    AlertDialog.Builder(parent.context).apply {
        setTitle("确认：")
        setMessage("真的要删除这条记录吗？")
        setNegativeButton("否") { _, _ ->


        }
        setPositiveButton("是") { _, _ ->
            db.delete("ErrorBook", "title = ?", arrayOf(errorBookQuestion.title))
            val intent = Intent("ErrorBookDataChange")

            context.sendBroadcast(intent)

        }


        show()
    }
}

override fun onResume() {
    super.onResume()
    Log.d("aaa","resume")
    val intentFilter = IntentFilter()
    intentFilter.addAction("ErrorBookDataChange")
    receiver = ErrorBookChangeReceiver()
    activity?.registerReceiver(receiver,intentFilter)
}

override fun onPause() {
    super.onPause()
    Log.d("aaa","pause")
    activity?.unregisterReceiver(receiver)

}
inner class ErrorBookChangeReceiver : BroadcastReceiver() {
        override fun onReceive(context: Context?, intent: Intent?) {
            initErrorBookList()
            val layoutManager = StaggeredGridLayoutManager(1, StaggeredGridLayoutManager.VERTICAL)
            errorbook_recycleview.layoutManager = layoutManager
            val adapter = ErrorBookAdapter(errorbooklist)
            errorbook_recycleview.adapter = adapter
        }
    }