行业动态

Android Studio

```kotlin

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import android.view.View

import android.widget.Button

import android.widget.EditText

import android.widget.Toast

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {

super.onCreate(savedInstanceState)

setContentView(R.layout.activity_main)

val downloadButton = findViewById(R.id.download_button)

val urlEditText = findViewById(R.id.url_edit_text)

downloadButton.setOnClickListener(View.OnClickListener {

val url = urlEditText.text.toString()

// Start a download task

DownloadTask(this).execute(url)

})

}

// AsyncTask to download the file

private class DownloadTask internal constructor(context: Context) : AsyncTask() {

private val context: Context = context

private var mProgressDialog: ProgressDialog? = null

override fun onPreExecute() {

super.onPreExecute()

// Create and show a progress dialog

mProgressDialog = ProgressDialog(context)

mProgressDialog?.setTitle("Downloading...")

mProgressDialog?.setMessage("Please wait...")

mProgressDialog?.setCancelable(false)

mProgressDialog?.show()

}

override fun doInBackground(vararg params: String): String {

val url = params[0]

// Download the file

val file = URL(url).openConnection().getInputStream()

val bytes = file.readBytes()

// Save the file to the device

val path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).toString()

val fileName = "downloaded_file.jpg"

val fileOutputStream = FileOutputStream("$path/$fileName")

fileOutputStream.write(bytes)

fileOutputStream.close()

return "File downloaded successfully"

}

override fun onPostExecute(result: String) {

super.onPostExecute(result)

// Dismiss the progress dialog

mProgressDialog?.dismiss()

// Show a toast message

Toast.makeText(context, result, Toast.LENGTH_SHORT).show()

}

}

}

```

XML Layout

```xml

xmlns:app="http://schemas.android/apk/res-auto"

xmlns:tools="http://schemas.android/tools"

android:layout_width="match_parent"

android:layout_height="match_parent">

android:id="@+id/url_edit_text"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:hint="Enter URL"

app:layout_constraintEnd_toEndOf="parent"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintTop_toTopOf="parent" />

android:id="@+id/download_button"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Download"

app:layout_constraintBottom_toBottomOf="parent"

app:layout_constraintEnd_toEndOf="parent"

app:layout_constraintStart_toStartOf="parent"

app:layout_constraintTop_toBottomOf="@+id/url_edit_text" />

```