Android中使用AsyncTask做下载进度条
Android中使用AsyncTask做下载进度条
AsyncTask是个不错的东西,可以使用它来做下载进度条。代码讲解如下:
- package com.example.downloadfile;
- import java.io.File;
- import java.io.FileOutputStream;
- import java.io.InputStream;
- import java.net.HttpURLConnection;
- import java.net.URL;
- import Android.app.Activity;
- import android.app.Dialog;
- import android.app.ProgressDialog;
- import android.os.AsyncTask;
- import android.os.Bundle;
- import android.os.Environment;
- import android.util.Log;
- import android.widget.TextView;
- public class DownloadFile extends Activity {
- public static final String LOG_TAG = "test";
- private ProgressDialog mProgressDialog;
- public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
- File rootDir = Environment.getExternalStorageDirectory();
- //定义要下载的文件名
- public String fileName = "test.jpg";
- public String fileURL = "https://lh4.googleusercontent.com/-HiJOyupc-tQ/TgnDx1_HDzI/AAAAAAAAAWo/DEeOtnRimak/s800/DSC04158.JPG";
- @Override
- public void onCreate(Bundle savedInstanceState)
- {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- TextView tv = new TextView(this);
- tv.setText("Android Download File With Progress Bar");
- //检查下载目录是否存在
- checkAndCreateDirectory("/mydownloads");
- //执行asynctask
- new DownloadFileAsync().execute(fileURL);
- }
- class DownloadFileAsync extends AsyncTask<String, String, String> {
- @Override
- protected void onPreExecute() {
- super.onPreExecute();
- showDialog(DIALOG_DOWNLOAD_PROGRESS);
- }
- @Override
- protected String doInBackground(String... aurl) {
- try {
- //连接地址
- URL u = new URL(fileURL);
- HttpURLConnection c = (HttpURLConnection) u.openConnection();
- c.setRequestMethod("GET");
- c.setDoOutput(true);
- c.connect();
- //计算文件长度
- int lenghtOfFile = c.getContentLength();
- FileOutputStream f = new FileOutputStream(new File(rootDir + "/my_downloads/", fileName));
- InputStream in = c.getInputStream();
- //下载的代码
- byte[] buffer = new byte[1024];
- int len1 = 0;
- long total = 0;
- while ((len1 = in.read(buffer)) > 0) {
- total += len1; //total = total + len1
- publishProgress("" + (int)((total*100)/lenghtOfFile));
- f.write(buffer, 0, len1);
- }
- f.close();
- } catch (Exception e) {
- Log.d(LOG_TAG, e.getMessage());
- }
- return null;
- }
- protected void onProgressUpdate(String... progress) {
- Log.d(LOG_TAG,progress[0]);
- mProgressDialog.setProgress(Integer.parseInt(progress[0]));
- }
- @Override
- protected void onPostExecute(String unused) {
- //dismiss the dialog after the file was downloaded
- dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
- }
- }
- public void checkAndCreateDirectory(String dirName){
- File new_dir = new File( rootDir + dirName );
- if( !new_dir.exists() ){
- new_dir.mkdirs();
- }
- }
- @Override
- protected Dialog onCreateDialog(int id) {
- switch (id) {
- case DIALOG_DOWNLOAD_PROGRESS: //we set this to 0
- mProgressDialog = new ProgressDialog(this);
- mProgressDialog.setMessage("Downloading file...");
- mProgressDialog.setIndeterminate(false);
- mProgressDialog.setMax(100);
- mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
- mProgressDialog.setCancelable(true);
- mProgressDialog.show();
- return mProgressDialog;
- default:
- return null;
- }
- }
- }
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