Android(安卓)下载网络url文件并显示进度

首先需要加上权限——访问网络跟存储卡：

<uses-permission android:name="android.permission.INTERNET"></uses-permission><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>

activity_main.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <ProgressBar      android:id="@+id/download_main_progressBarlist"     android:layout_width="fill_parent"      android:layout_height="wrap_content"      style="?android:attr/progressBarStyleHorizontal"     />  <TextView     android:id="@+id/download_main_Text"     android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:layout_alignLeft="@+id/download_main_progressBarlist"     android:layout_below="@+id/download_main_progressBarlist"     android:layout_marginTop="42dp"     android:text="当前进度" /> <Button     android:id="@+id/download_main_Button"     android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:layout_alignLeft="@+id/download_main_Text"     android:layout_below="@+id/download_main_Text"     android:layout_marginTop="39dp"     android:text="下载" />"</RelativeLayout>

MainActivity：

import java.io.File;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.os.Handler;import android.os.Message;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button; import android.widget.ProgressBar;import android.widget.TextView;import android.widget.Toast;/** * 文件下载 * @author 胡汉三 * */public class MainActivity extends Activity {private static final String Path="文件的HTTP地址/ttt.mp3";private static String fileName = "ttt.mp3";private static String filePath= "/download/";private ProgressBar progressBar; private TextView textView;private Button button;private int FileLength;  private int DownedFileLength=0;private InputStream inputStream;private URLConnection connection;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);progressBar=(ProgressBar) findViewById(R.id.download_main_progressBarlist);textView=(TextView) findViewById(R.id.download_main_Text);button=(Button) findViewById(R.id.download_main_Button);button.setOnClickListener(new ButtonListener());}class ButtonListener implements OnClickListener{@Overridepublic void onClick(View v) {DownedFileLength=0;Thread thread=new Thread(){public void run(){try {DownFile(Path);} catch (Exception e) { }} };thread.start();}   }private Handler handler=new Handler(){public void handleMessage(Message msg){if (!Thread.currentThread().isInterrupted()) {switch (msg.what) {case 0:progressBar.setMax(FileLength);Log.i("文件长度----------->", progressBar.getMax()+"");  break;case 1:progressBar.setProgress(DownedFileLength);int x=DownedFileLength*100/FileLength;textView.setText(x+"%");break;case 2:Toast.makeText(getApplicationContext(), "下载完成", Toast.LENGTH_LONG).show();break;default:break;}}   }};private void DownFile(String urlString){/* * 连接到服务器 */try {URL url=new URL(urlString);connection=url.openConnection();if (connection.getReadTimeout()==5) {Log.i("---------->", "当前网络有问题");// return;}inputStream=connection.getInputStream();} catch (MalformedURLException e1) {// TODO Auto-generated catch blocke1.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}/* * 文件的保存路径和和文件名其中Nobody.mp3是在手机SD卡上要保存的路径，如果不存在则新建 */String savePAth=Environment.getExternalStorageDirectory()+filePath;File file1=new File(savePAth);if (!file1.exists()) {file1.mkdir(); }String savePathString=Environment.getExternalStorageDirectory()+filePath+fileName;File file =new File(savePathString);if (!file.exists()) { try {file.createNewFile();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}   }/* * 向SD卡中写入文件,用Handle传递线程 */Message message=new Message();try {RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rwd");randomAccessFile.setLength(FileLength);byte[]buf = new byte[1024*4];FileLength=connection.getContentLength();message.what=0;handler.sendMessage(message);int length = 0;while ((length=inputStream.read(buf))!=-1) {randomAccessFile.write(buf,0,length);DownedFileLength+=length;Log.i("-------->", DownedFileLength+"");Message message1=new Message();message1.what=1;  handler.sendMessage(message1);}inputStream.close(); randomAccessFile.close();Message message2=new Message();message2.what=2;handler.sendMessage(message2);} catch (FileNotFoundException e) {   // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}

如此这般，下载文件显示进度条就OK了

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