Android中实现下载URL地址的网络资源的实例分享_安卓软件开发教程-查字典教程网

通过URL来获取网络资源并下载资源简单实例：

package com.android.xiong.urltest; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.MalformedURLException; import java.net.URL; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.Menu; import android.widget.ImageView; public class MainActivity extends Activity { ImageView show; Bitmap bitmap; Handler handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what == 0x123) { // 使用ImageView显示该图片 show.setImageBitmap(bitmap); } } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); show = (ImageView) findViewById(R.id.show); new Thread() { @Override public void run() { // 定义一个URL对象 URL url; try { url = new URL( "http://img1.gtimg.com/news/pics/hv1/37/195/1468/95506462.jpg"); // 打开该URL的资源输入流 InputStream is = url.openStream(); // 从InputStream中解析出图片 bitmap = BitmapFactory.decodeStream(is); // 发送消息 handler.sendEmptyMessage(0x123); is.close(); // 再次打开RL对应的资源输入流 is = url.openStream(); // 打开手机文件对应的输出流 OutputStream os = openFileOutput("KEQIANG.JPG", MODE_APPEND); byte[] buff = new byte[1024]; int hasRead = 0; // 将URL资源下载到本地 while ((hasRead = is.read(buff)) > 0) { os.write(buff, 0, hasRead); } is.close(); os.close(); } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }.start(); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }

网络资源多线程下载：

package com.example.threaddown; import java.util.Timer; import java.util.TimerTask; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.ProgressBar; public class MainActivity extends Activity { EditText url; EditText target; Button downBn; ProgressBar bar; DownUtil downUtil; private int mDownStatus; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // 获取程序界面中的三个界面控制 url = (EditText) findViewById(R.id.url); target = (EditText) findViewById(R.id.target); downBn = (Button) findViewById(R.id.downBn); bar = (ProgressBar) findViewById(R.id.br); // 创建一个Handler对象 final Handler handler = new Handler() { @Override public void handleMessage(Message msg) { if (msg.what == 0x123) { bar.setProgress(mDownStatus); } } }; downBn.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // 初始化DownUtil对象 downUtil = new DownUtil(url.getText().toString(), target .getText().toString(), 6); new Thread() { @Override public void run() { try { // 开始下载 downUtil.download(); } catch (Exception e) { e.printStackTrace(); } // 定义每秒调度获取一次系统的完成进度 final Timer timer = new Timer(); timer.schedule(new TimerTask() { @Override public void run() { // 获取下载任务的完成比例 double completeRate = downUtil .getCompleteRate(); mDownStatus = (int) (completeRate * 1000); // 发送消息通知届满更新的进度条 handler.sendEmptyMessage(0x123); // 下载完成之后取消任务进度 if (mDownStatus >= 100) { timer.cancel(); } } }, 0, 1000); } }.start(); } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }

package com.example.threaddown; import java.io.IOException; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; public class DownUtil { // 定义下载资源的路径 private String path; // 指定所下载的文件的保存位置 private String targetFile; // 定义需要使用多少线程下载资源 private int threadNum; // 定义下载的线程对象 private DownThread[] threads; // 定义下载的文件总大小 private int fileSize; public DownUtil(String path, String targetFile, int threadNum) { this.path = path; this.targetFile = targetFile; this.threadNum = threadNum; } public void download() throws IOException { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5000); conn.setRequestMethod("GET"); conn.setRequestProperty("Accept", "*/*"); conn.setRequestProperty("Accept-Language", "zh-CN"); conn.setRequestProperty("Charset", "UTF-8"); conn.setRequestProperty("Connection", "Keep-Alive"); // 得到文件的大小 fileSize = conn.getContentLength(); conn.disconnect(); int currentPartsSize = fileSize / threadNum + 1; RandomAccessFile file = new RandomAccessFile(targetFile, "rw"); // 设置本地文件的大小 file.setLength(fileSize); file.close(); for (int i = 0; i < threadNum; i++) { // 计算每条线程的下载位置 int startPos = i * currentPartsSize; // 每个线程使用一个RandomAccessFile进行下载 RandomAccessFile current = new RandomAccessFile(targetFile, "rw"); // 定义该线程的下载位置 current.seek(startPos); // 创建下载线程 threads[i] = new DownThread(startPos, currentPartsSize, current); // 启动线程下载 threads[i].start(); } } // 获取下载的完成百分比 public double getCompleteRate() { // 统计多条线程已经下载的总大小 int sumSize = 0; for (int i = 0; i < threadNum; i++) { sumSize += threads[i].length; } return sumSize * 1.0 / fileSize; } private class DownThread extends Thread { // 定义当前线程下载的位置 private int startPos; // 定义当前线程下载文件的大小 private int currentPartsSize; // 当前线程下载的文件块 private RandomAccessFile currentPart; // 定义该线程已下载的字节数 private int length; public DownThread(int startPos, int currentPartsSize, RandomAccessFile currentPart) { this.startPos = startPos; this.currentPart = currentPart; this.currentPartsSize = currentPartsSize; } @Override public void run() { try { URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url .openConnection(); conn.setConnectTimeout(5000); conn.setRequestMethod("GET"); conn.setRequestProperty("Accept", "*/*"); conn.setRequestProperty("Accept-Language", "zh-CN"); conn.setRequestProperty("Charset", "UTF-8"); conn.setRequestProperty("Connection", "Keep-Alive"); InputStream in = conn.getInputStream(); in.skip(startPos); int hasRead = 0; byte[] buffer = new byte[1024]; // 读取网络数据，并写入本地文件 while (length < currentPartsSize && (hasRead = in.read(buffer)) > 0) { currentPart.write(buffer, 0, hasRead); // 累计该线程下载的总大小 length += hasRead; } currentPart.close(); in.close(); } catch (Exception e) { e.printStackTrace(); } } } }

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