本文所述为Android实现下载文件功能的完整示例代码，对于学习和研究android编程相信会有一定的帮助，尤其是对Android初学者有一定的借鉴价值。

完整功能代码如下：

package com.test;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;import java.net.URL;import java.net.URLConnection;import android.app.Activity;import android.content.Intent;import android.net.Uri;import android.os.Bundle;import android.util.Log;import android.view.View;import android.webkit.URLUtil;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;public class Main extends Activity { private TextView mTextView01; private EditText mEditText01; private Button mButton01; private static final String TAG = "DOWNLOADAPK"; private String currentFilePath = ""; private String currentTempFilePath = ""; private String strURL=""; private String fileEx=""; private String fileNa=""; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mTextView01 = (TextView)findViewById(R.id.myTextView1); mButton01 = (Button)findViewById(R.id.myButton1); mEditText01 =(EditText)findViewById(R.id.myEditText1); mButton01.setOnClickListener(new Button.OnClickListener() { public void onClick(View v) { // 文件会下载至local端 mTextView01.setText("下载中..."); strURL = mEditText01.getText().toString(); fileEx = strURL.substring(strURL.lastIndexOf(".") +1,strURL.length()).toLowerCase(); fileNa = strURL.substring(strURL.lastIndexOf("/") +1,strURL.lastIndexOf(".")); getFile(strURL); } } ); mEditText01.setOnClickListener(new EditText.OnClickListener() { public void onClick(View arg0){ mEditText01.setText(""); mTextView01.setText("远程安装程序(请输入URL)"); } }); } private void getFile(final String strPath) { try { if (strPath.equals(currentFilePath) ) { getDataSource(strPath); } currentFilePath = strPath; Runnable r = new Runnable() { public void run() { try { getDataSource(strPath); } catch (Exception e) { Log.e(TAG, e.getMessage(), e); } } }; new Thread(r).start(); } catch(Exception e) { e.printStackTrace(); } } private void getDataSource(String strPath) throws Exception { if (!URLUtil.isNetworkUrl(strPath)) { mTextView01.setText("错误的URL"); } else { URL myURL = new URL(strPath); URLConnection conn = myURL.openConnection(); conn.connect(); InputStream is = conn.getInputStream(); if (is == null) { throw new RuntimeException("stream is null"); } File myTempFile = File.createTempFile(fileNa, "."+fileEx); currentTempFilePath = myTempFile.getAbsolutePath(); FileOutputStream fos = new FileOutputStream(myTempFile); byte buf[] = new byte[128]; do { int numread = is.read(buf); if (numread <= 0) { break; } fos.write(buf, 0, numread); }while (true); openFile(myTempFile); try { is.close(); } catch (Exception ex) { Log.e(TAG, "error: " + ex.getMessage(), ex); } } } private void openFile(File f) { Intent intent = new Intent(); intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); intent.setAction(android.content.Intent.ACTION_VIEW); String type = getMIMEType(f); intent.setDataAndType(Uri.fromFile(f),type); startActivity(intent); } private String getMIMEType(File f) { String type=""; String fName=f.getName(); String end=fName.substring(fName.lastIndexOf(".") +1,fName.length()).toLowerCase(); if(end.equals("m4a")||end.equals("mp3")||end.equals("mid")|| end.equals("xmf")||end.equals("ogg")||end.equals("wav")) { type = "audio"; } else if(end.equals("3gp")||end.equals("mp4")) { type = "video"; } else if(end.equals("jpg")||end.equals("gif")||end.equals("png")|| end.equals("jpeg")||end.equals("bmp")) { type = "image"; } else if(end.equals("apk")) { type = "application/vnd.android.package-archive"; } else { type="*"; } if(end.equals("apk")) { } else { type += "/*"; } return type; } private void delFile(String strFileName) { File myFile = new File(strFileName); if(myFile.exists()) { myFile.delete(); } } protected void onPause() { mTextView01 = (TextView)findViewById(R.id.myTextView1); mTextView01.setText("下载成功"); super.onPause(); } protected void onResume() { delFile(currentTempFilePath); super.onResume(); }}

读者可以在该实例的基础上进行修改与完善，使之更符合自身项目需求。