Android实现下载文件功能的方法

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 += "
 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。

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