Android中圖片的上傳和下載

在實現一個Android的WEB服務用戶端，比如微博，論壇用戶端時，經常會使用到圖片的上傳和下載。在這裡介紹如何利用HttpClient實現圖片的上傳和下載功能。

1 圖片上傳：上傳圖片時，首先獲得圖片的路徑，建立檔案，並將圖片轉化為位元組流寫入到request，並發送該請求。

用戶端代碼：       

[java] <span style="font-size:16px;">    File file = new File(imageUrl);  
        String httpUrl = httpDomain+"AddImageServlet"+"?gid="+gid;  
        HttpPost request = new HttpPost(httpUrl);   
        HttpClient httpClient = new DefaultHttpClient(); 
        FileEntity entity = new FileEntity(file,"binary/octet-stream"); 
        HttpResponse response; 
try { 
            request.setEntity(entity); 
            entity.setContentEncoding("binary/octet-stream"); 
            response = httpClient.execute(request); 
             
//如果返回狀態為200，獲得返回的結果  
 if(response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){   
……//圖片上傳成功             
} 
} 
catch(Exception e){  
} 
</span> 
<span style="font-size:16px;"> File file = new File(imageUrl); 
  String httpUrl = httpDomain+"AddImageServlet"+"?gid="+gid;
        HttpPost request = new HttpPost(httpUrl); 
        HttpClient httpClient = new DefaultHttpClient();
        FileEntity entity = new FileEntity(file,"binary/octet-stream");
      HttpResponse response;
try {
   request.setEntity(entity);
   entity.setContentEncoding("binary/octet-stream");
      response = httpClient.execute(request);
   
//如果返回狀態為200，獲得返回的結果
 if(response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){ 
……//圖片上傳成功          
}
}
catch(Exception e){
}
</span>

 

伺服器端所做的工作則是接收該位元組流，寫入檔案中，並在伺服器中相應檔案夾中儲存該檔案，並記錄該檔案的路徑，將圖片檔案路徑寫入到資料庫中儲存。

伺服器端代碼：

 

[java] <span style="font-size:16px;">//獲得新聞id  
        String gid = request.getParameter("gid");        
        String filePath = getRealPath(request) + "\\userpic\\";  
        //      定義上傳檔案的最大位元組   
        int MAX_SIZE = 102400 * 102400;          
        //      聲明檔案讀入類   
        DataInputStream in = null;  
        FileOutputStream fileOut = null;             
        //      取得用戶端上傳的資料類型   
        String contentType = request.getContentType();               
        if(contentType.indexOf("binary/octet-stream") >= 0){  
            //      讀入上傳的資料   
            in = new DataInputStream(request.getInputStream());  
            int formDataLength = request.getContentLength();  
            //  如果圖片過大  
            if(formDataLength > MAX_SIZE){  
                String errormsg=("上傳的檔案位元組數不可以超過" + MAX_SIZE); 
                out.println(errormsg); 
                return ; 
            }  
        //      儲存上傳檔案的資料   
        byte dataBytes[] = new byte[formDataLength];  
        int byteRead = 0;  
        int totalBytesRead = 0;  
        //      上傳的資料儲存在byte數組   
        while(totalBytesRead < formDataLength){  
        byteRead = in.read(dataBytes,totalBytesRead,formDataLength);  
        totalBytesRead += byteRead;  
          }  
        String fileName = filePath + gid+".png"; 
         //     檢查上傳檔案的目錄是否存在   
        File fileDir = new File(filePath);  
        if(!fileDir.exists()){  
        fileDir.mkdirs();  
        } 
        //      建立檔案的寫出類   
        fileOut = new FileOutputStream(fileName);  
        //      儲存檔案的資料   
        fileOut.write(dataBytes);  
        fileOut.close(); 
         
        //儲存檔案的路徑名  
……   
</span> 
<span style="font-size:16px;">//獲得新聞id
  String gid = request.getParameter("gid");  
  String filePath = getRealPath(request) + "\\userpic\\"; 
  //     定義上傳檔案的最大位元組
     int MAX_SIZE = 102400 * 102400;     
     //     聲明檔案讀入類
     DataInputStream in = null;
     FileOutputStream fileOut = null;       
     //     取得用戶端上傳的資料類型
     String contentType = request.getContentType();          
     if(contentType.indexOf("binary/octet-stream") >= 0){
      //     讀入上傳的資料
      in = new DataInputStream(request.getInputStream());
      int formDataLength = request.getContentLength();
      // 如果圖片過大 www.2cto.com
      if(formDataLength > MAX_SIZE){
       String errormsg=("上傳的檔案位元組數不可以超過" + MAX_SIZE);
       out.println(errormsg);
       return ;
      }
     //     儲存上傳檔案的資料
     byte dataBytes[] = new byte[formDataLength];
  int byteRead = 0;
  int totalBytesRead = 0;
  //     上傳的資料儲存在byte數組
  while(totalBytesRead < formDataLength){
  byteRead = in.read(dataBytes,totalBytesRead,formDataLength);
  totalBytesRead += byteRead;
    }
  String fileName = filePath + gid+".png";
   //     檢查上傳檔案的目錄是否存在
     File fileDir = new File(filePath);
     if(!fileDir.exists()){
     fileDir.mkdirs();
     }
     //     建立檔案的寫出類
     fileOut = new FileOutputStream(fileName);
     //     儲存檔案的資料
     fileOut.write(dataBytes);
     fileOut.close();
    
     //儲存檔案的路徑名
…… 
</span>

 

2 圖片下載：首先獲得網狀圖片的圖片地址，發送請求後，伺服器將會返回該圖片的位元組流，利用BitmapFactory.decodeStream()方法將位元組流轉化為圖片並返回。具體代碼如下：

 

[java] <span style="font-size:16px;">//獲得網路中的圖片  
    public Bitmap getGossipImage(String gid){        
        String httpUrl = httpDomain+"userpic/"+gid+".png";       
        Bitmap bitmap = null;           
        HttpGet httpRequest = new HttpGet(httpUrl);   
        //取得HttpClient 對象    
        HttpClient httpclient = new DefaultHttpClient();   
        try {   
            //請求httpClient ，取得HttpRestponse    
            HttpResponse httpResponse = httpclient.execute(httpRequest);   
            if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK){   
                //取得相關資訊 取得HttpEntiy    
                HttpEntity httpEntity = httpResponse.getEntity();   
                InputStream is = httpEntity.getContent();                  
                bitmap = BitmapFactory.decodeStream(is);   
                is.close();    
            }else{   
                 Toast.makeText(context, "串連失敗!", Toast.LENGTH_SHORT).show();       
            }    
               
        } catch (ClientProtocolException e) {   
            e.printStackTrace();   
        } catch (IOException e) {    
            e.printStackTrace();   
        }     
        return bitmap; 
    } 
 
</span> 
<span style="font-size:16px;">//獲得網路中的圖片
 public Bitmap getGossipImage(String gid){  
  String httpUrl = httpDomain+"userpic/"+gid+".png";   
  Bitmap bitmap = null;    
        HttpGet httpRequest = new HttpGet(httpUrl); 
        //取得HttpClient 對象 
        HttpClient httpclient = new DefaultHttpClient(); 
        try { 
            //請求httpClient ，取得HttpRestponse 
            HttpResponse httpResponse = httpclient.execute(httpRequest); 
            if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK){ 
                //取得相關資訊 取得HttpEntiy 
                HttpEntity httpEntity = httpResponse.getEntity(); 
                InputStream is = httpEntity.getContent();                
                bitmap = BitmapFactory.decodeStream(is); 
                is.close();  
            }else{ 
                Toast.makeText(context, "串連失敗!", Toast.LENGTH_SHORT).show();     
            }  
             
        } catch (ClientProtocolException e) { 
            e.printStackTrace(); 
        } catch (IOException e) {  
            e.printStackTrace(); 
        }   
  return bitmap;
 }

</span>

 

摘自 北京大學-Google Android實驗室