從asynctask更新Imageview

我已經有了ImageView的列表視圖，然後在AsyncTask（適用於我應用程序中任何類型文件的通用下載器）的幫助下開始下載圖像列表。我需要將每個下載的圖像插入到ImageView後。所以我認爲我需要從我的AsyncTask到主線程的某種回調，但是如何去做它我不知道？從asynctask更新Imageview

這裏是我的AsyncTask代碼

DownloadFileFromURL下來=（DownloadFileFromURL）新DownloadFileFromURL（目的地）.execute（「http://example.com」）;

public class DownloadFileFromURL extends AsyncTask<String, String, String> { 

private String Destination; 

public DownloadFileFromURL(String UrlDestination){ 
    this.Destination=UrlDestination; 
} 

/** 
* Before starting background thread Show Progress Bar Dialog 
* */ 
@Override 
protected void onPreExecute() { 
    super.onPreExecute(); 

} 

/** 
* Downloading file in background thread 
* */ 
@Override 
protected String doInBackground(String... f_url) { 
    int count; 
    try { 
     URL url = new URL(f_url[0]); 
     URLConnection connection = url.openConnection(); 
     connection.connect(); 
     // this will be useful so that you can show a tipical 0-100% 
     // progress bar 
     int lenghtOfFile = connection.getContentLength(); 
     // download the file 
     InputStream input = new BufferedInputStream(url.openStream(),8192); 
     // Output stream 

     Log.d("City.xml:",this.Destination); 

     File targetFile = new File(this.Destination); 
     File parent = targetFile.getParentFile(); 
     if(!parent.exists() && !parent.mkdirs()){ 
      Log.e("Error: ", ": " + parent); 
     } 


     //OutputStream output = new FileOutputStream(Environment.getExternalStorageDirectory().toString() + "/"+this.Destination); 
     OutputStream output = new FileOutputStream(targetFile); 

     byte data[] = new byte[1024]; 

     long total = 0; 

     while ((count = input.read(data)) != -1) { 
      total += count; 
      // publishing the progress.... 
      // After this onProgressUpdate will be called 
      publishProgress("" + (int) ((total * 100)/lenghtOfFile)); 

      // writing data to file 
      output.write(data, 0, count); 
     } 

     // flushing output 
     output.flush(); 

     // closing streams 
     output.close(); 
     input.close(); 

    } catch (Exception e) { 
     Log.e("Error: ", e.getMessage()); 
    } 

    return null; 
} 

/** 
* Updating progress bar 
* */ 
protected void onProgressUpdate(String... progress) { 
    // setting progress percentage 
} 

/** 
* After completing background task Dismiss the progress dialog 
* **/ 
@Override 
protected void onPostExecute(String file_url) { 
    // dismiss the dialog after the file was downloaded 

}

}

來源

2014-01-30 SERG

看AsyncTask documentation

方法onPostExecute(result)被稱爲UI Thread所以你可以修改你的ListView它。

UPDATE：

您可以創建界面：

interface IOnFileDownloadedListener{ 

    public void onFileDownloaded(String filePath); // or type other than string 
}

然後在類DownloadFileFromURL你可以（在構造函數爲例）通過類實現IOnFileDownloadedListener莫名其妙。

然後下載文件，你可以檢查，如果偵聽器爲null（如果你決定允許不經過任何監聽器），如果不爲空，你可以調用後onFileDownloaded

public class DownloadFileFromURL extends AsyncTask<String, String, String> { 

private String Destination; 
private IOnFileDownloadedListener Listener = null; 

public DownloadFileFromURL(String UrlDestination){ 
    this.Destination=UrlDestination; 
} 

public DownloadFileFromURL(String UrlDestination, IOnFileDownloadedListener FDListener){ 
    this(UrlDestination); 
    Listener = FDListener; 
} 

... 

@Override 
protected void onPostExecute(String file_url) { 
    if(this.Listener != null) this.Listener.onFileDownloaded(this.Destination); 
}

來源

2014-01-30 10:53:05 Ari

我用這個DownloadFileFromURL類下載不同的文件，不僅圖像，所以我想將它保存更普遍的，一個不能修改，或將其設置爲特定的ListView – SERG

@SERG I更新了答案。 – Ari

您可以從伊斯利服務器中使用庫畢加索加載圖片：

http://square.github.io/picasso/

下面是一個例子：

Picasso.with(context).load("http://yoururlserver.com/yourimage.png").into(imageView);

來源

2014-01-30 10:52:48

看simple library to display images in Android ListView

來源

2014-01-30 10:57:08 ryderz8

我建議使用庫Android通用圖像加載器（https://github.com/nostra13/Android-Universal-Image-Loader）。

您可以easilly加載：

String imageUri = "http://www.yoursite.com/image.png"; // Image url 
imageLoader.displayImage(imageUri, imageView); // imageView - your imageView

來源

2014-01-30 11:47:14

從asynctask更新Imageview

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