Android使用json从服务器下载图像答案

【问题标题】：Android download image from server using jsonAndroid使用json从服务器下载图像
【发布时间】：2012-02-07 12:25:22
【问题描述】：

我的应用程序包含几个按钮，我想要的是通过单击任何按钮，它将引导我到一个 URL，该 URL 又将我带到一个 json 对象页面，然后为我提供一个要显示的图像源我的安卓设备。

例如：按钮 1 -> http://a.b.c.d/loadview.htm?buttonid=B1 -> Json 对象（img src- url 到图像文件） -> 显示在我的 android 设备上。

提前致谢：)

【问题讨论】：

标签： android json

【解决方案1】：

这是工作代码：从服务器下载图像并在 android 中显示

public void onCreate(Bundle savedInstanceState) 

{ 

Bitmap bitmap = DownloadImage("http://www.aaa.com/images//29_13.jpeg");

ImageView img = (ImageView) findViewById(R.id.imagefromserver);

img.setImageBitmap(bitmap);

}


private InputStream OpenHttpConnection(String urlString) 
    throws IOException

 {

 InputStream in = null;

        int response = -1;

        URL url = new URL(urlString); 
        URLConnection conn = url.openConnection();

        if (!(conn instanceof HttpURLConnection))                     
            throw new IOException("Not an HTTP connection");

        try{
            HttpURLConnection httpConn = (HttpURLConnection) conn;
            httpConn.setAllowUserInteraction(false);
            httpConn.setInstanceFollowRedirects(true);
            httpConn.setRequestMethod("GET");
            httpConn.connect(); 

            response = httpConn.getResponseCode();                 
            if (response == HttpURLConnection.HTTP_OK) {
                in = httpConn.getInputStream();                                 
            }                     
        }
        catch (Exception ex)
        {
            throw new IOException("Error connecting");            
        }
        return in;     
    }
    private Bitmap DownloadImage(String URL)
    {        
        Bitmap bitmap = null;
        InputStream in = null;        
        try {
            in = OpenHttpConnection(URL);
            bitmap = BitmapFactory.decodeStream(in);
            in.close();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        return bitmap;                
    }

【讨论】：

【解决方案2】：

You need to open a HttpConnection with the url to image source and download it.
Here is the code: 

Bitmap getTheBitmap(String yourImgSrcUrl)
{
URL url = null;
Bitmap bitmap = null;
DataInputStream fileInputStream = null;
try
{
String urlPath = yourImgSrcUrl;
urlPath = urlPath.replace(" ", "%20"); // to replace any blank spaces
url = new URL(urlPath);
connection = (HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.setUseCaches(false);
connection.setRequestMethod("GET");

fileInputStream = new DataInputStream(connection.getInputStream());
byte[] bitmapBytes= new byte[fileInputStream.available()];
fileInputStream.read(bitmapBytes);
fileInputStream.close();
bitmap = BitmapFactory.decodeByteArray(bitmapBytes, 0, bitmapBytes.length);
return bitmap;
}
catch (IOException e) 
        {
            e.printStackTrace();
return null;
        }
}


Kindly check that Bitmap you are getting is not null before setting in the ImageView else it will throw exception.

【讨论】：

嗨，我将位图设为空。可能是什么问题。

【解决方案3】：

您的示例网址不起作用，但无论如何我都会尝试解释：

    WebRequest request = HttpWebRequest.Create("test.aspx");
    WebResponse response = request.GetResponse();

    using (StreamReader streamReader = new StreamReader(response.GetResponseStream()))
    {
        string json = streamReader.ReadToEnd();

        JavaScriptSerializer ser = new JavaScriptSerializer();
        var deserializedObject = ser.Deserialize(json, typeof(ControllerBuilder));

        if(deserializedObject != null)
            //cast object to the correct type and use it.
    }

我不建议使用内置 JavaScriptSerializer 类，因为我遇到了性能问题。更好的工具是：

http://james.newtonking.com/pages/json-net.aspx

希望对你有所帮助！

【讨论】：