android获取网络图片的用法

关于android获取网络图片主要是吧网络图片的数据流读入到内存中然后用

Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length);

方法来将图片流传化为bitmap类型这样才能用到

imageView.setImageBitmap(bitMap);

来进行转化，这些大家都了解，主要的问题在获取bitmap时候居然为null 怎么回事呢？我开始的时候遇见这个问题，并且困扰了一段时间，最后发现错误了
下面是我的错误代码

     byte[] data = GetImageForNet.getImage(path);     int length = data.length;         Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length);     imageView.setImageBitmap(bitMap);

下面是 GetImageForNet.getImage()方法的代码清单

public static byte[] getImage(String path) throws Exception {URL url = new URL(path);HttpURLConnection httpURLconnection =  (HttpURLConnection)url.openConnection();httpURLconnection.setRequestMethod("GET");httpURLconnection.setReadTimeout(6*1000);InputStream in = null;byte[] b = new byte[1024];int len = -1;if (httpURLconnection.getResponseCode() == 200) { in = httpURLconnection.getInputStream(); in.read(b);                         in.close();                         return b;                          }return null;}

看起来没有问题获取网络图片输入流，填充二进制数组，返回二进制数组，然后使用 Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length); data就是返回的二进制数组
获取bitMap 看起来没有问题，可是bitMap就是为null！汗！最后慢慢整理思路，排除法去查找出现异常的地方，最后发现可能BitmapFactory.decodeByteArray方法中所需要的data不一定是传统意义上的字节数组，查看android api，最后发现BitmapFactory.decodeByteArray所需要的data字节数组并不是想象中的数组！而是把输入流传化为字节内存输出流的字节数组格式，找到原因后改进一下，成功！附上成功后的代码

  try {    byte[] data = GetImageForNet.getImage(path);    String d = new String(data);   // File file = new File("1.jpg");    //OutputStream out = new FileOutputStream(file);    //out.write(data);    //out.close();    int length = data.length;    Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length);    imageView.setImageBitmap(bitMap);    //imageView.seti} catch (Exception e) {Log.i(TAG, e.toString());Toast.makeText(DataActivity.this, "获取图片失败", 1).show();}

下面是改进后的 GetImageForNet.getImage()方法的代码清单

public static byte[] getImage(String path) throws Exception {URL url = new URL(path);HttpURLConnection httpURLconnection =  (HttpURLConnection)url.openConnection();httpURLconnection.setRequestMethod("GET");httpURLconnection.setReadTimeout(6*1000);InputStream in = null;byte[] b = new byte[1024];int len = -1;if (httpURLconnection.getResponseCode() == 200) { in = httpURLconnection.getInputStream(); byte[] result = readStream(in); in.close(); return result; }return null;}public static byte[] readStream(InputStream in) throws Exception{ByteArrayOutputStream outputStream = new ByteArrayOutputStream();byte[] buffer = new byte[1024];int len = -1;while((len = in.read(buffer)) != -1) {outputStream.write(buffer, 0, len);}outputStream.close();in.close();return outputStream.toByteArray();}

转自：http://www.4ucode.com/Study/Topic/1952873

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