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();
	}

评论

1 楼 蜗牛/ 2011-09-21  

楼主我现在遇到这样一个问题，这里有一张图片的byte数组，改如何转为Bitmap.通过BitmapFactory.decodeByteArray(data, 0, length);同样返回NULL