android获取网络图片的用法

关于 android获取网络图片主要是把网络图片的数据流读入到内存中然后用
1.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
1.imageView.setImageBitmap(bitMap);
来进行转化
在获取bitmap时候出现null
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！
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

正确代码：
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();

}