为什么异常了

Question

使用下面这个获取数据的方法发生异常，怎么回事？请大家帮忙看看，连了网。public static InputStream getRequest(String path) throws Exception {            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setConnectTimeout(5000);            if (conn.getResponseCode() == 200){                    return conn.getInputStream();            }            return null;    }

Answer 1

这一句iv.setImageBitmap(bm);
11-01 08:13:40.134: W/System.err(1066): java.lang.NullPointerException
怎么解决呢

Answer 2

没初始化
例如
ImageView iv;
iv.setImageBitmap(bm);
这样就会报错

Answer 3

iv=(ImageView)findViewById(R.id.iv);  初始化了

Answer 4

我把整个例子贴出来public class TestActivity extends Activity{
private ImageView iv;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
Log.e("e","start");
String path="http://img.my.csdn.net/uploads/201210/29/1351519538_9960.png";
try {
InputStream is=ImageUtil.getRequest(path);
byte[] b=ImageUtil.readInputStream(is);
Bitmap bm=ImageUtil.byteToBitmap(b);

iv=(ImageView)findViewById(R.id.iv);
URL uri=new URL(path);
iv.setImageBitmap(bm);
} catch (Exception e) {
// TODO Auto-generated catch block
Log.e("e","ec");
e.printStackTrace();
}
}


}
class ImageUtil {    public static InputStream getRequest(String path) throws Exception {            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setConnectTimeout(5000);            if (conn.getResponseCode() == 200){                    return conn.getInputStream();            }
            Log.e("e","null");
            return null;    }
    public static byte[] readInputStream(InputStream inStream) throws Exception {        ByteArrayOutputStream outSteam = new ByteArrayOutputStream();        byte[] buffer = new byte[4096];        int len = 0;        while ((len = inStream.read(buffer)) != -1) {                outSteam.write(buffer, 0, len);        }        outSteam.close();        inStream.close();        return outSteam.toByteArray();}
    public static Bitmap byteToBitmap(byte[] byteArray){        if(byteArray.length!=0){          return BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);         }         else {          return null;         }  }
}

Answer 5

<uses-permission android:name="android.permission.INTERNET"/>
这个权限加上了吗

Answer 6

哦，太粗心了，没setContentView,谢谢大家.