publicclass TestActivity extends Activity {    privatefinalstatic String TAG = "IcsTestActivity";    privatefinalstatic String ALBUM_PATH            = Environment.getExternalStorageDirectory() + "/download_test/";    private ImageView mImageView;    private Button mBtnSave;    private ProgressDialog mSaveDialog = null;    private Bitmap mBitmap;    private String mFileName;    private String mSaveMessage;


    @Override    protectedvoid onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mImageView = (ImageView)findViewById(R.id.imgSource);
        mBtnSave = (Button)findViewById(R.id.btnSave);        new Thread(connectNet).start();        // 下载图片
        mBtnSave.setOnClickListener(new Button.OnClickListener(){            publicvoid onClick(View v) {
                mSaveDialog = ProgressDialog.show(IcsTestActivity.this, "保存图片", "图片正在保存中，请稍等...", true);                new Thread(saveFileRunnable).start();
        }
        });
    }    /**
     * Get image from newwork
     * @param path The path of image
     * @return byte[]
     * @throws Exception     */publicbyte[] getImage(String path) throws Exception{
        URL url = new URL(path);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setConnectTimeout(5 * 1000);
        conn.setRequestMethod("GET");
        InputStream inStream = conn.getInputStream();        if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){            return readStream(inStream);
        }        returnnull;
    }    /**
     * Get image from newwork
     * @param path The path of image
     * @return InputStream
     * @throws Exception     */public InputStream getImageStream(String path) throws Exception{
        URL url = new URL(path);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setConnectTimeout(5 * 1000);
        conn.setRequestMethod("GET");        if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){            return conn.getInputStream();
        }        returnnull;
    }    /**
     * Get data from stream
     * @param inStream
     * @return byte[]
     * @throws Exception     */publicstaticbyte[] readStream(InputStream inStream) throws Exception{
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();        byte[] buffer = newbyte[1024];        int len = 0;        while( (len=inStream.read(buffer)) != -1){
            outStream.write(buffer, 0, len);
        }
        outStream.close();
        inStream.close();        return outStream.toByteArray();
    }    /**
     * 保存文件
     * @param bm
     * @param fileName
     * @throws IOException     */publicvoid saveFile(Bitmap bm, String fileName) throws IOException {
        File dirFile = new File(ALBUM_PATH);        if(!dirFile.exists()){
            dirFile.mkdir();
        }
        File myCaptureFile = new File(ALBUM_PATH + fileName);
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(myCaptureFile));
        bm.compress(Bitmap.CompressFormat.JPEG, 80, bos);
        bos.flush();
        bos.close();
    }    private Runnable saveFileRunnable = new Runnable(){
        @Override        publicvoid run() {            try {
                saveFile(mBitmap, mFileName);
                mSaveMessage = "图片保存成功！";
            } catch (IOException e) {
                mSaveMessage = "图片保存失败！";
                e.printStackTrace();
            }
            messageHandler.sendMessage(messageHandler.obtainMessage());
        }

    };    private Handler messageHandler = new Handler() {
        @Override        publicvoid handleMessage(Message msg) {
            mSaveDialog.dismiss();
            Log.d(TAG, mSaveMessage);
            Toast.makeText(IcsTestActivity.this, mSaveMessage, Toast.LENGTH_SHORT).show();
        }
    };    /*
     * 连接网络
     * 由于在4.0中不允许在主线程中访问网络，所以需要在子线程中访问     */private Runnable connectNet = new Runnable(){
        @Override        publicvoid run() {            try {
                String filePath = "http://img.my.csdn.net/uploads/201211/21/1353511891_4579.jpg";
                mFileName = "test.jpg";                //以下是取得图片的两种方法//////////////// 方法1：取得的是byte数组, 从byte数组生成bitmapbyte[] data = getImage(filePath);                if(data!=null){
                    mBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);// bitmap
                }else{
                    Toast.makeText(IcsTestActivity.this, "Image error!", 1).show();
                }                //////////////////////////////////////////////////////////******** 方法2：取得的是InputStream，直接从InputStream生成bitmap ***********/
                mBitmap = BitmapFactory.decodeStream(getImageStream(filePath));                //********************************************************************/                // 发送消息，通知handler在主线程中更新UI
                connectHanlder.sendEmptyMessage(0);
                Log.d(TAG, "set image ...");
            } catch (Exception e) {
                Toast.makeText(IcsTestActivity.this,"无法链接网络！", 1).show();
                e.printStackTrace();
            }

        }

    };    private Handler connectHanlder = new Handler() {
        @Override        publicvoid handleMessage(Message msg) {
            Log.d(TAG, "display image");            // 更新UI，显示图片if (mBitmap != null) {
                mImageView.setImageBitmap(mBitmap);// display image            }
        }
    };

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
<Button        android:id="@+id/btnSave"
          android:layout_width="wrap_content" 
        android:layout_height="wrap_content"
        android:text="保存图片"/>
<ImageView        android:id="@+id/imgSource"
          android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:adjustViewBounds="true"/></LinearLayout>