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Android瀑布流照片墻實(shí)現(xiàn)，體驗(yàn)不規(guī)則排列的美感Demo。
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/** 
 * 自定義的ScrollView，在其中動(dòng)態(tài)地對(duì)圖片進(jìn)行添加。 
 * 
 * @author guolin 
 */ 
public class MyScrollView extends ScrollView implements OnTouchListener { 
  
    /** 
     * 每頁(yè)要加載的圖片數(shù)量 
     */ 
    public static final int PAGE_SIZE = 15; 
  
    /** 
     * 記錄當(dāng)前已加載到第幾頁(yè) 
     */ 
    private int page; 
  
    /** 
     * 每一列的寬度 
     */ 
    private int columnWidth; 
  
    /** 
     * 當(dāng)前第一列的高度 
     */ 
    private int firstColumnHeight; 
  
    /** 
     * 當(dāng)前第二列的高度 
     */ 
    private int secondColumnHeight; 
  
    /** 
     * 當(dāng)前第三列的高度 
     */ 
    private int thirdColumnHeight; 
  
    /** 
     * 是否已加載過(guò)一次layout，這里onLayout中的初始化只需加載一次 
     */ 
    private boolean loadOnce; 
  
    /** 
     * 對(duì)圖片進(jìn)行管理的工具類(lèi) 
     */ 
    private ImageLoader imageLoader; 
  
    /** 
     * 第一列的布局 
     */ 
    private LinearLayout firstColumn; 
  
    /** 
     * 第二列的布局 
     */ 
    private LinearLayout secondColumn; 
  
    /** 
     * 第三列的布局 
     */ 
    private LinearLayout thirdColumn; 
  
    /** 
     * 記錄所有正在下載或等待下載的任務(wù)。 
     */ 
    private static Set<loadimagetask> taskCollection; 
  
    /** 
     * MyScrollView下的直接子布局。 
     */ 
    private static View scrollLayout; 
  
    /** 
     * MyScrollView布局的高度。 
     */ 
    private static int scrollViewHeight; 
  
    /** 
     * 記錄上垂直方向的滾動(dòng)距離。 
     */ 
    private static int lastScrollY = -1; 
  
    /** 
     * 記錄所有界面上的圖片，用以可以隨時(shí)控制對(duì)圖片的釋放。 
     */ 
    private List<imageview> imageViewList = new ArrayList<imageview>(); 
  
    /** 
     * 在Handler中進(jìn)行圖片可見(jiàn)性檢查的判斷，以及加載更多圖片的操作。 
     */ 
    private static Handler handler = new Handler() { 
  
        public void handleMessage(android.os.Message msg) { 
            MyScrollView myScrollView = (MyScrollView) msg.obj; 
            int scrollY = myScrollView.getScrollY(); 
            // 如果當(dāng)前的滾動(dòng)位置和上次相同，表示已停止?jié)L動(dòng) 
            if (scrollY == lastScrollY) { 
                // 當(dāng)滾動(dòng)的最底部，并且當(dāng)前沒(méi)有正在下載的任務(wù)時(shí)，開(kāi)始加載下一頁(yè)的圖片 
                if (scrollViewHeight + scrollY >= scrollLayout.getHeight() 
                        && taskCollection.isEmpty()) { 
                    myScrollView.loadMoreImages(); 
                } 
                myScrollView.checkVisibility(); 
            } else { 
                lastScrollY = scrollY; 
                Message message = new Message(); 
                message.obj = myScrollView; 
                // 5毫秒后再次對(duì)滾動(dòng)位置進(jìn)行判斷 
                handler.sendMessageDelayed(message, 5); 
            } 
        }; 
  
    }; 
  
    /** 
     * MyScrollView的構(gòu)造函數(shù)。 
     * 
     * @param context 
     * @param attrs 
     */ 
    public MyScrollView(Context context, AttributeSet attrs) { 
        super(context, attrs); 
        imageLoader = ImageLoader.getInstance(); 
        taskCollection = new HashSet<loadimagetask>(); 
        setOnTouchListener(this); 
    } 
  
    /** 
     * 進(jìn)行一些關(guān)鍵性的初始化操作，獲取MyScrollView的高度，以及得到第一列的寬度值。并在這里開(kāi)始加載第一頁(yè)的圖片。 
     */ 
    @Override 
    protected void onLayout(boolean changed, int l, int t, int r, int b) { 
        super.onLayout(changed, l, t, r, b); 
        if (changed && !loadOnce) { 
            scrollViewHeight = getHeight(); 
            scrollLayout = getChildAt(0); 
            firstColumn = (LinearLayout) findViewById(R.id.first_column); 
            secondColumn = (LinearLayout) findViewById(R.id.second_column); 
            thirdColumn = (LinearLayout) findViewById(R.id.third_column); 
            columnWidth = firstColumn.getWidth(); 
            loadOnce = true; 
            loadMoreImages(); 
        } 
    } 
  
    /** 
     * 監(jiān)聽(tīng)用戶(hù)的觸屏事件，如果用戶(hù)手指離開(kāi)屏幕則開(kāi)始進(jìn)行滾動(dòng)檢測(cè)。 
     */ 
    @Override 
    public boolean onTouch(View v, MotionEvent event) { 
        if (event.getAction() == MotionEvent.ACTION_UP) { 
            Message message = new Message(); 
            message.obj = this; 
            handler.sendMessageDelayed(message, 5); 
        } 
        return false; 
    } 
  
    /** 
     * 開(kāi)始加載下一頁(yè)的圖片，每張圖片都會(huì)開(kāi)啟一個(gè)異步線程去下載。 
     */ 
    public void loadMoreImages() { 
        if (hasSDCard()) { 
            int startIndex = page * PAGE_SIZE; 
            int endIndex = page * PAGE_SIZE + PAGE_SIZE; 
            if (startIndex < Images.imageUrls.length) { 
                Toast.makeText(getContext(), "正在加載...", Toast.LENGTH_SHORT) 
                        .show(); 
                if (endIndex > Images.imageUrls.length) { 
                    endIndex = Images.imageUrls.length; 
                } 
                for (int i = startIndex; i < endIndex; i++) { 
                    LoadImageTask task = new LoadImageTask(); 
                    taskCollection.add(task); 
                    task.execute(Images.imageUrls[i]); 
                } 
                page++; 
            } else { 
                Toast.makeText(getContext(), "已沒(méi)有更多圖片", Toast.LENGTH_SHORT) 
                        .show(); 
            } 
        } else { 
            Toast.makeText(getContext(), "未發(fā)現(xiàn)SD卡", Toast.LENGTH_SHORT).show(); 
        } 
    } 
  
    /** 
     * 遍歷imageViewList中的每張圖片，對(duì)圖片的可見(jiàn)性進(jìn)行檢查，如果圖片已經(jīng)離開(kāi)屏幕可見(jiàn)范圍，則將圖片替換成一張空?qǐng)D。 
     */ 
    public void checkVisibility() { 
        for (int i = 0; i < imageViewList.size(); i++) { 
            ImageView imageView = imageViewList.get(i); 
            int borderTop = (Integer) imageView.getTag(R.string.border_top); 
            int borderBottom = (Integer) imageView 
                    .getTag(R.string.border_bottom); 
            if (borderBottom > getScrollY() 
                    && borderTop < getScrollY() + scrollViewHeight) { 
                String imageUrl = (String) imageView.getTag(R.string.image_url); 
                Bitmap bitmap = imageLoader.getBitmapFromMemoryCache(imageUrl); 
                if (bitmap != null) { 
                    imageView.setImageBitmap(bitmap); 
                } else { 
                    LoadImageTask task = new LoadImageTask(imageView); 
                    task.execute(imageUrl); 
                } 
            } else { 
                imageView.setImageResource(R.drawable.empty_photo); 
            } 
        } 
    } 
  
    /** 
     * 判斷手機(jī)是否有SD卡。 
     * 
     * @return 有SD卡返回true，沒(méi)有返回false。 
     */ 
    private boolean hasSDCard() { 
        return Environment.MEDIA_MOUNTED.equals(Environment 
                .getExternalStorageState()); 
    } 
  
    /** 
     * 異步下載圖片的任務(wù)。 
     * 
     * @author guolin 
     */ 
    class LoadImageTask extends AsyncTask<string, void,="" bitmap=""> { 
  
        /** 
         * 圖片的URL地址 
         */ 
        private String mImageUrl; 
  
        /** 
         * 可重復(fù)使用的ImageView 
         */ 
        private ImageView mImageView; 
  
        public LoadImageTask() { 
        } 
  
        /** 
         * 將可重復(fù)使用的ImageView傳入 
         * 
         * @param imageView 
         */ 
        public LoadImageTask(ImageView imageView) { 
            mImageView = imageView; 
        } 
  
        @Override 
        protected Bitmap doInBackground(String... params) { 
            mImageUrl = params[0]; 
            Bitmap imageBitmap = imageLoader 
                    .getBitmapFromMemoryCache(mImageUrl); 
            if (imageBitmap == null) { 
                imageBitmap = loadImage(mImageUrl); 
            } 
            return imageBitmap; 
        } 
  
        @Override 
        protected void onPostExecute(Bitmap bitmap) { 
            if (bitmap != null) { 
                double ratio = bitmap.getWidth() / (columnWidth * 1.0); 
                int scaledHeight = (int) (bitmap.getHeight() / ratio); 
                addImage(bitmap, columnWidth, scaledHeight); 
            } 
            taskCollection.remove(this); 
        } 
  
        /** 
         * 根據(jù)傳入的URL，對(duì)圖片進(jìn)行加載。如果這張圖片已經(jīng)存在于SD卡中，則直接從SD卡里讀取，否則就從網(wǎng)絡(luò)上下載。 
         * 
         * @param imageUrl 
         *            圖片的URL地址 
         * @return 加載到內(nèi)存的圖片。 
         */ 
        private Bitmap loadImage(String imageUrl) { 
            File imageFile = new File(getImagePath(imageUrl)); 
            if (!imageFile.exists()) { 
                downloadImage(imageUrl); 
            } 
            if (imageUrl != null) { 
                Bitmap bitmap = ImageLoader.decodeSampledBitmapFromResource( 
                        imageFile.getPath(), columnWidth); 
                if (bitmap != null) { 
                    imageLoader.addBitmapToMemoryCache(imageUrl, bitmap); 
                    return bitmap; 
                } 
            } 
            return null; 
        } 
  
        /** 
         * 向ImageView中添加一張圖片 
         * 
         * @param bitmap 
         *            待添加的圖片 
         * @param imageWidth 
         *            圖片的寬度 
         * @param imageHeight 
         *            圖片的高度 
         */ 
        private void addImage(Bitmap bitmap, int imageWidth, int imageHeight) { 
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams( 
                    imageWidth, imageHeight); 
            if (mImageView != null) { 
                mImageView.setImageBitmap(bitmap); 
            } else { 
                ImageView imageView = new ImageView(getContext()); 
                imageView.setLayoutParams(params); 
                imageView.setImageBitmap(bitmap); 
                imageView.setScaleType(ScaleType.FIT_XY); 
                imageView.setPadding(5, 5, 5, 5); 
                imageView.setTag(R.string.image_url, mImageUrl); 
                findColumnToAdd(imageView, imageHeight).addView(imageView); 
                imageViewList.add(imageView); 
            } 
        } 
  
        /** 
         * 找到此時(shí)應(yīng)該添加圖片的一列。原則就是對(duì)三列的高度進(jìn)行判斷，當(dāng)前高度最小的一列就是應(yīng)該添加的一列。 
         * 
         * @param imageView 
         * @param imageHeight 
         * @return 應(yīng)該添加圖片的一列 
         */ 
        private LinearLayout findColumnToAdd(ImageView imageView, 
                int imageHeight) { 
            if (firstColumnHeight <= secondColumnHeight) { 
                if (firstColumnHeight <= thirdColumnHeight) { 
                    imageView.setTag(R.string.border_top, firstColumnHeight); 
                    firstColumnHeight += imageHeight; 
                    imageView.setTag(R.string.border_bottom, firstColumnHeight); 
                    return firstColumn; 
                } 
                imageView.setTag(R.string.border_top, thirdColumnHeight); 
                thirdColumnHeight += imageHeight; 
                imageView.setTag(R.string.border_bottom, thirdColumnHeight); 
                return thirdColumn; 
            } else { 
                if (secondColumnHeight <= thirdColumnHeight) { 
                    imageView.setTag(R.string.border_top, secondColumnHeight); 
                    secondColumnHeight += imageHeight; 
                    imageView 
                            .setTag(R.string.border_bottom, secondColumnHeight); 
                    return secondColumn; 
                } 
                imageView.setTag(R.string.border_top, thirdColumnHeight); 
                thirdColumnHeight += imageHeight; 
                imageView.setTag(R.string.border_bottom, thirdColumnHeight); 
                return thirdColumn; 
            } 
        } 
  
        /** 
         * 將圖片下載到SD卡緩存起來(lái)。 
         * 
         * @param imageUrl 
         *            圖片的URL地址。 
         */ 
        private void downloadImage(String imageUrl) { 
            if (Environment.getExternalStorageState().equals( 
                    Environment.MEDIA_MOUNTED)) { 
                Log.d("TAG", "monted sdcard"); 
            } else { 
                Log.d("TAG", "has no sdcard"); 
            } 
            HttpURLConnection con = null; 
            FileOutputStream fos = null; 
            BufferedOutputStream bos = null; 
            BufferedInputStream bis = null; 
            File imageFile = null; 
            try { 
                URL url = new URL(imageUrl); 
                con = (HttpURLConnection) url.openConnection(); 
                con.setConnectTimeout(5 * 1000); 
                con.setReadTimeout(15 * 1000); 
                con.setDoInput(true); 
                con.setDoOutput(true); 
                bis = new BufferedInputStream(con.getInputStream()); 
                imageFile = new File(getImagePath(imageUrl)); 
                fos = new FileOutputStream(imageFile); 
                bos = new BufferedOutputStream(fos); 
                byte[] b = new byte[1024]; 
                int length; 
                while ((length = bis.read(b)) != -1) { 
                    bos.write(b, 0, length); 
                    bos.flush(); 
                } 
            } catch (Exception e) { 
                e.printStackTrace(); 
            } finally { 
                try { 
                    if (bis != null) { 
                        bis.close(); 
                    } 
                    if (bos != null) { 
                        bos.close(); 
                    } 
                    if (con != null) { 
                        con.disconnect(); 
                    } 
                } catch (IOException e) { 
                    e.printStackTrace(); 
                } 
            } 
            if (imageFile != null) { 
                Bitmap bitmap = ImageLoader.decodeSampledBitmapFromResource( 
                        imageFile.getPath(), columnWidth); 
                if (bitmap != null) { 
                    imageLoader.addBitmapToMemoryCache(imageUrl, bitmap); 
                } 
            } 
        } 
  
        /** 
         * 獲取圖片的本地存儲(chǔ)路徑。 
         * 
         * @param imageUrl 
         *            圖片的URL地址。 
         * @return 圖片的本地存儲(chǔ)路徑。 
         */ 
        private String getImagePath(String imageUrl) { 
            int lastSlashIndex = imageUrl.lastIndexOf("/"); 
            String imageName = imageUrl.substring(lastSlashIndex + 1); 
            String imageDir = Environment.getExternalStorageDirectory() 
                    .getPath() + "/PhotoWallFalls/"; 
            File file = new File(imageDir); 
            if (!file.exists()) { 
                file.mkdirs(); 
            } 
            String imagePath = imageDir + imageName; 
            return imagePath; 
        } 
    } 
  
}</string,></loadimagetask></imageview></imageview></loadimagetask> 

源碼下載：http://down.51cto.com/data/1980596