android：在viewpager中使用gridview顯示156個圖像

Question

我想使用18頁的Viewpager顯示156個縮略圖，每個頁面有9個縮略圖。 我已經實現如下：

Index_gridview類：

public void init() 
{  
    PageCount = (int) Math.ceil(mThumbIds.length / PAGE_SIZE);  
    mLists = new ArrayList<GridView>();  

    for (int i = 0; i < PageCount; i++) 
    {  
        GridView gv = new GridView(this);  
        gv.setAdapter(new MyGridViewAdapter(this, mStrs, mThumbIds, i, icon_dimension));  
        gv.setGravity(Gravity.CENTER);  
        gv.setClickable(true);  
        gv.setFocusable(true);  
        gv.setNumColumns(NUMOFCOLUMN);  
        gv.setStretchMode(GridView.STRETCH_COLUMN_WIDTH);
        gv.setHorizontalSpacing(gridview_horizontal_padding);
        gv.setVerticalSpacing(gridview_vertical_padding);
        mLists.add(gv);  
    }         
    page_number.setText("1/"+PageCount);
}  

GridViewAdapter類：

public class MyGridViewAdapter extends BaseAdapter 
{   
    private Animation zoom     = null;
    // view
    int icon_width, icon_height;
    Typeface tf;
    private Context mContext;  
    private List<String> mLists;  
    public static final int PAGE_SIZE = 9; // showing how many items in 1 page  

    public MyGridViewAdapter(Context pContext, String[] pStrs, Integer[] image_ref, int page, int width) 
    {  
        this.mContext = pContext;  
        mLists = new ArrayList<String>();  
        int i = page * PAGE_SIZE;  
        int end = i + PAGE_SIZE;  
        while ((i < image_ref.length) && (i < end)) 
        {  
            mLists.add(pStrs[i]); 
            i++;  
        }  

        icon_width = width;
        icon_height = icon_width;

        tf = Typeface.createFromAsset(mContext.getAssets(),"fonts/HomegirlKiddo.ttf");   
    }  

    @Override  
    public int getCount() 
    {           
        return mLists.size();  
    }  
    @Override  
    public Object getItem(int position) 
    {           
        return mLists.get(position);  
    }  
    @Override  
    public long getItemId(int position) 
    {     
        return position;  
    }  

    @Override  
    public View getView(int position, View convertView, ViewGroup parent) 
    {
        ViewHolder holder;
        if (convertView == null)
        {
            LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.menugrid, parent, false);
            holder = new ViewHolder();

            holder.img = (ImageView) convertView.findViewById(R.id.imageicon);
            convertView.setTag(holder);
        } 
        else
        {
            holder = (ViewHolder) convertView.getTag();
        }


        final int myNum = Integer.parseInt(mLists.get(position)) -1;
        ImageView imageView = holder.img;

        try
        {
            imageView.setImageBitmap(decodeSampledBitmapFromResource(mContext.getResources(), mThumbIds[myNum], icon_width, icon_width));   
        }
        catch (OutOfMemoryError e)
        {
            ((Index_Gridview)mContext).custom_toast("System Out-of-Error! Restarting...");
            ((Index_Gridview)mContext).restart_app();  
        }


        imageView.setOnClickListener(new OnImageClickListener(myNum));       
        return convertView;
    }

private Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) 
{
    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inPreferredConfig = Bitmap.Config.ARGB_8888;
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeResource(res, resId, options);

    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeResource(res, resId, options);
}

private int calculateInSampleSize (BitmapFactory.Options options, int reqWidth, int reqHeight) 
{
    // Raw height and width of image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) 
    {   
        // Calculate ratios of height and width to requested height and width
        final int heightRatio = Math.round((float) height / (float) reqHeight);
        final int widthRatio = Math.round((float) width / (float) reqWidth);

        // Choose the smallest ratio as inSampleSize value, this will guarantee
        // a final image with both dimensions larger than or equal to the requested height and width.
        inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
    }   
    return inSampleSize;
} 

class ViewHolder 
{
    ImageView img;
}

// References to our images in res > drawable
public Integer[] mThumbIds =  new Integer[] 
    {
        R.drawable.t_aaa, 
        R.drawable.t_bbb, 
                    ....listing of 156 image references here
    }

題：

我已經嘗試通過'decodeSampledBitmapFromResource'導入縮略圖。 原始縮略圖各約為75KB。

它很容易遇到OOM。 如何增強代碼以減輕OOM錯誤？

謝謝！！

Answer 1

您可以嘗試使用RAM和磁盤緩存來重用您的位圖。

這是android支持v4中LRUCache的鏈接：

http://developer.android.com/reference/android/support/v4/util/LruCache.html

這是Jake Wharton對DiskLRUCache項目的鏈接

https://github.com/JakeWharton/DiskLruCache

Answer 2

你必須自己做一些記憶管理 - 毫無疑問。 您可以回收屏幕外頁面並在必要時重新加載它們。 LRUCache非常好，但它會將所有內存用於圖像。

您的畫廊不是那么大，您可以考慮將其保存在本機內存中。 你需要30MB的hdpi 800x480屏幕到150MB的高清屏幕。 使用JNI和C調用，您可以向android詢問安裝在硬件中的整個內存（512 - 1GB）。 這樣的內存不是Java堆的一部分，因此您不必擔心應用程序中其他內容缺少內存。

當然，這不是完美的解決方案，因為占用的內存比系統提供的內存多，這將導致分配失敗。 你必須照顧它。

鏈接： http ： //code.google.com/p/native-buffer/

NativeBuffer是一種緩存，它使用C分配的內存來存儲圖像數據。 它比重新加載圖像或在SD卡上緩存它們要快得多。

Answer 3

https://code.google.com/p/android-query/wiki/AsyncAPI?tm=6在一個示例中使用我知道https://play.google.com/store/apps/details?id=com.app .ive它可以處理任意數量的圖像....

我認為重新發明輪子並不好，希望它可以幫助你實現你想要的。

謝謝