提高gridview的滚动性能

Question

我正在使用显示从assets 文件夹加载的图像的gridView。

gridview 显示来自 assets 的 50 多张图像，但该 gridview 的性能很差，并且存在滚动时滞。

示例代码为：

protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.ameme);

    GridView myGallery = (GridView) findViewById(R.id.gridView1);

    mBitArray = new Bitmap[5];

    //This is just a sample code

    try
    {
        //these images are stored in the root of "assets"
        mBitArray[0] = getBitmapFromAsset("AM0.jpg");
        mBitArray[1] = getBitmapFromAsset("AM1.jpg");
        mBitArray[2] = getBitmapFromAsset("AM2.jpg");
        mBitArray[3] = getBitmapFromAsset("AM3.jpg");
        mBitArray[4] = getBitmapFromAsset("AM4.jpg");
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }

    myGallery.setAdapter(new GalleryAdapter(this, mBitArray));
}
 public class GalleryAdapter extends BaseAdapter
    {
        private Context mContext;
        private Bitmap[] mImageArray;

        public GalleryAdapter(Context context, Bitmap[] imgArray)
        {
            mContext = context;
            mImageArray = imgArray;
        }

        public int getCount()
        {
            return mImageArray.length;
        }

        public Object getItem(int position)
        {
            return position;
        }

        public long getItemId(int position)
        {
            return position;
        }
        public View getView(int position, View convertView, ViewGroup parent)
        {
            final ImageView imgView = new ImageView(mContext);


            imgView.setImageBitmap(mImageArray[position]);

            final RelativeLayout borderImg = new RelativeLayout(mContext);

            borderImg.setPadding(8, 8, 8, 8);
            borderImg.setGravity(Gravity.CENTER | Gravity.BOTTOM);
            borderImg.setBackgroundColor(Color.rgb(7,35,63));

            borderImg.addView(imgView);
            imgView.setLayoutParams(new RelativeLayout.LayoutParams(100,100));

            return borderImg;
        }

    }
 private Bitmap getBitmapFromAsset(String strName) throws IOException
    {
        AssetManager assetManager = getAssets();

        InputStream istr = assetManager.open(strName);

        Bitmap bitmap = BitmapFactory.decodeStream(istr);
        istr.close();

        return bitmap;
    }
 }

如何使gridView() 的滚动更顺畅？

Answer 1

ConvertView 保存回收的视图。你应该检查它是否为空。如果它不为空，则可以再次重用前一行。希望这段代码能有所改进。还有一种称为ViewHolder 模式的模式很有用，但不适用于您的情况。

 public View getView(int position, View convertView, ViewGroup parent)
    {

       if(convertView == null){

        final ImageView imgView = new ImageView(mContext);
        final RelativeLayout borderImg = new RelativeLayout(mContext);

        imgView.setLayoutParams(new RelativeLayout.LayoutParams(100,100));
        borderImg.setPadding(8, 8, 8, 8);
        borderImg.setGravity(Gravity.CENTER | Gravity.BOTTOM);
        borderImg.setBackgroundColor(Color.rgb(7,35,63));

        borderImg.addView(imgView);

        convertView.setTag(borderImg);

   }else{
       borderImg = (RelativeLayout)convertView.getTag();
   }

       imgView.setImageBitmap(mImageArray[position]);

   return borderImg;
}

另外我猜位图可能很大，尝试阅读此http://developer.android.com/training/displaying-bitmaps/load-bitmap.html 并优化它们。