1

当我在我的 中来回滚动时GridView，我的图像无法正确回收，最终将在整个网格中显示相同的图像。

回收问题

适配器

public class ImageAdapter extends BaseAdapter {
    private Context mContext;
    private List<String> mList;
    private int mheight;
    private int mwidth;
    private Bitmap nBitmap;

    public ImageAdapter(Context context, List<String> list, int height, int width) {
        mContext = context;
        mList = list;
        mheight = height;
        mwidth = width;
    }

    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position).toString();
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {
            imageView = new ImageView(mContext);
            InputStream is;
            try {
                is = mContext.getAssets().open(mList.get(position));
                Bitmap bm = BitmapFactory.decodeStream(is);
                Bitmap mBitmap = Bitmap.createScaledBitmap(bm, mwidth / 3, mwidth / 3, false);
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);

                this.nBitmap = mBitmap;
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } else {
            imageView = (ImageView) convertView;
        }
        imageView.setImageBitmap(nBitmap);
        return imageView;
    }
}

我试图从 Ui 线程中解码位图，滚动工作很快，但是在启动应用程序时缩略图被 1 个 1 加载，并且回收的缩略图视图从原始视图和低内存设备上的低内存设备应用程序崩溃，同时从 AsyncTask 加载缩略图这里是更新的代码

public class ImageAdapter extends BaseAdapter {
private Context mContext;
private List<String> mList;
private int mheight;
private int mwidth;
private InputStream is;

public ImageAdapter(Context context, List<String> list, int height, int width) {
    mContext = context;
    mList = list;
    mheight = height;
    mwidth = width;
}


@Override
public int getCount() {
    return mList.size();
}

@Override
public Object getItem(int position) {
    return mList.get(position).toString();
}

@Override
public long getItemId(int position) {
    return 0;
}





@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView;
    if (convertView == null) {
        imageView = new ImageView(mContext);
    } else {
        imageView = (ImageView) convertView;
    }


    InputStream is;
    try {
        is = mContext.getAssets().open(mList.get(position));
        Loadimage task = new Loadimage(imageView , mheight , mwidth);
        task.execute(is);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return imageView ;

}
 public class Loadimage extends AsyncTask<InputStream, Void, Bitmap>{
private final WeakReference<ImageView> imageViewReference;


private InputStream is = null;
private int width;


public Loadimage(ImageView imageView, int mheight, int mwidth) {
     imageViewReference = new WeakReference<ImageView>(imageView);
     this.width=mwidth;

    // TODO Auto-generated constructor stub
}

@Override
protected Bitmap doInBackground(InputStream... params) {
    is = params[0];

    if (is !=null) {

        Bitmap bitmap  = BitmapFactory.decodeStream(is);
        Bitmap nBitmap =Bitmap.createScaledBitmap(bitmap,width/3 , width/3, false);
        return nBitmap;     
    }
    return null; 
  }
 @Override
 protected void onPostExecute(Bitmap bitmap) {
    if (imageViewReference != null && bitmap != null) {
        final ImageView imageView = imageViewReference.get();
        if (imageView != null) {
            imageView.setImageBitmap(bitmap);
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        }


}

}

4

1 回答 1

3

您需要将生成位图的块移到if/then. 现在，您只在convertView == null.

我相信你的代码是正确的：

public class ImageAdapter extends BaseAdapter {
    private Context mContext;
    private List<String> mList;
    private int mheight;
    private int mwidth;

    public ImageAdapter(Context context, List<String> list, int height, int width) {
        mContext = context;
        mList = list;
        mheight = height;
        mwidth = width;
    }

    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position).toString();
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {
            imageView = new ImageView(mContext);
        } else {
            imageView = (ImageView) convertView;
        }

        InputStream is;
        try {
            is = mContext.getAssets().open(mList.get(position));
            Bitmap bm = BitmapFactory.decodeStream(is);
            Bitmap bitmap = Bitmap.createScaledBitmap(bm, mwidth / 3, mwidth / 3, false);
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);

            imageView.setImageBitmap(bitmap);
        } catch (IOException e) {
            e.printStackTrace();
        }

        return imageView;
    }
}

您的滚动不会很流畅，并且您会得到很多丢帧，因为您的位图解码代码效率低下（没有缓存），而且这一切都发生在 UI 线程上，这对响应能力不利。当前代码中的瓶颈不是ImageViews 的分配和垃圾收集。

瓶颈是（可能到目前为止）您对Bitmaps 的处理和创建。

您可以查看以下链接以获取建议：

有效地显示位图

特别是这个：

从 UI 线程处理位图

于 2013-03-21T23:53:56.650 回答