Question

我正在使用游标获取联系人数据并尝试将其加载到ListView

中

我根据QuickContact APIDemos样本（API级别8）开发了我的代码

这是我的代码，我已经修改了一下，但我面临性能问题如果我删除了联系人照片代码，那么性能会很好，否则就像拖动列表一样太慢

适配器代码

    private class ContactListAdapter extends ResourceCursorAdapter{

         Cursor cur;
        public ContactListAdapter(Context context, int layout, Cursor c) {
            super(context, layout, c);

            cur = c;
            // TODO Auto-generated constructor stub
        }

        @Override
        public void bindView(View view, Context arg1, Cursor arg2) {
            // TODO Auto-generated method stub
            final ContactListItemCache cache = (ContactListItemCache) view.getTag();
            TextView nameView = cache.nameView;
            QuickContactBadge photoView = cache.photoView;            

            cur.copyStringToBuffer(cur.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME), cache.nameBuffer);
            int size = cache.nameBuffer.sizeCopied;
            cache.nameView.setText(cache.nameBuffer.data, 0, size);          

            long contactId = cur.getLong(cur.getColumnIndex(ContactsContract.Contacts._ID));
            Uri contactUri = Uri.withAppendedPath(ContactsContract.Contacts.CONTENT_URI, String.valueOf(contactId));


           InputStream input = ContactsContract.Contacts.openContactPhotoInputStream(getContentResolver(), contactUri);            
            cache.photoView.setImageBitmap(BitmapFactory.decodeStream(input));


        }

        @Override
        public View newView(Context context, Cursor cursor, ViewGroup parent) {

            View view = super.newView(context, cursor, parent);
            ContactListItemCache cache = new ContactListItemCache();
            cache.nameView = (TextView) view.findViewById(R.id.name);
            cache.photoView = (QuickContactBadge) view.findViewById(R.id.badge);
            view.setTag(cache);

            return view;

        }
       }
       final static class ContactListItemCache {
            public TextView nameView;
            public QuickContactBadge photoView;
            public CharArrayBuffer nameBuffer = new CharArrayBuffer(128);
        }
}

获取联系人代码

private Cursor getContacts()
   {
        // Run query
        Uri uri = ContactsContract.Contacts.CONTENT_URI;
        String[] projection = new String[] {
                ContactsContract.Contacts._ID,
                ContactsContract.Contacts.DISPLAY_NAME,
                ContactsContract.Contacts.LOOKUP_KEY
        };
        String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" +
                (mShowInvisible ? "0" : "1") + "'";
        String[] selectionArgs = null;
        String sortOrder = ContactsContract.Contacts.DISPLAY_NAME + " COLLATE             LOCALIZED ASC";

        return managedQuery(uri, projection, selection, selectionArgs, sortOrder);
}

注意：我经历了这个线程，但我们都使用不同的方法 Load contact photo in a listview performance

修改

我已按照代码写下来但是调用了

imageDownloader.download(contactUri, 
(ImageView) cache.photoView , 
getContentResolver(), 
contactId);

下载图片代码

Bitmap downloadBitmap(Uri url) {
        final int IO_BUFFER_SIZE = 4 * 1024;

        InputStream inputStream = null;
        try {
            inputStream = ContactsContract.Contacts.openContactPhotoInputStream(resolver, url);            

            if(inputStream ==null){

                return  BitmapFactory.decodeStream(inputStream);
            }else
            {

                return  BitmapFactory.decodeStream(new FlushedInputStream(inputStream));

            }
            // return BitmapFactory.decodeStream(inputStream);
            // Bug on slow connections, fixed in future release.

        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }

    }

但问题是我正在使用这段代码，并在几秒后快速向下滚动 QuickBadgeContact小部件正在加载，之前没有任何内容出现在QuickBadgeContact的占位符中。

查看图片

enter image description here

有时图像会在很长时间后出现，请看这里

enter image description here

所以它不能正常工作联系ListView在android工作中，如果我们滚动得快得多，那么aslo QuickBadgeContact将默认存在并充当占位符，QuickBadgeContact内的图像稍后加载但在我的代码中整个徽章出现在几秒钟

我只需要继续将图片加载到有照片的联系人，并让其他人不动，因为这是加载黑色位图，其中没有为用户找到图像，但我不知道我该怎么做？ /强>

Answer 1

保持应用程序响应的简单规则是：不要在UI线程上执行I / O操作。 bindView（）实现会破坏规则，因为它从数据库中读取位图。在慢速I / O操作完成时，主线程被阻塞。

您应该创建AsyncTasks来加载图像。最佳实践AFAIK是在您的应用程序中拥有一个完全可重用的ImageCache类......使用如下方法：

public static void getImage(Uri imageUri, ImageView imageView);

即。你给它一个URI和一个ImageView引用，它将负责在后台线程上下载图像并在它准备好时更新ImageView。

还有更多的东西......未完成的请求需要被取消，你应该在WeakReferences中保存ImageViews以避免泄漏它所属的Activity（有一个关于这个的Android Developer的博客文章）。

Answer 2

我认为延迟加载是你的答案。这是使用ListView的ScrollListener实现的。

在活动中它看起来像这样：

public class ListViewActivity extends Activity {

    public boolean mBusy = false;
    // even more initializing

    @Override
    public void onCreate(Bundle savedInstanceState) {
        // The code to build the activity
        ListView listView = findViewById(R.id.ListView);
        listView.setOnScrollListener(listViewOnScrollListener);
        listView.setAdapter(new ContactListAdapter(this, R.layout.whatsoever, null)
        // it is important to give the Adapter 'this' as context because we need the mBusy boolean
        // we should populate the adapter later in onCreate...
        // even more code
    }

    private AbsListView.OnScrollListener listViewOnScrollListener = new AbsListView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(AbsListView absListView, int scrollState) {
            if (absListView instanceof ListView) {
                ListView listView = (ListView)absListView;
                switch (scrollState) {
                case AbsListView.OnScrollListener.SCROLL_STATE_IDLE:
                    mBusy = false;
                    // Find out which elements of the ListView are visible to the user
                    int first = listView.getFirstVisiblePosition();
                    int childMargin = 0;
                    if (first < listView.getHeaderViewsCount()) {
                        first = listView.getHeaderViewsCount();
                        childMargin = listView.getHeaderViewsCount();
                    }
                    int last = listView.getLastVisiblePosition();
                    if (last > (listView.getCount() - listView.getFooterViewsCount() - 1)) {
                        last = listView.getCount() - listView.getFooterViewsCount() - 1;
                    }

                    for (int i = first; i <= last; i++) {
                        // This is for only populating the visible items of the list
                        // Action to perform the loading of your contactPhoto
                        // or displaying it
                        // maybe you call a method from the adapter to populate the views
                        adapter.loadImageBadges(listView.getChildAt(i - first + childMargin)),i);  
                    }
                    break;
                case AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
                    mBusy = true;
                    break;
                case AbsListView.OnScrollListener.SCROLL_STATE_FLING:
                    mBusy = true;
                    break;
                }
            }
        }

        @Override
        public void onScroll(AbsListView absListView, int i, int i1, int i2) {
            // Do something when the list is scrolling
        }
      };

    // The rest of the activity code

}

适配器将获得其他代码：

private class ContactListAdapter extends ResourceCursorAdapter {

    public ContactListAdapter(Context context, int layout, Cursor c) {
        super(context, layout, c);
        cur = c;
    }

    @Override
    public void bindView(View view, Context arg1, Cursor arg2) {
        // TODO Auto-generated method stub
        final ContactListItemCache cache = (ContactListItemCache) view.getTag();
        TextView nameView = cache.nameView;           
        cur.copyStringToBuffer(cur.getColumnIndexOrThrow(ContactsContract.Contacts.DISPLAY_NAME), cache.nameBuffer);
        int size = cache.nameBuffer.sizeCopied;
        cache.nameView.setText(cache.nameBuffer.data, 0, size);          

        if (!context.mBusy) {
            // Do the expensive things only if the list is not scrolling...
            loadImageBadges(convertView, arg2.getPosition())
        } else {
            // initialize with dummy data
        }
    }

    public void ImageBadges(View view, int position) {
        final ContactListItemCache cache = (ContactListItemCache) view.getTag();
        QuickContactBadge photoView = cache.photoView;            
        long contactId = cur.getLong(cur.getColumnIndex(ContactsContract.Contacts._ID));
        Uri contactUri = Uri.withAppendedPath(ContactsContract.Contacts.CONTENT_URI, String.valueOf(contactId));
        InputStream input = ContactsContract.Contacts.openContactPhotoInputStream(getContentResolver(), contactUri);            
        cache.photoView.setImageBitmap(BitmapFactory.decodeStream(input));
    }

    // The rest of the adapter code

}

通过采用此代码，您将获得延迟加载，只会填充当前可见的视图，因此性能应该像您提到的那样增加。

另外一个有意义的方法是缓存光标加载时检索到的照片。

修改

上面提到的代码是在http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/List13.html - ＆gt;的Android示例中借用和采用的。缓慢的适配器

编辑2：

我同意Reuben Scratton将适配器的硬件工作部分（例如图像处理）放入另一个线程中。

Answer 3

我和你有同样的问题，我找到了这个解决方案。您可以查看默认Android Contacts中的ContactsPhotoLoader。将mPhotoLoader.loadPhoto(contactAvatar, photoId);放入getView，contactAvatar为ImageView，photoID为Contacts.PHOTO_ID（根据联系方式）

联系人列表与联系人照片创建性能问题

3 个答案: