我使用okhttp从http请求中获取数据并使用它来填充RecyclerView，数据只是我用Picasso加载的一个图像和我放在CardView中的一些文本。
第一个问题是，有时当我打开应用程序时，只有当我从可见区域滚动行并向后滚动时才开始下载/显示图像，有时它会跳过一些行并将空格留空直到我再次向下滚动，如果我不这样做，我只看到空格
第二个问题是滚动时似乎正在替换图像，当我滚动到一个新项目时，我可以看到来自不同行的旧图像一秒钟然后它被右边的替换图像。
我试图在任何地方寻找解决方案而没有任何修复它，继承了整个活动代码：
public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private List<GalleryItem> mGalleryItems;
GalleryAdapter adapter;
private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;
LinearLayoutManager mLayoutManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRecyclerView = (RecyclerView) findViewById(R.id.grid_view);
mGalleryItems = new ArrayList<>();
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);
getItems("http://www.reddit.com/r/aww.json");
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy > 0) {
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
loading = false;
Log.v("...", "Last Item Wow !");
getItems("https://www.reddit.com/r/aww.json?after=t3_40x6ke");
}
}
}
}
});
adapter = new GalleryAdapter(mGalleryItems, this);
mRecyclerView.setAdapter(adapter);
}
@Override
public void onDestroy(){
super.onDestroy();
}
public void getItems(String url){
OkHttpClient client = new OkHttpClient();
File cacheDirectory = new File(MainActivity.this.getCacheDir(), "http");
int cacheSize = 10 * 1024 * 1024;
Cache cache = new Cache(cacheDirectory, cacheSize);
client.setCache(cache);
Request request = new Request.Builder()
.url(url)
.build();
Call call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Request request, IOException e) {
}
@Override
public void onResponse(Response response) throws IOException {
final String json = response.body().string();
if (response.isSuccessful()) {
try {
mGalleryItems.addAll(parseItems(json));
} catch (JSONException e) {
e.printStackTrace();
Log.i("BEHS", e.getMessage());
}
runOnUiThread(new Runnable() {
@Override
public void run() {
adapter.notifyDataSetChanged();
}
});
}
}
});
}
private List<GalleryItem> parseItems(String json) throws JSONException {
JSONObject jsonMovie = new JSONObject(json);
JSONObject firstData = jsonMovie.getJSONObject("data");
JSONArray children = firstData.getJSONArray("children");
List<GalleryItem> items = new ArrayList();
for(int i = 2; i < children.length(); i++ ){
JSONObject jsonObject = children.getJSONObject(i);
JSONObject childrenObject = jsonObject.getJSONObject("data");
GalleryItem item = new GalleryItem();
item.setTitle(childrenObject.getString("title"));
item.setUrl(childrenObject.getString("url"));
item.setThumbnail(childrenObject.getString("thumbnail"));
//if(!childrenObject.getString("url").endsWith(".jpg")){
// continue;
// }else{
items.add(item);
// }
}
return items;
}
private class GalleryHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
private ImageView mImageView;
private TextView mTextView;
private String mUrl;
public GalleryHolder(View itemView) {
super(itemView);
itemView.setOnClickListener(this);
mImageView = (ImageView) itemView.findViewById(R.id.country_photo);
mTextView = (TextView) itemView.findViewById(R.id.country_name);
}
public void bindImage(GalleryItem item ){
Picasso.with(MainActivity.this).load(item.getThumbnail()).tag(MainActivity.this).into(new Target() {
@Override
public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
Palette pallete = Palette.from(bitmap).generate();
int color = pallete.getMutedColor(MainActivity.this.getResources().getColor(android.R.color.black));
mTextView.setBackgroundColor(color);
mImageView.setImageBitmap(bitmap);
}
@Override
public void onBitmapFailed(Drawable errorDrawable) {
}
@Override
public void onPrepareLoad(Drawable placeHolderDrawable) {
}
});
}
public void bindUrl(String url){
mUrl = url;
}
@Override
public void onClick(View view) {
Intent i = new Intent(MainActivity.this, ItemActivity.class);
i.putExtra("url", mUrl);
Log.i(mUrl, mUrl);
startActivity(i);
}
}
private class GalleryAdapter extends RecyclerView.Adapter<GalleryHolder>{
private List<GalleryItem> mImages;
private Context mContext;
public GalleryAdapter(List<GalleryItem> images, Context context){
mContext = context;
mImages = images;
}
@Override
public GalleryHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
View view = inflater.inflate(R.layout.list_item, parent, false);
return new GalleryHolder(view);
}
@Override
public void onBindViewHolder(GalleryHolder holder, int position) {
holder.mTextView.setText(mImages.get(position).getTitle());
holder.bindImage(mImages.get(position));
holder.bindUrl(mImages.get(position).getUrl());
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public int getItemCount() {
return mImages.size();
}
}
}
答案 0 :(得分：4)
您似乎是异步图像加载陷阱的牺牲品。
问题＃1：
您可以看到图像工作者仅在onBindViewHolder触发时触发。这意味着在绘制视图时会发生图像的实际下载/获取。如果没有关于GalleryItem中发生的事情的更多信息，我猜你的应用程序在后台时，图像字节数据被清除/垃圾收集 - 并且由于绑定发生在滚动期间，这就是为什么你没有看到任何图像。
或许可以查看图片缓存：http://developer.android.com/training/displaying-bitmaps/cache-bitmap.html
问题＃2：
如果您不想查看旧图片，请将图片视图位图设置为null，作为onBindViewHolder中的第一项。
在伪代码中：
...
@Override
public void onBindViewHolder(GalleryHolder holder, int position) {
holder.imageView.setBitmap(null);
}
...