我有一个带有GridLinearLayout和自定义适配器的RecyclerView。每个项目的内容是使用json下载并解析它的图片。
基本上是一个图片网格。
一切工作都很好，但是，当向下滚动内容并再次上升时，它会显示每个项目中的先前视图不到一秒钟，然后再显示正确的图片。
我该怎么做才能预防或解决这个问题？提前感谢您提供的任何帮助和/或指导。
这是适配器代码：
package jahirfiquitiva.project.adapters;
import android.content.Context;
import android.graphics.Bitmap;
import android.support.v7.graphics.Palette;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.TextView;
import jahirfiquitiva.project.activities.WallpapersActivity;
import com.koushikdutta.async.future.FutureCallback;
import com.koushikdutta.ion.Ion;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
import jahirfiquitiva.project.R;
public class WallpapersAdapter extends RecyclerView.Adapter<WallpapersAdapter.WallsHolder> {
public interface ClickListener {
void onClick(WallsHolder view, int index, boolean longClick);
}
private ArrayList<HashMap<String, String>> data;
private final Context context;
private boolean usePalette = true;
private final ClickListener mCallback;
private final Map<String, Palette> mPaletteCache = new WeakHashMap<>();
public WallpapersAdapter(Context context, ClickListener callback) {
this.context = context;
this.data = new ArrayList<>();
this.mCallback = callback;
}
public void setData(ArrayList<HashMap<String, String>> data) {
this.data = data;
notifyDataSetChanged();
}
@Override
public WallsHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(context);
return new WallsHolder(inflater.inflate(R.layout.wallpaper_item, parent, false));
}
@Override
public void onBindViewHolder(final WallsHolder holder, int position) {
Animation anim = AnimationUtils.loadAnimation(context, android.R.anim.fade_in);
HashMap<String, String> jsondata = data.get(position);
holder.name.setText(jsondata.get(WallpapersActivity.NAME));
final String wallurl = jsondata.get(WallpapersActivity.WALL);
holder.wall.startAnimation(anim);
holder.wall.setTag(wallurl);
Ion.with(context)
.load(wallurl)
.asBitmap()
.setCallback(new FutureCallback<Bitmap>() {
@Override
public void onCompleted(Exception e, Bitmap result) {
holder.progressBar.setVisibility(View.GONE);
if (e != null) {
e.printStackTrace();
} else if (holder.wall.getTag() != null && holder.wall.getTag().equals(wallurl)) {
holder.wall.setImageBitmap(result);
if (usePalette) {
Palette p;
if (mPaletteCache.containsKey(wallurl)) {
p = mPaletteCache.get(wallurl);
} else {
p = new Palette.Builder(result).generate();
mPaletteCache.put(wallurl, p);
}
if (p != null) {
Palette.Swatch wallSwatch = p.getVibrantSwatch();
if (wallSwatch != null) {
holder.titleBg.setBackgroundColor(wallSwatch.getRgb());
holder.titleBg.setAlpha(1);
holder.name.setTextColor(wallSwatch.getTitleTextColor());
holder.name.setAlpha(1);
}
}
}
}
}
});
}
@Override
public int getItemCount() {
return data.size();
}
public class WallsHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {
public final View view;
public final ImageView wall;
public final TextView name;
public final ProgressBar progressBar;
public final LinearLayout titleBg;
WallsHolder(View v) {
super(v);
view = v;
wall = (ImageView) v.findViewById(R.id.wall);
name = (TextView) v.findViewById(R.id.name);
progressBar = (ProgressBar) v.findViewById(R.id.progress);
titleBg = (LinearLayout) v.findViewById(R.id.titlebg);
view.setOnClickListener(this);
view.setOnLongClickListener(this);
}
@Override
public void onClick(View v) {
int index = getLayoutPosition();
if (mCallback != null)
mCallback.onClick(this, index, false);
}
@Override
public boolean onLongClick(View v) {
int index = getLayoutPosition();
if (mCallback != null)
mCallback.onClick(this, index, true);
return false;
}
}
}
答案 0 :(得分：3)
顾名思义RecyclerView回收视图以优化内存，以便显示上一个视图的内容。由于您从互联网加载图像，因此加载图像所需的时间很少，因此可以观察到之前图像的内容。您可以执行以下操作之一。
1）在加载实际图像之前从本地资源设置默认图像，最好是小尺寸图像以保存内存。这样的东西
//load default image first
holder.wall.setImageResource(R.id.your_default_image_resource);
//load actual image
Ion.with(context)
.load(wallurl)
.asBitmap()
.setCallback(new FutureCallback<Bitmap>() {
@Override
public void onCompleted(Exception e, Bitmap result) {
holder.progressBar.setVisibility(View.GONE);
if (e != null) {
e.printStackTrace();
} else if (holder.wall.getTag() != null && holder.wall.getTag().equals(wallurl)) {
holder.wall.setImageBitmap(result);
if (usePalette) {
Palette p;
if (mPaletteCache.containsKey(wallurl)) {
p = mPaletteCache.get(wallurl);
} else {
p = new Palette.Builder(result).generate();
mPaletteCache.put(wallurl, p);
}
if (p != null) {
Palette.Swatch wallSwatch = p.getVibrantSwatch();
if (wallSwatch != null) {
holder.titleBg.setBackgroundColor(wallSwatch.getRgb());
holder.titleBg.setAlpha(1);
holder.name.setTextColor(wallSwatch.getTitleTextColor());
holder.name.setAlpha(1);
}
}
}
}
}
});
2）在加载图像之前将ImageView可见性设置为GONE / INVISIBLE，并在加载图像后再次使其可见。
//hide the imageview
holder.wall.setVisibility(View.INVISIBLE);
Ion.with(context)
.load(wallurl)
.asBitmap()
.setCallback(new FutureCallback<Bitmap>() {
@Override
public void onCompleted(Exception e, Bitmap result) {
holder.progressBar.setVisibility(View.GONE);
if (e != null) {
e.printStackTrace();
} else if (holder.wall.getTag() != null && holder.wall.getTag().equals(wallurl)) {
//show the imageview and set bitmap
holder.wall.setVisibility(View.VISIBLE);
holder.wall.setImageBitmap(result);
if (usePalette) {
Palette p;
if (mPaletteCache.containsKey(wallurl)) {
p = mPaletteCache.get(wallurl);
} else {
p = new Palette.Builder(result).generate();
mPaletteCache.put(wallurl, p);
}
if (p != null) {
Palette.Swatch wallSwatch = p.getVibrantSwatch();
if (wallSwatch != null) {
holder.titleBg.setBackgroundColor(wallSwatch.getRgb());
holder.titleBg.setAlpha(1);
holder.name.setTextColor(wallSwatch.getTitleTextColor());
holder.name.setAlpha(1);
}
}
}
}
}
});
答案 1 :(得分：3)
覆盖onViewRecycled (VH holder)以将图像设置为空。
像这样：
public void onViewRecycled (VH holder) {
holder.wall.setImageBitmap(null);
}
答案 2 :(得分：0)
我认为你应该像这样添加占位符：
Ion.with(context).load("http://example.com/image.png")
.withBitmap()
.placeholder(R.drawable.placeholder_image)
.error(R.drawable.error_image)
.intoImageView(imageView);
或首先设置默认图像。
holder.wall.setImageResource(R.drawable.placeholder_image);