我创建了一个小应用程序，它连接到OMDB并使用它的API来获取电影数据。 正如您在下面的电影中看到的，如果我滚动得非常快，我可以看到重新填充的图像。调试显示它们确实被重新下载。我应该提一下，我不保留文件的任何物理副本。
这被认为是正常行为还是我遗漏了什么？
链接： https://youtu.be/2dO3XwGd5g8
RecyclerView类
package com.example.themoviekeeper.ui;
import android.app.Activity;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.themoviekeeper.R;
import com.example.themoviekeeper.db.MyMovie;
import com.example.themoviekeeper.networking.Task_DownloadImage;
import java.util.ArrayList;
/**
* Created by Xcalibur on 30/12/2016.
*/
public class RecyclerViewAdapter_Search extends RecyclerView.Adapter<RecyclerViewAdapter_Search.MyViewHolder>{
private ArrayList<MyMovie> _list;
private Activity _activity;
private LayoutInflater inflater;
public RecyclerViewAdapter_Search(ArrayList<MyMovie> list, Activity activity) {
_list = list;
_activity = activity;
inflater = LayoutInflater.from(_activity);
}
@Override
public RecyclerViewAdapter_Search.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.view_search, parent, false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
String year = _list.get(position).getYear();
String title = _list.get(position).getTitle();
String type = _list.get(position).getType();
String poster = _list.get(position).getPoster();
holder.tv_year.setText(year);
holder.tv_type.setText(type);
holder.tv_title.setText(title);
Task_DownloadImage dlImage = new Task_DownloadImage(_activity,holder);
String [] imageUrl ={poster};
dlImage.execute(imageUrl);
}
@Override
public int getItemCount() {
return _list.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv_year,tv_title,tv_type;
public ImageView iv_poster;
public MyViewHolder(View itemView) {
super(itemView);
tv_title = (TextView)itemView.findViewById(R.id.tv_title_searchview);
tv_type = (TextView)itemView.findViewById(R.id.tv_type_searchview);
tv_year = (TextView)itemView.findViewById(R.id.tv_year_searchview);
iv_poster = (ImageView)itemView.findViewById(R.id.iv_searchview);
}
}
}
执行实际图像下载的Asynctask
package com.example.themoviekeeper.networking;
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import com.example.themoviekeeper.R;
import com.example.themoviekeeper.ui.RecyclerViewAdapter_Search;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
/**
* Created by Xcalibur on 30/12/2016.
*/
public class Task_DownloadImage extends AsyncTask<String, Integer,Bitmap>
{
private Activity mActivity;
private ProgressDialog mDialog;
private RecyclerViewAdapter_Search.MyViewHolder mHolder;
public Task_DownloadImage(Activity activity, RecyclerViewAdapter_Search.MyViewHolder holder) {
mHolder = holder;
mActivity = activity;
mDialog = new ProgressDialog(mActivity);
}
protected Bitmap doInBackground(String... urls) {
Log.d("doInBackground", "starting download of image");
Bitmap image = downloadImage(urls[0]);
return image;
}
protected void onPreExecute() {
//ImageView imageView = (ImageView) mActivity.findViewById(R.id.imageView);
//imageView.setImageBitmap(null);
// Reset the progress bar
// mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
// mDialog.setCancelable(true);
// mDialog.setMessage("Loading...");
// mDialog.setProgress(0);
//TextView errorMsg = (TextView) mActivity.findViewById(R.id.textView);
//errorMsg.setVisibility(View.INVISIBLE);
}
protected void onProgressUpdate(Integer... progress) {
// mDialog.show();
// mDialog.setProgress(progress[0]);
}
protected void onPostExecute(Bitmap result) {
if (result != null) {
mHolder.iv_poster.setImageBitmap(result);
// ImageView imageView = (ImageView)mActivity.findViewById(R.id.imageView);
// imageView.setImageBitmap(result);
}
else {
// TextView errorMsg = (TextView)mActivity.findViewById(R.id.textView);
// errorMsg.setVisibility(View.VISIBLE);
// errorMsg.setText("Problem downloading image. Try again later");
}
// Close the progress dialog
//mDialog.dismiss();
}
private Bitmap downloadImage(String urlString) {
URL url;
try {
url = new URL(urlString);
HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
InputStream is = httpCon.getInputStream();
int fileLength = httpCon.getContentLength();
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead, totalBytesRead = 0;
byte[] data = new byte[2048];
mDialog.setMax(fileLength);
// Read the image bytes in chunks of 2048 bytes
while ((nRead = is.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
totalBytesRead += nRead;
publishProgress(totalBytesRead);
}
buffer.flush();
byte[] image = buffer.toByteArray();
Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
return bitmap;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}