Question

我正在使用picasso将图像从服务器加载到列表视图项目，如下所示：

public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View participantView;
    if(convertView == null) {
        participantView = inflater.inflate(R.layout.participant_item, parent, false);
    } else {
        participantView = convertView;
    }

    TextView textView = (TextView) participantView.findViewById(R.id.participantName);
    textView.setText(getItem(position).getName());
    ImageView imageView = (ImageView) participantView.findViewById(R.id.participantImage);
    String profilePic = getItem(position).getProfilePic();

    if(!profilePic.equals("None")) {
        Log.d("tom.debug", "creating picture for user: " + getItem(position).getName());
        Picasso.with(this.context)
            .load(urlToProfilePics + profilePic)
            .placeholder(R.drawable.sample_0)
            .resize(52, 52)
            .into(imageView);
    } else {
        //load the place holder into the image view
        Picasso.with(this.context).load(R.drawable.sample_0);
    }

    if(!getItem(position).isHere()) {
        imageView.setColorFilter(Color.DKGRAY, PorterDuff.Mode.MULTIPLY);
    }

    return participantView;
}

if语句下的调试日志仅针对真正拥有个人资料图片的用户触发。（没有用户将获得None）的值。

然而，其他列表视图项目的部分（没有个人资料照片）也会加载图片。

另一个有用的事实（我认为）：当在列表中上下滚动时，获取错误的项目会发生变化。

我不确定我在这里失踪了什么。

Answer 1

确保每次要从适配器上的getView（）上使用Picasso时，都要调用 cancelRequest 。

// 1st: reset the imageView
Picasso.with(this.context).cancelRequest(holder.imageView); 

// 2nd start a new load for the imageView
Picasso.with(this.context).load(...).into(holder.imageView);

原因是您从 convertView 参数重用的视图属于Picasso可能已经为另一张图片加载的上一行。

这在使用convertView时才真正有用，如果您刚刚为新布局充气，则不需要它。但您可以随时致电以使代码更容易。

Answer 2

请参考以下代码。首先是我的grid_row.xml文件。它是网格项布局文件

<ProgressBar
    android:layout_height="70dp"
    android:layout_width="70dp"
    android:id="@+id/myprogress"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_below="@+id/title"       />

<View
    android:layout_width="2dp"
    android:layout_height="2dp"/>

<ImageView
    android:layout_height="165dp"
    android:id="@+id/imageView1"
    android:layout_width="125dp"
    android:scaleType="fitXY"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"/>

<View
    android:layout_width="2dp"
    android:layout_height="2dp"/>

<TextView
    android:text="TextView"
    android:layout_height="wrap_content"
    android:id="@+id/title"
    android:layout_width="wrap_content"
    android:layout_below="@+id/imageView1"
    android:textStyle="bold"
    android:layout_marginTop="2dp"
    android:layout_centerHorizontal="true"
    android:textSize="20sp"
    android:ellipsize="marquee">
</TextView>

<View
    android:layout_width="2dp"
    android:layout_height="2dp"/>

<TextView
    android:text="TextView"
    android:layout_height="wrap_content"
    android:id="@+id/subTitle"
    android:layout_width="wrap_content"
    android:layout_below="@+id/title"
    android:layout_marginTop="2dp"
    android:layout_centerHorizontal="true"
    android:textSize="18sp"
    android:ellipsize="marquee">
</TextView>

 </RelativeLayout>

然后请继续使用适配器类作为参考。

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.drawable.Drawable;
import android.util.Log;
 import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;


import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.FailReason;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
import    com.nostra13.universalimageloader.core.display.FadeInBitmapDisplayer;
import com.nostra13.universalimageloader.core.listener.ImageLoadingListener;
import com.nostra13.universalimageloader.core.listener.ImageLoadingProgressListener;
import com.nostra13.universalimageloader.core.listener.SimpleImageLoadingListener;
import com.squareup.picasso.Picasso;

import java.util.ArrayList;

/**
 * Created by mpatil on 28/05/15.
 */
public class GridViewAdapter extends BaseAdapter
{
private ArrayList<String> listTitle;
private ArrayList<String> listSubTitle;
private ArrayList<String> imgp;

private Context activity;
ViewHolder view;
Configuration_Parameter m_config=Configuration_Parameter.getInstance();

public GridViewAdapter(Context activity,ArrayList<String> listTitle, ArrayList<String> subTitle,ArrayList<String> img)
{
    super();
    this.listTitle = listTitle;
    this.imgp = img;
    this.listSubTitle=subTitle;
    this.activity = activity;


}

@Override
public int getCount()
{
    // TODO Auto-generated method stub
    return listTitle.size();
}

@Override
public String getItem(int position)
{
    // TODO Auto-generated method stub
    return (String) (String) view.imgViewFlag.getTag();
}


@Override
public long getItemId(int position)
{
    // TODO Auto-generated method stub
    return 0;
}

public static class ViewHolder
{
    public ImageView imgViewFlag;
    public TextView txtViewTitle;
    public TextView txtViewSubTitle;
    public ProgressBar pg;

    public ViewHolder(View v)
    {

    }
    public ViewHolder()
    {
    }
}

@Override
public View getView(final int position, View convertView, ViewGroup parent)
{
    // TODO Auto-generated method stub
    View participentView=convertView;

    if(participentView == null || participentView.getTag() == null)
    {
        LayoutInflater inflater = null;
        inflater=(LayoutInflater) parent.getContext().getSystemService(activity.LAYOUT_INFLATER_SERVICE);
        view = new ViewHolder();
        participentView = inflater.inflate(R.layout.grid_layout, null);
        view.txtViewTitle = (TextView) participentView.findViewById(R.id.title);
        view.txtViewSubTitle = (TextView) participentView.findViewById(R.id.subTitle);
        view.pg=(ProgressBar)participentView.findViewById(R.id.myprogress);
        view.imgViewFlag = (ImageView) participentView.findViewById(R.id.imageView1);


        participentView.setTag(view);
    }
    else
    {
        view = (ViewHolder) participentView.getTag();
    }

        //download and display image from url

    view.txtViewTitle.setText(listTitle.get(position));
    view.txtViewSubTitle.setText(listSubTitle.get(position) + " subitem");
    ImageLoader imageLoader = null;
    imageLoader= ImageLoader.getInstance();

    DisplayImageOptions options = new DisplayImageOptions.Builder()
            .showImageForEmptyUri(R.drawable.paceholder) // resource or drawable
            .showImageOnFail(R.drawable.error_page_logo) // resource or drawable
            .resetViewBeforeLoading(false)  // default
            .delayBeforeLoading(1000)
            .cacheInMemory(true) // default
            .cacheOnDisk(true) // default
        .build();


    m_config.imageLoader.displayImage(imgp.get(position), view.imgViewFlag,options,new SimpleImageLoadingListener()
    {
        @Override
        public void onLoadingStarted(String imageUri, View v)
        {
            Log.i("Inside onLoadingStarted " + position,"Yes");
            view.imgViewFlag.setVisibility(View.INVISIBLE);
            view.pg.setVisibility(View.VISIBLE);
            view.imgViewFlag.setVisibility(View.INVISIBLE);
        }
        @Override
        public void onLoadingFailed(String imageUri, View v, FailReason failReason)
        {
            Log.i("Inside onLoadingFailed " + position,"Yes");
            view.pg.setVisibility(View.GONE);

        }
        @Override
         public void onLoadingComplete(String imageUri, View v, Bitmap    loadedImage)
        {
            Log.i("Ins onLoadingComplete " + position, "Yes");
            view.pg.setVisibility(View.GONE);
            view.imgViewFlag.setVisibility(View.VISIBLE);
            view.imgViewFlag.invalidate();
        }

    });



    return participentView;
 }

 }

我相信这肯定会有所帮助。感谢NOSTRA这样一个很棒的图书馆。竖起大拇指...！！！快乐编码... :)

Answer 3

在你的getView（）方法中，改变你的Picasso代码：

        try {
                Picasso.with(mActivity).
                        cancelRequest(holder.mImgCity);
                Picasso.with(mActivity).
                        load(getItem(position).getBackgroundImg()).
                        error(R.drawable.image_1).
                        into(holder.mImgCity);
            }
            catch (IllegalArgumentException e)
            {
                e.printStackTrace();
                holder.mImgCity.setImageResource(R.drawable.image_1); //<-- Important line
            }

<强>更新

在getView（）方法中使用Viewholder概念。只有这样才能完成所有工作。

Answer 4

我想我已经陷入了同样的境地。我建议你的适配器使用ViewHolder模式。

这将是这样的。

public View getView(int position, View convertView, ViewGroup parent) {

    final ViewHolder holder;
    View participantView = convertView;
    if (participantView == null || participantView.getTag() == null) {
        LayoutInflater inflater = (LayoutInflater) mContext
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            // don't forget to inflate the same layout
        participantView = inflater.inflate(R.layout.participant_item, null);
        holder = getHolder(participantView);
        assert participantView != null;
        participantView.setTag(holder);
    } else {
        holder = (ViewHolder) participantView.getTag();
    }

    holder.textView.setText(getItem(position).getName());
    String profilePic = getItem(position).getProfilePic();

    if(!profilePic.equals("None")) {
        Log.d("tom.debug", "creating picture for user: " + getItem(position).getName());
        Picasso.with(this.context)
        .load(urlToProfilePics + profilePic)
        .placeholder(R.drawable.sample_0)
        .resize(52, 52)
        .into(holder.imageView);
    } else {
        //load the place holder into the image view
        Picasso.with(this.context).load(R.drawable.sample_0);
    }

    if(!getItem(position).isHere()) {
        holder.imageView.setColorFilter(Color.DKGRAY, PorterDuff.Mode.MULTIPLY);
    }

    resetViews(participantView);

    return participantView;
}

void resetViews(View v) {
    ViewHolder mHolder = new ViewHolder(v);
    mHolder.textView.invalidate();
    mHolder.imageView.invalidate();
}

static class ViewHolder { 
  TextView textView;
  ImageView imageView;
}

毕加索将图片加载到列表适配器中的错误图像视图中

4 个答案: