Picasso的网格视图无法加载图片

Question

我正在尝试使用picasso使用gridview和imageview（在运行时）将图像作为网格加载。代码失败，无法启动活动ComponentInfo {com.dbprox.tagpic / com.dbprox.tagpic.ImageGallaryPicasso}：java.lang.NullPointerException

＆＃13;

＆＃13;

package com.dbprox.tagpic;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.os.Environment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.GridView;
import android.widget.ImageView;

import com.squareup.picasso.Picasso;

import java.io.File;
import java.util.ArrayList;

public class ImageGallaryPicasso extends Activity {

    ArrayList<String> stringArrayList = new ArrayList<String>();
    String path= Environment.getExternalStorageDirectory().toString()+"/Pictures";
    File f=new File(path);
    File file[]=f.listFiles();

    String [] stringArray = stringArrayList.toArray(new String[stringArrayList.size()]);




    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_gallary_picasso);

        for (int i = 0; i < file.length; i++) {

            stringArrayList.add(file[i].getAbsolutePath());

        }
        GridView gridview = (GridView) findViewById(R.id.imagegridview);
         //LoadPicassaImages();

            gridview.setAdapter(new ImageListAdapter(this, stringArray));



    }

    class ImageListAdapter extends ArrayAdapter {


        private Context context;
        private LayoutInflater inflater;

        private String[] imageUrls;




        public ImageListAdapter(Context context, String[] imageUrls) {
            super(context, R.layout.activity_image_gallary_picasso, imageUrls);

            this.context = context;
            this.imageUrls = imageUrls;

            inflater = LayoutInflater.from(context);
        }

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


            if (null == convertView) {
                convertView = inflater.inflate(R.layout.activity_image_gallary_picasso, parent, false);
            }



            Picasso
                    .with(context)
                    .load(imageUrls[position])
                    .fit() // will explain later
                    .into((ImageView) convertView);

            return convertView;
        }
    }

}

＆＃13;

＆＃13;

＆＃13;

Answer 1

在适配器中试用此代码，

    ViewHolder viewHolder;

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

        if (null == convertView) {
            convertView = inflater.inflate(R.layout.activity_image_gallary_picasso, parent, false);
            viewHolder = new ViewHolder();
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.your_imageview);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        Picasso.with(context)
               .load(imageUrls[position])
               .fit() // will explain later
               .into(viewHolder.imageView);

        return convertView;
    }

    public class ViewHolder{
        ImageView imageView;
    }