java - Android GridView 重绘问题

Question

我创建了一个允许用户拍照并上传到网络服务器的应用程序。然后该图像在 Activity 中的 GridView 中变得可见

我虽然一切正常，但是我拍的照片越多，我发现的问题就越多

当用户开始滚动时，gridview 中的图像似乎正在重新绘制自己，有效地再次向用户显示相同的图像(并不总是以相同的顺序)

我读过其他帖子，其中有人为类似的事情而苦苦挣扎，但这些修复似乎对我不起作用

GridView Redraw Problems

提前感谢所有帮助

这是我的 gridview Activity

package com.example.alex.jsonparsegridview;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.view.View;
import android.widget.AdapterView.OnItemClickListener;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.HashMap;

public class MainActivity extends Activity {

    GridView gridView;

    static final String[] MOBILE_OS = new String[]{
            "Android", "iOS", "Windows", "Blackberry"};

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new JSONParse().execute();

        TextView tv = (TextView)findViewById(R.id.footerText);


        tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                Intent myIntent = new Intent(MainActivity.this, CameraActivity.class);
                myIntent.putExtra("dir", "BS"); //Optional parameters
                MainActivity.this.startActivity(myIntent);
            }
        });


    }


    private class JSONParse extends AsyncTask<String, String, JSONArray> {
        private ProgressDialog pDialog;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            pDialog = new ProgressDialog(MainActivity.this);
            pDialog.setMessage("Getting Data ...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();

        }

        @Override
        protected JSONArray doInBackground(String... args) {

            JSONParser jParser = new JSONParser();

            // Getting JSON from URL

            String url = "http://www.500kgiveaway.co.uk/getimagesmob.php";
            JSONArray json = jParser.getJSONFromUrl(url);
            return json;
        }

        @Override
        protected void onPostExecute(JSONArray json) {
            pDialog.dismiss();
                // Getting JSON Array from URL

                JSONArray android = json;


                //copied from onCreate
                gridView = (GridView) findViewById(R.id.gridView1);

                gridView.setAdapter(new ImageAdapter(MainActivity.this, android));

                gridView.setOnItemClickListener(new OnItemClickListener() {
                    public void onItemClick(AdapterView<?> parent, View v,
                                            int position, long id) {
                        Toast.makeText(
                                getApplicationContext(),
                                ((TextView) v.findViewById(R.id.grid_item_label))
                                        .getText(), Toast.LENGTH_SHORT).show();
                    }
                });

                //End Copy





        }
    }
}

这是我的图像适配器(使用 picasso 定制)

package com.example.alex.jsonparsegridview;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.squareup.picasso.Picasso;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class ImageAdapter extends BaseAdapter {
    private Context context;
    private JSONArray android;
    private String TAG_PATH = "path";
    ArrayList<HashMap<String, String>> oslist = new ArrayList<HashMap<String, String>>();


    public ImageAdapter(Context context,  JSONArray android) {
        this.context = context;
        this.android = android;
    }

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


        View gridView = null;

             try {
                 if (convertView == null) {

                     LayoutInflater inflater = (LayoutInflater) context
                             .getSystemService(Context.LAYOUT_INFLATER_SERVICE);


                 JSONObject c = android.getJSONObject(position);

                // Storing  JSON item in a Variable
                String path = c.getString(TAG_PATH);

                // Adding value HashMap key => value

                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_PATH, path);

                oslist.add(map);

                gridView = new View(context);

                // get layout from mobile.xml
                gridView = inflater.inflate(R.layout.mobile, null);

                // set value into textview
                TextView textView = (TextView) gridView
                        .findViewById(R.id.grid_item_label);
                textView.setText(path.toString());

                // set image based on selected text
                ImageView imageView = (ImageView) gridView
                        .findViewById(R.id.grid_item_image);


                Picasso.with(context).load("http://www.500kgiveaway.co.uk/" + path).resize(400,400).into(imageView);

                 } else {
                     gridView = (View) convertView;
                 }

             } catch (JSONException e) {
                e.printStackTrace();
            }

        return gridView;
    }

    @Override
    public int getCount() {
       return android.length();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

}

Answer 1

问题出在您的 getView() 函数中。 GridView 通过将 View 传递给 convertView 中的 getView() 来重用 View 。然而，这些 View 不一定已经加载了正确的图像，它们是以前用于在不同位置显示网格中不同单元格的 View 。因此，如果 convertView 不为 null，它可以让您不必膨胀 View ，但您仍然必须将图像加载到其中。

像这样重新安排你的代码:

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

    View gridView = null;

    try {
        if (convertView == null) {
             LayoutInflater inflater = (LayoutInflater) context
                     .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

             gridView = new View(context);

             // get layout from mobile.xml
             gridView = inflater.inflate(R.layout.mobile, null);              
        }
        else
        {
             gridView = convertView;
        }

        JSONObject c = android.getJSONObject(position);

        // Storing  JSON item in a Variable
        String path = c.getString(TAG_PATH);

        // set value into textview
        TextView textView = (TextView) gridView
                .findViewById(R.id.grid_item_label);
        textView.setText(path.toString());

        // set image based on selected text
        ImageView imageView = (ImageView) gridView
                .findViewById(R.id.grid_item_image);

        Picasso.with(context).load("http://www.500kgiveaway.co.uk/" + path).resize(400,400).into(imageView);

        // Adding value HashMap key => value
        HashMap<String, String> map = new HashMap<String, String>();
        map.put(TAG_PATH, path);
        // TODO: add some checks so you don't add it if it's already in the list? 
        oslist.add(map);

     } catch (JSONException e) {
        e.printStackTrace();
    }

    return gridView;
}

我不知道关于您的HashMap 的程序逻辑是什么，但您可能只想在第一次加载图像时将它添加到oslist。请注意，您不能为此使用 (convertView == null) 测试，因为 convertView 可能已用于完全不同的图像。