android - 我想在服务器的 gridview 中显示图像意味着我有图像的 URL

Question

当我显示数组中的图像时， GridView 工作正常，但当我尝试显示服务器中的图像时，它将无法工作并给出空白屏幕。我有以下代码，请告诉我哪里做错了。

1.Gridview主类

package com.grid_example;      

import android.app.Activity;
import android.os.Bundle;
import android.widget.GridView;

public class Grid_exampleActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        GridView gridview = (GridView) findViewById(R.id.gridview);
        gridview.setAdapter(new ImageAdapter(this));
    }
}

2.ImageAddpter类从服务器获取图像并显示在gridview中

package com.grid_example;    

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.ListAdapter;

public class ImageAdapter extends BaseAdapter {
    private Context mContext;
    String path;
    Bitmap bmp;
    // Bitmap[] bitmapArray = new Bitmap[20];
    ArrayList<Bitmap> bitmapArray = new ArrayList<Bitmap>(20);

    public ImageAdapter(Context c) {
    mContext = c;
    }

    public int getCount() {
        return bitmapArray.size();
    }

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

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

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }

        imageView.setImageBitmap(bitmapArray.get(position));
        return imageView;
    }

    // references to our images

    ImageAdapter() {
        String xml = XMLfunctions_wallpaper.getXML();
        Document doc = XMLfunctions_wallpaper.XMLfromString(xml);
        // Document doc = XMLfunctions.XMLfromString(this.getResources().openRawResource(R.raw.music));
        NodeList nodes = doc.getElementsByTagName("content");
        for(int i=0;i<nodes.getLength();i++){
            Element e=(Element)nodes.item(i);               
            try{
                path=XMLfunctions_wallpaper.getValue(e,"previews");
                System.out.println(path);
                URL ulrn = new URL(path);
                HttpURLConnection con = (HttpURLConnection)ulrn.openConnection();
                InputStream is = con.getInputStream();
                 bmp = BitmapFactory.decodeStream(is);
                 // Bitmap  bm = Bitmap.createBitmap(bmp);            
                 bitmapArray.add(bmp); // Add a bitmap          
            }catch(Exception e1){}              
        }
    }
}

3.XMLFunction_wallpaper类用于解析图像

    package com.grid_example;

    import java.io.IOException;
    import java.io.StringReader;
    import java.io.UnsupportedEncodingException;
    import java.net.MalformedURLException;

    import javax.xml.parsers.DocumentBuilder;
    import javax.xml.parsers.DocumentBuilderFactory;
    import javax.xml.parsers.ParserConfigurationException;

    import org.apache.http.HttpEntity;
    import org.apache.http.HttpResponse;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.DefaultHttpClient;
    import org.apache.http.util.EntityUtils;
    import org.w3c.dom.Document;
    import org.w3c.dom.Element;
    import org.w3c.dom.Node;
    import org.w3c.dom.NodeList;
    import org.xml.sax.Attributes;
    import org.xml.sax.InputSource;
    import org.xml.sax.SAXException;    

    public class XMLfunctions_wallpaper {

    public final static Document XMLfromString(String xml){

        Document doc = null;

        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        try {

            DocumentBuilder db = dbf.newDocumentBuilder();

            InputSource is = new InputSource();
            is.setCharacterStream(new StringReader(xml));
            doc = db.parse(is); 

        } catch (ParserConfigurationException e) {
            System.out.println("XML parse error: " + e.getMessage());
            return null;
        } catch (SAXException e) {
            System.out.println("Wrong XML file structure: " + e.getMessage());
            return null;
        } catch (IOException e) {
            System.out.println("I/O exeption: " + e.getMessage());
            return null;
        }

        return doc;

    }

    /** Returns element value
      * @param elem element (it is XML tag)
      * @return Element value otherwise empty String
      */
     public final static String getElementValue( Node elem ) {
         Node kid;
         if( elem != null){
             if (elem.hasChildNodes()){
                 for( kid = elem.getFirstChild(); kid != null; kid = kid.getNextSibling() ){
                     if( kid.getNodeType() == Node.TEXT_NODE  ){
                         return kid.getNodeValue();
                     }
                 }
             }
         }
         return "";
     }

     public static String getXML(){  
            String line = null;

            try {

                DefaultHttpClient httpClient = new DefaultHttpClient();
                //HttpPost httpPost = new HttpPost("http://hellosunshine.in/keyss/music.xml");
                HttpPost httpPost = new HttpPost("http://m.hellosunshine.in/content/wallpaper.xml");

                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                line = EntityUtils.toString(httpEntity);

            } catch (UnsupportedEncodingException e) {
                line = "<results status=\"error\"><msg>Can't connect to server</msg></results>";
            } catch (MalformedURLException e) {
                line = "<results status=\"error\"><msg>Can't connect to server</msg></results>";
            } catch (IOException e) {
                line = "<results status=\"error\"><msg>Can't connect to server</msg></results>";
            }

            return line;    
    }

    public static int numResults(Document doc){     
        Node results = doc.getDocumentElement();
        int res = -1;

        try{
            res = Integer.valueOf(results.getAttributes().getNamedItem("count").getNodeValue());
        }catch(Exception e ){
            res = -1;
        }

        return res;
    }

    public static String getValue(Element item, String str) {       
        NodeList n = item.getElementsByTagName(str);        
        return XMLfunctions_wallpaper.getElementValue(n.item(0));
    }    
}

4.我的gridview布局

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/gridview"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:numColumns="auto_fit"
    android:verticalSpacing="10dp"
    android:horizontalSpacing="10dp"
    android:columnWidth="90dp"
    android:stretchMode="columnWidth"
    android:gravity="center"
/>

感谢任何帮助。

Answer 1

如果您从解析 XML 中获取的图像 URL 是正确的，那么您可以先创建一个 Bitmap 数组，然后将其传递到您的适配器。将 URL 转换为 Bitmap 的代码如下:(如果您没有的话。)

public static Bitmap getBitmapFromURL(String src) {
    try {
        Log.d("URL",src);
        URL url = new URL(src);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setDoInput(true);
        connection.connect();
        InputStream input = connection.getInputStream();
        Bitmap myBitmap = BitmapFactory.decodeStream(input);
        return myBitmap;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

编辑:这是您需要使用的 ArrayAdapter 类，而不是 BaseAdapter 类。

public class CustomAdapter extends ArrayAdapter<ImageView>{
Activity context;
int linearResource;
public CustomAdapter(Context context, int resources, List<ImageView> objects){
    super(context, resources, objects);
    this.context=(Activity) context;
}
public View getView(int position, View convertView, ViewGroup parent){
    ImageView imageView;

    LayoutInflater mInflater = context.getLayoutInflater();
    if (convertView == null){
        row = getItem(position);
    }
    else{
        imageView= (ImageView) mInflater.inflate(R.layout.images, null);
        //or imageView=new imageView(context);
    }

    return imageView;
}
}

在GridView中设置适配器时，使用以下代码。

gridView.setAdapter(new CustomAdapter(this, 0, imageData));//Where imageData is the ArraList<ImageView> type and where you've stored your ImageViews.