根據url路徑獲取圖片並顯示到ListView中

項目開發中我們需要從網絡獲取圖片顯示到控件中，很多開源框架如Picasso可以實現圖片下載和緩存功能。這里介紹的是一種簡易的網絡圖片獲取方式並把它顯示到ListView中。

本案例實現的效果如下：

項目結構：

根據部分開源代碼，我修改並封裝了一個網絡圖片加載的工具類GetImageByUrl，通過調用其中的setImage方法，傳入待顯示圖片的ImageView控件和該圖片的url路徑這兩個參數即可實現獲取網絡圖片的功能。

GetImageByUrl.java

package com.leo.imagelistview.util;

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

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;

/** * 根據圖片url路徑獲取圖片 * * @author LeoLeoHan * */
public class GetImageByUrl {

    private PicHandler pic_hdl;
    private ImageView imgView;
    private String url;


    /** * 通過圖片url路徑獲取圖片並顯示到對應控件上 * * @param imgView * @param url */
    public void setImage(ImageView imgView, String url) {
        this.url = url;
        this.imgView = imgView;
        pic_hdl = new PicHandler();
        Thread t = new LoadPicThread();
        t.start();
    }


    class LoadPicThread extends Thread {
        @Override
        public void run() {
            Bitmap img = getUrlImage(url);
            System.out.println(img + "---");
            Message msg = pic_hdl.obtainMessage();
            msg.what = 0;
            msg.obj = img;
            pic_hdl.sendMessage(msg);
        }
    }

    class PicHandler extends Handler {

        @Override
        public void handleMessage(Message msg) {
            Bitmap myimg = (Bitmap) msg.obj;
            imgView.setImageBitmap(myimg);
        }

    }

    public Bitmap getUrlImage(String url) {
        Bitmap img = null;
        try {
            URL picurl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) picurl
                    .openConnection();
            conn.setConnectTimeout(6000);
            conn.setDoInput(true);
            conn.setUseCaches(false);
            conn.connect();
            InputStream is = conn.getInputStream();
            img = BitmapFactory.decodeStream(is);
            is.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return img;
    }
}
  
  
  
          

---

下面的代碼就是實現ListView顯示網絡圖片。
首先創建一個自定義的布局文件images_item.xml和自定義的ImageAdapter。

images_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" >

    <ImageView  android:id="@+id/iv_image" android:layout_width="80dp" android:layout_height="80dp" />

    <LinearLayout  android:layout_width="0dp" android:layout_height="80dp" android:layout_weight="1" android:orientation="vertical" >

        <TextView  android:id="@+id/tv_url" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="5dp" android:textSize="15sp" />
    </LinearLayout>

</LinearLayout>
  
  
  
          

ImageAdapter.java

package com.leo.imagelistview.adapter;

import java.util.List;
import java.util.Map;

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

import com.leo.imagelistview.R;
import com.leo.imagelistview.util.GetImageByUrl;

/** * * @author LeoLeoHan * */
public class ImageAdapter extends BaseAdapter {
    // 要顯示的數據的集合
    private List<Map<String, Object>> data;
    // 接受上下文
    private Context context;
    // 聲明內部類對象
    private ViewHolder viewHolder;

    /** * 構造函數 * * @param context * @param data */
    public ImageAdapter(Context context, List<Map<String, Object>> data) {
        this.context = context;
        this.data = data;
    }

    // 返回的總個數
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return data.size();
    }

    // 返回每個條目對應的數據
    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return data.get(position);
    }

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

    // 返回這個條目對應的控件對象
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // 判斷當前條目是否為null
        if (convertView == null) {
            viewHolder = new ViewHolder();
            convertView = View.inflate(context, R.layout.images_item, null);
            viewHolder.iv_image = (ImageView) convertView
                    .findViewById(R.id.iv_image);
            viewHolder.tv_url = (TextView) convertView
                    .findViewById(R.id.tv_url);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        // 獲取List集合中的map對象
        Map<String, Object> map = data.get(position);
        // 獲取圖片的url路徑
        String url = map.get("url").toString();
        // 這里調用了圖片加載工具類的setImage方法將圖片直接顯示到控件上
        GetImageByUrl getImageByUrl = new GetImageByUrl();
        getImageByUrl.setImage(viewHolder.iv_image, url);
        viewHolder.tv_url.setText(url);

        return convertView;
    }

    /** * 內部類 記錄單個條目中所有屬性 * * @author LeoLeoHan * */
    class ViewHolder {
        public ImageView iv_image;
        public TextView tv_url;
    }

}
  
  
  
          

MainActivity.java

package com.leo.imagelistview;

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

import com.leo.imagelistview.adapter.ImageAdapter;

import android.app.Activity;
import android.os.Bundle;
import android.widget.BaseAdapter;
import android.widget.ListView;

public class MainActivity extends Activity {

    private List<Map<String, Object>> data = new ArrayList<Map<String, Object>>();
    //聲明控件
    private ListView lv_images;

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

        // 獲取ListView對象
        lv_images = (ListView) findViewById(R.id.lv_images);
        //獲取數據
        getData();
        BaseAdapter adapter = new ImageAdapter(this, data);
        //設置適配器
        lv_images.setAdapter(adapter);

    }

    /** * 簡單添加一些網絡圖片的url路徑 * 實際開發中url路徑是從服務器中解析json數據 */
    public void getData() {
        String url1 = "http://my.csdn.net/uploads/avatar/6/A/7/1_leoleohan.jpg";
        String url2 = "http://img1.cache.netease.com/men/2014/6/2/2014060213070843617.jpg";
        String url3 = "http://static2.businessinsider.com/image/522f7a076da811e1404b39a9-480-/jony-ive-9.png";
        String url4 = "http://y0.ifengimg.com/8e16f14474b61551/2013/0731/rdn_51f878236017c.jpg";

        Map<String, Object> map1 = new HashMap<String, Object>();
        map1.put("url", url1); 

        Map<String, Object> map2 = new HashMap<String, Object>();
        map2.put("url", url2);

        Map<String, Object> map3 = new HashMap<String, Object>();
        map3.put("url", url3);

        Map<String, Object> map4 = new HashMap<String, Object>();
        map4.put("url", url4);

        data.add(map1);
        data.add(map2);
        data.add(map3);
        data.add(map4);
    }
}
  
  
  
          

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="${relativePackage}.${activityClass}" >

    <ListView  android:id="@+id/lv_images" android:layout_width="match_parent" android:layout_height="match_parent" />

</RelativeLayout>
  
  
  
          

轉載來源：https://blog.csdn.net/LeoLeoHan/article/details/46553317