通过imageload获取网络图片

新建类继承Application，全局初始化，清单文件需要声明注册
<application android:name=".App"

package com.example.imageloader;

import android.app.Application;
import android.os.Environment;

import com.nostra13.universalimageloader.cache.disc.DiskCache;
import com.nostra13.universalimageloader.cache.disc.impl.ext.LruDiskCache;
import com.nostra13.universalimageloader.cache.disc.naming.FileNameGenerator;
import com.nostra13.universalimageloader.cache.disc.naming.HashCodeFileNameGenerator;
import com.nostra13.universalimageloader.cache.memory.MemoryCache;
import com.nostra13.universalimageloader.cache.memory.impl.LruMemoryCache;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;

import java.io.IOException;

//优先于所有页面(Activity)创建
//主要负责应用全局初始化
//该对象也是一个context
public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();

        //ctrl + h 查看累的继承结构
        //MemoryCache

        //DiskCache

        //FileNameGenerator

        //怎么调用api
        //要什么参数
        //怎么给这个参数

        //Builder
        //构建模式
        //链式调用
        //全局配置
        ImageLoaderConfiguration configuration = null;
        DisplayImageOptions options = new DisplayImageOptions.Builder()
                .build();
        //try {

        //
            configuration = new ImageLoaderConfiguration.Builder(this)
                    //配置:内存 磁盘 缓存
                    //.memoryCache(new LruMemoryCache())
                    //.memoryCacheSize()
                    //内存缓存大小
                    .memoryCacheSizePercentage(10)
                    //配置磁盘缓存:目录 文件名生成  大小
                    //.diskCache(new LruDiskCache(getCacheDir(), new HashCodeFileNameGenerator(), 10*1024*1024))
                    .diskCacheSize(50*1024*1024)
                    //线程配置
                    //任务优先级配置
                    //FIFO
                    //加载图片1   2  3  4  5
                    //LIFO
                    //.tasksProcessingOrder(QueueProcessingType.)
                    //默认显示配置
                    //.defaultDisplayImageOptions(options)
                    .build();
        //} catch (IOException e) {
        //    e.printStackTrace();
        //}

        //初始化:只有第一次初始化有效果
        ImageLoader.getInstance().init(configuration);

        //无效果
        //ImageLoader.getInstance().init(null);
    }
}

package com.example.imageloader;

import android.content.Context;
import android.graphics.Bitmap;
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.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.assist.FailReason;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
import com.nostra13.universalimageloader.core.display.BitmapDisplayer;
import com.nostra13.universalimageloader.core.display.CircleBitmapDisplayer;
import com.nostra13.universalimageloader.core.display.FadeInBitmapDisplayer;
import com.nostra13.universalimageloader.core.display.RoundedBitmapDisplayer;
import com.nostra13.universalimageloader.core.listener.ImageLoadingListener;

import java.util.ArrayList;
import java.util.List;

public class MyBaseAdafter extends BaseAdapter {
    private Context context;
    private List<Bean.DataBean>mlist;

    public MyBaseAdafter(Context context) {
        this.context = context;
        mlist = new ArrayList<>();
    }
public void setListData(List<Bean.DataBean> list){
        this.mlist = list;
        notifyDataSetChanged();
}
    @Override
    public int getCount() {
        return mlist.size();
    }

    @Override
    public Bean.DataBean getItem(int position) {
        return mlist.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHoder viewHoder;
        if(convertView==null){
            convertView = LayoutInflater.from(context).inflate(R.layout.item,parent,false);
            viewHoder = new ViewHoder();
            viewHoder.textView1 = convertView.findViewById(R.id.textview1);
            viewHoder.textView2 = convertView.findViewById(R.id.textview2);
            viewHoder.imageView = convertView.findViewById(R.id.imageview);
            convertView.setTag(viewHoder);
        }else{
            viewHoder = (ViewHoder) convertView.getTag();
        }
        viewHoder.textView1.setText(mlist.get(position).getNews_title());
        viewHoder.textView2.setText(mlist.get(position).getNews_summary());

        // 1280 * 720   -> 1280 * 720   *   每个像素占用字节数16
        //

        //RGB_565       red green blue     红绿蓝 的颜色      r占5byte   g占6byte    b占5byte
        //A RGB_4444 A RGB_8888
        //ALPHA_8

        //BitmapDisplayer

        DisplayImageOptions options = new DisplayImageOptions.Builder()
                //配置色彩模式
                .bitmapConfig(Bitmap.Config.RGB_565)
                //配置  是否缓存
                .cacheInMemory(true)//内存缓冲
                .cacheOnDisk(true)  //磁盘缓冲
                //配置 默认显示
                .showImageOnLoading(R.mipmap.ic_launcher)
                .showImageOnFail(R.mipmap.ic_launcher)
                .showImageForEmptyUri(R.mipmap.ic_launcher)

                //配置图片如何缩放
                .imageScaleType(ImageScaleType.EXACTLY)

                //显示效果:圆形
                //.displayer(new CircleBitmapDisplayer())
                //圆角
                //.displayer(new RoundedBitmapDisplayer(8))
                .displayer(new FadeInBitmapDisplayer(2000))
                .build();

       //加载图片
        ImageLoader
                .getInstance()
                .displayImage(getItem(position).getPic_url(), viewHoder.imageView, options);

        //只加载图片
        //回调返回bitmap
        //ImageLoader.getInstance().loadImage();

        return convertView;
    }
    class ViewHoder{
        private TextView textView1,textView2;
        private ImageView imageView;
    }
}