本文主要是介绍ImageLoader进阶（结合ListView、ViewPager使用），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
代码下载地址
点击打开链接即可下载
先看主页面的布局ac_home.xml,里面只有一个Button，进入ListView界面展现图片列表
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="fill_parent" ><LinearLayoutandroid:layout_width="fill_parent"android:layout_height="fill_parent"android:orientation="vertical" ><Buttonandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_margin="10dip"android:onClick="onImageListClick"android:text="@string/button_image_list" /></LinearLayout></ScrollView>先看一些数据类Constants--一些图片的链接地址
package com.nostra13.example.universalimageloader;public final class Constants {// 一堆图片链接public static final String[] IMAGES = new String[] {// Heavy images"http://img.mukewang.com/55237dcc0001128c06000338-300-170dd.jpg","http://img.mukewang.com/55237dcc0001128c06000338.jpg","http://img.mukewang.com/55249cf30001sdffae8a06000338-300-170.jpg","http://img.mukewang.com/55249csfsf30001ae8a06000338.jpg","http://img.mukewang.com/5523711700016d1606000338-300-170.jpg","http://img.mukewang.com/5523711700016d1606000338.jpg","http://img.mukewang.com/551e470500018dd806000338-300-170.jpg","http://img.mukewang.com/551e470500018dd806000338.jpg","http://img.mukewang.com/551de0570001134f06000338-300-170.jpg","http://img.mukewang.com/551de0570001134f06000338.jpg","http://img.mukewang.com/552640c300018a9606000338-300-170.jpg"};private Constants() {}// 额外类public static class Extra {public static final String IMAGES = "com.nostra13.example.universalimageloader.IMAGES";public static final String IMAGE_POSITION = "com.nostra13.example.universalimageloader.IMAGE_POSITION";}
}
在看UILApplication这里面的imageLoader配置初始化
UILApplication
package com.nostra13.example.universalimageloader;import android.app.Application;
import android.content.Context;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;public class UILApplication extends Application {@Overridepublic void onCreate() {super.onCreate();initImageLoader(getApplicationContext());}public static void initImageLoader(Context context) {ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(context)// 3个线程池.threadPriority(Thread.NORM_PRIORITY - 2).threadPoolSize(3)// 不缓存图片的多种尺寸在内存中.denyCacheImageMultipleSizesInMemory()// 将保存的时候的URI名称用MD5.discCacheFileNameGenerator(new Md5FileNameGenerator()).tasksProcessingOrder(QueueProcessingType.LIFO)//设置加载显示图片队列进程 .writeDebugLogs() // Remove for release app.build();ImageLoader.getInstance().init(config);}
}接下来application也需要进行相应的变化
<!-- 网络访问权限 --><uses-permission android:name="android.permission.INTERNET" /><!-- 文件写入SD卡权限 --><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /><applicationandroid:name=".UILApplication"android:icon="@drawable/ic_launcher"android:label="@string/app_name" ><activityandroid:name=".HomeActivity"android:label="@string/app_name" ><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity><activityandroid:name=".ImageListActivity"android:label="@string/ac_name_image_list" /><activityandroid:name=".ImagePagerActivity"android:label="@string/ac_name_image_pager" /></application>接下来看主界面的代码
HomeActivity
package com.nostra13.example.universalimageloader;import static com.nostra13.example.universalimageloader.Constants.IMAGES;import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AbsListView;import com.nostra13.example.universalimageloader.Constants.Extra;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.utils.L;public class HomeActivity extends Activity {protected ImageLoader imageLoader = ImageLoader.getInstance();@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.ac_home);}// 点击进入ListView展示界面public void onImageListClick(View view) {Intent intent = new Intent(this, ImageListActivity.class);intent.putExtra(Extra.IMAGES, IMAGES);startActivity(intent);}@Overridepublic void onBackPressed() {imageLoader.stop(); // 停止加载图片super.onBackPressed();}}接下来就进入了ListView展示界面了，布局文件就是一个listView视图
ac_image_list.xml
<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"android:id="@android:id/list"android:layout_width="fill_parent"android:layout_height="fill_parent" />
listview的item布局item_list_image.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="wrap_content" ><ImageViewandroid:id="@+id/image"android:layout_width="72dip"android:layout_height="72dip"android:layout_margin="3dip"android:adjustViewBounds="true"android:contentDescription="@string/descr_image"android:scaleType="centerCrop" /><TextViewandroid:id="@+id/text"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_gravity="left|center_vertical"android:layout_marginLeft="20dip"android:textSize="22sp" /></LinearLayout>ImageListActivity 接下来看listView界面的主要代码了
package com.nostra13.example.universalimageloader;import java.util.Collections;
import java.util.LinkedList;
import java.util.List;import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;import com.nostra13.example.universalimageloader.Constants.Extra;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.assist.ImageLoadingListener;
import com.nostra13.universalimageloader.core.assist.SimpleImageLoadingListener;
import com.nostra13.universalimageloader.core.display.FadeInBitmapDisplayer;
import com.nostra13.universalimageloader.core.display.RoundedBitmapDisplayer;public class ImageListActivity extends Activity {protected ImageLoader imageLoader = ImageLoader.getInstance();DisplayImageOptions options; // DisplayImageOptions是用于设置图片显示的类String[] imageUrls; // 图片路径protected AbsListView listView;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.ac_image_list);Bundle bundle = getIntent().getExtras();imageUrls = bundle.getStringArray(Extra.IMAGES);// 使用DisplayImageOptions.Builder()创建DisplayImageOptionsoptions = new DisplayImageOptions.Builder().showStubImage(R.drawable.ic_stub) // 设置图片下载期间显示的图片.showImageForEmptyUri(R.drawable.ic_empty) // 设置图片Uri为空或是错误的时候显示的图片.showImageOnFail(R.drawable.ic_error) // 设置图片加载或解码过程中发生错误显示的图片.cacheInMemory(true) // 设置下载的图片是否缓存在内存中.cacheOnDisc(true) // 设置下载的图片是否缓存在SD卡中.displayer(new RoundedBitmapDisplayer(20)) // 设置成圆角图片.build(); // 创建配置过得DisplayImageOption对象listView = (ListView) findViewById(android.R.id.list);((ListView) listView).setAdapter(new ItemAdapter());listView.setOnItemClickListener(new OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> parent, View view,int position, long id) {// 点击列表项转入ViewPager显示界面Intent intent = new Intent(ImageListActivity.this, ImagePagerActivity.class);intent.putExtra(Extra.IMAGES, imageUrls);intent.putExtra(Extra.IMAGE_POSITION, position);startActivity(intent);}});}@Overridepublic void onBackPressed() {AnimateFirstDisplayListener.displayedImages.clear();super.onBackPressed();}/*** 自定义列表项适配器*/class ItemAdapter extends BaseAdapter {private ImageLoadingListener animateFirstListener = new AnimateFirstDisplayListener();private class ViewHolder {public TextView text;public ImageView image;}@Overridepublic int getCount() {return imageUrls.length;}@Overridepublic Object getItem(int position) {return position;}@Overridepublic long getItemId(int position) {return position;}@Overridepublic View getView(final int position, View convertView,ViewGroup parent) {View view = convertView;final ViewHolder holder;if (convertView == null) {view = getLayoutInflater().inflate(R.layout.item_list_image,parent, false);holder = new ViewHolder();holder.text = (TextView) view.findViewById(R.id.text);holder.image = (ImageView) view.findViewById(R.id.image);view.setTag(holder); // 给View添加一个格外的数据} else {holder = (ViewHolder) view.getTag(); // 把数据取出来}holder.text.setText("Item " + (position + 1)); // TextView设置文本/*** 显示图片 参数1：图片url 参数2：显示图片的控件 参数3：显示图片的设置 参数4：监听器*/imageLoader.displayImage(imageUrls[position], holder.image,options, animateFirstListener);return view;}}/*** 图片加载第一次显示监听器*/private static class AnimateFirstDisplayListener extendsSimpleImageLoadingListener {static final List<String> displayedImages = Collections.synchronizedList(new LinkedList<String>());@Overridepublic void onLoadingComplete(String imageUri, View view,Bitmap loadedImage) {if (loadedImage != null) {ImageView imageView = (ImageView) view;// 是否第一次显示boolean firstDisplay = !displayedImages.contains(imageUri);if (firstDisplay) {// 图片淡入效果FadeInBitmapDisplayer.animate(imageView, 500);displayedImages.add(imageUri);}}}}
}点击listview的条目进入Viewpager界面，接下来看Viewpager的布局文件
ac_image_pager.xml、
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"android:id="@+id/pager"android:layout_width="fill_parent"android:layout_height="fill_parent" />
item_pager_image.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="fill_parent"android:padding="1dip" ><ImageViewandroid:id="@+id/image"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="center"android:adjustViewBounds="true"android:contentDescription="@string/descr_image" /><ProgressBarandroid:id="@+id/loading"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="center"android:visibility="gone" /></FrameLayout>ImagePagerActivity 接下来看viewpager的代码了
package com.nostra13.example.universalimageloader;import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.Toast;import com.nostra13.example.universalimageloader.Constants.Extra;
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.assist.SimpleImageLoadingListener;
import com.nostra13.universalimageloader.core.display.FadeInBitmapDisplayer;public class ImagePagerActivity extends Activity {private static final String STATE_POSITION = "STATE_POSITION";DisplayImageOptions options;ViewPager pager;protected ImageLoader imageLoader = ImageLoader.getInstance();public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.ac_image_pager);Bundle bundle = getIntent().getExtras();String[] imageUrls = bundle.getStringArray(Extra.IMAGES);// 当前显示View的位置int pagerPosition = bundle.getInt(Extra.IMAGE_POSITION, 0);// 如果之前有保存用户数据if (savedInstanceState != null) {pagerPosition = savedInstanceState.getInt(STATE_POSITION);}options = new DisplayImageOptions.Builder().showImageForEmptyUri(R.drawable.ic_empty).showImageOnFail(R.drawable.ic_error).resetViewBeforeLoading(true).cacheOnDisc(true).imageScaleType(ImageScaleType.EXACTLY).bitmapConfig(Bitmap.Config.RGB_565).displayer(new FadeInBitmapDisplayer(300)).build();pager = (ViewPager) findViewById(R.id.pager);pager.setAdapter(new ImagePagerAdapter(imageUrls));pager.setCurrentItem(pagerPosition); // 显示当前位置的View}@Overridepublic void onSaveInstanceState(Bundle outState) {// 保存用户数据outState.putInt(STATE_POSITION, pager.getCurrentItem());}private class ImagePagerAdapter extends PagerAdapter {private String[] images;private LayoutInflater inflater;ImagePagerAdapter(String[] images) {this.images = images;inflater = getLayoutInflater();}@Overridepublic void destroyItem(ViewGroup container, int position, Object object) {((ViewPager) container).removeView((View) object);}@Overridepublic void finishUpdate(View container) {}@Overridepublic int getCount() {return images.length;}@Overridepublic Object instantiateItem(ViewGroup view, int position) {View imageLayout = inflater.inflate(R.layout.item_pager_image, view, false);ImageView imageView = (ImageView) imageLayout.findViewById(R.id.image);final ProgressBar spinner = (ProgressBar) imageLayout.findViewById(R.id.loading);imageLoader.displayImage(images[position], imageView, options, new SimpleImageLoadingListener() {@Overridepublic void onLoadingStarted(String imageUri, View view) {spinner.setVisibility(View.VISIBLE);}@Overridepublic void onLoadingFailed(String imageUri, View view, FailReason failReason) {String message = null;switch (failReason.getType()) { // 获取图片失败类型case IO_ERROR: // 文件I/O错误message = "Input/Output error";break;case DECODING_ERROR: // 解码错误message = "Image can't be decoded";break;case NETWORK_DENIED: // 网络延迟message = "Downloads are denied";break;case OUT_OF_MEMORY: // 内存不足message = "Out Of Memory error";break;case UNKNOWN: // 原因不明message = "Unknown error";break;}Toast.makeText(ImagePagerActivity.this, message, Toast.LENGTH_SHORT).show();spinner.setVisibility(View.GONE);}@Overridepublic void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {spinner.setVisibility(View.GONE); // 不显示圆形进度条}});((ViewPager) view).addView(imageLayout, 0); // 将图片增加到ViewPagerreturn imageLayout;}@Overridepublic boolean isViewFromObject(View view, Object object) {return view.equals(object);}@Overridepublic void restoreState(Parcelable state, ClassLoader loader) {}@Overridepublic Parcelable saveState() {return null;}@Overridepublic void startUpdate(View container) {}}
}
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