android Universal-Image-Loader框架学习（下）

一.GridView显示图片加进度框：

在Universal-Image-Loader框架可以让加载图片变的简单，下面我们看一下如何在GridView中使用附加上进度条。

效果图：

主界面：

<span style="font-size:18px;">public class GridActivity extends Activity{

	private GridView grid;
	public static final String[] IMAGES = new String[] {
		"http://img.dapixie.com/uploads/allimg/111105/1-111105145231.jpg",
		"http://img3.3lian.com/2014/c2/61/d/1.jpg",
		"http://img3.3lian.com/2014/c2/61/d/2.jpg",
		"http://img3.3lian.com/2014/c2/61/d/3.jpg",
		"http://img3.3lian.com/2014/c2/61/d/4.jpg",
		"http://img3.3lian.com/2014/c2/61/d/5.jpg",
		"http://img3.3lian.com/2014/c2/61/d/6.jpg",
		"http://img3.3lian.com/2014/c2/61/d/7.jpg",
		"http://img3.3lian.com/2014/c2/61/d/8.jpg",
		"http://img3.3lian.com/2014/c2/61/d/9.jpg",
		"http://img3.3lian.com/2014/c2/61/d/10.jpg",
		"http://img3.3lian.com/2014/c2/61/d/11.jpg",
		"http://img3.3lian.com/2014/c2/61/d/12.jpg" };

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

		grid = (GridView)findViewById(R.id.grid);
		grid.setAdapter(new ImageAdapter(this));

	}
	@Override
	protected void onDestroy() {
		super.onDestroy();
		ImageLoader.getInstance().clearMemoryCache();// 清空缓存
		ImageLoader.getInstance().clearDiskCache();//清空缓存
		ImageLoader.getInstance().stop();// 停止
	}

	private static class ImageAdapter extends BaseAdapter {

		private static final String[] IMAGE_URLS = GridActivity.IMAGES;

		private LayoutInflater inflater;

		private DisplayImageOptions options;

		ImageAdapter(Context context) {
			inflater = LayoutInflater.from(context);

			options = new DisplayImageOptions.Builder()
					.showImageOnLoading(R.drawable.ic_stub)
					.showImageForEmptyUri(R.drawable.ic_empty)
					.showImageOnFail(R.drawable.ic_error)
					.cacheInMemory(true)
					.cacheOnDisk(true)
					.considerExifParams(true)
					.bitmapConfig(Bitmap.Config.RGB_565)
					.build();
		}

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

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

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

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			final ViewHolder holder;
			View view = convertView;
			if (view == null) {
				view = inflater.inflate(R.layout.grid_listview_item, parent, false);
				holder = new ViewHolder();
				assert view != null;
				holder.imageView = (ImageView) view.findViewById(R.id.image);
				holder.progressBar = (ProgressBar) view.findViewById(R.id.progress);
				view.setTag(holder);
			} else {
				holder = (ViewHolder) view.getTag();
			}

			ImageLoader.getInstance()
					.displayImage(IMAGE_URLS[position], holder.imageView, options, new SimpleImageLoadingListener() {
						@Override
						public void onLoadingStarted(String imageUri, View view) {
							//设置进度条为0
							holder.progressBar.setProgress(0);
							//开始下载时显示
							holder.progressBar.setVisibility(View.VISIBLE);
						}

						@Override
						public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
							//下载失败隐藏
							holder.progressBar.setVisibility(View.GONE);
						}

						@Override
						public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
							//下载失败隐藏
							holder.progressBar.setVisibility(View.GONE);
						}
					}, new ImageLoadingProgressListener() {
						@Override
						public void onProgressUpdate(String imageUri, View view, int current, int total) {
							//current当前进度，total总进度
							holder.progressBar.setProgress(Math.round(100.0f * current / total));
						}
					});

			return view;
		}
	}

	static class ViewHolder {
		ImageView imageView;
		ProgressBar progressBar;
	}
}</span>

主界面布局：

<span style="font-size:18px;"><?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="vertical" >

    <GridView
	android:id="@+id/grid"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:gravity="center"
	android:horizontalSpacing="4dip"
	android:numColumns="3"
	android:stretchMode="columnWidth"
	android:verticalSpacing="4dip"
	android:padding="4dip" />

</LinearLayout>
</span>

grid_item布局：

<span style="font-size:18px;"><?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="match_parent"
	android:layout_height="120dip">

	<ImageView
		android:id="@+id/image"
		android:layout_width="match_parent"
		android:layout_height="120dip"
		android:adjustViewBounds="true"
		android:contentDescription="@string/descr_image"
		android:scaleType="centerCrop" />

	<ProgressBar
		android:id="@+id/progress"
		android:layout_width="match_parent"
		android:layout_height="wrap_content"
		android:indeterminate="false"
		android:max="100"
		android:layout_gravity="bottom"
		style="@style/ProgressBarStyle" />
</FrameLayout></span>

进度条样式：

<span style="font-size:18px;"><style name="ProgressBarStyle" parent="@android:style/Widget.Holo.ProgressBar.Horizontal"/></span>

ImageLoader配置：

<span style="font-size:18px;">public class MyApp extends Application {

	@Override
	public void onCreate() {
		super.onCreate();
		initImageLoader1(getApplicationContext());

	}
	/*
	 * 自定义配置
	 */
	public static void initImageLoader(Context context) {
		ImageLoaderConfiguration.Builder config = new ImageLoaderConfiguration.Builder(
				context);
		config.threadPoolSize(3);//线程池内加载的数量
		config.threadPriority(Thread.NORM_PRIORITY - 2);
		config.denyCacheImageMultipleSizesInMemory();// 不缓存图片的多种尺寸在内存中
		config.diskCacheFileNameGenerator(new Md5FileNameGenerator());// 将保存的时候的URI名称用MD5
		config.diskCacheSize(50 * 1024 * 1024); // 50 MiB
		config.tasksProcessingOrder(QueueProcessingType.LIFO);
		config.writeDebugLogs();// Remove for release app
		// 初始化ImageLoader使用
		ImageLoader.getInstance().init(config.build());
	}

	/*
	 * 默认的配置，一般没有特殊的要求的时候就使用默认就好了。
	 */
	public static void initImageLoader1(Context context) {
		// 创建默认的ImageLoader配置参数
		ImageLoaderConfiguration configuration = ImageLoaderConfiguration.createDefault(context);
		// 初始化ImageLoader使用
		ImageLoader.getInstance().init(configuration);
	}
}</span>

这个例子是从上篇文章继续写的，也是在它项目里继续写的。

如果你想在滑动中停止加载，而在停止滑动后再继续加载图片，Universal-Image-Loader也提供了这样的功能，PauseOnScrollListener这个类就是监听。

listView.setOnScrollListener(new PauseOnScrollListener(ImageLoader.getInstance(), pauseOnScroll, pauseOnFling));

PauseOnScrollListener的第一个参数是图片加载对象ImageLoader，第二个是控制是否在滑动过程中暂停加载图片，如果需要暂停传true就行了，第三个参数控制猛的滑动界面的时候图片是否加载。