Android:万能框架——universal-image-loader——ViewPager异步加载图片

最新推荐文章于 2024-04-03 19:21:33 发布

转载最新推荐文章于 2024-04-03 19:21:33 发布 · 1.6k 阅读

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#viewpager #异步 #框架 #android #universal-image-load

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本文介绍了一个基于Android平台的ImagePagerActivity实现方式，该Activity利用ViewPager展示图片，并使用Universal Image Loader加载图片资源。文章详细展示了如何配置DisplayImageOptions，以及如何自定义适配器来实现图片的加载和显示。

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.assist.FailReason;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
import com.nostra13.universalimageloader.core.assist.SimpleImageLoadingListener;
import com.nostra13.universalimageloader.core.display.FadeInBitmapDisplayer;
import com.nostra13.universalimageloader.core.display.RoundedBitmapDisplayer;

/**
 * ViewPager 页面
 */
public class ImagePagerActivity extends BaseActivity {

	private static final String STATE_POSITION = "STATE_POSITION";

	DisplayImageOptions options;

	ViewPager pager;

	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.ac_image_pager);

		Bundle bundle = getIntent().getExtras();
		assert bundle != null;
		String[] imageUrls = bundle.getStringArray(Extra.IMAGES);
		int pagerPosition = bundle.getInt(Extra.IMAGE_POSITION, 0);

		if (savedInstanceState != null) {
			pagerPosition = savedInstanceState.getInt(STATE_POSITION);
		}

		options = new DisplayImageOptions.Builder()
			.showImageForEmptyUri(R.drawable.ic_empty)//uri为空的时候显示
			.showImageOnFail(R.drawable.ic_error)// 加载失败时显示
			.resetViewBeforeLoading(true)
			.cacheOnDisc(true)//设置是否先从磁盘读取
			.imageScaleType(ImageScaleType.EXACTLY)
			.bitmapConfig(Bitmap.Config.RGB_565)
			.considerExifParams(true)
			.displayer(new FadeInBitmapDisplayer(300))//设置显示动画，渐变300ms
			.build();

		pager = (ViewPager) findViewById(R.id.pager);
		pager.setAdapter(new ImagePagerAdapter(imageUrls));//设置适配器
		pager.setCurrentItem(pagerPosition);//设置当前item
	}

	@Override
	public void onSaveInstanceState(Bundle outState) {
		outState.putInt(STATE_POSITION, pager.getCurrentItem());
	}

	private class ImagePagerAdapter extends PagerAdapter {

		private String[] images;
		private LayoutInflater inflater;

		//通过构造函数注入image地址
		ImagePagerAdapter(String[] images) {
			this.images = images;
			inflater = getLayoutInflater();
		}

		@Override
		public void destroyItem(ViewGroup container, int position, Object object) {
			container.removeView((View) object);
		}

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

		/**
		 * 实例化item
		 */
		@Override
		public Object instantiateItem(ViewGroup view, int position) {
			//实例化总布局
			View imageLayout = inflater.inflate(R.layout.item_pager_image, view, false);
			assert imageLayout != null;
			
			//图片组件
			ImageView imageView = (ImageView) imageLayout.findViewById(R.id.image);
			
			//进度条组件
			final ProgressBar spinner = (ProgressBar) imageLayout.findViewById(R.id.loading);

			imageLoader.displayImage(images[position], imageView, options, new SimpleImageLoadingListener() {
				@Override
				public void onLoadingStarted(String imageUri, View view) {
					//开始加载，设置进度条可见
					spinner.setVisibility(View.VISIBLE);
				}

				//下载失败
				@Override
				public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
					String message = null;
					switch (failReason.getType()) {
						case IO_ERROR:
							message = "Input/Output error";
							break;
						case DECODING_ERROR:
							message = "Image can't be decoded";
							break;
						case NETWORK_DENIED:
							message = "Downloads are denied";
							break;
						case OUT_OF_MEMORY:
							message = "Out Of Memory error";
							break;
						case UNKNOWN:
							message = "Unknown error";
							break;
					}
					Toast.makeText(ImagePagerActivity.this, message, Toast.LENGTH_SHORT).show();

					spinner.setVisibility(View.GONE);
				}

				@Override
				public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
					spinner.setVisibility(View.GONE);//加载完成关闭进度条
				}
			});

			view.addView(imageLayout, 0);
			return imageLayout;
		}

		@Override
		public boolean isViewFromObject(View view, Object object) {
			return view.equals(object);
		}

		@Override
		public void restoreState(Parcelable state, ClassLoader loader) {
		}

		@Override
		public Parcelable saveState() {
			return null;
		}
	}
}

源文件下载地址：http://pan.baidu.com/s/1bnf6CbX