ImageLoader框架+gridView 加载网络图片与下载

桃扇骨 2022-08-05 21:29 178阅读 0赞

在处理加载图片的时候经常遇见 OOM的错误，这个demo引用了ImageLoader框架，解决了listView滑动时的卡顿，重用机制得到了更好的体验，增加了下载网络图片的功能，下载后图片的目录在 Download 目录下，代码中没有创建Download 文件夹，手机根目录没有此文件夹的请注意。

特意整理了demo，简单易上手，希望对大家有用。 jar包在libs目录下 。我是用的gridView，listView同理。

# [点我下载demo][demo] #

先看图片：

![Center][]

![Center 1][]

demo中只有两个类，简单易懂。

imageUrls 存放的是图片的网址，使用网址是需要注意，有的图片的网址有很多代码的，那种是转码过的，可以看看我在网上找的网址，一级一级的很清楚，最好找这种来测试。

还有一点需要注意的是，imageLoader需要初始化：imageLoader.init(ImageLoaderConfiguration.createDefault(MainActivity.this));

options = 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   
.bitmapConfig(Bitmap.Config.RGB\_565)  
.build();         // 创建配置过得DisplayImageOption对象

完成了一个类就可以实现第一张图片的效果了。

package com.example.gridview_imageloader;
    
    import com.nostra13.universalimageloader.core.DisplayImageOptions;
    import com.nostra13.universalimageloader.core.ImageLoader;
    import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
    
    import android.os.Bundle;
    import android.app.Activity;
    import android.content.Intent;
    import android.graphics.Bitmap;
    import android.view.Menu;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.AdapterView;
    import android.widget.BaseAdapter;
    import android.widget.GridView;
    import android.widget.ImageView;
    import android.widget.AdapterView.OnItemClickListener;
    
    public class MainActivity extends Activity {
    	String[] imageUrls;
    	protected ImageLoader imageLoader;
    	DisplayImageOptions options;
    	@Override
    	protected void onCreate(Bundle savedInstanceState) {
    		super.onCreate(savedInstanceState);
    		setContentView(R.layout.activity_main);
    		imageLoader = ImageLoader.getInstance();
    		imageLoader.init(ImageLoaderConfiguration.createDefault(MainActivity.this));
    		imageUrls = new String[]{"http://www.baidu.com/img/bdlogo.gif",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201410/apic6568.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201411/apic7677.jpg",
    				"http://pic1.sc.chinaz.com/files/pic/pic9/201410/apic6867.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201411/apic7788.jpg",
    				"http://pic2.sc.chinaz.com/files/pic/pic9/201411/apic7776.jpg",
    				"http://pic1.sc.chinaz.com/files/pic/pic9/201410/apic7203.jpg",
    				"http://pic2.sc.chinaz.com/files/pic/pic9/201410/apic7238.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201408/apic5360.jpg",
    				"http://pic1.sc.chinaz.com/files/pic/pic9/201407/apic5280.jpg",
    				"http://pic1.sc.chinaz.com/files/pic/pic9/201406/apic4599.jpg",
    				"http://pic2.sc.chinaz.com/files/pic/pic9/201406/apic4221.jpg",
    				"http://pic1.sc.chinaz.com/files/pic/pic9/201405/apic3974.jpg",
    				"http://pic2.sc.chinaz.com/files/pic/pic9/201405/apic3859.jpg",
    				"http://pic2.sc.chinaz.com/files/pic/pic9/201404/apic195.jpg",
    				"http://pic1.sc.chinaz.com/files/pic/pic9/201403/apic669.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic603.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic331.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic306.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic307.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic308.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic309.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic310.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic311.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic312.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic313.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic314.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic315.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic316.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic317.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic318.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic319.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic320.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic321.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic322.jpg",
    				"http://pic.sc.chinaz.com/files/pic/pic9/201403/apic323.jpg"};
    		options = new DisplayImageOptions.Builder()
    		.showStubImage(R.drawable.ic_stub)
    		.showImageForEmptyUri(R.drawable.ic_empty)
    		.showImageOnFail(R.drawable.ic_error)
    		.cacheInMemory(true)
    		.cacheOnDisc(true)
    		.bitmapConfig(Bitmap.Config.RGB_565)
    		.build();
    		GridView gridView = (GridView) findViewById(R.id.gridview);
    		gridView.setAdapter(new ImageAdapter());
    		gridView.setOnItemClickListener(new OnItemClickListener() {
    			@Override
    			public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    				startImagePagerActivity(position);
    			}
    		});
    	}
    	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";
    	}
    	private void startImagePagerActivity(int position) {
    		Intent intent = new Intent(this, ImagePagerActivity.class);
    		intent.putExtra(Extra.IMAGES, imageUrls);
    		intent.putExtra(Extra.IMAGE_POSITION, position);
    		startActivity(intent);
    	}
    	
    	
    	public class ImageAdapter extends BaseAdapter {
    		@Override
    		public int getCount() {
    			return imageUrls.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 ImageView imageView;
    			if (convertView == null) {
    				imageView = (ImageView) getLayoutInflater().inflate(R.layout.item_grid_image, parent, false);
    			} else {
    				imageView = (ImageView) convertView;
    			}
    			imageLoader.displayImage(imageUrls[position], imageView, options);
    			return imageView;
    		}
    	}
    	
    }

接下来看第二个类，第二个类是点击item时显示的activity，包括下载图片，也在这个类中。

package com.example.gridview_imageloader;
    
    import java.io.File;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    import org.apache.http.HttpEntity;
    import org.apache.http.HttpResponse;
    import org.apache.http.HttpStatus;
    import org.apache.http.client.ClientProtocolException;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.impl.client.DefaultHttpClient;
    
    import com.nostra13.universalimageloader.core.DisplayImageOptions;
    import com.nostra13.universalimageloader.core.ImageLoader;
    import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
    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 android.os.Bundle;
    import android.os.Parcelable;
    import android.app.Activity;
    import android.app.AlertDialog;
    import android.app.AlertDialog.Builder;
    import android.content.DialogInterface;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.support.v4.view.PagerAdapter;
    import android.support.v4.view.ViewPager;
    import android.util.Log;
    import android.view.LayoutInflater;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ImageView;
    import android.widget.ProgressBar;
    import android.widget.Toast;
    
    public class ImagePagerActivity extends Activity {
    	private static final String STATE_POSITION = "STATE_POSITION";
    	DisplayImageOptions options;
    	ViewPager pager;
    	int positionPosition;
    	String[] imageUrls;
    	protected ImageLoader imageLoader;
    	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";
    	}
    	@Override
    	protected void onCreate(Bundle savedInstanceState) {
    		super.onCreate(savedInstanceState);
    		setContentView(R.layout.activity_image_pager);
    		imageLoader = ImageLoader.getInstance();
    		imageLoader.init(ImageLoaderConfiguration.createDefault(ImagePagerActivity.this));
    		
    		Bundle bundle = getIntent().getExtras();
    		imageUrls = bundle.getStringArray(Extra.IMAGES);
    		//记录 当前图片的位置。
    		int pagerPosition = bundle.getInt(Extra.IMAGE_POSITION, 0);
    		//保存用户之前的数据
    		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);
    	}
    	
    	
    	private class ImagePagerAdapter extends PagerAdapter {
    
    		private String[] images;
    		private LayoutInflater inflater;
    
    		ImagePagerAdapter(String[] images) {
    			this.images = images;
    			inflater = getLayoutInflater();
    		}
    
    		@Override
    		public void destroyItem(ViewGroup container, int position, Object object) {
    			((ViewPager) container).removeView((View) object);
    		}
    
    		@Override
    		public void finishUpdate(View container) {
    		}
    
    		@Override
    		public int getCount() {
    			return images.length;
    		}
    
    		@Override
    		public Object instantiateItem(ViewGroup view, int position) {
    			positionPosition = 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() {
    				@Override
    				public void onLoadingStarted(String imageUri, View view) {
    					spinner.setVisibility(View.VISIBLE);
    				}
    
    				@Override
    				public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
    					String message = null;
    					// 获取图片失败类型
    					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);		
    				}
    			});
    
    			((ViewPager) 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;
    		}
    
    		@Override
    		public void startUpdate(View container) {
    		}
    	}
    	
    	
    	//按钮。按菜单键，弹出  下载和取消。
    	public boolean onCreateOptionsMenu(Menu menu) {
    		menu.add(0, 1, 1, "下载");
    		menu.add(0, 2, 2, "分享");
    		menu.add(0, 3, 3, "取消");
    		return super.onCreateOptionsMenu(menu);
    	}
    	
    	public boolean onOptionsItemSelected(MenuItem item) {
    		switch (item.getItemId()) {
    		case 1:
    			//下载图片。
    			new Thread() {
    				public void run() {
    					downloadImages(imageUrls[positionPosition-1]);
    				};
    			}.start();
    			break;
    
    		case 2:
    			Toast.makeText(getApplicationContext(), "分享", 1000).show();
    			break;
    		}
    		return super.onOptionsItemSelected(item);
    	}
    
    	//从网络上下载图片。
    	public void downloadImages(String imageUrl){
    		 HttpGet httpRequest = new HttpGet(imageUrl);  
    	        //取得HttpClient 对象  
    	        HttpClient httpclient = new DefaultHttpClient();  
    	        try {  
    	            //请求httpClient ，取得HttpRestponse  
    	            HttpResponse httpResponse = httpclient.execute(httpRequest);  
    	            if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK){  
    	                //取得相关信息 取得HttpEntiy  
    	                HttpEntity httpEntity = httpResponse.getEntity();  
    	                //获得一个输入流  
    	                InputStream is = httpEntity.getContent();  
    	                System.out.println(is.available());  
    	                System.out.println("Get, Yes!");  
    	                Log.e("====================", is.available()+"");
    	                Log.e("====================", "Get, Yes!");
    	                Bitmap bitmap = BitmapFactory.decodeStream(is);  
    	                is.close();  
    	                //时间命名
    	                SimpleDateFormat format = new SimpleDateFormat("yyyyMMddHHmmss");//获取当前时间，进一步转化为字符串
    			        Date date =new Date();
    			        String pictureName=format.format(date);
    	                saveMyBitmap(pictureName, bitmap);
    	            }  
    	              
    	        } catch (ClientProtocolException e) {  
    	            // TODO Auto-generated catch block  
    	            e.printStackTrace();  
    	        } catch (IOException e) {  
    	            // TODO Auto-generated catch block  
    	            e.printStackTrace();  
    	        }  
    	}
    	
    	public void saveMyBitmap(String bitName,Bitmap mBitmap){
    		  File f = new File("/sdcard/download/" + bitName + ".jpg");
    		  try {
    		   f.createNewFile();
    		  } catch (IOException e) {
    		   // TODO Auto-generated catch block
    		 
    		  }
    		  FileOutputStream fOut = null;
    		  try {
    		   fOut = new FileOutputStream(f);
    		  } catch (FileNotFoundException e) {
    		   e.printStackTrace();
    		  }
    		  mBitmap.compress(Bitmap.CompressFormat.PNG, 100, fOut);
    		  
    		  runOnUiThread(new Runnable() {		
    				public void run() {
    					//show the image
    					 Toast.makeText(getApplicationContext(), "下载成功", 1000).show();
    				}
    			});
    		 
    		  try {
    		   fOut.flush();
    		  } catch (IOException e) {
    		   e.printStackTrace();
    		  }
    		  try {
    		   fOut.close();
    		  } catch (IOException e) {
    		   e.printStackTrace();
    		  }
    		 }
    
    }

相信看代码大家应该看得懂了。就不多解释了，因为追究深了我也不会。

最后注意一下权限问题。

<uses-permission android:name="android.permission.INTERNET" />
        
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

如果有什么问题欢迎留言大家一起探讨。

转载请注明出处：http://blog.csdn.net/u011368551/article/details/41724211

[demo]: http://download.csdn.net/detail/u011368551/8224223
[Center]: /images/20220806/3f0b3504127f411ca133da9d390fb167.png
[Center 1]: /images/20220806/da9ad12a99074033b055038221fdad22.png