网上的资源普遍上是ListView异步加载图片,比较少有GirdView异步加载图片,参考了ListView异步加载图片的做法把GridView的异步加载图片功能做出来,方法和思想大同小异,本文章把GridView异步加载内存卡和网络图片希望对大家有用。效果图如下:
一、主界面代码:
import java.util.ArrayList; import java.util.List; import android.app.Activity; import android.os.Bundle; import android.widget.GridView; public class MainActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); GridView gridView=(GridView)findViewById(R.id.gridview); List<ImageAndText> list = new ArrayList<ImageAndText>(); String[] paths=new String[15]; for(int i=0;i<15;i++){ int index=i; paths[i]="/sdcard/"+String.valueOf(index+1)+".jpg";//自己动手向SD卡添加15张图片,如:1.jpg } for(int i=0;i<15;i++){ list.add(new ImageAndText(paths[i], String.valueOf(i))); } gridView.setAdapter(new ImageAndTextListAdapter(this, list, gridView)); } }
二、以下代码是实现异步获取图片的主方法,SoftReference是软引用,是为了更好的为了系统回收变量,重复的URL直接返回已有的资源,实现回调函数,让数据成功后,更新到UI线程。
import java.io.IOException; import java.io.InputStream; import java.lang.ref.SoftReference; import java.net.MalformedURLException; import java.net.URL; import java.util.HashMap; import android.R.drawable; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.BitmapFactory.Options; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.Drawable; import android.os.Handler; import android.os.Message; import android.util.Log; import android.widget.ImageView; public class AsyncImageLoader { private HashMap<String, SoftReference<Drawable>> imageCache; public AsyncImageLoader() { imageCache = new HashMap<String, SoftReference<Drawable>>(); } public Drawable loadDrawable(final String imageUrl, final ImageCallback imageCallback) { if (imageCache.containsKey(imageUrl)) { SoftReference<Drawable> softReference = imageCache.get(imageUrl); Drawable drawable = softReference.get(); if (drawable != null) { return drawable; } } final Handler handler = new Handler() { public void handleMessage(Message message) { imageCallback.imageLoaded((Drawable) message.obj, imageUrl); } }; new Thread() { @Override public void run() { Drawable drawable = loadImageFromUrl(imageUrl); imageCache.put(imageUrl, new SoftReference<Drawable>(drawable)); Message message = handler.obtainMessage(0, drawable); handler.sendMessage(message); } }.start(); return null; } public static Drawable loadImageFromUrl(String url) { // /** // * 加载网络图片 // */ // URL m; // InputStream i = null; // try { // m = new URL(url); // i = (InputStream) m.getContent(); // } catch (MalformedURLException e1) { // e1.printStackTrace(); // } catch (IOException e) { // e.printStackTrace(); // } // Drawable d = Drawable.createFromStream(i, "src"); /** * 加载内存卡图片 */ Options options=new Options(); options.inSampleSize=2; Bitmap bitmap=BitmapFactory.decodeFile(url, options); Drawable drawable=new BitmapDrawable(bitmap); return drawable; } public interface ImageCallback { public void imageLoaded(Drawable imageDrawable, String imageUrl); } }
import java.util.List; import cn.wangmeng.test.AsyncImageLoader.ImageCallback; import android.app.Activity; import android.graphics.drawable.Drawable; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ArrayAdapter; import android.widget.GridView; import android.widget.ImageView; import android.widget.ListView; import android.widget.TextView; public class ImageAndTextListAdapter extends ArrayAdapter<ImageAndText> { private GridView gridView; private AsyncImageLoader asyncImageLoader; public ImageAndTextListAdapter(Activity activity, List<ImageAndText> imageAndTexts, GridView gridView1) { super(activity, 0, imageAndTexts); this.gridView = gridView1; asyncImageLoader = new AsyncImageLoader(); } public View getView(int position, View convertView, ViewGroup parent) { Activity activity = (Activity) getContext(); // Inflate the views from XML View rowView = convertView; ViewCache viewCache; if (rowView == null) { LayoutInflater inflater = activity.getLayoutInflater(); rowView = inflater.inflate(R.layout.griditem, null); viewCache = new ViewCache(rowView); rowView.setTag(viewCache); } else { viewCache = (ViewCache) rowView.getTag(); } ImageAndText imageAndText = getItem(position); // Load the image and set it on the ImageView String imageUrl = imageAndText.getImageUrl(); ImageView imageView = viewCache.getImageView(); imageView.setTag(imageUrl); Drawable cachedImage = asyncImageLoader.loadDrawable(imageUrl, new ImageCallback() { public void imageLoaded(Drawable imageDrawable, String imageUrl) { ImageView imageViewByTag = (ImageView) gridView.findViewWithTag(imageUrl); if (imageViewByTag != null) { imageViewByTag.setImageDrawable(imageDrawable); } } }); if (cachedImage == null) { imageView.setImageResource(R.drawable.icon); }else{ imageView.setImageDrawable(cachedImage); } // Set the text on the TextView TextView textView = viewCache.getTextView(); textView.setText(imageAndText.getText()); return rowView; } }
public class ImageAndText { private String imageUrl; private String text; public ImageAndText(String imageUrl, String text) { this.imageUrl = imageUrl; this.text = text; } public String getImageUrl() { return imageUrl; } public String getText() { return text; } }
public class ViewCache { private View baseView; private TextView textView; private ImageView imageView; public ViewCache(View baseView) { this.baseView = baseView; } public TextView getTextView() { if (textView == null) { textView = (TextView) baseView.findViewById(R.id.text); } return textView; } public ImageView getImageView() { if (imageView == null) { imageView = (ImageView) baseView.findViewById(R.id.image); } return imageView; } }
1、griditem:
<?xml version="1.0" encoding="UTF-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="100dip" android:paddingBottom="4dip" android:layout_width="fill_parent"> <ImageView android:id="@+id/image" android:layout_height="80dip" android:layout_width="80dip" android:layout_centerHorizontal="true" android:scaleType="centerCrop"> </ImageView> <TextView android:id="@+id/text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/image" android:layout_centerHorizontal="true" > </TextView> </RelativeLayout>
2、main
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <GridView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/gridview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:numColumns="4" android:verticalSpacing="10dp" android:horizontalSpacing="10dp" android:columnWidth="80dp" android:stretchMode="columnWidth" android:gravity="center" android:background="#ffffff" /> </LinearLayout>