【安卓知识点汇总】 UI加载大卫星图处理

本Blog 接上一篇：【安卓知识点汇总】Bitmap位图解码

依然使用到自己封装好的两个工具类：

HttpUtils
BitmapTools
这里就不赘述了，工具类详情见上篇。

这里定义bean类图片数据封装：便于调用

public class Images {

/**
* 提供可以访问的字符串的url
*/
public final static String[] imageUrls = new String[] {
"https://lh6.googleusercontent.com/-55osAWw3x0Q/URquUtcFr5I/AAAAAAAAAbs/rWlj1RUKrYI/s1024/A%252520Photographer.jpg",
"https://lh4.googleusercontent.com/--dq8niRp7W4/URquVgmXvgI/AAAAAAAAAbs/-gnuLQfNnBA/s1024/A%252520Song%252520of%252520Ice%252520and%252520Fire.jpg",
"https://lh5.googleusercontent.com/-7qZeDtRKFKc/URquWZT1gOI/AAAAAAAAAbs/hqWgteyNXsg/s1024/Another%252520Rockaway%252520Sunset.jpg",
"https://lh3.googleusercontent.com/--L0Km39l5J8/URquXHGcdNI/AAAAAAAAAbs/3ZrSJNrSomQ/s1024/Antelope%252520Butte.jpg",
"https://lh6.googleusercontent.com/-8HO-4vIFnlw/URquZnsFgtI/AAAAAAAAAbs/WT8jViTF7vw/s1024/Antelope%252520Hallway.jpg",
"https://lh4.googleusercontent.com/-WIuWgVcU3Qw/URqubRVcj4I/AAAAAAAAAbs/YvbwgGjwdIQ/s1024/Antelope%252520Walls.jpg",
"https://lh4.googleusercontent.com/-xBPxWpD4yxU/URquxWHk8AI/AAAAAAAAAbs/ARDPeDYPiMY/s1024/Lava%252520from%252520the%252520Sky.jpg",
"https://lh3.googleusercontent.com/-897VXrJB6RE/URquxxxd-5I/AAAAAAAAAbs/j-Cz4T4YvIw/s1024/Leica%25252050mm%252520Summilux.jpg",
"https://lh5.googleusercontent.com/-qSJ4D4iXzGo/URquyDWiJ1I/AAAAAAAAAbs/k2pBXeWehOA/s1024/Leica%25252050mm%252520Summilux.jpg",
"https://lh6.googleusercontent.com/-dwlPg83vzLg/URquylTVuFI/AAAAAAAAAbs/G6SyQ8b4YsI/s1024/Leica%252520M8%252520%252528Front%252529.jpg",
"https://lh3.googleusercontent.com/-R3_EYAyJvfk/URquzQBv8eI/AAAAAAAAAbs/b9xhpUM3pEI/s1024/Light%252520to%252520Sand.jpg",
"https://lh3.googleusercontent.com/-fHY5h67QPi0/URqu0Cp4J1I/AAAAAAAAAbs/0lG6m94Z6vM/s1024/Little%252520Bit%252520of%252520Paradise.jpg",
"https://lh5.googleusercontent.com/-TzF_LwrCnRM/URqu0RddPOI/AAAAAAAAAbs/gaj2dLiuX0s/s1024/Lone%252520Pine%252520Sunset.jpg",
"https://lh5.googleusercontent.com/-kI_QdYx7VlU/URqvLXCB6gI/AAAAAAAAAbs/N31vlZ6u89o/s1024/Yet%252520Another%252520Rockaway%252520Sunset.jpg",
"https://lh4.googleusercontent.com/-e9NHZ5k5MSs/URqvMIBZjtI/AAAAAAAAAbs/1fV810rDNfQ/s1024/Yosemite%252520Tree.jpg" };

...
...
}

主代码逻辑实现：

public class MainActivity extends Activity {
private ListView listView;
// 图片的链接
private String[] imageUrls = Images.imageUrls;
private ImageAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) this.findViewById(R.id.listView1);
adapter = new ImageAdapter();
listView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}

public class ImageAdapter extends BaseAdapter {

@Override
public int getCount() {
// TODO Auto-generated method stub
return imageUrls.length;
}

@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return imageUrls[position];
}

@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View view = null;
if (convertView == null) {
view = LayoutInflater.from(MainActivity.this).inflate(
R.layout.item, null);
} else {
view = convertView;
}
ImageView imageView = (ImageView) view
.findViewById(R.id.imageView1);
// 从网络中获取数据，填充到imageview中
// 可能会造成图片的错位：
loadBitmap(imageUrls[position], imageView);
return view;
}

}

/**
* 在滑动这些ListView的时候，会对就的布局进行资源回收，如果ListView结合异步任务操作的时候，不能确保重用的布局被及时回收
*
* @author jack
*
*/
static class AsyncDrawable extends BitmapDrawable {
private final SoftReference<BitmapWorkerTask> softReference;

public AsyncDrawable(Resources resources, Bitmap bitmap,
BitmapWorkerTask bitmapWorkerTask) {
super(resources, bitmap);
softReference = new SoftReference<MainActivity.BitmapWorkerTask>(
bitmapWorkerTask);
}

public BitmapWorkerTask getBitmapWorkerTask() {
return softReference.get();
}
}

/**
* 异步任务
*
* @author jack
*
*/
class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
private SoftReference<ImageView> imageSoftReference;
private String data = "";

public BitmapWorkerTask(ImageView imageView) {
imageSoftReference = new SoftReference<ImageView>(imageView);
}

@Override
protected Bitmap doInBackground(String... params) {
// TODO Auto-generated method stub
data = params[0];
byte[] result = HttpUtils.sendPost(data);
// 解码过程
return BitmapTools.decodeBitmap(result, 100, 100);
}

@Override
protected void onPostExecute(Bitmap bitmap) {
// TODO Auto-generated method stub
super.onPostExecute(bitmap);
if (isCancelled()) {
bitmap = null;
}
if (imageSoftReference != null && bitmap != null) {
final ImageView imageView = imageSoftReference.get();
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (this == bitmapWorkerTask && imageView != null) {
imageView.setImageBitmap(bitmap);
}
}
}
}

private static BitmapWorkerTask getBitmapWorkerTask(ImageView imageView) {
if (imageView != null) {
final Drawable drawable = imageView.getDrawable();
if (drawable instanceof AsyncDrawable) {
final AsyncDrawable asyncDrawable = (AsyncDrawable) drawable;
return asyncDrawable.getBitmapWorkerTask();
}
}
return null;
}

/**
*
* @param data
* @param imageView
* @return
*/
public static boolean cancelPotntialWork(String data, ImageView imageView) {
final BitmapWorkerTask bitmapWorkerTask = getBitmapWorkerTask(imageView);
if (bitmapWorkerTask != null) {
final String bitmapData = bitmapWorkerTask.data;
if (bitmapData != data) {
bitmapWorkerTask.cancel(true);
} else {
return false;
}
}
return true;
}

/**
* 加载图片
*
* @param data
* @param imageView
*/
public void loadBitmap(String data, ImageView imageView) {
Bitmap placeBitmap = BitmapFactory.decodeResource(getResources(),
R.drawable.empty_photo);
if (cancelPotntialWork(data, imageView)) {
final BitmapWorkerTask task = new BitmapWorkerTask(imageView);
final AsyncDrawable asyncDrawable = new AsyncDrawable(
getResources(), placeBitmap, task);
imageView.setImageDrawable(asyncDrawable);
task.execute(data);
}
}

}

另：layout文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" >
</ListView>
</RelativeLayout>

子布局：item.xml:

<?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" >

<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

</LinearLayout>

上述表述也很详细，这里就不罗列了。