我在我的项目中实现了着名的lazy load image library并为我的listview实现了ViewHolder模式，但我的listview的滚动仍然不顺畅。有什么我想念的吗？
这是我的代码。
public View getView(int position, View convertView, ViewGroup parent) {
View vi = convertView; // trying to reuse a recycled view
ViewHolder holder = null;
if (vi == null) {
vi = inflater.inflate(R.layout.realstate_listview_items,
parent, false);
holder = new ViewHolder();
holder.txtRealstateAddress = (TextView) vi
.findViewById(R.id.txtRealstateAddress);
holder.txtRealstateHomeTypeBroker = (TextView) vi
.findViewById(R.id.txtRealstateHomeTypeBroker);
holder.txtRealstatePrice = (TextView) vi
.findViewById(R.id.txtRealstatePrice);
holder.txtRealStateStatus = (TextView) vi
.findViewById(R.id.txtRealStateStatus);
holder.imgRealstatePhoto = (ImageView) vi
.findViewById(R.id.imgRealstatePhoto);
vi.setTag(holder);
} else {
holder = (ViewHolder) vi.getTag();
}
if (isThreadCompleted) {
if (position == selectedItem) {
View view = (View) holder.txtRealstateAddress.getParent()
.getParent().getParent();
view.setBackgroundColor(Color.parseColor("#BFB495"));
} else {
View view = (View) holder.txtRealstateAddress.getParent()
.getParent().getParent();
view.setBackgroundColor(Color.TRANSPARENT);
}
holder.txtRealstateAddress
.setText(RealStateParsedData.realstate_address
.get(position));
holder.txtRealstateHomeTypeBroker
.setText(RealStateParsedData.realstate_propertytype
.get(position)
+ "\n"
+ RealStateParsedData.realstate_broker
.get(position));
holder.txtRealstatePrice.setText("$"
+ RealStateParsedData.realstate_price.get(position));
holder.txtRealStateStatus.setVisibility(View.VISIBLE);
holder.txtRealStateStatus
.setText(RealStateParsedData.realstate_status
.get(position));
if (RealStateParsedData.realstate_status.get(position).equals(
"Active")) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
holder.txtRealStateStatus.setBackground(getResources()
.getDrawable(
R.drawable.real_estate_text_bg_active));
} else {
holder.txtRealStateStatus
.setBackgroundDrawable(getResources()
.getDrawable(
R.drawable.real_estate_text_bg_active));
}
} else {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
holder.txtRealStateStatus
.setBackground(getResources().getDrawable(
R.drawable.real_estate_text_bg_pending));
} else {
holder.txtRealStateStatus
.setBackgroundDrawable(getResources()
.getDrawable(
R.drawable.real_estate_text_bg_pending));
}
}
imageLoader.DisplayImage(data.get(position),
holder.imgRealstatePhoto);
} else {
holder.txtRealStateStatus.setVisibility(View.INVISIBLE);
}
return vi;
}
}
private static class ViewHolder {
TextView txtRealstateAddress;
TextView txtRealstateHomeTypeBroker;
TextView txtRealstatePrice;
TextView txtRealStateStatus;
ImageView imgRealstatePhoto;
}
更新
ImageLoader类
package com.fedorvlasov.lazylist;
public class ImageLoader {
MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews = Collections
.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
Handler handler = new Handler();// handler to display images in UI thread
public ImageLoader(Context context) {
fileCache = new FileCache(context);
executorService = Executors.newFixedThreadPool(5);
}
final int stub_id = R.drawable.img_bg_temp;
public void DisplayImage(String url, ImageView imageView) {
imageViews.put(imageView, url);
Bitmap bitmap = memoryCache.get(url);
if (bitmap != null)
imageView.setImageBitmap(bitmap);
else {
queuePhoto(url, imageView);
imageView.setImageResource(stub_id);
}
}
private void queuePhoto(String url, ImageView imageView) {
PhotoToLoad p = new PhotoToLoad(url, imageView);
executorService.submit(new PhotosLoader(p));
}
private Bitmap getBitmap(String url) {
File f = fileCache.getFile(url);
// from SD cache
Bitmap b = decodeFile(f);
if (b != null)
return b;
// from web
try {
Bitmap bitmap = null;
URL imageUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) imageUrl
.openConnection();
conn.setConnectTimeout(30000);
conn.setReadTimeout(30000);
conn.setInstanceFollowRedirects(true);
InputStream is = conn.getInputStream();
OutputStream os = new FileOutputStream(f);
Utils.CopyStream(is, os);
os.close();
conn.disconnect();
bitmap = decodeFile(f);
return bitmap;
} catch (Throwable ex) {
ex.printStackTrace();
if (ex instanceof OutOfMemoryError)
memoryCache.clear();
return null;
}
}
// decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f) {
try {
// decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
FileInputStream stream1 = new FileInputStream(f);
BitmapFactory.decodeStream(stream1, null, o);
stream1.close();
// Find the correct scale value. It should be the power of 2.
final int REQUIRED_SIZE = 128;
int width_tmp = o.outWidth, height_tmp = o.outHeight;
int scale = 1;
while (true) {
if (width_tmp / 2 < REQUIRED_SIZE
|| height_tmp / 2 < REQUIRED_SIZE)
break;
width_tmp /= 2;
height_tmp /= 2;
scale *= 2;
}
// decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
FileInputStream stream2 = new FileInputStream(f);
Bitmap bitmap = BitmapFactory.decodeStream(stream2, null, o2);
stream2.close();
return bitmap;
} catch (FileNotFoundException e) {
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
// Task for the queue
private class PhotoToLoad {
public String url;
public ImageView imageView;
public PhotoToLoad(String u, ImageView i) {
url = u;
imageView = i;
}
}
class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad) {
this.photoToLoad = photoToLoad;
}
@Override
public void run() {
try {
if (imageViewReused(photoToLoad))
return;
Bitmap bmp = getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if (imageViewReused(photoToLoad))
return;
BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad);
handler.post(bd);
} catch (Throwable th) {
th.printStackTrace();
}
}
}
boolean imageViewReused(PhotoToLoad photoToLoad) {
String tag = imageViews.get(photoToLoad.imageView);
if (tag == null || !tag.equals(photoToLoad.url))
return true;
return false;
}
// Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable {
Bitmap bitmap;
PhotoToLoad photoToLoad;
public BitmapDisplayer(Bitmap b, PhotoToLoad p) {
bitmap = b;
photoToLoad = p;
}
public void run() {
if (imageViewReused(photoToLoad))
return;
if (bitmap != null)
photoToLoad.imageView.setImageBitmap(bitmap);
else
photoToLoad.imageView.setImageResource(stub_id);
}
}
public void clearCache() {
memoryCache.clear();
fileCache.clear();
}
}
UPDATE2
这是我的realestate_lisview_items.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:padding="5dp" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/listview_bg" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignTop="@+id/imgRealstatePhoto"
android:layout_marginLeft="5dp"
android:layout_marginTop="10dp"
android:layout_toLeftOf="@+id/imageView1"
android:layout_toRightOf="@+id/imgRealstatePhoto"
android:orientation="vertical" >
<TextView
android:id="@+id/txtRealstateAddress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#7D7D7D"
android:textSize="15sp"
android:textStyle="bold" />
<TextView
android:id="@+id/txtRealstateHomeTypeBroker"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="end"
android:maxLines="3"
android:text="Loading...."
android:textColor="#867C7D"
android:textScaleX="1.025"
android:textSize="12sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/linearLayout1"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:layout_below="@+id/linearLayout1"
android:gravity="bottom"
android:orientation="horizontal" >
<TextView
android:id="@+id/txtRealstatePrice"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="0.75"
android:textColor="#006B9E"
android:textSize="12sp"
android:textStyle="bold" />
<TextView
android:id="@+id/txtRealStateStatus"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/real_estate_text_bg_pending"
android:ellipsize="end"
android:gravity="center"
android:maxLines="1"
android:singleLine="true"
android:textColor="@android:color/white"
android:textSize="12sp" />
</LinearLayout>
<ImageView
android:id="@+id/imgRealstatePhoto"
android:layout_width="90dp"
android:layout_height="90dp"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:scaleType="centerCrop"
android:src="@drawable/ellectedofficialsoverlay" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:src="@drawable/expand_ico" />
</RelativeLayout>
</RelativeLayout>
</RelativeLayout>
几件事：
RealStateParsedData.realstate_status.get(position)-我会保存它。holder.txtRealStateStatus.setVisibility(View.GONE);而不是INVISIBLE可以更好地进行布局realstate_listview_items布局 - 复杂的布局可能会使列表变得非常慢 - 它的层次结构是否复杂？有透支吗？无论如何，在Android中内置了很多很好的工具，只是为了它 - 在开发者选项中启用Debug GPU overdraw和Profile GPU rendering。
编辑
为了在查看回收时取消任务，你应该将RecyclerListener设置为列表视图，onMovedToScrapHeap你应该取消你的PhotoToLoad任务（这应该通过为每个视图保存它的任务来完成）。
无论如何 - 通过查看您的图像加载器现在我将其更改为使用AsyncTask，看看google如何建议加载图像。
这可能不是理想的答案。但我想分享我的经验。我有平滑滚动的问题我试过堆栈溢出建议的每个方法，但最后我发现问题是在设计中使用的大尺寸drawable图像。因此，请检查设计中使用的可绘制图像。