我有一个让我疯狂的大问题。我有一个安装了所有应用程序的ListView，但滚动速度非常慢，所以我想改进它。我试图放一个线程，但它没有解决问题。这是代码
ApplicationAdapter
public class ApplicationAdapter extends ArrayAdapter<ApplicationInfo> {
private List<ApplicationInfo> appsList = null;
private Context context;
private PackageManager packageManager;
Holder holder;
public ApplicationAdapter(Context context, int textViewResourceId,
List<ApplicationInfo> appsList) {
super(context, textViewResourceId, appsList);
this.context = context;
this.appsList = appsList;
packageManager = context.getPackageManager();
}
@Override
public View getView(int position, View convertView, ViewGroup parent){
View view = convertView;
final Holder holder;
if (null == view) {
LayoutInflater layoutInflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = layoutInflater.inflate(R.layout.snippet_list_row, null);
holder = new Holder();
holder.appName = (TextView) view.findViewById(R.id.app_name);
holder.packageName = (TextView) view.findViewById(R.id.app_paackage);
holder.iconview = (ImageView) view.findViewById(R.id.app_icon);
view.setTag(holder);
}
else
{
holder = (Holder)view.getTag();
}
final ApplicationInfo data = appsList.get(position);
if (null != data) {
holder.appName.setText(data.loadLabel(packageManager));
holder.packageName.setText(data.packageName);
holder.iconview.setImageDrawable(data.loadIcon(packageManager));
}
return view;
}
static class Holder
{
TextView appName, packageName;
ImageView iconview;
}
}
活动
public class Activity_Eclair extends ListActivity {
public PackageManager packageManager = null;
public List<ApplicationInfo> applist = null;
public ApplicationAdapter listadaptor = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_eclair);
ListView lv = getListView();
lv.setFastScrollEnabled(true);
lv.setScrollingCacheEnabled(false);
registerForContextMenu(lv);
packageManager = getPackageManager();
new LoadApplications().execute();
Button bottone1 = (Button)findViewById(R.id.button1);
bottone1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
new LoadApplications().execute();
}
});};
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
ApplicationInfo app = applist.get(position);
Uri packageUri = Uri.parse("package:"+app.packageName);
Intent uninstallIntent = new Intent(Intent.ACTION_DELETE, packageUri);
startActivity(uninstallIntent);
}
public List<ApplicationInfo> checkForLaunchIntent(List<ApplicationInfo> list) {
ArrayList<ApplicationInfo> applist = new ArrayList<ApplicationInfo>();
for (ApplicationInfo info : list) {
try {
if (null != packageManager.getLaunchIntentForPackage(info.packageName)) {
applist.add(info);
}
} catch (Exception e) {
e.printStackTrace();
}
}
return applist;
}
private class LoadApplications extends AsyncTask<Void, Void, Void> {
public ProgressDialog progress = null;
@Override
protected Void doInBackground(Void... params) {
applist = checkForLaunchIntent(packageManager.getInstalledApplications(PackageManager.GET_META_DATA));
listadaptor = new ApplicationAdapter(Activity_Eclair.this,
R.layout.snippet_list_row, applist);
return null;
}
@Override
protected void onCancelled() {
super.onCancelled();
}
protected void onDestroy() {
if(progress!=null)
if(progress.isShowing()){
progress.dismiss();
}
}
@Override
protected void onPostExecute(Void result) {
setListAdapter(listadaptor);
progress.dismiss();
super.onPostExecute(result);
}
@Override
protected void onPreExecute() {
progress = ProgressDialog.show(Activity_Eclair.this, null,
"Loading...");
super.onPreExecute();
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
}
private final static int UPDATE_MENU_OPTION = 1;
private final static int DELETE_MENU_OPTION = 2;
private final static int TRUNCATE_MENU_OPTION = 3;
private final static int DELETE = 4;
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
}
@Override
public boolean onContextItemSelected(MenuItem item) {
AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
final long examId = info.id;
ApplicationInfo app = applist.get((int) info.id);
switch (item.getItemId()) {
case UPDATE_MENU_OPTION:
try {
Intent intent = packageManager
.getLaunchIntentForPackage(app.packageName);
if (null != intent) {
startActivity(intent);
}
} catch (ActivityNotFoundException e) {
Toast.makeText(Activity_Eclair.this, e.getMessage(),
Toast.LENGTH_LONG).show();
} catch (Exception e) {
Toast.makeText(Activity_Eclair.this, e.getMessage(),
Toast.LENGTH_LONG).show();
}
return true;
case DELETE_MENU_OPTION:
Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id="+app.packageName));
startActivity(browserIntent);
return true;
case TRUNCATE_MENU_OPTION:
try {
//Open the specific App Info page:
Intent intent = new Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
intent.setData(Uri.parse("package:" + app.packageName));
startActivity(intent);
} catch ( ActivityNotFoundException e ) {
//e.printStackTrace();
//Open the generic Apps page:
Intent intent = new Intent(android.provider.Settings.ACTION_MANAGE_APPLICATIONS_SETTINGS);
startActivity(intent);
}
return true;
case DELETE:
{
Uri packageUri = Uri.parse("package:"+app.packageName);
Intent uninstallIntent = new Intent(Intent.ACTION_DELETE, packageUri);
startActivity(uninstallIntent);
}
return true;
default:
return super.onContextItemSelected(item);
}
}
我声明我已经尝试过在StackOverflow和Web上提供的大量代码片段，但是无法正常工作。 }
答案 0 :(得分：1)
1 - 编辑清单文件添加到活动
android:hardwareAccelerated="true"
2-高速缓存并绘制图标到ImageView oneByOne我们需要4个类女巫：
Utils.class
public class Utils {
public static void CopyStream(InputStream is, OutputStream os)
{
final int buffer_size=1024;
try
{
byte[] bytes=new byte[buffer_size];
for(;;)
{
int count=is.read(bytes, 0, buffer_size);
if(count==-1)
break;
os.write(bytes, 0, count);
}
}
catch(Exception ex){}
}
}
MemoryCache.class
public class MemoryCache {
private static final String TAG = "MemoryCache";
private Map<String, Bitmap> cache=Collections.synchronizedMap(
new LinkedHashMap<String, Bitmap>(10,1.5f,true));//Last argument true for LRU ordering
private long size=0;//current allocated size
private long limit=1000000;//max memory in bytes
public MemoryCache(){
//use 25% of available heap size
setLimit(Runtime.getRuntime().maxMemory()/4);
}
public void setLimit(long new_limit){
limit=new_limit;
Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB");
}
public Bitmap get(String id){
try{
if(!cache.containsKey(id))
return null;
return cache.get(id);
}catch(NullPointerException ex){
ex.printStackTrace();
return null;
}
}
public void put(String id, Bitmap bitmap){
try{
if(cache.containsKey(id))
size-=getSizeInBytes(cache.get(id));
cache.put(id, bitmap);
size+=getSizeInBytes(bitmap);
checkSize();
}catch(Throwable th){
th.printStackTrace();
}
}
private void checkSize() {
Log.i(TAG, "cache size="+size+" length="+cache.size());
if(size>limit){
Iterator<Entry<String, Bitmap>> iter=cache.entrySet().iterator();
while(iter.hasNext()){
Entry<String, Bitmap> entry=iter.next();
size-=getSizeInBytes(entry.getValue());
iter.remove();
if(size<=limit)
break;
}
Log.i(TAG, "Clean cache. New size "+cache.size());
}
}
public void clear() {
try{
cache.clear();
size=0;
}catch(NullPointerException ex){
ex.printStackTrace();
}
}
long getSizeInBytes(Bitmap bitmap) {
if(bitmap==null)
return 0;
return bitmap.getRowBytes() * bitmap.getHeight();
}
}
FileCache.class
public class FileCache {
private File cacheDir;
String cacheFile = "cachefolder";
public FileCache(Context context, String subfolder ){
//Find the dir to save cached images
if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),cacheFile+"/"+subfolder);
else
cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
public FileCache(Context context){
//Find the dir to save cached images
if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),cacheFile);
else
cacheDir=context.getCacheDir();
if(!cacheDir.exists())
cacheDir.mkdirs();
}
public File getFile(String url){
//I identify images by hashcode. Not a perfect solution, good for the demo.
String filename = String.valueOf(url.hashCode());
//Another possible solution (thanks to grantland)
//String filename = URLEncoder.encode(url);
File f = new File(cacheDir, filename);
return f;
}
public void clear(){
File[] files=cacheDir.listFiles();
if(files==null)
return;
for(File f:files)
f.delete();
}
}
ImageLoader.class：
public class ImageLoader {
public static int REQUIRED_SIZE=100;
public MemoryCache memoryCache = new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
int stub_id = R.drawable.drawing_image;
public ImageLoader(Context context){
fileCache=new FileCache(context);
executorService=Executors.newFixedThreadPool(5);
}
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 Bitmap bitmap_to_circel( Bitmap bitmap)
{
return bitmap;
Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
BitmapShader shader = new BitmapShader (bitmap, TileMode.CLAMP, TileMode.CLAMP);
Paint paint = new Paint();
paint.setShader(shader);
paint.setAntiAlias(true);
paint.setFilterBitmap(true);
paint.setDither(true);
Canvas c = new Canvas(circleBitmap);
c.drawCircle(bitmap.getWidth()/2, bitmap.getHeight()/2, bitmap.getWidth()/2, paint);
return circleBitmap;
}*/
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();
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;
BitmapFactory.decodeStream(new FileInputStream(f),null,o);
//Find the correct scale value. It should be the power of 2.
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;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {}
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() {
if(imageViewReused(photoToLoad))
return;
Bitmap bmp=getBitmap(photoToLoad.url);
memoryCache.put(photoToLoad.url, bmp);
if(imageViewReused(photoToLoad))
return;
BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
Activity a=(Activity)photoToLoad.imageView.getContext();
a.runOnUiThread(bd);
}
}
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();
}
}
3 - 将ImageLoader添加到ApplicationAdapter并启动显示图像
public class ApplicationAdapter extends ArrayAdapter<ApplicationInfo> {
private List<ApplicationInfo> appsList = null;
private Context context;
private PackageManager packageManager;
Holder holder;
//added imageloader here <<------------------
ImageLoader imgLoader;
public ApplicationAdapter(Context context, int textViewResourceId,
List<ApplicationInfo> appsList) {
super(context, textViewResourceId, appsList);
this.context = context;
this.appsList = appsList;
packageManager = context.getPackageManager();
//Register image loader class <<---------------------
imgLoader = new ImageLoader(context);
}
@Override
public View getView(int position, View convertView, ViewGroup parent){
View view = convertView;
final Holder holder;
if (null == view) {
LayoutInflater layoutInflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = layoutInflater.inflate(R.layout.snippet_list_row, null);
holder = new Holder();
holder.appName = (TextView) view.findViewById(R.id.app_name);
holder.packageName = (TextView) view.findViewById(R.id.app_paackage);
holder.iconview = (ImageView) view.findViewById(R.id.app_icon);
view.setTag(holder);
}
else
{
holder = (Holder)view.getTag();
}
final ApplicationInfo data = appsList.get(position);
if (null != data) {
holder.appName.setText(data.loadLabel(packageManager));
holder.packageName.setText(data.packageName);
//now load icon provide Url and ImageView only and keep the rest to the class
//provide fill link url to the icon the class will download it , cache it , display it
//next time when scroll again to this position the icon will be displayed from cache file
imgLoader.DisplayImage(data.icon_link_url_with_http, holder.iconview);
}
return view;
}
static class Holder
{
TextView appName, packageName;
ImageView iconview;
}
}
现在您的列表视图即使具有1k ImageView
也会快速滚动答案 1 :(得分：0)
holder.iconview.setImageDrawable(data.loadIcon(packageManager));
每次设置图像时都会这样做，图像非常慢，会碰到磁盘并以满刻度加载图像。有些应用程序有非常大的启动器图标，这可以快速杀死你的ram。在创建列表视图之前，将所有图像加载到ram或缓存文件夹中，它将运行得更快。