說，我有：兩種活動之間傳遞圖像的最快方式是什麼？
Activity含有ImageView imageView1活性1
和
Activity含有ImageView imageView2，活性2
和我有一個字符串的URL指向一個圖像（由Picasso緩存） ，我已經加載到imageView1。 如何啓動Activitiy2並以最快的方式將相同的圖像加載到ImageView2中？
目前，我打電話Picasso.load().into()上的URL一旦活動啓動。這很快，但我正在尋找更快的東西。
Picasso.with(mContext)
.load(myUrl)
.into(imageView2);
任何建議將非常感激。
畢加索下載完整的圖像，並在磁盤/存儲保存原始圖像。假設原始圖像尺寸爲800x800，並且您試圖將此圖像加載到尺寸爲100x100的視圖中，那麼畢加索將需要一些時間來重新調整尺寸。 你可能想試試Glide [1]。 Glide可以同時緩存重新調整大小的圖像和原始圖像。 （檢查Glide＃diskCachingStratedgy）
另外，如果使用.noFade（）選項，那麼在Picasso中，圖像可能會加載得更快。
[1] https://inthecheesefactory.com/blog/get-to-know-glide-recommended-by-google/en
我認爲它已經夠快了。畢加索從共享內存緩存中獲取它，並將其存儲爲可以使用的位圖。它比使用intent.putExtra（「image」.bitmapByteArray）或使用具有解碼或編碼位圖的文件更快。
您需要創建三個類用於將圖像存儲在緩存中，並且加載圖像速度更快。 1. ImageLoader.java 2. FileCache.java 3. MemoryCache.java
ImageLoader.java
package com.thefinal3.Camera;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.widget.ImageView;
import com.thefinal3.R;
import com.thefinal3.Utils.Utils;
/**
* Created by Akash patel on 03-05-2016.
*/
public class ImageLoader {
MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService;
public ImageLoader(Context context){
fileCache=new FileCache(context);
executorService=Executors.newFixedThreadPool(5);
}
final int stub_id= R.drawable.ic_no_image;
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();
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.
final int REQUIRED_SIZE=70;
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();
}
}
FileCache.java
package com.thefinal3.Camera;
import android.content.Context;
import java.io.File;
/**
* Created by Akash patel on 03-05-2016.
*/
public class FileCache {
private File cacheDir;
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(),"TTImages_cache");
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();
}
}
MemoryCache.java
package com.thefinal3.Camera;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import android.graphics.Bitmap;
import android.util.Log;
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;
//NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
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();//least recently accessed item will be the first one iterated
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{
//NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
cache.clear();
size=0;
}catch(NullPointerException ex){
ex.printStackTrace();
}
}
long getSizeInBytes(Bitmap bitmap) {
if(bitmap==null)
return 0;
return bitmap.getRowBytes() * bitmap.getHeight();
}
}
創建上述三個分類後你只需要像這樣在imageview中加載圖像：
ImageLoader imageLoader = new ImageLoader(activity);
imageLoader.DisplayImage(bean.getPhotoURL(),holder.imgSelectedPhoto);
謝謝您的回答，我會得到它的眼睛儘快 – Matteo
加載和緩存圖像是一個低級別運行。一般來說，在應用程序中嵌入低級代碼是非常錯誤的。 –
你能提供一個「快速」（如0.1秒）的定量測量嗎？你可以很容易地做到這一點 -
Intent intent = new Intent(this, NewActivity.class);
intent.putExtra("BitmapImage", bitmap);
和檢索它 -
Intent intent = getIntent();
Bitmap bitmap = (Bitmap) intent.getParcelableExtra("BitmapImage");
正確。問題是我有大量的照片，轉換爲位圖是一個昂貴的過程..我應該嘗試轉換onClick，但這可能會失去我正在尋找的「速度」。 目前我的加載時間約爲2秒，我想呆在0.5 – Matteo
找到.noFade（）方法正是我所期待的，謝謝！ – Matteo