我正在尝试使用ViewPager创建一个Image Slider。 会有图像url数组。我想下载这些图像并将其显示在ViewPager中。 我已经通过一些链接，但找不到适合我的问题的解决方案。 谁能帮我？ 提前谢谢。
答案 0 :(得分：0)
package com.app.cr.cache;
import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;
import java.util.WeakHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
import android.app.Activity;
import android.content.ContentUris;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.net.Uri;
import android.os.Handler;
import android.os.ParcelFileDescriptor;
import android.util.SparseArray;
import android.util.SparseIntArray;
import com.app.cr.R;
import com.app.cr.ui.ImageViewProgress;
import com.app.cr.utility.Utility;
public class ImageLoader {
public MemoryCache memoryCache = new MemoryCache();
public FileCache fileCache;
private Map<ImageViewProgress, String> imageViews = Collections
.synchronizedMap(new WeakHashMap<ImageViewProgress, String>());
ExecutorService executorService;
Handler handler = new Handler();
private Activity context;
static final int default_image = R.drawable.transparent;
static final int[] color = new int[] { R.color.first, R.color.second,
R.color.third, R.color.fourth, R.color.fifth, R.color.six,
R.color.seven, R.color.eight };
SparseArray<Bitmap> sparseArrayBitmap = new SparseArray<>();
SparseIntArray sparseArrayInt = new SparseIntArray();
private AtomicBoolean paused = new AtomicBoolean(false);
private Object pauseLock = new Object();
public ImageLoader(Activity context) {
this.context = context;
fileCache = new FileCache(context);
executorService = Executors.newFixedThreadPool(3);
}
public void displayImageResource(int resourceId, ImageViewProgress imageView) {
imageView.setImageResource(resourceId);
imageView.showImage(true);
}
public void displayImageUri(Uri uri, ImageViewProgress imageView) {
if (uri == null) {
imageView.setImageResource(R.drawable.ic_people);
imageView.showImage(true);
return;
}
imageView.setImageUri(uri);
imageView.showImage(true);
}
public void displayImage(String url, ImageViewProgress imageView) {
if (url == null || url.length() == 0) {
Utility.log("ImageLoader", "url length zero");
if (imageView != null) {
imageView.showImage(false);
}
return;
}
imageViews.put(imageView, url);
Bitmap bitmap = memoryCache.get(url);
if (bitmap != null) {
imageView.setImageBitmap(bitmap);
} else {
if (sparseArrayInt.get(url.hashCode()) != 0) {
Bitmap b = sparseArrayBitmap.get(sparseArrayInt.get(url
.hashCode()));
if (b != null) {
imageView.setImageBitmap(b);
return;
}
}
queuePhoto(url, imageView);
imageView.setImageResource(default_image);
imageView.showImage(false);
}
}
private void queuePhoto(String url, ImageViewProgress imageView) {
PhotoToLoad p = new PhotoToLoad(url, imageView);
executorService.submit(new PhotosLoader(p));
}
// Task for the queue
private class PhotoToLoad {
public String url;
public ImageViewProgress imageView;
public PhotoToLoad(String u, ImageViewProgress i) {
url = u;
imageView = i;
}
}
class PhotosLoader implements Runnable {
PhotoToLoad photoToLoad;
PhotosLoader(PhotoToLoad photoToLoad) {
this.photoToLoad = photoToLoad;
}
@Override
public void run() {
if (waitIfPaused())
return;
try {
if (imageViewReused(photoToLoad))
return;
Bitmap bmp = getBitmap(photoToLoad.url);
if (imageViewReused(photoToLoad))
return;
BitmapDisplayer bd = new BitmapDisplayer(bmp, photoToLoad);
handler.post(bd);
} catch (Throwable th) {
th.printStackTrace();
}
}
}
private boolean waitIfPaused() {
AtomicBoolean pause = getPaused();
if (pause.get()) {
synchronized (getPauseLock()) {
if (pause.get()) {
try {
getPauseLock().wait();
} catch (InterruptedException e) {
return true;
}
}
}
}
return false;
}
public Bitmap getBitmap(String url) {
File f = FileCache.getFile(url);
Bitmap b = decodeFile(f, false);
if (b != null) {
memoryCache.put(url, b);
return b;
} else {
return getColourBitmap(url);
}
}
int lastColorId = 0;
private int getRandomColor() {
int colorId = color[new Random().nextInt(color.length)];
if (lastColorId == colorId) {
colorId = getRandomColor();
}
lastColorId = colorId;
return colorId;
}
private Bitmap getColourBitmap(String url) {
int colorId = getRandomColor();
sparseArrayInt.put(url.hashCode(), colorId);
Bitmap bitmap = sparseArrayBitmap.get(colorId);
if (bitmap == null) {
sparseArrayBitmap.put(colorId, makeColorFillBitmap(colorId));
bitmap = sparseArrayBitmap.get(colorId);
}
Utility.log("color :" + colorId, " hash : " + url.hashCode());
if (bitmap == null) {
return makeColorFillBitmap(colorId);
} else {
return bitmap;
}
}
private Bitmap makeColorFillBitmap(int color) {
int width = 150;
int height = 150;
Bitmap outBitmap = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(outBitmap);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(context.getResources().getColor(color));
canvas.drawRect(0, 0, width, height, paint);
return outBitmap;
}
public static Bitmap decodeFile(File f, boolean useForFileCheck) {
if (f == null || !f.exists()) {
return null;
}
try {
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
FileInputStream stream1 = new FileInputStream(f);
BitmapFactory.decodeStream(stream1, null, o);
stream1.close();
final int REQUIRED_SIZE = 160;
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;
}
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) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
boolean imageViewReused(PhotoToLoad photoToLoad) {
String tag = imageViews.get(photoToLoad.imageView);
if (tag == null || !tag.equals(photoToLoad.url))
return true;
return false;
}
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(default_image);
}
}
public void clearCache() {
if (imageViews != null) {
imageViews.clear();
}
Map<String, Bitmap> cache = memoryCache.getCache();
Iterator<Entry<String, Bitmap>> entries = cache.entrySet().iterator();
while (entries.hasNext()) {
Entry<String, Bitmap> thisEntry = (Entry<String, Bitmap>) entries
.next();
Bitmap value = (Bitmap) thisEntry.getValue();
if (value != null) {
value.recycle();
value = null;
}
entries.remove();
}
memoryCache.clear();
// fileCache.clear();
if (sparseArrayBitmap != null) {
sparseArrayBitmap.clear();
}
if (sparseArrayInt != null) {
sparseArrayInt.clear();
}
Utility.log("===Memory Cache===", "All Cleared.");
}
public static boolean getAlbumart(File f, Long album_id, Activity activity) {
try {
if (bitmap != null) {
bitmap.recycle();
bitmap = null;
}
final Uri sArtworkUri = Uri
.parse("content://media/external/audio/albumart");
Uri uri = ContentUris.withAppendedId(sArtworkUri, album_id);
ParcelFileDescriptor pfd = activity.getContentResolver()
.openFileDescriptor(uri, "r");
if (pfd != null) {
FileDescriptor fd = pfd.getFileDescriptor();
copyFdToFile(fd, f);
}
if (f != null && f.exists()) {
if (bitmap.isRecycled()) {
bitmap = decodeFile(f, false);
FileOutputStream outputStream = null;
try {
outputStream = new FileOutputStream(f);
bitmap.compress(Bitmap.CompressFormat.JPEG, 100,
outputStream);
} catch (Exception e) {
} finally {
if (outputStream != null) {
outputStream.flush();
outputStream.close();
}
}
}
}
} catch (Exception e) {
return false;
}
return true;
}
private static Bitmap bitmap = null;
public static void copyFdToFile(FileDescriptor src, File dst)
throws IOException {
FileChannel inChannel = new FileInputStream(src).getChannel();
FileChannel outChannel = new FileOutputStream(dst).getChannel();
try {
inChannel.transferTo(0, inChannel.size(), outChannel);
} finally {
if (inChannel != null)
inChannel.close();
if (outChannel != null)
outChannel.close();
}
}
public void onPaused() {
paused.set(true);
}
public void onResumed() {
paused.set(false);
synchronized (pauseLock) {
pauseLock.notifyAll();
}
}
public AtomicBoolean getPaused() {
return paused;
}
public void setPaused(AtomicBoolean paused) {
this.paused = paused;
}
public Object getPauseLock() {
return pauseLock;
}
public void setPauseLock(Object pauseLock) {
this.pauseLock = pauseLock;
}
}
package com.app.cr.cache;
import java.io.File;
import android.content.Context;
public class FileCache {
public static File cacheDir;
public FileCache(Context context) {
if (android.os.Environment.getExternalStorageState().equals(
android.os.Environment.MEDIA_MOUNTED)) {
cacheDir = new File(
android.os.Environment.getExternalStorageDirectory(),
"Player");
} else {
cacheDir = context.getCacheDir();
}
if (!cacheDir.exists()) {
cacheDir.mkdirs();
}
}
public static File getFile(String url) {
String filename = String.valueOf(url.hashCode());
File f = new File(cacheDir, filename);
return f;
}
public static File getFileAbsoluteFileName(String url) {
File f = new File(cacheDir, url);
return f;
}
public void clear() {
File[] files = cacheDir.listFiles();
if (files == null)
return;
for (File f : files)
f.delete();
}
}
package com.app.cr.cache;
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.LruCache;
import com.app.cr.utility.Utility;
public class MemoryCache {
private static final String TAG = "MemoryCache.java";
private Map<String, Bitmap> cache = Collections
.synchronizedMap(new LinkedHashMap<String, Bitmap>(10, 1.5f, true));
private LruCache<String, Bitmap> lruCache = null;
private long size = 0;
private long limit = 1000000;
public MemoryCache() {
setLimit(Runtime.getRuntime().maxMemory() / 8);
lruCache = new LruCache<String, Bitmap>((int) Runtime.getRuntime()
.maxMemory() / 8) {
@Override
protected int sizeOf(String key, Bitmap value) {
return getBitmapSize(value);
}
};
}
public Map<String, Bitmap> getCache() {
return cache;
}
public void setLimit(long new_limit) {
limit = new_limit;
Utility.log(TAG, "MemoryCache will use up to " + limit / 1024. / 1024.
+ "MB");
}
public synchronized Bitmap get(String id) {
if (lruCache != null) {
final Bitmap memBitmap = lruCache.get(id);
if (memBitmap != null) {
return memBitmap;
}
}
try {
if (!cache.containsKey(id))
return null;
return cache.get(id);
} catch (NullPointerException ex) {
ex.printStackTrace();
return null;
}
}
public synchronized void put(String id, Bitmap bitmap) {
if (id == null || bitmap == null) {
return;
}
// Add to memory cache
if (lruCache != null && lruCache.get(id) == null) {
lruCache.put(id, bitmap);
return;
}
try {
if (cache.containsKey(id))
size -= getSizeInBytes(cache.get(id));
cache.put(id, bitmap);
size += getSizeInBytes(bitmap);
checkSize();
} catch (Throwable th) {
th.printStackTrace();
}
}
public static int getBitmapSize(Bitmap bitmap) {
return bitmap.getRowBytes() * bitmap.getHeight();
}
private synchronized void checkSize() {
// Utility.log(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;
}
// Utility.log(TAG, "Clean cache. New size " + cache.size());
}
}
public void clear() {
try {
if (lruCache != null)
lruCache.evictAll();
cache.clear();
size = 0;
} catch (NullPointerException ex) {
ex.printStackTrace();
}
}
long getSizeInBytes(Bitmap bitmap) {
if (bitmap == null)
return 0;
return bitmap.getRowBytes() * bitmap.getHeight();
}
}