Androidとmysqlを使用してフォトアルバムを作成しています。写真は、リモート サーバー上のフォルダーに保存されます。ローカル データベースにはフィールドが含まれており imgUri、このフィールドはイメージ パスを表します。
これらの写真を Android アプリに取り込む最も簡単な方法について説明してもらえますか (カルーセルを使用しています)。
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2 に答える
1
ImageViews を実際にローカル データベースにある Image Sources にバインドする方法のみを探していると思います
以下のクラスをそのまま作成します。これにより、URL から画像が取得され、ImageView にバインドされます。
同じ問題に対処しているときに、ネット上のどこかからこのクラスを取得しました
/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.AZone.egba;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.methods.HttpGet;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.net.http.AndroidHttpClient;
import android.os.AsyncTask;
import android.os.Handler;
import android.util.Log;
import android.widget.ImageView;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.concurrent.ConcurrentHashMap;
// From the XMLAdapters sample code. Really helpful.
/**
* This helper class download images from the Internet and binds those with the
* provided ImageView.
* <p>
* It requires the INTERNET permission, which should be added to your
* application's manifest file.
* </p>
* A local cache of downloaded images is maintained internally to improve
* performance.
*/
public class ImageDownloader {
private static final String LOG_TAG = "ImageDownloader";
private static final int HARD_CACHE_CAPACITY = 40;
private static final int DELAY_BEFORE_PURGE = 30 * 1000; // in milliseconds
// Hard cache, with a fixed maximum capacity and a life duration
private final HashMap<String, Bitmap> mHardBitmapCache = new LinkedHashMap<String, Bitmap>(
HARD_CACHE_CAPACITY / 2, 0.75f, true) {
private static final long serialVersionUID = 1L;
@Override
protected boolean removeEldestEntry(LinkedHashMap.Entry<String, Bitmap> eldest) {
if (size() > HARD_CACHE_CAPACITY) {
// Entries push-out of hard reference cache are transferred to
// soft reference cache
sSoftBitmapCache.put(eldest.getKey(), new SoftReference<Bitmap>(eldest.getValue()));
return true;
} else
return false;
}
};
// Soft cache for bitmap kicked out of hard cache
private final static ConcurrentHashMap<String, SoftReference<Bitmap>> sSoftBitmapCache =
new ConcurrentHashMap<String, SoftReference<Bitmap>>(HARD_CACHE_CAPACITY / 2);
private final Handler purgeHandler = new Handler();
private final Runnable purger = new Runnable() {
public void run() {
clearCache();
}
};
/**
* Download the specified image from the Internet and binds it to the
* provided ImageView. The binding is immediate if the image is found in the
* cache and will be done asynchronously otherwise. A null bitmap will be
* associated to the ImageView if an error occurs.
*
* @param url The URL of the image to download.
* @param imageView The ImageView to bind the downloaded image to.
*/
public void download(String url, ImageView imageView) {
download(url, imageView, null);
}
/**
* Same as {@link #download(String, ImageView)}, with the possibility to
* provide an additional cookie that will be used when the image will be
* retrieved.
*
* @param url The URL of the image to download.
* @param imageView The ImageView to bind the downloaded image to.
* @param cookie A cookie String that will be used by the http connection.
*/
public void download(String url, ImageView imageView, String cookie) {
resetPurgeTimer();
Bitmap bitmap = getBitmapFromCache(url);
if (bitmap == null) {
forceDownload(url, imageView, cookie);
} else {
cancelPotentialDownload(url, imageView);
imageView.setImageBitmap(bitmap);
}
}
/*
* Same as download but the image is always downloaded and the cache is not
* used. Kept private at the moment as its interest is not clear. private
* void forceDownload(String url, ImageView view) { forceDownload(url, view,
* null); }
*/
/**
* Same as download but the image is always downloaded and the cache is not
* used. Kept private at the moment as its interest is not clear.
*/
private void forceDownload(String url, ImageView imageView, String cookie) {
// State sanity: url is guaranteed to never be null in
// DownloadedDrawable and cache keys.
if (url == null) {
imageView.setImageDrawable(null);
return;
}
if (cancelPotentialDownload(url, imageView)) {
BitmapDownloaderTask task = new BitmapDownloaderTask(imageView);
DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task);
imageView.setImageDrawable(downloadedDrawable);
task.execute(url, cookie);
}
}
/**
* Clears the image cache used internally to improve performance. Note that
* for memory efficiency reasons, the cache will automatically be cleared
* after a certain inactivity delay.
*/
public void clearCache() {
mHardBitmapCache.clear();
sSoftBitmapCache.clear();
}
private void resetPurgeTimer() {
purgeHandler.removeCallbacks(purger);
purgeHandler.postDelayed(purger, DELAY_BEFORE_PURGE);
}
/**
* Returns true if the current download has been canceled or if there was no
* download in progress on this image view. Returns false if the download in
* progress deals with the same url. The download is not stopped in that
* case.
*/
private static boolean cancelPotentialDownload(String url, ImageView imageView) {
BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView);
if (bitmapDownloaderTask != null) {
String bitmapUrl = bitmapDownloaderTask.url;
if ((bitmapUrl == null) || (!bitmapUrl.equals(url))) {
bitmapDownloaderTask.cancel(true);
} else {
// The same URL is already being downloaded.
return false;
}
}
return true;
}
/**
* @param imageView Any imageView
* @return Retrieve the currently active download task (if any) associated
* with this imageView. null if there is no such task.
*/
private static BitmapDownloaderTask getBitmapDownloaderTask(ImageView imageView) {
if (imageView != null) {
Drawable drawable = imageView.getDrawable();
if (drawable instanceof DownloadedDrawable) {
DownloadedDrawable downloadedDrawable = (DownloadedDrawable) drawable;
return downloadedDrawable.getBitmapDownloaderTask();
}
}
return null;
}
/**
* @param url The URL of the image that will be retrieved from the cache.
* @return The cached bitmap or null if it was not found.
*/
private Bitmap getBitmapFromCache(String url) {
// First try the hard reference cache
synchronized (mHardBitmapCache) {
final Bitmap bitmap = mHardBitmapCache.get(url);
if (bitmap != null) {
// Bitmap found in hard cache
// Move element to first position, so that it is removed last
mHardBitmapCache.remove(url);
mHardBitmapCache.put(url, bitmap);
return bitmap;
}
}
// Then try the soft reference cache
SoftReference<Bitmap> bitmapReference = sSoftBitmapCache.get(url);
if (bitmapReference != null) {
final Bitmap bitmap = bitmapReference.get();
if (bitmap != null) {
// Bitmap found in soft cache
return bitmap;
} else {
// Soft reference has been Garbage Collected
sSoftBitmapCache.remove(url);
}
}
return null;
}
/**
* The actual AsyncTask that will asynchronously download the image.
*/
class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> {
private static final int IO_BUFFER_SIZE = 4 * 1024;
private String url;
private final WeakReference<ImageView> imageViewReference;
public BitmapDownloaderTask(ImageView imageView) {
imageViewReference = new WeakReference<ImageView>(imageView);
}
/**
* Actual download method.
*/
@Override
protected Bitmap doInBackground(String... params) {
final AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
url = params[0];
final HttpGet getRequest = new HttpGet(url);
String cookie = params[1];
if (cookie != null) {
getRequest.setHeader("cookie", cookie);
}
try {
HttpResponse response = client.execute(getRequest);
final int statusCode = response.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
Log.w("ImageDownloader", "Error " + statusCode +
" while retrieving bitmap from " + url);
return null;
}
final HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream inputStream = null;
OutputStream outputStream = null;
try {
inputStream = entity.getContent();
final ByteArrayOutputStream dataStream = new ByteArrayOutputStream();
outputStream = new BufferedOutputStream(dataStream, IO_BUFFER_SIZE);
copy(inputStream, outputStream);
outputStream.flush();
final byte[] data = dataStream.toByteArray();
final Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
// FIXME : Should use NOTE FIXME was in the orriginal
// file.
// BitmapFactory.decodeStream(inputStream) instead.
// final Bitmap bitmap =
// BitmapFactory.decodeStream(inputStream);
return bitmap;
} finally {
if (inputStream != null) {
inputStream.close();
}
if (outputStream != null) {
outputStream.close();
}
entity.consumeContent();
}
}
} catch (IOException e) {
getRequest.abort();
Log.w(LOG_TAG, "I/O error while retrieving bitmap from " + url, e);
} catch (IllegalStateException e) {
getRequest.abort();
Log.w(LOG_TAG, "Incorrect URL: " + url);
} catch (Exception e) {
getRequest.abort();
Log.w(LOG_TAG, "Error while retrieving bitmap from " + url, e);
} finally {
if (client != null) {
client.close();
}
}
return null;
}
/**
* Once the image is downloaded, associates it to the imageView
*/
@Override
protected void onPostExecute(Bitmap bitmap) {
if (isCancelled()) {
bitmap = null;
}
// Add bitmap to cache
if (bitmap != null) {
synchronized (mHardBitmapCache) {
mHardBitmapCache.put(url, bitmap);
}
}
if (imageViewReference != null) {
ImageView imageView = imageViewReference.get();
BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView);
// Change bitmap only if this process is still associated with
// it
if (this == bitmapDownloaderTask) {
imageView.setImageBitmap(bitmap);
}
}
}
public void copy(InputStream in, OutputStream out) throws IOException {
byte[] b = new byte[IO_BUFFER_SIZE];
int read;
while ((read = in.read(b)) != -1) {
out.write(b, 0, read);
}
}
}
/**
* A fake Drawable that will be attached to the imageView while the download
* is in progress.
* <p>
* Contains a reference to the actual download task, so that a download task
* can be stopped if a new binding is required, and makes sure that only the
* last started download process can bind its result, independently of the
* download finish order.
* </p>
*/
static class DownloadedDrawable extends ColorDrawable {
private final WeakReference<BitmapDownloaderTask> bitmapDownloaderTaskReference;
public DownloadedDrawable(BitmapDownloaderTask bitmapDownloaderTask) {
super(Color.BLACK);
bitmapDownloaderTaskReference =
new WeakReference<BitmapDownloaderTask>(bitmapDownloaderTask);
}
public BitmapDownloaderTask getBitmapDownloaderTask() {
return bitmapDownloaderTaskReference.get();
}
}
}
これが完了したら、このようなアクティビティからこのクラスにアクセスする必要があります
private ImageDownloader mDownload = null; // before onCreate Statement
mDownload = new ImageDownloader(); //where you want to bind the images to image views
mDownload.download(ImageURL, mImageView);
ImageURLデータベースから http 形式で取得する画像の URL
mImageViewは、画像ビュー コントロールです。
出力 は、レイアウトで画像ビューを配置した方法のようになります
于 2013-04-08T10:54:28.137 に答える