我正在使用 android 和 mysql 创建一个相册。照片存储在远程服务器上的文件夹中。本地数据库包含一个字段 imgUri，该字段代表图像路径。
有人可以向我描述将这些照片放入我的 android 应用程序（我正在使用轮播）的最简单方法吗？
问问题
501 次
2 回答
1
我认为您只是在寻找如何将 ImageViews 绑定到实际位于本地数据库中的图像源
照原样创建下面的类，它将从 URL 中获取图像并将其绑定到您的 ImageViews
当我处理同样的问题时，我从网上的某个地方得到了这门课
/*
* 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();
}
}
}
完成此操作后，您必须像这样从您的活动中访问此类
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是您将以 http 形式从数据库中获取的图像 url
mImageView是您的图像视图控件...
输出 看起来就像您在布局中排列图像视图的方式
于 2013-04-08T10:54:28.137 回答
0
您将需要一个 Web 服务，可以是表示图像 URL 的 XML 或 JSON，其余的将由普通流处理。希望我明白你在问什么:)
于 2013-04-08T10:43:53.563 回答