在上一篇專題Android開發之圖片處理專題(二):利用AsyncTask和回調接口實現圖片的異步加載和壓縮中我們實現了listView的圖片的大量加載。今天,我們換一種方式,採用線程池的方式來實現。
我們需要準備兩個東西:
1、圖片下載任務類
2、線程池。
1、圖片下載任務類。
/**
* @ClassName: AsyncImageTask
* @author victor_freedom ([email protected])
* @createddate 2015-2-1 下午10:58:52
* @Description: 圖片異步加載任務
*/
public class AsyncImageTask implements Runnable {
private final String TAG = "AsyncImageTask";
// 任務標識ID,其實就是圖片緩存路徑
private String taskId;
// 傳入需要設定的ImageView
private ImageView imageView;
// 圖片下載路徑
private String destUrl;
// 下載失敗顯示圖片的ID
private int failImage = -1;
// 默認圖片ID
private int defaultImage = -1;
// 壓縮比例
private int sampleSize = 1;
// 是否設置爲background
private boolean forBackground = false;
private boolean canceled = false;
// 消息管理器
private AsyncHandler handler = null;
// 動畫
private Animation animation = null;
public final static int OK = 1;
public final static int FAIL = 2;
public final static int EXSIT = 3;
private boolean forHome = false;
/**
* 構造函數
*
* @param imageView
* ImageView
* @param url
* 圖片地址
*/
public AsyncImageTask(ImageView imageView, String url) {
this(null, imageView, url);
}
/**
* 構造函數
*
* @param taskId
* 任務id
* @param imageView
* ImageView
* @param url
* 圖片地址
*/
public AsyncImageTask(String taskId, ImageView imageView, String url) {
if (null == taskId || taskId.trim().length() == 0) {
// 任務標識用圖片緩存地址來標識唯一
String tid = CacheName.getCachePath(imageView.getContext(), url);
this.taskId = tid;
} else {
this.taskId = taskId;
}
if (null != imageView) {
this.imageView = imageView;
this.imageView.setTag(this.taskId);
}
this.destUrl = url;
this.handler = new AsyncHandler();
}
/**
* taskId
*
* @return the taskId
*/
public String getTaskId() {
return taskId;
}
/**
* @param taskId
* the taskId to set
*/
public void setTaskId(String taskId) {
this.taskId = taskId;
}
/**
* forHome
*
* @return the forHome
*/
public boolean isForHome() {
return forHome;
}
/**
* @param forHome
* the forHome to set
*/
public void setForHome(boolean forHome) {
this.forHome = forHome;
}
/**
* defaultImage
*
* @return the defaultImage
*/
public int getDefaultImage() {
return defaultImage;
}
/**
* @param defaultImage
* the defaultImage to set
*/
public void setDefaultImage(int defaultImage) {
this.defaultImage = defaultImage;
}
/**
* 獲取下載失敗顯示的圖片資源id
*
* @return int
*/
public int getFailImage() {
return failImage;
}
/**
* 設置下載失敗後要顯示圖片資源id
*
* @param failImage
* R.drawable.xxx
*/
public void setFailImage(int failImage) {
this.failImage = failImage;
}
/**
* 獲取圖片的壓縮比例
*
* @return int
*/
public int getSampleSize() {
return sampleSize;
}
/**
* 設置圖片的採樣率
*
* @param sampleSize
* 最好爲2的指數倍
*/
public void setSampleSize(int sampleSize) {
if (sampleSize > 0) {
this.sampleSize = sampleSize;
}
}
/**
* 下載圖片後是否設置爲背景圖
*
* @return 是背景圖返回true,否則返回false
*/
public boolean isForBackground() {
return forBackground;
}
/**
* 設置是否顯示爲背景圖
*
* @param forBackground
* 默認爲false
*/
public void setForBackground(boolean forBackground) {
this.forBackground = forBackground;
}
/**
* canceled
*
* @return the canceled
*/
public boolean isCanceled() {
return canceled;
}
/**
* 取消當前任務
*
* @param canceled
* the canceled to set
*/
public void setCanceled(boolean canceled) {
this.canceled = canceled;
}
/**
* imageView
*
* @return the imageView
*/
public ImageView getImageView() {
return imageView;
}
/**
* @param imageView
* the imageView to set
*/
public void setImageView(ImageView imageView) {
this.imageView = imageView;
}
/**
* destUrl
*
* @return the destUrl
*/
public String getDestUrl() {
return destUrl;
}
/**
* @param destUrl
* the destUrl to set
*/
public void setDestUrl(String destUrl) {
this.destUrl = destUrl;
}
/**
* handler
*
* @return the handler
*/
public AsyncHandler getHandler() {
return handler;
}
/**
* @param handler
* the handler to set
*/
public void setHandler(AsyncHandler handler) {
this.handler = handler;
}
/**
* animation
*
* @return the animation
*/
public Animation getAnimation() {
return animation;
}
/**
* 設置圖片下載成功後的動畫效果
*
* @param animation
* the animation to set
*/
public void setAnimation(Animation animation) {
this.animation = animation;
}
@Override
public void run() {
// 拿到緩存地址
String destPath = CacheName.getCachePath(imageView.getContext(),
destUrl);
// 創建文件
File file = new File(destPath);
Message msg = handler.obtainMessage();
// 判斷該文件是否已經下載過
if (!file.exists()) {
// 如果沒有,則下載
if (download(destUrl, destPath + ".tmp")) {
// 創建臨時緩存文件
File temp = new File(destPath + ".tmp");
// 按照下載文件命名
temp.renameTo(file);
msg.what = OK;
msg.obj = destPath;
} else {
// 如果下載失敗,刪除臨時文件
msg.what = FAIL;
deleteTemp(destPath + ".tmp");
}
} else {
msg.what = EXSIT;
msg.obj = destPath;
}
if (!canceled) {
handler.sendMessage(msg);
} else {
// 如果中斷了下載,則清除臨時文件
deleteTemp(destPath + ".tmp");
}
}
private void deleteTemp(String path) {
File file = new File(path);
if (file.exists()) {
file.delete();
}
}
private boolean download(String imageUrl, String destPath) {
// 刪除同名臨時文件
deleteTemp(destPath);
boolean success = false;
URL url = null;
InputStream is = null;
OutputStream out = null;
HttpURLConnection conn = null;
// 下載 圖片
try {
url = new URL(imageUrl);
conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(20000);
conn.setReadTimeout(5 * 60 * 1000);
conn.setDoInput(true);
conn.setRequestProperty("Accept-Language", "zh-cn");
conn.setRequestProperty(
"User-Agent",
"Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.connect();
if (conn.getResponseCode() == 200) {
is = conn.getInputStream();
int read = 0;
byte[] buffer = new byte[1024];
// 拿到緩存路徑的輸入流
out = new FileOutputStream(destPath);
while ((read = is.read(buffer)) != -1) {
// 寫入數據
out.write(buffer, 0, read);
}
// 返回成功標識位
success = true;
} else {
Log.d(TAG, "the respond code is ---> " + conn.getResponseCode());
Log.d(TAG, "the url is:" + imageUrl);
}
} catch (MalformedURLException e) {
Log.d(TAG, "MalformedURLException ---> " + e.toString());
} catch (IOException e) {
Log.d(TAG, "IOException ---> " + e.toString());
} finally {
try {
if (out != null) {
out.flush();
out.close();
}
if (conn != null) {
conn.disconnect();
}
} catch (IOException e) {
Log.d(TAG, e.toString());
}
}
return success;
}// end download
/**
* @ClassName: AsyncHandler
* @author victor_freedom ([email protected])
* @createddate 2015-2-1 下午11:16:28
* @Description: 消息首發器
*/
final class AsyncHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case FAIL:
doFail(msg);
break;
default:
if (forHome) {
imageView.setScaleType(ScaleType.FIT_XY);
}
doSuccess(msg);
break;
}
}
/**
* @Title: doFail
* @Description: 下載失敗後,設定指定的失敗圖片
* @param msg
* @throws
*/
private void doFail(Message msg) {
if (forBackground && failImage != -1) {
imageView.setBackgroundResource(failImage);
} else if (!forBackground && failImage != -1) {
imageView.setImageResource(failImage);
}
}
/**
* @Title: doSuccess
* @Description: 下載成功後,顯示
* @param msg
* @throws
*/
private void doSuccess(Message msg) {
//拿到路徑
String path = (String) msg.obj;
//壓縮存放圖片
BitmapManager.getInstance().putBitmap(path, sampleSize);
//拿到圖片
Bitmap bitmap = BitmapManager.getInstance().getBitmap(path);
String tag = (String) imageView.getTag();
//圖片設定
if ((null != bitmap) && tag == null || tag.equals(taskId)) {
if (forBackground) {
imageView.setBackgroundDrawable(new BitmapDrawable(bitmap));
} else if (!forBackground) {
imageView.setImageBitmap(bitmap);
}
//是否執行動畫
if (msg.what == OK && null != animation) {
imageView.setAnimation(animation);
animation.start();
}
}
}
}// end AsyncHandler
}
2、線程池創建
/**
* @ClassName: TaskQueue
* @author victor_freedom ([email protected])
* @createddate 2015-2-1 下午11:31:19
* @Description: 圖片異步任務管理器
*/
public final class TaskQueue {
private final static String TAG = "TaskQueue";
private static TaskQueue taskQueue = null;
private static ThreadPoolExecutor threadPool = null;// 線程池
private final static int CORE_SIZE = 2; // 最小工作線程數量
private final static int MAX_SIZE = 3; // 最大共作線程數量
private final static int QUEUE_SIZE = 20; // 線程緩衝隊列容量
private final static long ALIVE_TIME = 10; // 某線程允許的最大空閒時長
private final static TimeUnit T_Unit = TimeUnit.SECONDS; // 空閒時長單位:秒
private static BlockingQueue<Runnable> queue = null; // 線程緩衝隊列
private static RejectedExecutionHandler rejectedHandler = new DiscardOldestPolicy(); // 線程池拒絕策略,當緩衝隊列滿時,工作隊列頭部的任務將被刪除
//新建任務隊列及線程池
private TaskQueue() {
queue = new LinkedBlockingQueue<Runnable>(QUEUE_SIZE);
threadPool = new ThreadPoolExecutor(CORE_SIZE, MAX_SIZE, ALIVE_TIME,
T_Unit, queue, rejectedHandler);
}
/**
* 採用單例設計
*
* @return TaskQueue
*/
public static TaskQueue getInstance() {
if (null == taskQueue) {
taskQueue = new TaskQueue();
}
return taskQueue;
}
/**
* 添加一個任務
*
* @param task
* AsyncImageTask
*/
public void addTask(AsyncImageTask task) {
//檢查本地是否已經存在緩存文件
if (!hadLocal(task)) {
boolean had = false;
//判斷任務隊列裏面是否已經存在該任務
for (int i = 0; i < queue.size(); i++) {
AsyncImageTask t = (AsyncImageTask) queue.element();
if (task.getTaskId().equals(t.getTaskId())) {
had = true;
Log.d(TAG, "the task id is:" + t.getTaskId());
break;
}
}
if (!had) {
//如果不存在,加入執行隊列
if (task.getDefaultImage() != -1) {
if (!task.isForBackground()) {
task.getImageView().setImageResource(
task.getDefaultImage());
} else {
task.getImageView().setBackgroundResource(
task.getDefaultImage());
}
}
threadPool.execute(task);
} else {
//如果已經存在,則不做修改。等待執行
if (task.getDefaultImage() != -1) {
if (!task.isForBackground()) {
task.getImageView().setImageResource(
task.getDefaultImage());
} else {
task.getImageView().setBackgroundResource(
task.getDefaultImage());
}
}
}
} else {
//如果有緩存,則直接拿本地的圖片來用
String destPath = CacheName.getCachePath(task.getImageView()
.getContext(), task.getDestUrl());
Message msg = new Message();
msg.what = AsyncImageTask.EXSIT;
msg.obj = destPath;
task.getHandler().sendMessage(msg);
}
}
/**
* 檢查本地是否已經存在緩存文件
*
* @param task
* @return 存在返回true,否則返回false
*/
private boolean hadLocal(AsyncImageTask task) {
String destPath = CacheName.getCachePath(task.getImageView()
.getContext(), task.getDestUrl());
File file = new File(destPath);
if (file.exists()) {
if (ImageCheck.isAvailable(destPath)) {
file.setLastModified(System.currentTimeMillis());
return true;
} else {
file.delete();
}
}
return false;
}
/**
* 關閉所有工作線程
*/
public void shutDown() {
threadPool.shutdown();
taskQueue = null;
queue = null;
}
}
3、adapter編寫
//拿到路徑
String url = Constant.PIC_BASE_URL + news.PicUrl;
//創建任務
AsyncImageTask task = new AsyncImageTask(holder.iv, url);
//設定默認圖片和下載失敗圖片
task.setDefaultImage(R.drawable.news_image_default);
task.setFailImage(R.drawable.news_image_default);
//加入到任務隊列中執行
TaskQueue.getInstance().addTask(task);