AsyncTask类启动了许多其他线程,因为我使用的是第三方库.我不确定该库打开了多少个线程,但是我想等待它们全部完成,然后使用它们获取的数据填充我的列表视图.
目前我正在睡觉10000毫秒,但这不切实际,因为我不知道它有多大.
这个问题的正确解决方案是什么？
task = new mTask();
task.execute(appsList);
new Thread(new Runnable() {
public void run() {
populateList();
}
}).start();
}
private class mTask extends AsyncTask<List<ApplicationInfo>,Void,Void> {
ProgressDialog progress;
@Override
protected void onPreExecute() {
progress = new ProgressDialog(MainActivity.this);
progress.setIndeterminate(true);
progress.show();
super.onPreExecute();
}
@SuppressWarnings("deprecation")
@Override
protected Void doInBackground(List<ApplicationInfo>... params) {
appDataManager = new AppDataManager(MainActivity.this,MysqLiteAdapter,MainActivity.this);
appDataManager.work(params[0]);
return null;
}
@Override
protected void onPostExecute(Void result) {
MysqLiteAdapter.close();
progress.dismiss();
super.onPostExecute(result);
}
}
@SuppressWarnings("deprecation")
public void populateList() {
try {
Thread.sleep(10000)
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
runOnUiThread(new Runnable() {
public void run() {
Cursor cursor;
MysqLiteAdapter.openToRead();
cursor = MysqLiteAdapter.queueAll();
ArrayList<String> appsList = new ArrayList<String>();
if (cursor.moveToFirst()) {
do {
appsList.add(cursor.getString(1));
} while (cursor.moveToNext());
}
cursor.moveToFirst();
ArrayAdapter<String> adp = new ArrayAdapter<String>(
MainActivity.this,android.R.layout.simple_list_item_1,appsList);
listContent.setAdapter(adp);
cursor.close();
MysqLiteAdapter.close();
Log.i("finished","finished");
}
});
}
AppDataManager
public void work(List<ApplicationInfo> appsList) {
List<ApplicationInfo> appList = appsList;
MysqLiteAdapter.openToWrite();
MysqLiteAdapter.deleteAll();
MysqLiteAdapter.close();
for (int i = 0; i < 5; i++) {
String name = appList.get(i).name;
String pack = appList.get(i).packageName;
// TODO AsyncTask
getHtml(pack,name);
}
}
public void getHtml(final String pack,final String name) {
String url = MARKET_URL + pack;
//AndroidQuery library. fetch html
aq.ajax(url,String.class,1000,new AjaxCallback<String>() {
@Override
public void callback(String url,String htm,AjaxStatus status) {
Log.i("status",status.getMessage());
parseHtml(htm,pack,name);
}
});
}
解决方法
首先,我将把populateList的调用移动到AsyncTask的onPostExecute方法中.我还会重写populateList以删除睡眠并假设它在UI线程上运行(消除runOnUiThread调用并将run方法的主体直接移动到populateList中).
现在,为了防止AsyncTask完成doInBackground,直到AppDataManager完成其工作.首先定义一个完成标志和一个可以同步的锁定对象：
private class mTask extends AsyncTask<List<ApplicationInfo>,Void> {
boolean complete;
static Object LOCK = new Object();
. . .
}
然后修改AppDataManager类,以在完成工作时提供对另一个对象的回调.定义字段回调并更新api和方法：
public void work(List<ApplicationInfo> appsList,Runnable callback) {
this.callback = callback; // define a field named "callback"
List<ApplicationInfo> appList = appsList;
MysqLiteAdapter.openToWrite();
MysqLiteAdapter.deleteAll();
MysqLiteAdapter.close();
for (int i = 0; i < 5; i++) {
String name = appList.get(i).name;
String pack = appList.get(i).packageName;
// TODO AsyncTask
getHtml(pack,name);
if (callback != null) {
callback.run();
}
}
});
}
protected Void doInBackground(List<ApplicationInfo>... params) {
appDataManager = new AppDataManager(MainActivity.this,MainActivity.this);
appDataManager.work(params[0],new Runnable() {
public void run() {
synchronized (LOCK) {
complete = true;
LOCK.notifyAll();
}
}
});
// wait for appDataManager.work() to finish...
synchronized (LOCK) {
while (!complete) {
LOCK.wait();
}
}
return null;
}
这应该做的工作.但是,您可能应该详细说明这一点以处理各种错误(例如,为AppDataManager提供错误通知机制).
更新我终于注意到你在AppDataManager中做了五个网络事务.因此,不是在ajax()的回调方法中立即运行回调,而是递减计数器,并且只有在计数器达到0时才回调.在进入调用getHtml()的循环之前,在work()中将计数器初始化为5.由于计数器将由单独的线程修改,因此需要同步对它的访问. (或者,您可以使用AtomicInteger作为计数器.
