我有一个android应用程序（用java编写），它有两个按钮（连接和请求数据）。
单击每个按钮后，将执行一项任务，并显示进度对话框，以显示任务完成的程度。
为了显示进度对话框，单击每个按钮时，任务将在线程上运行。
connect按钮只有一个任务-在线程上运行。但是，请求数据按钮执行两个任务-线程上的第一个任务类似于连接按钮，但还有第二个任务refreshInfo（），该任务必须在线程上的progThread第一个任务完成后运行。
private Button connectButton;
private Button requestDataButton;
private ProgressDialog connectionDialog;
private ProgressDialog requestDataDialog;
private ProgressThread progThread;
private int currentDialog;
public void connectClick(View view) //When the connect button is clicked
{
performAction(1); //Run the thread to perform the action
}
public void requestDownloadClick(View view) //When the request data button is clicked
{
performAction(2); //Run the thread to perform the action
refreshInfo(); //Do something else
}
private void performAction(int type)
{
currentDialog = type;
showDialog(type);
try
{
progThread.join();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
这里的关键方法是执行操作（int类型）。我基本上不希望这个方法在progThread完成运行之前完成。
正如你所看到的，我已经尝试了progThread.join（）来阻止该方法继续运行，直到progThread完成运行，但是由于progThread及显示进度对话框，运行Progress.join，当前，当您单击该按钮时，第一个任务正在执行，但对话框只在最后闪烁。
有人能想出一种运行线程的方法吗？正常显示Progress Dialog，然后运行第二个方法（如果有）。
我已经包含了下面的线程代码，以备不时之需。
private class ProgressThread extends Thread
{
final static int DONE = 0;
final static int RUNNING = 1; // Class constants defining state of the thread
private Handler progressHandler;
int mState;
int total;
ProgressThread(Handler _handler) // Constructor with an argument that specifies Handler on main thread to which messages will be sent by this thread.
{
progressHandler = _handler;
}
public void run() // Invoked automatically when the Thread starts.
{
mState = RUNNING;
updateProgressBar();
connectButton = (Button) findViewById(R.id.btnConnect);
requestDataButton = (Button) findViewById(R.id.btnRequestDownload);
while (mState == RUNNING)
{
if (currentDialog == 1)
{
try
{
doSomething();
if (something)
{
setState(DONE);
total = 100;
updateProgressBar();
removeDialog(1);
connectButton.setEnabled(false);
}
else
{
total = total + 20;
if (something has reached a limit)
{
setState(DONE);
total = 0;
updateProgressBar();
removeDialog(1);
}
}
updateProgressBar();
}
catch (Exception e)
{
}
}
if (currentDialog == 2)
{
try
{
doSomething();
total = 10;
updateProgressBar();
doSomething();
total = 70;
updateProgressBar();
if (something) //If the download info has not been got
{
setState(DONE);
total = 0;
updateProgressBar();
removeDialog(2);
runOnUiThread(new Runnable()
{
public void run()
{
connectButton.setEnabled(true);
requestDataButton.setEnabled(true);
}
});
}
else
{
total = 100;
updateProgressBar();
setState(DONE);
removeDialog(2);
runOnUiThread(new Runnable()
{
public void run()
{
requestDataButton.setEnabled(false);
}
});
}
}
catch (Exception e)
{
removeDialog(2);
setState(DONE);
runOnUiThread(new Runnable()
{
public void run()
{
connectButton.setEnabled(true);
requestDataButton.setEnabled(true);
}
});
}
}
}
}
// Set current state of thread (use state=ProgressThread.DONE to stop thread)
public void setState(int state)
{
mState = state;
}
public void updateProgressBar()
{
Message msg = progressHandler.obtainMessage(); // Send message (with current value of total as data) to Handler on UI thread so that it can update the progress bar
Bundle b = new Bundle();
b.putInt("total", total);
msg.setData(b);
progressHandler.sendMessage(msg);
}
}
final Handler handler = new Handler() // Handler on the main (UI) thread that will receive messages from the second thread and update the progress.
{
public void handleMessage(Message msg)
{
int total = msg.getData().getInt("total"); // Get the current value of the variable total from the message data and update the progress bar
switch (currentDialog)
{
case 1 :
connectionDialog.setProgress(total);
break;
case 2 :
requestDataDialog.setProgress(total);
break;
}
}
};
protected Dialog onCreateDialog(int id)
{
switch (currentDialog)
{
case 1 :
connectionDialog = new ProgressDialog(this);
connectionDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
connectionDialog.setMax(100);
connectionDialog.setProgress(0);
connectionDialog.setMessage("Connecting To The Device");
progThread = new ProgressThread(handler);
progThread.start();
return connectionDialog;
case 2 :
requestDataDialog = new ProgressDialog(this);
requestDataDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
requestDataDialog.setMax(100);
requestDataDialog.setProgress(0);
requestDataDialog.setMessage("Requesting Download Data");
progThread = new ProgressThread(handler);
progThread.start();
return requestDataDialog;
default :
return null;
}
}
Android API提供了一个AsyncTask类，该类有两个方法doInBackground和onPostExecute。您必须覆盖它们，在doInBackground中执行任何必须执行的操作，并且当作业完成时，将运行onPostExecute回调。还有一个onProgressUpdate回调，这正是您所需要的。
查看AsyncTask类。它应该能够做你想做的事。
http://developer.android.com/reference/android/os/AsyncTask.html
似乎还有其他答案。AsyncTask是前进的方向。
但是，如果您想推进线程实现，只需在第一个线程的运行方法结束时start()下一个线程即可。
听起来您需要使用大小为1 的Countdown Latch