我为Android编写了一个网络（JSch）异步任务。出于某种原因，AsyncTask永远不会结束，直到我再次调用buttonClick（）。这是我的代码：
public class MainActivity extends AppCompatActivity
{ @覆盖 protected void onCreate（Bundle savedInstanceState） { super.onCreate（savedInstanceState）; 的setContentView（R.layout.activity_main）; }
protected void buttonClick(View view)
{
System.out.println(" --------------------------------- ");
System.out.println(" CONNECT BUTTON CLICKED!");
System.out.println(" --------------------------------- ");
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... params)
{
connect();
System.out.println("Connect done");
return null;
}
protected Void onPostExecute()
{
System.out.println("PostExec done");
return null;
}
}.execute();
System.out.println("Done with ASyncTask");
String text = output;
TextView tv = (TextView)findViewById(R.id.ayy);
tv.setText(text);
}
private int d;
private String output;
private void debug()
{
System.out.println("Debug" + d);
d++;
}
private void connect()
{
d = 1;
debug();
JSch jsch = new JSch();
String host = "[edited out]";
String user = "[edited out]";
String password = "[edited out for obvious reasons]";
String command = "uname -a";
int port = 2223;
try {
debug();
Session session = jsch.getSession(user, host, port);
debug();
UserInfo ui = new MyUserInfo();
debug();
session.setUserInfo(ui);
debug();
session.connect();
debug();
Channel channel = session.openChannel("exec");
debug();
((ChannelExec) channel).setCommand(command);
debug();
channel.setInputStream(null);
debug();
((ChannelExec) channel).setErrStream(System.err);
debug();
InputStream in = channel.getInputStream();
debug();
channel.connect();
debug();
byte[] tmp = new byte[1024];
while(true) {
while(in.available() > 0) {
int i = in.read(tmp, 0, 1024);
if(i < 0) break;
output = output + new String(tmp, 0, i);
}
if(channel.isClosed()) {
if(in.available() > 0) continue;
System.out.println("exit-status: " + channel.getExitStatus());
break;
}
try {
Thread.sleep(1000);
} catch(Exception ee) {
}
}
channel.disconnect();
session.disconnect();
} catch(Exception e) {
System.err.println("Exception: " + e);
e.printStackTrace();
}
}
}
class MyUserInfo implements UserInfo, UIKeyboardInteractive
{
public String getPassword()
{
return passwd;
}
public boolean promptYesNo(String str)
{
/*Object[] options = {"yes", "no"};
int foo = JOptionPane.showOptionDialog(null,
str,
"Warning",
JOptionPane.DEFAULT_OPTION,
JOptionPane.WARNING_MESSAGE,
null, options, options[0]);
return foo == 0; */
return true;
}
String passwd;
public String getPassphrase()
{
return null;
}
public boolean promptPassphrase(String message)
{
return true;
}
public boolean promptPassword(String message)
{
passwd = "[edited out]";
return true;
}
public void showMessage(String message)
{
System.out.println("MSG: " + message);
}
/*
final GridBagConstraints gbc =
new GridBagConstraints(0, 0, 1, 1, 1, 1,
GridBagConstraints.NORTHWEST,
GridBagConstraints.NONE,
new Insets(0, 0, 0, 0), 0, 0);
private Container panel;
*/
public String[] promptKeyboardInteractive(String destination,
String name,
String instruction,
String[] prompt,
boolean[] echo)
{ System.out.println("promptKeyboardInteractive");/*
panel = new JPanel();
panel.setLayout(new GridBagLayout());
gbc.weightx = 1.0;
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.gridx = 0;
panel.add(new JLabel(instruction), gbc);
gbc.gridy++;
gbc.gridwidth = GridBagConstraints.RELATIVE;
JTextField[] texts = new JTextField[prompt.length];
for(int i = 0; i < prompt.length; i++) {
gbc.fill = GridBagConstraints.NONE;
gbc.gridx = 0;
gbc.weightx = 1;
panel.add(new JLabel(prompt[i]), gbc);
gbc.gridx = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weighty = 1;
if(echo[i]) {
texts[i] = new JTextField(20);
} else {
texts[i] = new JPasswordField(20);
}
panel.add(texts[i], gbc);
gbc.gridy++;
}
if(JOptionPane.showConfirmDialog(null, panel,
destination + ": " + name,
JOptionPane.OK_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE)
== JOptionPane.OK_OPTION) {
String[] response = new String[prompt.length];
for(int i = 0; i < prompt.length; i++) {
response[i] = texts[i].getText();
}
return response;
} else {
return null; // cancel
}
*/
return null;
}
}
我完全清楚代码是一团糟，但是一旦我开始工作，我就会把它清理干净。
点击一下按钮后输出：
04-13 15:45:33.451 26826-26826/com.example.ryan.jschtest I/System.out: ---------------------------------
04-13 15:45:33.451 26826-26826/com.example.ryan.jschtest I/System.out: CONNECT BUTTON CLICKED!
04-13 15:45:33.451 26826-26826/com.example.ryan.jschtest I/System.out: ---------------------------------
04-13 15:45:33.452 26826-26826/com.example.ryan.jschtest I/System.out: Done with Asynctask
04-13 15:45:33.452 26826-26925/com.example.ryan.jschtest I/System.out: Debug1
04-13 15:45:33.457 26826-26925/com.example.ryan.jschtest I/System.out: Debug2
04-13 15:45:33.470 26826-26925/com.example.ryan.jschtest I/System.out: Debug3
04-13 15:45:33.470 26826-26925/com.example.ryan.jschtest I/System.out: Debug4
04-13 15:45:33.470 26826-26925/com.example.ryan.jschtest I/System.out: Debug5
04-13 15:45:33.472 26826-26925/com.example.ryan.jschtest I/System.out: Connecting: 192.168.1.18:2223
04-13 15:45:34.008 26826-26925/com.example.ryan.jschtest I/System.out: Debug6
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug7
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug8
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug9
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug10
04-13 15:45:34.014 26826-26925/com.example.ryan.jschtest I/System.out: Debug11
04-13 15:45:34.076 26826-26925/com.example.ryan.jschtest I/System.out: Debug12
04-13 15:45:35.112 26826-26925/com.example.ryan.jschtest I/System.out: exit-status: 0
04-13 15:45:35.115 26826-26925/com.example.ryan.jschtest I/System.out: Connect done
点击2次按钮后输出：
04-13 15:45:33.451 26826-26826/com.example.ryan.jschtest I/System.out: ---------------------------------
04-13 15:45:33.451 26826-26826/com.example.ryan.jschtest I/System.out: CONNECT BUTTON CLICKED!
04-13 15:45:33.451 26826-26826/com.example.ryan.jschtest I/System.out: ---------------------------------
04-13 15:45:33.452 26826-26826/com.example.ryan.jschtest I/System.out: Done with Asynctask
04-13 15:45:33.452 26826-26925/com.example.ryan.jschtest I/System.out: Debug1
04-13 15:45:33.457 26826-26925/com.example.ryan.jschtest I/System.out: Debug2
04-13 15:45:33.470 26826-26925/com.example.ryan.jschtest I/System.out: Debug3
04-13 15:45:33.470 26826-26925/com.example.ryan.jschtest I/System.out: Debug4
04-13 15:45:33.470 26826-26925/com.example.ryan.jschtest I/System.out: Debug5
04-13 15:45:34.008 26826-26925/com.example.ryan.jschtest I/System.out: Debug6
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug7
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug8
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug9
04-13 15:45:34.013 26826-26925/com.example.ryan.jschtest I/System.out: Debug10
04-13 15:45:34.014 26826-26925/com.example.ryan.jschtest I/System.out: Debug11
04-13 15:45:34.076 26826-26925/com.example.ryan.jschtest I/System.out: Debug12
04-13 15:45:35.112 26826-26925/com.example.ryan.jschtest I/System.out: exit-status: 0
04-13 15:45:35.115 26826-26925/com.example.ryan.jschtest I/System.out: Connect done
04-13 15:47:32.784 26826-26826/com.example.ryan.jschtest I/System.out: ---------------------------------
04-13 15:47:32.784 26826-26826/com.example.ryan.jschtest I/System.out: CONNECT BUTTON CLICKED!
04-13 15:47:32.784 26826-26826/com.example.ryan.jschtest I/System.out: ---------------------------------
04-13 15:47:32.785 26826-26826/com.example.ryan.jschtest I/System.out: Done with Asynctask
04-13 15:47:32.785 26826-28694/com.example.ryan.jschtest I/System.out: Debug1
04-13 15:47:32.786 26826-28694/com.example.ryan.jschtest I/System.out: Debug2
04-13 15:47:32.786 26826-28694/com.example.ryan.jschtest I/System.out: Debug3
04-13 15:47:32.786 26826-28694/com.example.ryan.jschtest I/System.out: Debug4
04-13 15:47:32.786 26826-28694/com.example.ryan.jschtest I/System.out: Debug5
04-13 15:47:33.370 26826-28694/com.example.ryan.jschtest I/System.out: Debug6
04-13 15:47:33.370 26826-28694/com.example.ryan.jschtest I/System.out: Debug7
04-13 15:47:33.370 26826-28694/com.example.ryan.jschtest I/System.out: Debug8
04-13 15:47:33.370 26826-28694/com.example.ryan.jschtest I/System.out: Debug9
04-13 15:47:33.370 26826-28694/com.example.ryan.jschtest I/System.out: Debug10
04-13 15:47:33.371 26826-28694/com.example.ryan.jschtest I/System.out: Debug11
04-13 15:47:33.436 26826-28694/com.example.ryan.jschtest I/System.out: Debug12
04-13 15:47:34.467 26826-28694/com.example.ryan.jschtest I/System.out: exit-status: 0
04-13 15:47:34.468 26826-28694/com.example.ryan.jschtest I/System.out: Connect done
答案 0 :(得分：-1)
解决：
public boolean connectComplete = false;
protected void buttonClick(View view)
{
ConnectTask ayy = new ConnectTask();
ayy.execute();
while(!connectComplete) {
try { Thread.sleep(100); } catch(Exception e) {System.out.println(e); e.printStackTrace; }
}
ayy.cancel(true);
connectComplete = false;
}
：
@Override
protected Void doInBackground(Void... params)
{
MainActivity.connect();
cancel(true);
System.out.println("Connect done");
connectComplete = true;
return null;
}