[英]Looping a Thread
在我的Android應用程序中,我想連續讀取傳入的數據(使用Telnet協議)。 我能夠讀取一行(然后該應用程序在空閑狀態下運行),並且我想知道如何創建一個簡單的無盡主循環。
我認為繞這條線循環是有意義的:
telnetThread.start();
我已經嘗試實現一個循環程序,但沒有成功。
這是我的代碼:
package com.example.clienttel;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import org.apache.commons.net.telnet.TelnetClient;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class MainActivity extends ActionBarActivity {
// Variables
public final String ADDRESS = "194.66.82.11";
public final int PORT = 50100;
public String NMEA = null;
public final String TAG = "TestApp";
public boolean first = true;
public MyTelnetClass mtc;
public Thread telnetThread;
// Handler in mainthread
Handler handler = new Handler() {
public void handleMessage(Message msg) {
String dataString = "";
Bundle bundle = msg.getData();
Log.d("handleMessage", bundle.toString());
if (bundle.containsKey("outgoingString")) {
dataString = bundle.getString("outgoingString");
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
createThread();
}
private void createThread() {
final Runnable runnable = new Runnable() {
public void run() {
try {
mtc = new MyTelnetClass();
mtc.mhandler = handler;
mtc.run();
Bundle b = new Bundle();
b.putString("TCPThread", "visible");
Message m = handler.obtainMessage();
m.setData(b);
handler.sendMessage(m);
} catch (Exception e) {
Log.e("createTCPThread", "exception: " + e.getMessage());
Bundle b = new Bundle();
b.putString("TCPThread", "unvisible");
Message m = handler.obtainMessage();
m.setData(b);
handler.sendMessage(m);
}
}
};
// create the thread needed and run it, LOOP HERE?
telnetThread = new Thread(runnable);
telnetThread.start();
}
// catch NMEA-sentences and send them using mhandler
class MyTelnetClass {
public Handler mhandler = null;
public void run() {
TelnetClient telnet = new TelnetClient();
Log.i(TAG, "telnetThread active");
if (first) {
// Connect To Server in 1st Iteration
try {
telnet.connect(ADDRESS, PORT);
} catch (IOException e) {
e.printStackTrace();
}
first = false;
}
// Process NMEA-sentences
InputStream inStream = telnet.getInputStream();
BufferedReader r = new BufferedReader(new InputStreamReader(inStream));
try {
NMEA = r.readLine();
} catch (IOException e) {
e.printStackTrace();
}
// Handler in MyTelnetClass to send back
Bundle b = new Bundle();
b.putString("outgoingString", NMEA);
Message m = mhandler.obtainMessage();
m.setData(b);
mhandler.sendMessage(m);
}
}
}
什么是處理該問題的有效方法?
編輯:
我將循環程序放在run()周圍,但是它只執行一次(我不確定循環是否可以這種方式工作):
public void run() {
try {
Looper.prepare(); // HERE...
Log.d(TAG,"executing run");
mtc = new MyTelnetClass();
mtc.mhandler = handler;
mtc.run();
Bundle b = new Bundle();
b.putString("TCPThread", "visible");
Message m = handler.obtainMessage();
m.setData(b);
handler.sendMessage(m);
Looper.loop(); // ...AND HERE
} catch (Exception e) {
Log.e("createTCPThread", "exception: " + e.getMessage());
Bundle b = new Bundle();
b.putString("TCPThread", "unvisible");
Message m = handler.obtainMessage();
m.setData(b);
handler.sendMessage(m);
}
}
您已經創建了一個線程,這是您的開始,但是它將運行一次。 如果您希望他循環運行,則需要放置循環。 循環需要從頭到尾都在run()
方法中,也可以根據需要使用。
如果您在一個值得贊揚的地方寫了一個循環,那會浪費時間(/內存),而且效果不好,它將一遍又一遍地創建相同的線程。 如果您在telnetThread.start();
是,這將導致大量線程,並且它們都將在大約同一時間運行。
如果在run()
函數中執行此操作,它將無限次運行(除非有條件),並且僅在循環的最后一次運行結束后才運行。
嘗試以下代碼:
{
new Thread () {
public void run() {
Message msg = Message.obtain();
msg.what=1;
try {
openTelnetConnection(url, mmsgH);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace(); }
}
}.start();
}
private void openTelnetConnection(String urlStr, Handler mhandler) throws IOException {
ProtocolConnection protConn = null;
String line = null;
try {
// Get your CONNECTION
BufferedReader is =
new BufferedReader(new InputStreamReader(protConn.getInputStream()));
while ((line = is.readLine( )) != null) {
Message msg = Message.obtain();
msg.what=1;
msg.obj=line;
mhandler.sendMessage(msg);
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch( SocketTimeoutException e){
e.printStackTrace();
} catch (IOException e) {
Log.d(TAG, "IOERR " +e);
e.printStackTrace();
Message msg = Message.obtain();
msg.what=2;
BufferedInputStream in = new BufferedInputStream(httpConn.getErrorStream());
line =new String(readStream(in));
msg.obj=line;
mhandler.sendMessage(msg);
}
finally {protConn.disconnect();}
}
正如@ChrisStratton和@amitfarag所說,一個簡單的while()
loop確實滿足了我的要求。 在我的情況下,不需要彎針:
while (true) {
try {
mtc = new MyTelnetClass();
mtc.mhandler = handler;
mtc.run();
Bundle b = new Bundle();
b.putString("TCPThread", "visible");
Message m = handler.obtainMessage();
m.setData(b);
handler.sendMessage(m);
} catch (Exception e) {
Log.e("createTCPThread", "exception: " + e.getMessage());
Bundle b = new Bundle();
b.putString("TCPThread", "unvisible");
Message m = handler.obtainMessage();
m.setData(b);
handler.sendMessage(m);
e.printStackTrace();
}
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