線程(Thread)

線程(Thread)是程序執行時的並行單位. 其中一個實現線程的途徑是擴展線程(extends Thread)實現一個新類並重寫其的run()方法. 這是一個使用線程的典型應用.

因為只有UI線程可以修改用戶界面, 因此我們必須通過消息(Message)和處理(Handler), 以顯示我們的線程狀態.



main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   >
<TextView 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="@string/hello"
   />
<Button 
   android:id="@+id/newthread"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="New a Thread" />
<Button 
   android:id="@+id/stoprunning"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Stop running" />
<Button 
   android:id="@+id/join"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="join" />
<Button 
   android:id="@+id/getstate"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="getState()" />
<TextView 
   android:id="@+id/markingrunning"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   />
</LinearLayout>

AndroidThread.java

package com.AndroidThread;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class AndroidThread extends Activity {

String strRunning = "-";
TextView tvMarkingrunning;
Button buttonNewThread, buttonStopRunning, buttonJoin, buttonGetState;
MyThread myThread;

   Handler myHandler = new Handler(){

 @Override
 public void handleMessage(Message msg) {
  // TODO Auto-generated method stub
  strRunning = rotateMarking(strRunning);
  tvMarkingrunning.setText("running: " + strRunning);
 }
   };

   public class MyThread extends Thread {
   
    private boolean running = false;
   
    public void setRunning(boolean b){
     running = b;
    }

 @Override
 public void run() {
  // TODO Auto-generated method stub
  while(running){
   try {
    Thread.sleep(500);
    myHandler.sendMessage(myHandler.obtainMessage());
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
 }
}
  
   private String rotateMarking(String marking){
    if (marking=="-"){
     return("\\");
    }
    else if (marking=="\\"){
     return("|");
    }
    else if (marking=="|"){
     return("/");
    }
    else{
     return("-");
    }
   }
  
   private void setButtonsEnable(boolean enableNewThread,
     boolean enableStopRunning,
     boolean enableJoin){
   
       buttonNewThread.setEnabled(enableNewThread);
       buttonStopRunning.setEnabled(enableStopRunning);
       buttonJoin.setEnabled(enableJoin);
   
   }
  
/** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
       tvMarkingrunning = (TextView)findViewById(R.id.markingrunning);
       buttonNewThread = (Button)findViewById(R.id.newthread);
       buttonStopRunning = (Button)findViewById(R.id.stoprunning);
       buttonJoin = (Button)findViewById(R.id.join);
       buttonGetState = (Button)findViewById(R.id.getstate);
      
       buttonNewThread.setOnClickListener(buttonNewThreadOnClickListener);
       buttonStopRunning.setOnClickListener(buttonStopRunningOnClickListener);
       buttonJoin.setOnClickListener(buttonJoinOnClickListener);
       buttonGetState.setOnClickListener(buttonGetStateOnClickListener);
      
       setButtonsEnable(true, false, false);

   }
  
   private Button.OnClickListener buttonGetStateOnClickListener =
    new Button.OnClickListener(){

  @Override
  public void onClick(View v) {
   // TODO Auto-generated method stub
   Toast.makeText(getBaseContext(), myThread.getState().toString(), Toast.LENGTH_LONG).show();
  }
   
   };
  
   private Button.OnClickListener buttonNewThreadOnClickListener =
    new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   myThread = new MyThread();
   myThread.setRunning(true);
   myThread.start();
   Toast.makeText(getBaseContext(), myThread.getState().toString(), Toast.LENGTH_LONG).show();
   setButtonsEnable(false, true, true);

  }
   };
  
   private Button.OnClickListener buttonStopRunningOnClickListener =
    new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   myThread.setRunning(false);
   Toast.makeText(getBaseContext(), myThread.getState().toString(), Toast.LENGTH_LONG).show();
   setButtonsEnable(true, false, false);
  }
   };
  
   private Button.OnClickListener buttonJoinOnClickListener =
    new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   boolean retry = true;
   myThread.setRunning(false);
   while(retry){
    try {
     myThread.join();
     retry = false;
    } catch (InterruptedException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }
   Toast.makeText(getBaseContext(), myThread.getState().toString(), Toast.LENGTH_LONG).show();
   setButtonsEnable(true, false, false);

  }
   };
}

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