在Android中实现多线程同步

1. java中对多线程访问控制可使用关键字synchronized
下面将以Producer Consumer模型介绍android中线程同步的使用。

步骤：
建立一android project，
修改main activity如下：

代码：

package com.test.thread;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class MultiThread extends Activity {

private static final String MultiThread_ACTIVITY_TAG = "MultiThread_TAG";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

CubbyHole c = new CubbyHole();
Producer p1 = new Producer(c, 1);
Consumer c1 = new Consumer(c, 1);

p1.start();
c1.start();

// Test log system.
//testLog();

setContentView(R.layout.main);

}

// This is a example to use android.util.Log.
public void testLog() {
Log.i(MultiThread_ACTIVITY_TAG, "=============================");

Log.d(MultiThread_ACTIVITY_TAG, "this is a DEBUG of MyAndroid. ");
Log.i(MultiThread_ACTIVITY_TAG, "this is a INFO of MyAndroid. ");
Log.w(MultiThread_ACTIVITY_TAG, "this is a WARNING of MyAndroid. ");
}

public class Producer extends Thread {
private CubbyHole cubbyhole;
private int number;

public Producer(CubbyHole c, int number) {
cubbyhole = c;
this.number = number;
}

public void run() {
for (int i = 0; i < 10; i++) {
cubbyhole.put(i);
Log.d(MultiThread_ACTIVITY_TAG, "Producer #" + this.number + " put: " + i);
//System.out.println("Producer #" + this.number + " put: " + i);
try {
sleep((int)(Math.random() * 100));
} catch (InterruptedException e) {}
}
}
}

public class CubbyHole {
private int contents;
private boolean available = false;

public synchronized int get() {
while (available == false) {
try {
wait();
} catch (InterruptedException e) { }
}

available = false;
notifyAll();
return contents;
}

public synchronized void put(int value) {
while (available == true) {
try {
wait();
} catch (InterruptedException e) { }
}
contents = value;
available = true;
notifyAll();
}
}

public class Consumer extends Thread {
private CubbyHole cubbyhole;
private int number;

public Consumer(CubbyHole c, int number) {
cubbyhole = c;
this.number = number;
}

public void run() {
int value = 0;
for (int i = 0; i < 10; i++) {
value = cubbyhole.get();
Log.d(MultiThread_ACTIVITY_TAG, "Consumer #" + this.number + " got: " + value);
//System.out.println("Consumer #" + this.number + " got: " + value);
}
}
}
}

2. 上面的代码中引入了android.util.Log包， 以拥有debug。
运行上面的工程后，在dbg窗口的Logcat区，显示打出的log。