android 设置线程的优先级

有两处API可以设置线程的优先级。

1、android.os.Process.setThreadPriority (int priority)
或
android.os.Process.setThreadPriority (int tid, int priority)

priority：【-20, 19】，高优先级 -> 低优先级。

2、java.lang.Thread.setPriority (int priority)

priority：【1, 10】，低优先级 -> 高优先级。

测试后发现，使用android自己的API（第1种方法）设置的优先级，对线程调度影响显著。

测试代码如下：

package com.test.testx;

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

public class TestThreadPriority extends Activity {
private static final String TAG ="TestThreadPriority";

private boolean mNeedExit = false;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

MyThread a = new MyThread("Thread A");
a.setOSPriority(Process.THREAD_PRIORITY_LOWEST); // 19
a.setPriority(Thread.MAX_PRIORITY); // 10

MyThread b = new MyThread("Thread B");
b.setOSPriority(Process.THREAD_PRIORITY_URGENT_AUDIO); // -19
b.setPriority(Thread.MIN_PRIORITY); // 1

a.start();
b.start();
}

@Override
public void onBackPressed() {
mNeedExit = true;
super.onBackPressed();
}

private class MyThread extends Thread {
private int mOSPriority = Process.THREAD_PRIORITY_DEFAULT;
private int mLoopCount = 0;

public MyThread(String threadName) {
super(threadName);
}

public void setOSPriority(int p) {
mOSPriority = p;
}

@Override
public void run() {
Process.setThreadPriority(mOSPriority);

while(!mNeedExit) {
mLoopCount ++;
Math.log(Math.random() * 1000); // calculation test

Log.d(TAG, new StringBuilder().append(getName())
.append(" os priority: ").append(mOSPriority)
.append(" java priority: ").append(getPriority())
.append(" loop count: ").append(mLoopCount).toString());
}

Log.d(TAG, new StringBuilder().append(getName()).append(" exiting...")
.append(" os priority: ").append(mOSPriority)
.append(" java priority: ").append(getPriority())
.append(" loop count: ").append(mLoopCount).toString());
}
}
}