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());
        }
    }
}