Android线程优先级规定及其设置的具体方法

Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); //设置线程优先级为后台，这样当多个线程并发后很多无关紧要的线程分配的CPU时间将会减少，有利于主线程的处理，有以下几种:

int THREAD_PRIORITY_AUDIO //标准音乐播放使用的线程优先级

int THREAD_PRIORITY_BACKGROUND //标准后台程序

int THREAD_PRIORITY_DEFAULT // 默认应用的优先级

int THREAD_PRIORITY_DISPLAY //标准显示系统优先级，主要是改善UI的刷新

int THREAD_PRIORITY_FOREGROUND //标准前台线程优先级

int THREAD_PRIORITY_LESS_FAVORABLE //低于favorable

int THREAD_PRIORITY_LOWEST //有效的线程最低的优先级

int THREAD_PRIORITY_MORE_FAVORABLE //高于favorable

int THREAD_PRIORITY_URGENT_AUDIO //标准较重要音频播放优先级

int THREAD_PRIORITY_URGENT_DISPLAY //标准较重要显示优先级，对于输入事件同样适用。

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.

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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());
        }
    }
}