更改线程优先级没有效果答案

【问题标题】：Changing thread priority doesn't have an effect更改线程优先级没有效果
【发布时间】：2012-01-26 13:55:17
【问题描述】：

我正在尝试使用android.os.Process.setThreadPriority() 更改主线程的优先级。我在优先级更改之前和之后都有日志消息，这里是代码：

public class TestActivity extends Activity {
    public final String TAG="TestActivity";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        int tid=(int)Thread.currentThread().getId();
        Log.d(TAG,"priority before change = " + android.os.Process.getThreadPriority(tid));
        Log.d(TAG,"priority before change = "+Thread.currentThread().getPriority());
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_DISPLAY);
        Log.d(TAG,"priority after change = " + android.os.Process.getThreadPriority(tid));
        Log.d(TAG,"priority after change = " + Thread.currentThread().getPriority());
    }
}

我得到以下输出：

priority before change (getThreadPriority) = 0
priority before change (currentThread().getPriority) = 5
priority after change (getThreadPriority) = 0
priority after change (currentThread().getPriority) = 5

这意味着优先级没有改变，无论我使用什么方法来评估它。 android.os.Process.THREAD_PRIORITY_DISPLAY = -4，所以在改变我的输出后应该等于-4，为什么它保持不变？为什么android.os.Process.setThreadPriority()没有效果？

附：我阅读了关于线程的谷歌文档，但我没有遇到任何解释android.os.Process.getThreadPriority() 和Thread.currentThread().getPriority() 之间区别的问题。为什么这些方法返回不同的值？

附言Thread.currentThread().setPriority() 工作正常。

【问题讨论】：

标签： android thread-priority

【解决方案1】：

您使用错误的 ThreadID 进行检查。

要获得正确的 id，您必须使用 android.os.Process.myTid();

固定代码：

package mypackage.test;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class TestActivity extends Activity {
    public final String TAG="TestActivity";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        int tid=android.os.Process.myTid();

        Log.d(TAG,"priority before change = " + android.os.Process.getThreadPriority(tid));
        Log.d(TAG,"priority before change = "+Thread.currentThread().getPriority());
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_DISPLAY);
        Log.d(TAG,"priority after change = " + android.os.Process.getThreadPriority(tid));
        Log.d(TAG,"priority after change = " + Thread.currentThread().getPriority());
    }
}

日志输出：

priority before change = 0
priority before change = 5
priority after change = -4
priority after change = 5

进一步参考：

http://developer.android.com/reference/android/os/Process.html#myTid()

【讨论】：