更改线程优先级没有效果

Question

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，所以更改后我的输出应该等于-4，为什么它保持不变？为什么android.os.Process.setThreadPriority()没有效果？

PS我阅读了有关线程的谷歌文档，但没有遇到任何解释 android.os.Process.getThreadPriority() 和 Thread.currentThread().getPriority()< 之间差异的问题/代码>。为什么这些方法返回不同的值？

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

Answer 1

您在检查中使用了错误的 ThreadID。

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

供进一步参考：

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