Android HandlerThread 使用介绍及简单解析
16lz
2021-01-23
一 先看看官方介绍：
（1）HandlerThread继承自线程Thread，内部封装了有Looper。
public class HandlerThread extends Thread Handy class for starting a new thread that has a looper. The looper can then be used to create handler classes. Note that start() must still be called.（2）常用方法：
1、Looper getLooper()//返回一个与当前线程关联的LooperThis method returns the Looper associated with this thread. 2、int getThreadId() Returns the identifier of this thread. 3、boolean quit() // HandlerThread退出资源 Quits the handler thread's looper. 4、boolean quitSafely() Quits the handler thread's looper safely. 5、void run() //执行方法（工作线程） If this thread was constructed using a separate Runnable run object, then that Runnable object's run method is called; otherwise, this method does nothing and returns.二 HandlerThread DEMO
布局文件：
<?xml version="1.0" encoding="utf-8"?><ScrollView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.troy.handlerthreaddemo.MainActivity"> <LinearLayout android:id="@+id/ll_container" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <TextView android:id="@+id/tv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:textSize="22dp" android:layout_marginBottom="18dp" android:text="三峡日泄洪流量时刻表" /> </LinearLayout></ScrollView>MainActivity.java:
public class MainActivity extends AppCompatActivity { private TextView tv; private HandlerThread mCheckMsgThread; //HandlerThread private Handler mCheckMsgHandler; //工作线程的Handler private boolean isUpdateInfo; private static final int MSG_UPDATE_INFO = 0x110; private Handler mUIHandler=new Handler();//与UI线程管理的Handler private LinearLayout ll_container; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tv=(TextView)findViewById(R.id.tv); ll_container=(LinearLayout)findViewById(R.id.ll_container); initBackThread();//创建工作线程 } private void initBackThread(){ mCheckMsgThread=new HandlerThread("check-message-coming"); mCheckMsgThread.start(); mCheckMsgHandler=new Handler(mCheckMsgThread.getLooper()){ @Override public void handleMessage(Message msg) { Log.i("TEST","msg.what :"+msg.what); checkForUpdate(); if(isUpdateInfo){ mCheckMsgHandler.sendEmptyMessageDelayed(MSG_UPDATE_INFO,1000);//自己触发自己 } } }; } private void checkForUpdate(){ try{ Thread.sleep(1000); mUIHandler.post(new Runnable() { @Override public void run() { Date date=new Date(); DateFormat format=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String time=format.format(date); String result="当前泄洪流量: <font color='red'>%d</font> 立方/秒 <font color='gray'>%s</font>"; result=String.format(result,(int)(Math.random()*3000+1000),time); TextView textView=new TextView(MainActivity.this); textView.setTextSize(20); textView.setPadding(0,5,0,5); textView.setText(Html.fromHtml(result)); ll_container.addView(textView); } }); }catch (InterruptedException e){ e.printStackTrace(); } } @Override protected void onResume(){ super.onResume(); //开始查询 isUpdateInfo = true; mCheckMsgHandler.sendEmptyMessage(MSG_UPDATE_INFO); } @Override protected void onPause(){ super.onPause(); //停止查询 isUpdateInfo = false; mCheckMsgHandler.removeMessages(MSG_UPDATE_INFO); } @Override protected void onDestroy() { super.onDestroy(); //释放资源 mCheckMsgThread.quit(); }}运行结果如下：
三 源码分析：
HandlerThread.java：
HandlerThread的创建：
public HandlerThread(String name) {//构造方法 super(name); mPriority = Process.THREAD_PRIORITY_DEFAULT; } public HandlerThread(String name, int priority) {//可设置线程优先级 int THREAD_PRIORITY_DEFAULT // 默认应用的优先级 super(name); mPriority = priority; }HandlerThread的启动：
@Override public void run() { mTid = Process.myTid(); Looper.prepare(); synchronized (this) { mLooper = Looper.myLooper(); notifyAll(); } Process.setThreadPriority(mPriority);//设置线程的优先级 onLooperPrepared(); Looper.loop();//开启消息循环 mTid = -1; }可以看到run()方法中调用了Looper.prepare()，Loop.loop();
prepare()呢，中创建了一个Looper对象，并且把该对象放到了该线程范围内的变量中（sThreadLocal），在Looper对象的构造过程中，初始化了一个MessageQueue，作为该Looper对象成员变量。loop()就开启了，不断的循环从MessageQueue中取消息处理了，当没有消息的时候会阻塞，有消息的到来的时候会唤醒。
那么，mCheckMsgThread.getLooper()做了什么：
/** * This method returns the Looper associated with this thread. If this thread not been started * or for any reason is isAlive() returns false, this method will return null. If this thread * has been started, this method will block until the looper has been initialized. * @return The looper. */ public Looper getLooper() { if (!isAlive()) { return null; } // If the thread has been started, wait until the looper has been created. synchronized (this) { while (isAlive() && mLooper == null) { try { wait();//如果mLooper为空的时候，就等待，直到 mLooper = Looper.myLooper(); 由notifyAll();来唤醒； } catch (InterruptedException e) { } } } return mLooper; }mCheckMsgThread.getLooper()返回的就是我们在run方法中创建的mLooper。
参考致谢：
1 Android HandlerThread 完全解析
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