一 先看看官方介紹：
（1）HandlerThread繼承自線程Thread，内部封裝了有Looper。
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：
、Looper getLooper()//傳回一個與目前線程關聯的Looper
This method returns the Looper associated with this thread.
2、int getThreadId()
Returns the identifier of this thread.
3、boolean quit() // HandlerThread退出資源
Quits the handler thread's looper.
4、boolean quitSafely()
Quits the handler thread's looper safely.
5、void run() //執行方法（工作線程）
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
布局檔案：
<?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="三峽日洩洪流量時刻表" />
</LinearLayout>
</ScrollView>
MainActivity.java:
public class MainActivity extends AppCompatActivity {
private TextView tv;
private HandlerThread mCheckMsgThread; //HandlerThread
private Handler mCheckMsgHandler; //工作線程的Handler
private boolean isUpdateInfo;
private static final int MSG_UPDATE_INFO = ;
private Handler mUIHandler=new Handler();//與UI線程管理的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();//建立工作線程
}
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,);//自己觸發自己
}
}
};
}
private void checkForUpdate(){
try{
Thread.sleep();
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="目前洩洪流量: <font color='red'>%d</font> 立方/秒 <font color='gray'>%s</font>";
result=String.format(result,(int)(Math.random()*+),time);
TextView textView=new TextView(MainActivity.this);
textView.setTextSize();
textView.setPadding(,,,);
textView.setText(Html.fromHtml(result));
ll_container.addView(textView);
}
});
}catch (InterruptedException e){
e.printStackTrace();
}
}
@Override
protected void onResume(){
super.onResume();
//開始查詢
isUpdateInfo = true;
mCheckMsgHandler.sendEmptyMessage(MSG_UPDATE_INFO);
}
@Override
protected void onPause(){
super.onPause();
//停止查詢
isUpdateInfo = false;
mCheckMsgHandler.removeMessages(MSG_UPDATE_INFO);
}
@Override
protected void onDestroy() {
super.onDestroy();
//釋放資源
mCheckMsgThread.quit();
}
}
運作結果如下：
三 源碼分析：
HandlerThread.java：
HandlerThread的建立：
public HandlerThread(String name) {//構造方法
super(name);
mPriority = Process.THREAD_PRIORITY_DEFAULT;
}
public HandlerThread(String name, int priority) {//可設定線程優先級 int THREAD_PRIORITY_DEFAULT // 預設應用的優先級
super(name);
mPriority = priority;
}
HandlerThread的啟動：
@Override
public void run() {
mTid = Process.myTid();
Looper.prepare();
synchronized (this) {
mLooper = Looper.myLooper();
notifyAll();
}
Process.setThreadPriority(mPriority);//設定線程的優先級
onLooperPrepared();
Looper.loop();//開啟消息循環
mTid = -;
}
可以看到run()方法中調用了Looper.prepare()，Loop.loop();
prepare()呢，中建立了一個Looper對象，并且把該對象放到了該線程範圍内的變量中（sThreadLocal），在Looper對象的構造過程中，初始化了一個MessageQueue，作為該Looper對象成員變量。loop()就開啟了，不斷的循環從MessageQueue中取消息處理了，當沒有消息的時候會阻塞，有消息的到來的時候會喚醒。
那麼，mCheckMsgThread.getLooper()做了什麼：
/**
* 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為空的時候，就等待，直到 mLooper = Looper.myLooper(); 由notifyAll();來喚醒；
} catch (InterruptedException e) {
}
}
}
return mLooper;
}
mCheckMsgThread.getLooper()傳回的就是我們在run方法中建立的mLooper。
參考緻謝：
1 Android HandlerThread 完全解析
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