HandlerThread源碼分析

2019-11-09 18:34:45

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HandlerThread源碼分析

public class HandlerThread extends Thread { //線程優先級 int mPRiority; //線程id int mTid = -1; Looper mLooper; public HandlerThread(String name) { super(name); mPriority = Process.THREAD_PRIORITY_DEFAULT; } public HandlerThread(String name, int priority) { super(name); mPriority = priority; } //可以覆寫，在循環之前做一些處理 protected void onLooperPrepared() { } //創建了looper并通知getLooper。在執行getLooper之前必須先執行thread的start方法，不然getLooper將返回null，容易引發空指針 @Override public void run() { mTid = Process.myTid(); Looper.prepare(); synchronized (this) { mLooper = Looper.myLooper(); notifyAll(); } Process.setThreadPriority(mPriority); onLooperPrepared(); Looper.loop(); mTid = -1; } public Looper getLooper() { if (!isAlive()) { return null; } synchronized (this) { while (isAlive() && mLooper == null) { try { wait(); } catch (InterruptedException e) { } } } return mLooper; } //looper停止接收新的任務并清空MessageQueue中的任務 public boolean quit() { Looper looper = getLooper(); if (looper != null) { looper.quit(); return true; } return false; } //looper停止接收新的任務并清空MessageQueue中的延時任務，非延時任務將繼續執行 public boolean quitSafely() { Looper looper = getLooper(); if (looper != null) { looper.quitSafely(); return true; } return false; } public int getThreadId() { return mTid; }}

Looper#quit相關源碼

public void quit() { mQueue.quit(false); }public void quitSafely() { mQueue.quit(true);}void quit(boolean safe) { if (!mQuitAllowed) { throw new IllegalStateException("Main thread not allowed to quit."); } synchronized (this) { if (mQuitting) { return; } mQuitting = true; if (safe) { removeAllFutureMessagesLocked(); } else { removeAllMessagesLocked(); } // We can assume mPtr != 0 because mQuitting was previously false. nativeWake(mPtr); } }private void removeAllMessagesLocked() { Message p = mMessages; while (p != null) { Message n = p.next; p.recycleUnchecked(); p = n; } mMessages = null; } private void removeAllFutureMessagesLocked() { final long now = SystemClock.uptimeMillis(); Message p = mMessages; if (p != null) { if (p.when > now) { removeAllMessagesLocked(); } else { Message n; for (;;) { n = p.next; if (n == null) { return; } if (n.when > now) { break; } p = n; } p.next = null; do { p = n; n = p.next; p.recycleUnchecked(); } while (n != null); } } }

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