Handler系列-怎么放入MessageQueue
链表：根据when从小到大排列
1.MessageQueue
public final class MessageQueue {Message mMessages; //消息链表表头
}2.Message
public final class Message implements Parcelable {/*package*/ long when;/*package*/ Message next;
}3.sendMessageDelayed流程
- delay加上SystemClock.uptimeMillis()
public class Handler {public final boolean sendMessageDelayed(Message msg, long delayMillis){if (delayMillis < 0) {delayMillis = 0;}//delayMillis这里会加上SystemClock.uptimeMillis()，变成whenreturn sendMessageAtTime(msg, SystemClock.uptimeMillis() + delayMillis);}public boolean sendMessageAtTime(Message msg, long uptimeMillis) {MessageQueue queue = mQueue;return enqueueMessage(queue, msg, uptimeMillis);}private boolean enqueueMessage(MessageQueue queue, Message msg, long uptimeMillis) {msg.target = this; //赋值Message的targetif (mAsynchronous) {msg.setAsynchronous(true);}return queue.enqueueMessage(msg, uptimeMillis);}
}- 通过链表头mMessages和when，找到msg该在的位置（根据when从小到大排列）
public final class MessageQueue {boolean enqueueMessage(Message msg, long when) {synchronized (this) {msg.markInUse();msg.when = when; //赋值Message的whenMessage p = mMessages; //表头赋值给pboolean needWake;if (p == null || when == 0 || when < p.when) {//链表为null或者when为0或者when的值比表头的when小// New head, wake up the event queue if blocked.msg.next = p;mMessages = msg; //msg成为表头needWake = mBlocked;} else {Message prev;for (;;) {prev = p;p = p.next;if (p == null || when < p.when) {//找到该放的位置了break;}}//插入msg：prev msg pmsg.next = p; prev.next = msg;}// We can assume mPtr != 0 because mQuitting is false.if (needWake) {nativeWake(mPtr);}}return true;}
}