回去简单看了哈Handler源码的东西，混了个眼熟，其中有个 ActivityThread的部分，这个就涉及到应用启动流程相关了...开始前我有回忆了下之前跟踪的知识，感觉过两天就忘记了，是怎么回事呀!!!
6524
6525 Looper.prepareMainLooper(); // 主线程准备Looper对象
6526
6527 ActivityThread thread = new ActivityThread();
6528 thread.attach(false);
6529
6530 if (sMainThreadHandler == null) {
6531 sMainThreadHandler = thread.getHandler();
6532 }
6538
6541 Looper.loop(); // 开始做轮询
100 /**
101 * Initialize the current thread as a looper, marking it as an
102 * application's main looper. The main looper for your application
103 * is created by the Android environment, so you should never need
104 * to call this function yourself. See also: {@link #prepare()}
105 */
106 public static void prepareMainLooper() {
107 prepare(false); // 创建Looper实例对象并保存到ThreadLocal sThreadLocal中；
108 synchronized (Looper.class) {
109 if (sMainLooper != null) {
110 throw new IllegalStateException("The main Looper has already been prepared.");
111 }
112 sMainLooper = myLooper(); // 获取sThreadLocal中保存的Looper实例对象；
113 }
114 }
115
129 public static void loop() {
130 final Looper me = myLooper();
131 if (me == null) {
132 throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread.");
133 }
134 final MessageQueue queue = me.mQueue;
135
136 // Make sure the identity of this thread is that of the local process,
137 // and keep track of what that identity token actually is.
138 Binder.clearCallingIdentity();
139 final long ident = Binder.clearCallingIdentity();
140
141 for (;;) {
142 Message msg = queue.next(); // might block 没有消息则阻塞
143 if (msg == null) {
144 // No message indicates that the message queue is quitting.
145 return;
146 }
163 try {
164 msg.target.dispatchMessage(msg); // 获取到队列消息，进行事件分发；
166 } finally {
167 if (traceTag != 0) {
168 Trace.traceEnd(traceTag);
169 }
170 }
194
195 msg.recycleUnchecked();
196 }
197 }
93 /**
94 * Handle system messages here. 处理系统消息
95 */
96 public void dispatchMessage(Message msg) {
97 if (msg.callback != null) {
98 handleCallback(msg);
99 } else {
100 if (mCallback != null) {
101 if (mCallback.handleMessage(msg)) {
102 return;
103 }
104 }
105 handleMessage(msg);
106 }
107 }
// Message与Handler的捆绑过程;
public final boolean sendMessage(Message msg)
{
return sendMessageDelayed(msg, 0);
}
.....
private boolean enqueueMessage(MessageQueue queue, Message msg, long uptimeMillis) {
msg.target = this; // 所以这个target就是 handler.sendMessage(message);的该handler本身;
if (mAsynchronous) {
msg.setAsynchronous(true);
}
return queue.enqueueMessage(msg, uptimeMillis);
}
流程，打算怎么入手了？？？想想看......
小萌新真的是搬砖，找了一堆链接，看人家怎么个流程，然后自己花了一天时间，先跟了一遍（不对，准确应该是搜索了一遍，O(∩_∩)O哈哈~）
直接上我跟的记录(Launcher起家、Android6.0.0_r5，其他版本不一定一样):
http://androidxref.com/6.0.0_r5/xref/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java#startActivity
[图片上传中...(image-822a40-1569550513684-2)]
[图片上传中...(image-f9919d-1569550513684-1)]
xref: /packages/apps/Launcher3/src/com/android/launcher3/Launcher.java
Step1:
1482 /**
1483 * Creates a view representing a shortcut inflated from the specified resource.
1484 *
1485 * @param parent The group the shortcut belongs to.
1486 * @param info The data structure describing the shortcut.
1487 *
1488 * @return A View inflated from layoutResId.
1489 */
1490 public View createShortcut(ViewGroup parent, ShortcutInfo info) {
1491 BubbleTextView favorite = (BubbleTextView) mInflater.inflate(R.layout.app_icon,
1492 parent, false);
1493 favorite.applyFromShortcutInfo(info, mIconCache);
1494 favorite.setCompoundDrawablePadding(mDeviceProfile.iconDrawablePaddingPx);
1495 favorite.setOnClickListener(this); // 给应用快捷方式设置点击事件
1496 favorite.setOnFocusChangeListener(mFocusHandler);
1497 return favorite;
1498 }
其他Step
其他Step，点击查看
目前也是混眼熟，要搞基本比较了解还得一段时间...主要是太菜了！
网友也是这样过来的 Activity启动流程 - 掘金：
[图片上传中...(image-729205-1569550513684-0)]
附上相关比较可以的链接（主要还是自己要参考然后慢慢看，毕竟不是一天两天的事情，难鸭！）：
https://blog.csdn.net/xgq330409675/article/details/78938926
https://blog.csdn.net/jiangwei0910410003/article/details/52549333
Activity启动流程 - 掘金
Android系统架构开篇 - Gityuan博客 | 袁辉辉的技术博客
Android中为什么主线程不会因为Looper.loop()里的死循环卡死？