ANR 弹窗的显示原理，2021安卓面试题
作者：互联网
应用并没有 ANR 弹窗，不过 logcat 有 ANR 相关信息，看一下 trace 文件：
----- pid 14608 at 2021-03-23 19:56:20 -----
Cmd line: demo.com.sam.demofactory:whatever
… 省略无关信息
“main” prio=5 tid=1 Sleeping
| group=“main” sCount=1 dsCount=0 flags=1 obj=0x73f13a80 self=0x78e7cc2a00
| sysTid=14608 nice=0 cgrp=default sched=0/0 handle=0x796c96d9a8
| state=S schedstat=( 57816925 3067496 80 ) utm=2 stm=3 core=4 HZ=100
| stack=0x7fe1d03000-0x7fe1d05000 stackSize=8MB
| held mutexes=
at java.lang.Thread.sleep(Native method)
- sleeping on <0x0a71f3e8> (a java.lang.Object)
at java.lang.Thread.sleep(Thread.java:373)
- locked <0x0a71f3e8> (a java.lang.Object)
at java.lang.Thread.sleep(Thread.java:314)
at demo.com.sam.demofactory.service.NoZuoNoDieService.onCreate(NoZuoNoDieService.kt:15)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:3426)
at android.app.ActivityThread.-wrap4(ActivityThread.java:-1)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1744)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:171)
at android.app.ActivityThread.main(ActivityThread.java:6611)
at java.lang.reflect.Method.invoke(Native method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
ANR 弹窗的显示原理
===========
我们来看一下这个没有弹窗的 ANR 是怎么发生的
首先来复习一下 说一说 Service 的启动流程
AMS 真正去启动 Service 调用的是 ActiveServices.realStartServiceLocked 方法：
// API 29 com.android.server.am.ActiveServices
private final void realStartServiceLocked(ServiceRecord r,
ProcessRecord app, boolean execInFg) throws RemoteException {
…
bumpServiceExecutingLocked(r, execInFg, “create”);
}
private final void bumpServiceExecutingLocked(ServiceRecord r, boolean fg, String why) {
…
scheduleServiceTimeoutLocked(r.app);
}
// 通过 Handler 延时发一条消息，延时时间则为 Service 触发的 ANR 时长
// SERVICE_TIMEOUT = 20*1000
// SERVICE_BACKGROUND_TIMEOUT = SERVICE_TIMEOUT * 10;
void scheduleServiceTimeoutLocked(ProcessRecord proc) {
if (proc.executingServices.size() == 0 || proc.thread == null) {
return;
}
Message msg = mAm.mHandler.obtainMessage(
ActivityManagerService.SERVICE_TIMEOUT_MSG);
msg.obj = proc;
mAm.mHandler.sendMessageDelayed(msg,
proc.execServicesFg ? SERVICE_TIMEOUT : SERVICE_BACKGROUND_TIMEOUT);
}
如果 Service 在规定时间内启动完成，则这个消息会被 remove 掉，我们今天要看一下超时之后，收到这个消息是怎么处理的。
// com.android.server.am.ActivityManagerService.MainHandler
final class MainHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case SERVICE_TIMEOUT_MSG: {
mServices.serviceTimeout((ProcessRecord)msg.obj);
} break;
}
}
mServices 是 ActiveServices：
// com.android.server.am.ActiveServices#serviceTimeout
void serviceTimeout(ProcessRecord proc) {
…
if (timeout != null && mAm.mProcessList.mLruProcesses.contains(proc)) {
Slog.w(TAG, "Timeout executing service: " + timeout);
…
mAm.mHandler.removeCallbacks(mLastAnrDumpClearer);
mAm.mHandler.postDelayed(mLastAnrDumpClearer, LAST_ANR_LIFETIME_DURATION_MSECS);
anrMessage = "executing service " + timeout.shortInstanceName;
}
…
if (anrMessage != null) {
proc.appNotResponding(null, null, null, null, false, anrMessage);
}
}
appNotResponding 就是最终处理 ANR 逻辑的代码了
// com.android.server.am.ProcessRecord
void appNotResponding(String activityShortComponentName,
ApplicationInfo aInfo,
…) {
…
if (isMonitorCpuUsage()) {
mService.updateC
puStatsNow();
}
…
if (isSilentAnr() && !isDebugging()) {
kill(“bg anr”, true);
return;
}
// Bring up the infamous App Not Responding dialog
Message msg = Message.obtain();
msg.what = ActivityManagerService.SHOW_NOT_RESPONDING_UI_MSG;
msg.obj = new AppNotRespondingDialog.Data(this, aInfo, aboveSystem);
mService.mUiHandler.sendMessage(msg);
}
如果 isSilentAnr() 为 true，则直接杀死所在进程，不会发送显示 ANR 弹窗的消息。来看下相关方法
boolean isSilentAnr() {
return !getShowBackground() && !isInterestingForBackgroundTraces();
}
private boolean getShowBackground() {
);
mService.mUiHandler.sendMessage(msg);
}
如果 isSilentAnr() 为 true，则直接杀死所在进程，不会发送显示 ANR 弹窗的消息。来看下相关方法
boolean isSilentAnr() {
return !getShowBackground() && !isInterestingForBackgroundTraces();
}
private boolean getShowBackground() {
标签：面试题,java,安卓,ActivityThread,2021,ANR,msg,android,proc 来源： https://blog.csdn.net/m0_66264533/article/details/122620715