摘抄自ANR原理分析
#5.1 ANR分类
由小节[3.5] InputMonitor.notifyANR完成, 当发生ANR时system log中会出现以下信息, 并且TAG=WindowManager:
Input event dispatching timed out xxx. Reason: + reason, 其中xxx取值:
窗口类型: sending to windowState.mAttrs.getTitle() 应用类型: sending to application appWindowToken.stringName 其他类型: 则为空. 至于Reason主要有以下类型:
## 5.1.1 reason类型
由小节[2.3.1]checkWindowReadyForMoreInputLocked完成， ANR reason主要有以下几类：
无窗口, 有应用：Waiting because no window has focus but there is a focused application that may eventually add a window when it finishes starting up.
窗口暂停: Waiting because the [targetType] window is paused.
窗口未连接: Waiting because the [targetType] window’s input channel is not registered with the input dispatcher. The window may be in the process of being removed.
窗口连接已死亡：Waiting because the [targetType] window’s input connection is [Connection.Status]. The window may be in the process of being removed.
窗口连接已满：Waiting because the [targetType] window’s input channel is full. Outbound queue length: [outboundQueue长度]. Wait queue length: [waitQueue长度].
按键事件，输出队列或事件等待队列不为空：Waiting to send key event because the [targetType] window has not finished processing all of the input events that were previously delivered to it. Outbound queue length: [outboundQueue长度]. Wait queue length: [waitQueue长度].
非按键事件，事件等待队列不为空且头事件分发超时500ms：Waiting to send non-key event because the [targetType] window has not finished processing certain input events that were delivered to it over 500ms ago. Wait queue length: [waitQueue长度]. Wait queue head age: [等待时长].
其中 targetType: 取值为”focused”或者”touched” Connection.Status: 取值为”NORMAL”，”BROKEN”，”ZOMBIE” 另外, findFocusedWindowTargetsLocked, findTouchedWindowTargetsLocked这两个方法中可以通过实现 updateDispatchStatisticsLocked()来分析anr问题.
#5.2 drop事件分类
由小节[2.1.2] dropInboundEventLocked完成，输出事件丢弃的原因：
DROP_REASON_POLICY: “inbound event was dropped because the policy consumed it”;
DROP_REASON_DISABLED: “inbound event was dropped because input dispatch is disabled”;
DROP_REASON_APP_SWITCH: “inbound event was dropped because of pending overdue app switch”;
DROP_REASON_BLOCKED: “inbound event was dropped because the current application is not responding and the user has started interacting with a different application””;
DROP_REASON_STALE: “inbound event was dropped because it is stale”;
其他:
doDispatchCycleFinishedLockedInterruptible的过程, 会记录分发时间超过2s的事件, findFocusedWindowTargetsLocked的过程, 可以统计等待时长信息.
