Android卡顿优化 | 自动化卡顿检测方案与优化(AndroidPerformanceMonitor / BlockCanary)

本文要点

• 为何需要自动化检测方案
• 自动卡顿检测方案原理
• 看一下Looper.loop()源码
• 实现思路
• AndroidPerformanceMonitor实战
• 基于AndroidPerformanceMonitor源码简析
• 接下来我们讨论一下方案的不足
• 自动检测方案优化

项目GitHub

为何需要自动化检测方案

• 前面提到过的系统工具只适合线下针对性分析，无法带到线上！
• 线上及测试环节需要自动化检测方案

方案原理

• 源于Android的消息处理机制；
  一个线程不管有多少Handler，只会有一个Looper存在，
  主线程中所有的代码，都会通过Looper.loop()执行；
• loop()中有一个mLogging对象，
  它在每个Message处理前后都会被调用：
  
• 如果主线程发生卡顿，
  一定是在dispatchMessage执行了耗时操作！
  

  Handler机制图

由此，我们便可以通过mLogging对象
对dispatchMessage执行的时间进行监控；

看一下Looper.loop()源码

    public static void loop() {
        final Looper me = myLooper();
        if (me == null) {
            throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread.");
        }
        final MessageQueue queue = me.mQueue;

        // Make sure the identity of this thread is that of the local process,
        // and keep track of what that identity token actually is.
        Binder.clearCallingIdentity();
        final long ident = Binder.clearCallingIdentity();

        // Allow overriding a threshold with a system prop. e.g.
        // adb shell 'setprop log.looper.1000.main.slow 1 && stop && start'
        final int thresholdOverride =
                SystemProperties.getInt("log.looper."
                        + Process.myUid() + "."
                        + Thread.currentThread().getName()
                        + ".slow", 0);

        boolean slowDeliveryDetected = false;

        for (;;) {
            Message msg = queue.next(); // might block
            if (msg == null) {
                // No message indicates that the message queue is quitting.
                return;
            }

            // This must be in a local variable, in case a UI event sets the logger
            final Printer logging = me.mLogging;
            if (logging != null) {
                logging.println(">>>>> Dispatching to " + msg.target + " " +
                        msg.callback + ": " + msg.what);
            }

            final long traceTag = me.mTraceTag;
            long slowDispatchThresholdMs = me.mSlowDispatchThresholdMs;
            long slowDeliveryThresholdMs = me.mSlowDeliveryThresholdMs;
            if (thresholdOverride > 0) {
                slowDispatchThresholdMs = thresholdOverride;
                slowDeliveryThresholdMs = thresho