背景

在app開(kāi)發(fā)過(guò)程中互站，經(jīng)常會(huì)出現(xiàn)由于在主線程執(zhí)行某些耗時(shí)操作(例如db，文件io操作等)導(dǎo)致頁(yè)面顯示會(huì)出現(xiàn)卡頓，影響用戶體驗(yàn)抠璃。本文主要講解一種基于Handler Message機(jī)制的卡頓檢測(cè)方案术奖，

原理 ：Android系統(tǒng)在執(zhí)行每個(gè)方法的時(shí)候礁遵，會(huì)在方法的開(kāi)始和結(jié)束打印日志。

在方法開(kāi)始執(zhí)行的時(shí)候采记，會(huì)打印

07-01 13:06:25.139 13471-13471/"" D/BlockDetector: BlockDetector init println x = >>>>> Dispatching to Handler (android.app.ActivityThread$H) {34d05903} null: 102
07-01 13:06:25.168 13471-13471/"" D/BlockDetector: BlockDetector init println x = >>>>> Dispatching to Handler (android.view.ViewRootImpl$ViewRootHandler) {3a8c2969} null: 6
07-01 13:06:25.219 13471-13471/"" D/BlockDetector: BlockDetector init println x = >>>>> Dispatching to Handler (android.view.ViewRootImpl$ViewRootHandler) {3a8c2969} null: 8

在方法結(jié)束執(zhí)行的時(shí)候佣耐，會(huì)打印

07-01 13:07:02.036 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@dae1898
07-01 13:07:02.275 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@3c2ef8f1
07-01 13:07:02.521 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@2b3f9cd6
07-01 13:07:02.758 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@2f632b57
07-01 13:07:03.003 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@b82644
07-01 13:07:03.247 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@6a9332d
07-01 13:07:03.505 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@2570b062
07-01 13:07:07.634 13471-13471/com.apache.fastandroid D/BlockDetector: BlockDetector init println x = <<<<< Finished to Handler (android.os.Handler) {29d2efdd} com.squareup.leakcanary.AndroidWatchExecutor$1@148525f3

利用這個(gè)特點(diǎn)，然后就可以攔截這些打印日志唧龄，在>>>>> Dispatching的時(shí)候兼砖，延時(shí)特定時(shí)間（例如500ms）開(kāi)始監(jiān)控耗時(shí)， 在<<<<< Finished的時(shí)候結(jié)束監(jiān)控，取消延時(shí)執(zhí)行代碼邏輯讽挟。如果延時(shí)的代碼邏輯有執(zhí)行懒叛，說(shuō)明當(dāng)前方法耗時(shí)超過(guò)了500ms，則把對(duì)應(yīng)的堆棧信息打印出來(lái)耽梅。

操作步驟

具體代碼如下:

/**
 *
 * 檢測(cè)主線程卡頓
 */

public class BlockDetector {

    public static void init() {
        if(DebugUtils.isDebug()) {
            Looper.getMainLooper().setMessageLogging(new Printer() {
                //分發(fā)和處理消息開(kāi)始前的log
                private static final String START = ">>>>> Dispatching";
                //分發(fā)和處理消息結(jié)束后的log
                private static final String END = "<<<<< Finished";

                @Override
                public void println(String x) {
                    NLog.d("BlockDetector init println x = %s",x);
                    if (x.startsWith(START)) {
                        //開(kāi)始計(jì)時(shí)
                        BlockMonitor.getInstance().startMonitor();
                    }
                    if (x.startsWith(END)) {
                        //結(jié)束計(jì)時(shí)
                        BlockMonitor.getInstance().removeMonitor();
                    }
                }
            });
        }
    }

public class BlockMonitor {
    private static final String TAG = "=============BlockMonitor============= \n %s";
    private static BlockMonitor sInstance = new BlockMonitor();
    private Handler mIoHandler;
    //方法耗時(shí)的卡口,500毫秒
    private static final long TIME_BLOCK = 500L;
    //存放一個(gè)msg周期的卡頓堆棧信息薛窥，防止重復(fù)打印
    private Set<String> mBlockStackTrace;

    private BlockMonitor() {
        HandlerThread logThread = new HandlerThread("BlockMonitor");
        logThread.start();
        mIoHandler = new Handler(logThread.getLooper());
        mBlockStackTrace = Collections.synchronizedSet(new HashSet<String>());
    }

    private Runnable mLogRunnable = new Runnable() {
        @Override
        public void run() {
            //繼續(xù)檢測(cè)
            startMonitor();
            //打印出執(zhí)行的耗時(shí)方法的棧消息
            StackTraceElement[] stackTrace = Looper.getMainLooper().getThread().getStackTrace();
            StringBuilder sb = new StringBuilder();
            for (StackTraceElement s : stackTrace) {
                sb.append(s.toString());
                sb.append("\n");
            }
            String s = sb.toString();
            if (!mBlockStackTrace.contains(s)) {
                mBlockStackTrace.add(s);
                //BlockLogUtils.e(TAG, s);
                NLog.e(TAG, s);
            }
        }
    };

    public static BlockMonitor getInstance() {
        return sInstance;
    }

    /**
     * 開(kāi)始計(jì)時(shí)
     */
    public void startMonitor() {
        NLog.d("BlockDetector startMonitor");
        mIoHandler.postDelayed(mLogRunnable, TIME_BLOCK);
    }

    /**
     * 停止計(jì)時(shí)
     */
    public void removeMonitor() {
        NLog.d("BlockDetector removeMonitor");
        mIoHandler.removeCallbacks(mLogRunnable);
        mBlockStackTrace.clear();
    }
}