Android進階：1、日誌打印和保存策略

時間 2020-02-11

原文原文鏈接

前言：
項目開始沒有作好日誌統計工做，每次有問題後端都得找前端對接，嚴重影響工做效率。最近特意在項目中加上日誌保存策略，在此分享，供須要的人學習。前端

一.更詳細的日誌信息
既然決定自定義一個log，那咱們就可讓它顯示更多的信息，如線程信息：threadId，threadName等：後端

private String getFunctionName() {
        StackTraceElement[] sts = Thread.currentThread().getStackTrace();
        if (sts == null) {
            return null;
        }

        for (StackTraceElement st : sts) {
            if (st.isNativeMethod()) {
                continue;
            }
            if (st.getClassName().equals(Thread.class.getName())) {
                continue;
            }
            if (st.getClassName().equals(this.getClass().getName())) {
                continue;
            }

            Thread t = Thread.currentThread();
            return "[T(id:" + t.getId() +
                    ", name:" + t.getName() +
                    ", priority:" + t.getPriority() +
                    ", groupName:" + t.getThreadGroup().getName() +
                    "): " + st.getFileName() + ":"
                    + st.getLineNumber() + " " + st.getMethodName() + " ]";
        }
        return "";
    }

StackTrace(堆棧軌跡)存放的就是方法調用棧的信息，咱們從中獲取方法執行的線程相關的信息，以及執行的方法名稱等。這些信息能幫助咱們更好的查找問題之所在。多線程

private void logPrint(int logLevel, Object msg) {
        if (isDebug) {
            String name = getFunctionName();
            customTag = TextUtils.isEmpty(customTag) ? defaultTag : customTag;
            Log.println(logLevel, customTag, name + " - " + msg);
        }
    }

使用Log.println方法打印相關信息便可。app

二.日誌保存策略
後端的人在測試的時候會遇到BUG，有時候不知道究竟是前端出了問題仍是後端的問題，爲了更好更快速的定位，後端應該知道前端的日誌保存在哪裏。這就須要咱們制定一個日誌保存策略。（即便要上傳日誌，也應該先保存成文件再上傳文件，否則每一條日誌調用一次接口，接口的壓力會很大，很不合理）ide

因爲保存日誌的過程是個耗時過程，咱們須要開啓線程去保存。可是日誌產生的頻率可能很高，又不能採用通常的線程去處理，太多的線程也會損耗性能。因此咱們應該考慮隊列的形式保存日誌，而後一條一條的去保存。oop

public void initSaveStrategy(Context context) {
        if (saveLogStrategy != null || !isDebug) {
            return;
        }
        final int MAX_BYTES = 1024 * 1024;
        String diskPath = Environment.getExternalStorageDirectory().getAbsolutePath();
        File cacheFile = context.getCacheDir();
        if (cacheFile != null) {
            diskPath = cacheFile.getAbsolutePath();
        }
        String folder = diskPath + File.separatorChar + "log";
        HandlerThread ht = new HandlerThread("SohuLiveLogger." + folder);
        ht.start();
        Handler handler = new SaveLogStrategy.WriteHandler(ht.getLooper(), folder, MAX_BYTES);
        saveLogStrategy = new SaveLogStrategy(handler);
    }

public static class WriteHandler extends Handler {

        private final String folder;
        private final int maxFileSize;

        WriteHandler(@NonNull Looper looper, @NonNull String folder, int maxFileSize) {
            super(checkNotNull(looper));
            this.folder = checkNotNull(folder);
            this.maxFileSize = maxFileSize;
        }

        @Override
        public void handleMessage(@NonNull Message msg) {
            String content = (String) msg.obj;
            FileWriter fileWriter = null;
            File logFile = getLogFile(folder, "logs");
            try {
                fileWriter = new FileWriter(logFile, true);
                writeLog(fileWriter, content);
                fileWriter.flush();
                fileWriter.close();
            } catch (IOException e) {
                if (fileWriter != null) {
                    try {
                        fileWriter.flush();
                        fileWriter.close();
                    } catch (IOException e1) {

                    }
                }
            }
        }

咱們使用HandlerThread來處理這個任務。HandlerThread是一個可使用handler的Thread。當咱們把消息保存到消息隊列中去以後會在線程中去處理，又能保證不會產生不少線程。其實這裏也可使用instentservice實現，這個服務適合量大而不太耗時的任務。性能

最後在一個方法中統一打印和保存便可：學習

private void logPrint(int logLevel, Object msg) {
        if (isDebug) {
            String name = getFunctionName();
            if (saveLogStrategy != null) {
                saveLogStrategy.log(Log.ERROR, customTag, name + " - " + msg);
            }
            Log.println(logLevel, customTag, name + " - " + msg);
        }
    }

自定義的log策略仍是比較簡單，主要就是這個思想：打印日誌信息詳細，保存要採用隊列的形式。一下是所有代碼：測試

public class Logger {
    public final static String tag = "";
    private static SaveLogStrategy saveLogStrategy;
    private final static boolean logFlag = true;
    private static Logger logger;
    private int logLevel = Log.VERBOSE;
    private static boolean isDebug = BuildConfig.DEBUG;
    private String customTag = null;

    private Logger(String customTag) {
        this.customTag = customTag;
    }

    public void initSaveStrategy(Context context) {
        if (saveLogStrategy != null || !isDebug) {
            return;
        }
        final int MAX_BYTES = 1024 * 1024;
        String diskPath = Environment.getExternalStorageDirectory().getAbsolutePath();
        File cacheFile = context.getCacheDir();
        if (cacheFile != null) {
            diskPath = cacheFile.getAbsolutePath();
        }
        String folder = diskPath + File.separatorChar + "log";
        HandlerThread ht = new HandlerThread("Logger." + folder);
        ht.start();
        Handler handler = new SaveLogStrategy.WriteHandler(ht.getLooper(), folder, MAX_BYTES);
        saveLogStrategy = new SaveLogStrategy(handler);
    }

    public static Logger getLogger(String tag) {
        if (logger == null) {
            logger = new Logger(tag);
        }
        return logger;
    }

    public static Logger getLogger() {
        if (logger == null) {
            logger = new Logger(tag);
        }
        return logger;
    }

    /**
     * Verbose(2) 級別日誌
     *
     * @param str String
     */
    public void v(Object str) {
        logLevel = Log.VERBOSE;
        logPrint(logLevel, str);
    }

    /**
     * Debug(3) 級別日誌
     *
     * @param str String
     */
    public void d(Object str) {
        logLevel = Log.DEBUG;
        logPrint(logLevel, str);
    }

    /**
     * Info(4) 級別日誌
     *
     * @param str String
     */
    public void i(Object str) {
        logLevel = Log.INFO;
        logPrint(logLevel, str);
    }

    /**
     * Warn(5) 級別日誌
     *
     * @param str String
     */
    public void w(Object str) {
        logLevel = Log.WARN;
        logPrint(logLevel, str);
    }

    /**
     * Error(6) 級別日誌
     *
     * @param str String
     */
    public void e(Object str) {
        logLevel = Log.ERROR;
        logPrint(logLevel, str);
    }

    private void logPrint(int logLevel, Object msg) {
        if (isDebug) {
            String name = getFunctionName();
            if (saveLogStrategy != null) {
                saveLogStrategy.log(Log.ERROR, customTag, name + " - " + msg);
            }
            Log.println(logLevel, customTag, name + " - " + msg);
        }
    }

    /**
     * 獲取當前方法名
     *
     * @return 方法名
     */
    private String getFunctionName() {
        StackTraceElement[] sts = Thread.currentThread().getStackTrace();
        if (sts == null) {
            return null;
        }

        for (StackTraceElement st : sts) {
            if (st.isNativeMethod()) {
                continue;
            }
            if (st.getClassName().equals(Thread.class.getName())) {
                continue;
            }
            if (st.getClassName().equals(this.getClass().getName())) {
                continue;
            }

            Thread t = Thread.currentThread();
            return "[Thread(id:" + t.getId() +
                    ", name:" + t.getName() +
                    ", priority:" + t.getPriority() +
                    ", groupName:" + t.getThreadGroup().getName() +
                    "): " + st.getFileName() + ":"
                    + st.getLineNumber() + " " + st.getMethodName() + " ]";
        }
        return "";
    }
}

public class SaveLogStrategy {

    @NonNull
    private final Handler handler;

    public SaveLogStrategy(@NonNull Handler handler) {
        this.handler = checkNotNull(handler);
    }

    public void log(int level, @Nullable String tag, @NonNull String message) {
        checkNotNull(message);
        handler.sendMessage(handler.obtainMessage(level, message));
    }

    static class WriteHandler extends Handler {

        private final String folder;
        private final int maxFileSize;

        WriteHandler(@NonNull Looper looper, @NonNull String folder, int maxFileSize) {
            super(checkNotNull(looper));
            this.folder = checkNotNull(folder);
            this.maxFileSize = maxFileSize;
        }

        @SuppressWarnings("checkstyle:emptyblock")
        @Override
        public void handleMessage(@NonNull Message msg) {
            String content = (String) msg.obj;
            FileWriter fileWriter = null;
            File logFile = getLogFile(folder, "logs");

            try {
                fileWriter = new FileWriter(logFile, true);

                writeLog(fileWriter, content);

                fileWriter.flush();
                fileWriter.close();
            } catch (IOException e) {
                if (fileWriter != null) {
                    try {
                        fileWriter.flush();
                        fileWriter.close();
                    } catch (IOException e1) {

                    }
                }
            }
        }

        private void writeLog(@NonNull FileWriter fileWriter, @NonNull String content) throws IOException {
            checkNotNull(fileWriter);
            checkNotNull(content);
            fileWriter.append("\n").append(content);
        }

        private File getLogFile(@NonNull String folderName, @NonNull String fileName) {
            checkNotNull(folderName);
            checkNotNull(fileName);

            File folder = new File(folderName);
            if (!folder.exists()) {
                if (!folder.mkdirs()) {
                    Log.println(Log.ERROR, "saveLog", "文件未建立成功，多是讀寫權限沒給");
                }
            }

            int newFileCount = 0;
            File newFile;
            File existingFile = null;

            newFile = new File(folder, String.format("%s_%s.txt", fileName, newFileCount));
            while (newFile.exists()) {
                existingFile = newFile;
                newFileCount++;
                newFile = new File(folder, String.format("%s_%s.txt", fileName, newFileCount));
            }

            if (existingFile != null) {
                if (existingFile.length() >= maxFileSize) {
                    return newFile;
                }
                return existingFile;
            }

            return newFile;
        }
    }
}

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