Android进阶：一、日志打印和保存策略

前言：

项目开始没有做好日志统计工作，每次有问题后台都得找前台对接，严重影响工作效率。最近特地在项目中加上日志保存策略，在此分享，供需要的人学习。

一.更详细的日志信息

既然决定自己设置一个log，那我们即可以让它显示更多的信息，如线程信息：threadId，threadName等：

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(堆栈轨迹)存放的就是方法调用栈的信息，我们从中获取方法执行的线程相关的信息，以及执行的方法名称等。这些信息能帮助我们更好的查找问题之所在。

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方法打印相关信息就可。

二.日志保存策略

后台的人在测试的时候会遇到BUG，有时候不知道究竟是前台出了问题还是后台的问题，为了更好更快速的定位，后台应该知道前台的日志保存在哪里。这就需要我们制定一个日志保存策略。（即便要上传日志，也应该先保存成文件再上传文件，不然每一条日志调用一次接口，接口的压力会很大，很不正当）

因为保存日志的过程是个耗时过程，我们需要开启线程去保存。但是日志产生的频率可能很高，又不能采用一般的线程去解决，太多的线程也会损耗性能。所以我们应该考虑队列的形式保存日志，而后一条一条的去保存。

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) {                    }                }            }        }

我们使用HandlerThread来解决这个任务。HandlerThread是一个可以使用handler的Thread。当我们把消息保存到消息队列中去之后会在线程中去解决，又能保证不会产生很多线程。其实这里也可以使用instentservice实现，这个服务适合量大而不太耗时的任务。

最后在一个方法中统一打印和保存就可：

    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);        }    }

自己设置的log策略还是比较简单，主要就是这个思想：打印日志信息详细，保存要采用队列的形式。一下是一律代码：

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) 级别日志     *     * @param str String     */    public void v(Object str) {        logLevel = Log.VERBOSE;        logPrint(logLevel, str);    }    /**     * Debug(3) 级别日志     *     * @param str String     */    public void d(Object str) {        logLevel = Log.DEBUG;        logPrint(logLevel, str);    }    /**     * Info(4) 级别日志     *     * @param str String     */    public void i(Object str) {        logLevel = Log.INFO;        logPrint(logLevel, str);    }    /**     * Warn(5) 级别日志     *     * @param str String     */    public void w(Object str) {        logLevel = Log.WARN;        logPrint(logLevel, str);    }    /**     * Error(6) 级别日志     *     * @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);        }    }    /**     * 获取当前方法名     *     * @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", "文件未创立成功，可能是读写权限没给");                }            }            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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