目标
收集 LogCat 的定期更新并将这些文本块保存（附加）到 SD 卡上的文件中
问题
由于特定时间戳，Log 类不提供更新
可能的解决方案
我的计划是定期运行类似于以下内容的代码：http ://www.helloandroid.com/tutorials/reading-logs-programatically 或https://stackoverflow.com/a/9039352/550471
但是，有一个显着的区别：使用-v time参数来确保每一行都带有时间戳。
每次收集 LogCat 数据后，应用程序将存储最后一个 Log 条目的时间戳。下次收集 LogCat 数据时，应用程序将搜索文本以查找时间戳，然后将数据块保存到自指定时间戳以来添加到日志的 sdcard。
可能的问题
如果在太短的时间内收集 LogCat 数据，则 CPU 正忙于处理大量“旧”数据。如果 Logcat 数据的收集时间过长，则可能会丢失一些数据。
有没有更好的办法 ？
这就是我想出的——当它不冻结时效果很好。
正如您可能知道的那样，Runtime.getRuntime().exec("")在 Android 中导致 ANR 的可能性比 Jelly Bean 更早。如果有人有解决 ANR 的方法，请分享。
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import android.os.Environment;
import android.util.Log;
/*
* For (compressed) buffer sizes, see: http://elinux.org/Android_Logging_System
* buffer:main = 64KB
* buffer:radio = 64KB
* buffer:system = 64KB
* buffer:event = 256KB
*
* NOTE: the 'command' must include "-d -v time" !!
* to switch buffers, use "-b <buffer>"
*/
public class LogCatReader {
// constants
private static final String CR = "\r\n";
private static final String END_OF_DATE_TIME = "): ";
private static final int DEFAULT_SEARCH_START_INDEX = 0;
// member variables
private StringBuilder mLog;
private LogThread mLogThread = null;
private String mLastLogReadToken = "";
private String mLogCommand = "";
private int mStringCapacity;
private File mFileTarget = null;
// constructor
public LogCatReader(String command, int capacity) {
mLogCommand = command;
mStringCapacity = capacity;
}
// returns complete logcat buffer
// note: takes about 1.5sec to finish
synchronized public StringBuilder getLogComplete() {
try {
// capacity should be about 25% bigger than buffer size since the
// buffer is compressed
mLog = new StringBuilder(mStringCapacity);
// command to capture log
Process process = Runtime.getRuntime().exec(mLogCommand);
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(process.getInputStream()));
String line;
while ((line = bufferedReader.readLine()) != null) {
// append() is costly if capacity needs to be increased, be sure
// to reserve enough in the first place
mLog.append(line + CR);
}
} catch (IOException e) {
}
return mLog;
}
public String getLogUpdatesOnly() {
String strReturn = "";
StringBuilder sbLog = getLogComplete();
try {
int iStartindex = DEFAULT_SEARCH_START_INDEX;
// if there exists a token from a previous search then use that
if (mLastLogReadToken.length() > 0) {
iStartindex = sbLog.indexOf(mLastLogReadToken);
// if string not found then start at beginning
if (iStartindex == -1) {
// start search at beginning of log
iStartindex = DEFAULT_SEARCH_START_INDEX;
}
}
int iEndindex = sbLog.length();
// if token is found then move index to the next line
if (iStartindex > DEFAULT_SEARCH_START_INDEX) {
iStartindex = sbLog.indexOf(CR, iStartindex);
if (iStartindex != -1) {
iStartindex += CR.length();
} else {
// return an empty string
iStartindex = iEndindex;
}
}
// grab the data between the start and end indices
strReturn = sbLog.substring(iStartindex, iEndindex);
// grab date/time token for next search
iStartindex = sbLog.lastIndexOf(END_OF_DATE_TIME);
if (iStartindex != -1) {
iEndindex = iStartindex;
iStartindex = sbLog.lastIndexOf(CR, iEndindex);
iStartindex += CR.length();
if (iStartindex == -1) {
// read from beginning
iStartindex = 0;
}
mLastLogReadToken = sbLog.substring(iStartindex, iEndindex);
}
} catch (Exception e) {
strReturn = "";
}
return strReturn;
}
public void startPeriodicLogCatReader(int timePeriod, String logfilename) {
if (mLogThread == null) {
mLogThread = new LogThread(timePeriod, logfilename);
mLogThread.start();
}
}
public void stopPeriodicLogCatReader() {
if (mLogThread != null) {
mLogThread.interrupt();
mLogThread = null;
}
}
private class LogThread extends Thread {
private boolean mInterrupted;
private int mTimePeriod;// in seconds
private String mLogref;
private BufferedWriter mBuffWriter = null;
public boolean mPauseLogCollection = false;
// constructor: logfilename is optional - pass null to not use
public LogThread(int timePeriod, String logfilename) {
mTimePeriod = timePeriod;
if (logfilename != null) {
File fLogFolder = new File(
Environment.getExternalStorageDirectory() + "/logfiles");
if (fLogFolder.exists() == false) {
if (fLogFolder.mkdirs() == false) {
Log.e("LogCatReader",
"Could not create "
+ fLogFolder.getAbsolutePath());
}
}
mFileTarget = new File(
Environment.getExternalStorageDirectory() + "/logfiles",
logfilename);
if (mFileTarget.exists() == false) {
try {
// file doesn't yet exist - create a fresh one !
mFileTarget.createNewFile();
} catch (IOException e) {
e.printStackTrace();
mFileTarget = null;
}
}
}
}
@Override
public void interrupt() {
mInterrupted = true;
super.interrupt();
}
@Override
public void run() {
super.run();
// initialization
mInterrupted = false;
// set up storage
if (mFileTarget != null) {
try {
mBuffWriter = new BufferedWriter(new FileWriter(
mFileTarget, true), 10240);
} catch (IOException e) {
e.printStackTrace();
}
}
while ((mInterrupted == false) && (mBuffWriter != null)) {
if (mPauseLogCollection == false) {
// read log updates
mLogref = getLogUpdatesOnly();
// save log updates to file
try {
mBuffWriter.append(mLogref);
mBuffWriter.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
if (!mInterrupted) {
try {
sleep(mTimePeriod * 1000);
} catch (InterruptedException e) {
}
}
}
if (mBuffWriter != null) {
try {
mBuffWriter.close();
mBuffWriter = null;
} catch (IOException e) {
e.printStackTrace();
}
}
}
}// end of inner class
}// end of outer class
我用来仅查找更新的过程是捕获 logcat 的最后一行的日期和时间，并将其用作下次搜索标记。
要使用这个类，下面是一个例子：
LogCatReader logcatPeriodicReader = new LogCatReader("logcat -b main -d -v time", 80 * 1024);//collect "main" buffer, exit after reading logcat
logcatPeriodicReader.startPeriodicLogReader(90, "log.txt");//read logcat every 90 secs