在Android开发中，遇到需要Debug启动过程中的问题时，往往会因为在启动过程中log丢失而异常麻烦，为此我们用了下面这个简单的方案。
假设你的应用或者framework的某些服务需要在开机时越快启动越好，那么在启动过程中某些log会丢失，但是程序的逻辑不会丢失，为此我们可以把需要分析的关键部位的log缓存在内存中，等到问题出现后系统稳定后再通过某些方式把缓存的log信息读出来，因为log是存在内存中的，所以不会有任何的丢失。
为了做到程序的灵活性，我们使用了检测文件是否存在来打开和关闭缓存功能，这样我们可以缓存功能的代码嵌入到程序本身，平时它都不会运行，只有当需要的时候，在特定的目录下建立一个文件后，它才会运行。同时为了不改变应用程序本身的代码就能读取缓存的信息，我们使用接收广播的形式来打印，下面是程序的源码，欢迎提供你的宝贵意见和建议：
package ;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Handler;
import android.os.Message;
import android.os.Process;
import android.util.Log;
public class LogAssist {
private static final String TAG = "LogAssist";
//control command
private static final String ACTION_PRINT = "action.logassist.print";
private static final String ACTION_CONTROL_PAUSE = "action.logassist.control.pause";
private static final String ACTION_CONTROL_RESUME = "action.logassist.control.resume";
private static final String ACTION_CONTROL_CLEAR = "action.logassist.control.clear";
//delay time to print the buffered log (ms)
private static final String ACTION_EXTRA_DELAY2PRINT = "delay";
//msg to print the log
private static final int MSG_PRINT = 2008;
//switch the log assist on or off by adding/removing this file
private static final String SWITCHER_FILE = "/data/data/com./logassist_enabled";
//maxium buffer used to cache the log
private static final int MAX_BUFFER_SIZE = 10241000;
//buffer size to clear when it is full
private static final int BUFFER_SIZE_TO_CLEAR = 512;
//start line of the log
private static final String STR_LOG_START_LINE = "----------------LogAssist Print------------\n";
static StringBuffer mLogBuffer;
static SimpleDateFormat mDateFormat;
static boolean mStarted = false;
static int mPid;
static Handler mPrintHandler = null;
public static void init(Context context) {
if (!needStart()) {
Log.d(TAG, "LogAssist is not enabled.");
return;
}
mLogBuffer = new StringBuffer(STR_LOG_START_LINE);
mDateFormat = new SimpleDateFormat("dd-M-yyyy hh:mm:ss.SSS");
mStarted = true;
mPid = Process.myPid();
registerControlReceiver(context);
Log.d(TAG, "LogAssist is enabled.");
}
static class PrintHandlerCallBack implements Handler.Callback {
@Override
public boolean handleMessage(Message msg) {
switch (msg.what) {
case MSG_PRINT:
print();
break;
}
return false;
}
}
private static void registerControlReceiver(Context context) {
BroadcastReceiver controlReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
Log.d(TAG, "received intent :"+intent.getAction());
if (intent == null) {
return;
}
String action = intent.getAction();
if (ACTION_PRINT.equals(action)) {
int delay = intent.getIntExtra(ACTION_EXTRA_DELAY2PRINT, 0);
Log.d(TAG, " intent :delay="+delay);
if (delay <=0) {
print();
} else {
if (mPrintHandler == null) {
mPrintHandler = new Handler(new PrintHandlerCallBack());
}
mPrintHandler.sendEmptyMessageDelayed(MSG_PRINT, delay);
}
} else if (ACTION_CONTROL_PAUSE.equals(action)) {
mStarted = false;
}else if (ACTION_CONTROL_RESUME.equals(action)) {
mStarted = true;
}else if (ACTION_CONTROL_CLEAR.equals(action)) {
mLogBuffer = new StringBuffer(STR_LOG_START_LINE);
}
}
};
IntentFilter ctrlIntentFilter = new IntentFilter();
ctrlIntentFilter.addAction(ACTION_PRINT);
ctrlIntentFilter.addAction(ACTION_CONTROL_PAUSE);
ctrlIntentFilter.addAction(ACTION_CONTROL_RESUME);
ctrlIntentFilter.addAction(ACTION_CONTROL_CLEAR);
context.registerReceiver(controlReceiver, ctrlIntentFilter);
}
//check the switch file to see we need run log assist
private static boolean needStart() {
File switcher = new File(SWITCHER_FILE);
return switcher.exists();
}
public static void log(String info) {
if (!mStarted) {
return;
}
if (mLogBuffer.length() >= MAX_BUFFER_SIZE) {
//if buffer is full, remove first part defined by BUFFER_SIZE_TO_CLEAR
if (mLogBuffer.length() > BUFFER_SIZE_TO_CLEAR) {
//if the cached size is bigger than size to be cleared
mLogBuffer.delete(0, BUFFER_SIZE_TO_CLEAR);
} else {
//if the cached size is not bigger than size to be cleared, reset the buffer
mLogBuffer = new StringBuffer(STR_LOG_START_LINE);
}
}
String date = mDateFormat.format(new Date());
int tid = Process.myTid();
mLogBuffer.append(date + " " + mPid + " " + tid + " " + info + "\n");
}
private static void print() {
if (mLogBuffer != null) {
Log.i(TAG, mLogBuffer.toString());
}
}
}
源码可从此下载： https://github.com/belyxiong/LogAssist
