Android log 方法

package test;

public abstract class Logger {
    private static Class<? extends Logger> mLoggerClass = null;
    public static final boolean DBG = true;
    public static final String TAG = null;
    public static final String LINE = "------->";

    private String mTag;

    public Logger() {
    }

    public Logger(String tag) {
        this.mTag = tag;
    }

    public static void registerLogger(Class<? extends Logger> loggerClass) {
        Logger.mLoggerClass = loggerClass;
    }

    public static void unregisterLogger() {
        Logger.mLoggerClass = null;
    }

    public static Logger getLogger(String tag) {
        tag = "[" + tag + "]";
        Logger logger = null;
        if (mLoggerClass != null) {
            try {
                logger = mLoggerClass.newInstance();
                logger.mTag = tag;
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        if (logger == null) {
            logger = new Log(tag);
        }
        return logger;
    }

    public String getTag() {
        return mTag;
    }

    public void d(String tag, String str) {
        debug(mTag + LINE + str);
    }

    public void i(String tag, String str) {
        info(mTag + LINE + str);
    }

    public void w(String tag, String str) {
        warn(mTag + LINE + str);
    }

    public void e(String tag, String str) {
        error(mTag + LINE + str);
    }

    public void d(String tag, String str, Throwable tr) {
        debug(mTag + LINE + str, tr);
    }

    public void i(String tag, String str, Throwable tr) {
        info(mTag + LINE + str, tr);
    }

    public void w(String tag, String str, Throwable tr) {
        warn(mTag + LINE + str, tr);
    }

    public void e(String tag, String str, Throwable tr) {
        error(mTag + LINE + str, tr);
    }

    protected abstract void debug(String str);

    protected abstract void info(String str);

    protected abstract void warn(String str);

    protected abstract void error(String str);

    protected abstract void debug(String str, Throwable tr);

    protected abstract void info(String str, Throwable tr);

    protected abstract void warn(String str, Throwable tr);

    protected abstract void error(String str, Throwable tr);
}

package test;

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.util.Date;

import android.os.Environment;

public class Log extends Logger {

    private static final String APP_TAG = "renwuto";
    private static final String LOG_FILE_NAME = "renwuto.txt";
    private static PrintStream logStream;
    private static final String LOG_ENTRY_FORMAT = "[%tF %tT]%s";

    public Log(String name) {
        super(name);
    }

    @Override
    protected void debug(String str) {
        android.util.Log.d(APP_TAG, str);
        write(str, null);
    }

    @Override
    protected void error(String str) {
        android.util.Log.e(APP_TAG, str);
        write(str, null);
    }

    @Override
    protected void info(String str) {
        android.util.Log.i(APP_TAG, str);
        write(str, null);
    }

    @Override
    protected void warn(String str) {
        android.util.Log.w(APP_TAG, str);
        write(str, null);
    }

    @Override
    protected void debug(String str, Throwable tr) {
        android.util.Log.d(APP_TAG, str);
        write(str, tr);
    }

    @Override
    protected void error(String str, Throwable tr) {
        android.util.Log.e(APP_TAG, str);
        write(str, tr);
    }

    @Override
    protected void info(String str, Throwable tr) {
        android.util.Log.i(APP_TAG, str);
        write(str, tr);
    }

    @Override
    protected void warn(String str, Throwable tr) {
        android.util.Log.w(APP_TAG, str);
        write(str, tr);
    }

    private void write(String msg, Throwable tr) {
        if (!Log.DBG) {
            return;
        }
        try {

            if (null == logStream) {
                synchronized (Log.class) {
                    if (null == logStream) {
                        init();
                    }
                }
            }

            Date now = new Date();
            if (null != logStream) {
                logStream.printf(LOG_ENTRY_FORMAT, now, now, msg);
                logStream.print("\n");
            }
            if (null != tr) {
                tr.printStackTrace(logStream);
                if (null != logStream) {
                    logStream.print("\n");
                }
            }

        } catch (Throwable t) {
            // Empty catch block
        }
    }

    public static void init() {
        if (!Log.DBG) {
            return;
        }
        try {
            File sdRoot = null;
            String state = Environment.getExternalStorageState();
            if (Environment.MEDIA_MOUNTED.equals(state)) {
                sdRoot = Environment.getExternalStorageDirectory();
            }
            if (sdRoot != null) {
                File logFile = new File(sdRoot, LOG_FILE_NAME);

                android.util.Log.d(APP_TAG, "Log to file : " + logFile);
                logStream = new PrintStream(new FileOutputStream(logFile, true), true);
            }
        } catch (Throwable e) {
            // Empty catch block
        }
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            super.finalize();
            if (logStream != null) {
                logStream.close();
            }
        } catch (Throwable t) {
            // Empty catch block
        }
    }
}

private static final Logger log = Logger.getLogger("DownloadThread");