直接上代码：

package com.example.callstatus;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.UnknownHostException;
import java.text.SimpleDateFormat;
import java.util.Date;

import android.annotation.SuppressLint;
import android.os.Environment;
import android.util.Log;

/**
 * Android开发调试日志工具类[支持保存到SD卡]<br>
 * <br>
 * 
 * 需要一些权限: <br>
 * <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <br>
 * <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /><br>
 * 
 * @author PMTOAM
 * 
 */
@SuppressLint("SimpleDateFormat")
public class MyLog
{

	public static final String CACHE_DIR_NAME = "dPhoneLog";
	
	public static boolean isDebugModel = true;// 是否输出日志
	public static boolean isSaveDebugInfo = true;// 是否保存调试日志
	public static boolean isSaveCrashInfo = true;// 是否保存报错日志

	public static void v(final String tag, final String msg)
	{
		if (isDebugModel)
		{
			Log.v(tag, "--> " + msg);
		}
	}

	public static void d(final String tag, final String msg)
	{
		if (isDebugModel)
		{
			Log.d(tag, "--> " + msg);
		}
	}

	public static void i(final String tag, final String msg)
	{
		if (isDebugModel)
		{
			Log.i(tag, "--> " + msg);
		}
	}

	public static void w(final String tag, final String msg)
	{
		if (isDebugModel)
		{
			Log.w(tag, "--> " + msg);
		}
	}

	/**
	 * 调试日志，便于开发跟踪。
	 * @param tag
	 * @param msg
	 */
	public static void e(final String tag, final String msg)
	{
		if (isDebugModel)
		{
			Log.e(tag, "--> " + msg);
		}

		if (isSaveDebugInfo)
		{
			new Thread()
			{
				public void run()
				{
					write(time() + tag + " --> " + msg + "\n");
				};
			}.start();
		}
	}

	/**
	 * try catch 时使用，上线产品可上传反馈。
	 * @param tag
	 * @param tr
	 */
	public static void e(final String tag, final Throwable tr)
	{
		if (isSaveCrashInfo)
		{
			new Thread()
			{
				public void run()
				{
					write(time() + tag + " [CRASH] --> "
							+ getStackTraceString(tr) + "\n");
				};
			}.start();
		}
	}

	/**
	 * 获取捕捉到的异常的字符串
	 * @param tr
	 * @return
	 */
	public static String getStackTraceString(Throwable tr)
	{
		if (tr == null)
		{
			return "";
		}

		Throwable t = tr;
		while (t != null)
		{
			if (t instanceof UnknownHostException)
			{
				return "";
			}
			t = t.getCause();
		}

		StringWriter sw = new StringWriter();
		PrintWriter pw = new PrintWriter(sw);
		tr.printStackTrace(pw);
		return sw.toString();
	}

	/**
	 * 标识每条日志产生的时间
	 * @return
	 */
	private static String time()
	{
		return "["
				+ new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date(
						System.currentTimeMillis())) + "] ";
	}

	/**
	 * 以年月日作为日志文件名称
	 * @return
	 */
	private static String date()
	{
		return new SimpleDateFormat("yyyy-MM-dd").format(new Date(System
				.currentTimeMillis()));
	}

	/**
	 * 保存到日志文件
	 * @param content
	 */
	public static synchronized void write(String content)
	{
		try
		{
			FileWriter writer = new FileWriter(getFile(), true);
			writer.write(content);
			writer.close();
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
	}

	/**
	 * 获取日志文件路径
	 * @return
	 */
	public static String getFile()
	{
		File sdDir = null;

		if (Environment.getExternalStorageState().equals(
				android.os.Environment.MEDIA_MOUNTED))
			sdDir = Environment.getExternalStorageDirectory();

		File cacheDir = new File(sdDir + File.separator + CACHE_DIR_NAME);
		if (!cacheDir.exists())
			cacheDir.mkdir();

		File filePath = new File(cacheDir + File.separator + date() + ".txt");

		return filePath.toString();
	}

}

Android开发调试日志工具类[支持保存到SD卡]