Category: Android

在android代码的每个Activity，都不厌其烦的写:

private static final String TAG = "MyActivity";

然后需要打印的地方输入:

Log.v(TAG, "index=" + i);

写太多的TAG，也麻烦，如果不写TAG,用 this.toString() 也可行，不过还是一样，于是写个包装Log类，自动处理是哪个Activity,调用哪个函数，如下：

/*
 * Copyright (C) 2010 Lytsing Huang http://lytsing.org
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.lytsing.android.util;

/**
 * Wrapper API for sending log output.
 */
public class Log {
    protected static final String TAG = "MyApplication";

    public Log() {
    }

    /**
     * Send a VERBOSE log message.
     * @param msg The message you would like logged.
     */
    public static void v(String msg) {
        android.util.Log.v(TAG, buildMessage(msg));
    }

    /**
     * Send a VERBOSE log message and log the exception.
     * @param msg The message you would like logged.
     * @param thr An exception to log
     */
    public static void v(String msg, Throwable thr) {
        android.util.Log.v(TAG, buildMessage(msg), thr);
    }

    /**
     * Send a DEBUG log message.
     * @param msg
     */
    public static void d(String msg) {
        android.util.Log.d(TAG, buildMessage(msg));
    }

    /**
     * Send a DEBUG log message and log the exception.
     * @param msg The message you would like logged.
     * @param tr An exception to log
     */
    public static void d(String msg, Throwable thr) {
        android.util.Log.d(TAG, buildMessage(msg), thr);
    }

    /**
     * Send an INFO log message.
     * @param msg The message you would like logged.
     */
    public static void i(String msg) {
        android.util.Log.i(TAG, buildMessage(msg));
    }

    /**
     * Send a INFO log message and log the exception.
     * @param msg The message you would like logged.
     * @param thr An exception to log
     */
    public static void i(String msg, Throwable thr) {
        android.util.Log.i(TAG, buildMessage(msg), thr);
    }

    /**
     * Send an ERROR log message.
     * @param msg The message you would like logged.
     */
    public static void e(String msg) {
        android.util.Log.e(TAG, buildMessage(msg));
    }

    /**
     * Send a WARN log message
     * @param msg The message you would like logged.
     */
    public static void w(String msg) {
        android.util.Log.w(TAG, buildMessage(msg));
    }

    /**
     * Send a WARN log message and log the exception.
     * @param msg The message you would like logged.
     * @param thr An exception to log
     */
    public static void w(String msg, Throwable thr) {
        android.util.Log.w(TAG, buildMessage(msg), thr);
    }

    /**
     * Send an empty WARN log message and log the exception.
     * @param thr An exception to log
     */
    public static void w(Throwable thr) {
        android.util.Log.w(TAG, buildMessage(""), thr);
    }
    
    /**
     * Send an ERROR log message and log the exception.
     * @param msg The message you would like logged.
     * @param thr An exception to log
     */
    public static void e(String msg, Throwable thr) {
        android.util.Log.e(TAG, buildMessage(msg), thr);
    }

    /**
     * Building Message
     * @param msg The message you would like logged.
     * @return Message String
     */
    protected static String buildMessage(String msg) {      
        StackTraceElement caller = new Throwable().fillInStackTrace().getStackTrace()[2];

         return new StringBuilder()
                .append(caller.getClassName())
                .append(".")
                .append(caller.getMethodName())
                .append("(): ")
                .append(msg).toString();
    }
}

LogDemo.java:

package org.lytsing.android.log;

import org.lytsing.android.util.Log;
import android.app.Activity;
import android.os.Bundle;

public class LogDemo extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        Log.i("index=" + 3);
    }
}

运行结果的Log信息，如下图：

需要的话，懒得复制粘贴，可以下载Log.java压缩文件包Log.tar.gz

此外Android 代码风格指南 特别说明了，日志记录开销很大，应尽量少用，写规范可靠的代码，减少对debug的依赖。