1 /*
2  * Copyright (C) 2012 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package com.example.android.common.logger;
17 
18 import android.util.Log;
19 
20 /**
21  * Helper class which wraps Android's native Log utility in the Logger interface.  This way
22  * normal DDMS output can be one of the many targets receiving and outputting logs simultaneously.
23  */
24 public class LogWrapper implements LogNode {
25 
26     // For piping:  The next node to receive Log data after this one has done its work.
27     private LogNode mNext;
28 
29     /**
30      * Returns the next LogNode in the linked list.
31      */
getNext()32     public LogNode getNext() {
33         return mNext;
34     }
35 
36     /**
37      * Sets the LogNode data will be sent to..
38      */
setNext(LogNode node)39     public void setNext(LogNode node) {
40         mNext = node;
41     }
42 
43     /**
44      * Prints data out to the console using Android's native log mechanism.
45      * @param priority Log level of the data being logged.  Verbose, Error, etc.
46      * @param tag Tag for for the log data.  Can be used to organize log statements.
47      * @param msg The actual message to be logged. The actual message to be logged.
48      * @param tr If an exception was thrown, this can be sent along for the logging facilities
49      *           to extract and print useful information.
50      */
51     @Override
println(int priority, String tag, String msg, Throwable tr)52     public void println(int priority, String tag, String msg, Throwable tr) {
53         // There actually are log methods that don't take a msg parameter.  For now,
54         // if that's the case, just convert null to the empty string and move on.
55         String useMsg = msg;
56         if (useMsg == null) {
57             useMsg = "";
58         }
59 
60         // If an exeption was provided, convert that exception to a usable string and attach
61         // it to the end of the msg method.
62         if (tr != null) {
63             msg += "\n" + Log.getStackTraceString(tr);
64         }
65 
66         // This is functionally identical to Log.x(tag, useMsg);
67         // For instance, if priority were Log.VERBOSE, this would be the same as Log.v(tag, useMsg)
68         Log.println(priority, tag, useMsg);
69 
70         // If this isn't the last node in the chain, move things along.
71         if (mNext != null) {
72             mNext.println(priority, tag, msg, tr);
73         }
74     }
75 }
76