LogWrapper.java

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/*
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 * Copyright (C) 2012 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.common.logger;
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import android.util.Log;
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/**
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 * Helper class which wraps Android's native Log utility in the Logger interface.  This way
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 * normal DDMS output can be one of the many targets receiving and outputting logs simultaneously.
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 */
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public class LogWrapper implements LogNode {
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    // For piping:  The next node to receive Log data after this one has done its work.
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    private LogNode mNext;
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    /**
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     * Returns the next LogNode in the linked list.
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     */
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    public LogNode getNext() {
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        return mNext;
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    }
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    /**
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     * Sets the LogNode data will be sent to..
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     */
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    public void setNext(LogNode node) {
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        mNext = node;
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    }
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    /**
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     * Prints data out to the console using Android's native log mechanism.
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     * @param priority Log level of the data being logged.  Verbose, Error, etc.
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     * @param tag Tag for for the log data.  Can be used to organize log statements.
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     * @param msg The actual message to be logged. The actual message to be logged.
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     * @param tr If an exception was thrown, this can be sent along for the logging facilities
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     *           to extract and print useful information.
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     */
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    @Override
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    public void println(int priority, String tag, String msg, Throwable tr) {
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        // There actually are log methods that don't take a msg parameter.  For now,
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        // if that's the case, just convert null to the empty string and move on.
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        String useMsg = msg;
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        if (useMsg == null) {
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            useMsg = "";
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        }
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        // If an exeption was provided, convert that exception to a usable string and attach
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        // it to the end of the msg method.
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        if (tr != null) {
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            msg += "\n" + Log.getStackTraceString(tr);
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        }
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        // This is functionally identical to Log.x(tag, useMsg);
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        // For instance, if priority were Log.VERBOSE, this would be the same as Log.v(tag, useMsg)
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        Log.println(priority, tag, useMsg);
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        // If this isn't the last node in the chain, move things along.
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        if (mNext != null) {
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            mNext.println(priority, tag, msg, tr);
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        }
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    }
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}