samples/browseable/FragmentTransition/src/com.example.android.common/logger/LogWrapper.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * 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 com.example.android.common.logger;

import android.util.Log;

/**
 * Helper class which wraps Android's native Log utility in the Logger interface.  This way
 * normal DDMS output can be one of the many targets receiving and outputting logs simultaneously.
 */
public class LogWrapper implements LogNode {

    // For piping:  The next node to receive Log data after this one has done its work.
    private LogNode mNext;

    /**
     * Returns the next LogNode in the linked list.
     */
    public LogNode getNext() {
        return mNext;
    }

    /**
     * Sets the LogNode data will be sent to..
     */
    public void setNext(LogNode node) {
        mNext = node;
    }

    /**
     * Prints data out to the console using Android's native log mechanism.
     * @param priority Log level of the data being logged.  Verbose, Error, etc.
     * @param tag Tag for for the log data.  Can be used to organize log statements.
     * @param msg The actual message to be logged. The actual message to be logged.
     * @param tr If an exception was thrown, this can be sent along for the logging facilities
     *           to extract and print useful information.
     */
    @Override
    public void println(int priority, String tag, String msg, Throwable tr) {
        // There actually are log methods that don't take a msg parameter.  For now,
        // if that's the case, just convert null to the empty string and move on.
        String useMsg = msg;
        if (useMsg == null) {
            useMsg = "";
        }

        // If an exeption was provided, convert that exception to a usable string and attach
        // it to the end of the msg method.
        if (tr != null) {
            msg += "\n" + Log.getStackTraceString(tr);
        }

        // This is functionally identical to Log.x(tag, useMsg);
        // For instance, if priority were Log.VERBOSE, this would be the same as Log.v(tag, useMsg)
        Log.println(priority, tag, useMsg);

        // If this isn't the last node in the chain, move things along.
        if (mNext != null) {
            mNext.println(priority, tag, msg, tr);
        }
    }
}