common/logger/LogView.java

/*
 * Copyright (C) 2013 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.content.Context;
import android.util.*;
import android.widget.TextView;

/** Simple TextView which is used to output log data received through the LogNode interface.
*/
public class LogView extends TextView implements LogNode {

    public LogView(Context context) {
        super(context);
    }

    public LogView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public LogView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    /**
     * Formats the log data and prints it out to the LogView.
     * @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) {
        String priorityStr = null;

        // For the purposes of this View, we want to print the priority as readable text.
        switch(priority) {
            case android.util.Log.VERBOSE:
                priorityStr = "VERBOSE";
                break;
            case android.util.Log.DEBUG:
                priorityStr = "DEBUG";
                break;
            case android.util.Log.INFO:
                priorityStr = "INFO";
                break;
            case android.util.Log.WARN:
                priorityStr = "WARN";
                break;
            case android.util.Log.ERROR:
                priorityStr = "ERROR";
                break;
            case android.util.Log.ASSERT:
                priorityStr = "ASSERT";
                break;
            default:
                break;
        }

        // Handily, the Log class has a facility for converting a stack trace into a usable string.
        String exceptionStr = null;
        if (tr != null) {
            exceptionStr = android.util.Log.getStackTraceString(tr);
        }

        // Take the priority, tag, message, and exception, and concatenate as necessary
        // into one usable line of text.
        StringBuilder outputBuilder = new StringBuilder();

        String delimiter = "\t";
        appendIfNotNull(outputBuilder, priorityStr, delimiter);
        appendIfNotNull(outputBuilder, tag, delimiter);
        appendIfNotNull(outputBuilder, msg, delimiter);
        appendIfNotNull(outputBuilder, exceptionStr, delimiter);

        // Actually display the text we just generated within the LogView.
        appendToLog(outputBuilder.toString());

        if (mNext != null) {
            mNext.println(priority, tag, msg, tr);
        }
    }

    public LogNode getNext() {
        return mNext;
    }

    public void setNext(LogNode node) {
        mNext = node;
    }

    /** Takes a string and adds to it, with a separator, if the bit to be added isn't null. Since
     * the logger takes so many arguments that might be null, this method helps cut out some of the
     * agonizing tedium of writing the same 3 lines over and over.
     * @param source StringBuilder containing the text to append to.
     * @param addStr The String to append
     * @param delimiter The String to separate the source and appended strings. A tab or comma,
     *                  for instance.
     * @return The fully concatenated String as a StringBuilder
     */
    private StringBuilder appendIfNotNull(StringBuilder source, String addStr, String delimiter) {
        if (addStr != null) {
            if (addStr.length() == 0) {
                delimiter = "";
            }

            return source.append(addStr).append(delimiter);
        }
        return source;
    }

    // The next LogNode in the chain.
    LogNode mNext;

    /** Outputs the string as a new line of log data in the LogView. */
    public void appendToLog(String s) {
        append("\n" + s);
    }


}