Android example source code file (Chronometer.java)

This example Android source code file (Chronometer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, attributeset, chronometer, content, formatter, handler, illegal, illegalformatexception, locale, object, onchronometerticklistener, os, override, string, stringbuilder, tag, tick_what, util, utilities, utils

The Chronometer.java Android example source code

/*
 * Copyright (C) 2008 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 android.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.text.format.DateUtils;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.RemoteViews.RemoteView;

import java.util.Formatter;
import java.util.IllegalFormatException;
import java.util.Locale;

/**
 * Class that implements a simple timer.
 * <p>
 * You can give it a start time in the {@link SystemClock#elapsedRealtime} timebase,
 * and it counts up from that, or if you don't give it a base time, it will use the
 * time at which you call {@link #start}.  By default it will display the current
 * timer value in the form "MM:SS" or "H:MM:SS", or you can use {@link #setFormat}
 * to format the timer value into an arbitrary string.
 *
 * @attr ref android.R.styleable#Chronometer_format
 */
@RemoteView
public class Chronometer extends TextView {
    private static final String TAG = "Chronometer";

    /**
     * A callback that notifies when the chronometer has incremented on its own.
     */
    public interface OnChronometerTickListener {

        /**
         * Notification that the chronometer has changed.
         */
        void onChronometerTick(Chronometer chronometer);

    }

    private long mBase;
    private boolean mVisible;
    private boolean mStarted;
    private boolean mRunning;
    private boolean mLogged;
    private String mFormat;
    private Formatter mFormatter;
    private Locale mFormatterLocale;
    private Object[] mFormatterArgs = new Object[1];
    private StringBuilder mFormatBuilder;
    private OnChronometerTickListener mOnChronometerTickListener;
    private StringBuilder mRecycle = new StringBuilder(8);
    
    private static final int TICK_WHAT = 2;
    
    /**
     * Initialize this Chronometer object.
     * Sets the base to the current time.
     */
    public Chronometer(Context context) {
        this(context, null, 0);
    }

    /**
     * Initialize with standard view layout information.
     * Sets the base to the current time.
     */
    public Chronometer(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    /**
     * Initialize with standard view layout information and style.
     * Sets the base to the current time.
     */
    public Chronometer(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a = context.obtainStyledAttributes(
                attrs,
                com.android.internal.R.styleable.Chronometer, defStyle, 0);
        setFormat(a.getString(com.android.internal.R.styleable.Chronometer_format));
        a.recycle();

        init();
    }

    private void init() {
        mBase = SystemClock.elapsedRealtime();
        updateText(mBase);
    }

    /**
     * Set the time that the count-up timer is in reference to.
     *
     * @param base Use the {@link SystemClock#elapsedRealtime} time base.
     */
    @android.view.RemotableViewMethod
    public void setBase(long base) {
        mBase = base;
        dispatchChronometerTick();
        updateText(SystemClock.elapsedRealtime());
    }

    /**
     * Return the base time as set through {@link #setBase}.
     */
    public long getBase() {
        return mBase;
    }

    /**
     * Sets the format string used for display.  The Chronometer will display
     * this string, with the first "%s" replaced by the current timer value in
     * "MM:SS" or "H:MM:SS" form.
     *
     * If the format string is null, or if you never call setFormat(), the
     * Chronometer will simply display the timer value in "MM:SS" or "H:MM:SS"
     * form.
     *
     * @param format the format string.
     */
    @android.view.RemotableViewMethod
    public void setFormat(String format) {
        mFormat = format;
        if (format != null && mFormatBuilder == null) {
            mFormatBuilder = new StringBuilder(format.length() * 2);
        }
    }

    /**
     * Returns the current format string as set through {@link #setFormat}.
     */
    public String getFormat() {
        return mFormat;
    }

    /**
     * Sets the listener to be called when the chronometer changes.
     * 
     * @param listener The listener.
     */
    public void setOnChronometerTickListener(OnChronometerTickListener listener) {
        mOnChronometerTickListener = listener;
    }

    /**
     * @return The listener (may be null) that is listening for chronometer change
     *         events.
     */
    public OnChronometerTickListener getOnChronometerTickListener() {
        return mOnChronometerTickListener;
    }

    /**
     * Start counting up.  This does not affect the base as set from {@link #setBase}, just
     * the view display.
     * 
     * Chronometer works by regularly scheduling messages to the handler, even when the 
     * Widget is not visible.  To make sure resource leaks do not occur, the user should 
     * make sure that each start() call has a reciprocal call to {@link #stop}. 
     */
    public void start() {
        mStarted = true;
        updateRunning();
    }

    /**
     * Stop counting up.  This does not affect the base as set from {@link #setBase}, just
     * the view display.
     * 
     * This stops the messages to the handler, effectively releasing resources that would
     * be held as the chronometer is running, via {@link #start}. 
     */
    public void stop() {
        mStarted = false;
        updateRunning();
    }

    /**
     * The same as calling {@link #start} or {@link #stop}.
     * @hide pending API council approval
     */
    @android.view.RemotableViewMethod
    public void setStarted(boolean started) {
        mStarted = started;
        updateRunning();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        mVisible = false;
        updateRunning();
    }

    @Override
    protected void onWindowVisibilityChanged(int visibility) {
        super.onWindowVisibilityChanged(visibility);
        mVisible = visibility == VISIBLE;
        updateRunning();
    }

    private synchronized void updateText(long now) {
        long seconds = now - mBase;
        seconds /= 1000;
        String text = DateUtils.formatElapsedTime(mRecycle, seconds);

        if (mFormat != null) {
            Locale loc = Locale.getDefault();
            if (mFormatter == null || !loc.equals(mFormatterLocale)) {
                mFormatterLocale = loc;
                mFormatter = new Formatter(mFormatBuilder, loc);
            }
            mFormatBuilder.setLength(0);
            mFormatterArgs[0] = text;
            try {
                mFormatter.format(mFormat, mFormatterArgs);
                text = mFormatBuilder.toString();
            } catch (IllegalFormatException ex) {
                if (!mLogged) {
                    Log.w(TAG, "Illegal format string: " + mFormat);
                    mLogged = true;
                }
            }
        }
        setText(text);
    }

    private void updateRunning() {
        boolean running = mVisible && mStarted;
        if (running != mRunning) {
            if (running) {
                updateText(SystemClock.elapsedRealtime());
                dispatchChronometerTick();
                mHandler.sendMessageDelayed(Message.obtain(mHandler, TICK_WHAT), 1000);
            } else {
                mHandler.removeMessages(TICK_WHAT);
            }
            mRunning = running;
        }
    }
    
    private Handler mHandler = new Handler() {
        public void handleMessage(Message m) {
            if (mRunning) {
                updateText(SystemClock.elapsedRealtime());
                dispatchChronometerTick();
                sendMessageDelayed(Message.obtain(this, TICK_WHAT), 1000);
            }
        }
    };

    void dispatchChronometerTick() {
        if (mOnChronometerTickListener != null) {
            mOnChronometerTickListener.onChronometerTick(this);
        }
    }
}