Android example source code file (SeekBar.java)

This example Android source code file (SeekBar.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

absseekbar, android, attributeset, content, onseekbarchangelistener, override, seekbar, util, utilities, utils

The SeekBar.java Android example source code

/*
 * Copyright (C) 2006 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.util.AttributeSet;



/**
 * A SeekBar is an extension of ProgressBar that adds a draggable thumb. The user can touch
 * the thumb and drag left or right to set the current progress level or use the arrow keys.
 * Placing focusable widgets to the left or right of a SeekBar is discouraged. 
 * <p>
 * Clients of the SeekBar can attach a {@link SeekBar.OnSeekBarChangeListener} to
 * be notified of the user's actions.
 *
 * @attr ref android.R.styleable#SeekBar_thumb
 */
public class SeekBar extends AbsSeekBar {

    /**
     * A callback that notifies clients when the progress level has been
     * changed. This includes changes that were initiated by the user through a
     * touch gesture or arrow key/trackball as well as changes that were initiated
     * programmatically.
     */
    public interface OnSeekBarChangeListener {
        
        /**
         * Notification that the progress level has changed. Clients can use the fromUser parameter
         * to distinguish user-initiated changes from those that occurred programmatically.
         * 
         * @param seekBar The SeekBar whose progress has changed
         * @param progress The current progress level. This will be in the range 0..max where max
         *        was set by {@link ProgressBar#setMax(int)}. (The default value for max is 100.)
         * @param fromUser True if the progress change was initiated by the user.
         */
        void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser);
    
        /**
         * Notification that the user has started a touch gesture. Clients may want to use this
         * to disable advancing the seekbar. 
         * @param seekBar The SeekBar in which the touch gesture began
         */
        void onStartTrackingTouch(SeekBar seekBar);
        
        /**
         * Notification that the user has finished a touch gesture. Clients may want to use this
         * to re-enable advancing the seekbar. 
         * @param seekBar The SeekBar in which the touch gesture began
         */
        void onStopTrackingTouch(SeekBar seekBar);
    }

    private OnSeekBarChangeListener mOnSeekBarChangeListener;
    
    public SeekBar(Context context) {
        this(context, null);
    }
    
    public SeekBar(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.seekBarStyle);
    }

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

    @Override
    void onProgressRefresh(float scale, boolean fromUser) {
        super.onProgressRefresh(scale, fromUser);

        if (mOnSeekBarChangeListener != null) {
            mOnSeekBarChangeListener.onProgressChanged(this, getProgress(), fromUser);
        }
    }

    /**
     * Sets a listener to receive notifications of changes to the SeekBar's progress level. Also
     * provides notifications of when the user starts and stops a touch gesture within the SeekBar.
     * 
     * @param l The seek bar notification listener
     * 
     * @see SeekBar.OnSeekBarChangeListener
     */
    public void setOnSeekBarChangeListener(OnSeekBarChangeListener l) {
        mOnSeekBarChangeListener = l;
    }
    
    @Override
    void onStartTrackingTouch() {
        if (mOnSeekBarChangeListener != null) {
            mOnSeekBarChangeListener.onStartTrackingTouch(this);
        }
    }
    
    @Override
    void onStopTrackingTouch() {
        if (mOnSeekBarChangeListener != null) {
            mOnSeekBarChangeListener.onStopTrackingTouch(this);
        }
    }
    
}