core/java/android/widget/SeekBar.java

/*
 * 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;
import android.view.accessibility.AccessibilityNodeInfo;


/**
 * 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 min..max where min
         *                 and max were set by {@link ProgressBar#setMin(int)} and
         *                 {@link ProgressBar#setMax(int)}, respectively. (The default values for
         *                 min is 0 and 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 defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
    }

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

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

        if (mOnSeekBarChangeListener != null) {
            mOnSeekBarChangeListener.onProgressChanged(this, progress, 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() {
        super.onStartTrackingTouch();
        if (mOnSeekBarChangeListener != null) {
            mOnSeekBarChangeListener.onStartTrackingTouch(this);
        }
    }

    @Override
    void onStopTrackingTouch() {
        super.onStopTrackingTouch();
        if (mOnSeekBarChangeListener != null) {
            mOnSeekBarChangeListener.onStopTrackingTouch(this);
        }
    }

    @Override
    public CharSequence getAccessibilityClassName() {
        return SeekBar.class.getName();
    }

    /** @hide */
    @Override
    public void onInitializeAccessibilityNodeInfoInternal(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfoInternal(info);

        if (canUserSetProgress()) {
            info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SET_PROGRESS);
        }
    }
}