alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Android example source code file (RatingBar.java)

This example Android source code file (RatingBar.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, drawing, graphics, onratingbarchangelistener, override, paint, ratingbar, rectshape, shape, typedarray, ui

The RatingBar.java Android example source code

/*
 * Copyright (C) 2007 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.drawable.shapes.RectShape;
import android.graphics.drawable.shapes.Shape;
import android.util.AttributeSet;

import com.android.internal.R;

/**
 * A RatingBar is an extension of SeekBar and ProgressBar that shows a rating in
 * stars. The user can touch/drag or use arrow keys to set the rating when using
 * the default size RatingBar. The smaller RatingBar style (
 * {@link android.R.attr#ratingBarStyleSmall}) and the larger indicator-only
 * style ({@link android.R.attr#ratingBarStyleIndicator}) do not support user
 * interaction and should only be used as indicators.
 * <p>
 * When using a RatingBar that supports user interaction, placing widgets to the
 * left or right of the RatingBar is discouraged.
 * <p>
 * The number of stars set (via {@link #setNumStars(int)} or in an XML layout)
 * will be shown when the layout width is set to wrap content (if another layout
 * width is set, the results may be unpredictable).
 * <p>
 * The secondary progress should not be modified by the client as it is used
 * internally as the background for a fractionally filled star.
 * 
 * @attr ref android.R.styleable#RatingBar_numStars
 * @attr ref android.R.styleable#RatingBar_rating
 * @attr ref android.R.styleable#RatingBar_stepSize
 * @attr ref android.R.styleable#RatingBar_isIndicator
 */
public class RatingBar extends AbsSeekBar {

    /**
     * A callback that notifies clients when the rating 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 OnRatingBarChangeListener {
        
        /**
         * Notification that the rating has changed. Clients can use the
         * fromUser parameter to distinguish user-initiated changes from those
         * that occurred programmatically. This will not be called continuously
         * while the user is dragging, only when the user finalizes a rating by
         * lifting the touch.
         * 
         * @param ratingBar The RatingBar whose rating has changed.
         * @param rating The current rating. This will be in the range
         *            0..numStars.
         * @param fromUser True if the rating change was initiated by a user's
         *            touch gesture or arrow key/horizontal trackbell movement.
         */
        void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser);

    }

    private int mNumStars = 5;

    private int mProgressOnStartTracking;
    
    private OnRatingBarChangeListener mOnRatingBarChangeListener;
    
    public RatingBar(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.RatingBar,
                defStyle, 0);
        final int numStars = a.getInt(R.styleable.RatingBar_numStars, mNumStars);
        setIsIndicator(a.getBoolean(R.styleable.RatingBar_isIndicator, !mIsUserSeekable));
        final float rating = a.getFloat(R.styleable.RatingBar_rating, -1);
        final float stepSize = a.getFloat(R.styleable.RatingBar_stepSize, -1);
        a.recycle();

        if (numStars > 0 && numStars != mNumStars) {
            setNumStars(numStars);            
        }
        
        if (stepSize >= 0) {
            setStepSize(stepSize);
        } else {
            setStepSize(0.5f);
        }
        
        if (rating >= 0) {
            setRating(rating);
        }
        
        // A touch inside a star fill up to that fractional area (slightly more
        // than 1 so boundaries round up).
        mTouchProgressOffset = 1.1f;
    }

    public RatingBar(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.ratingBarStyle);
    }

    public RatingBar(Context context) {
        this(context, null);
    }
    
    /**
     * Sets the listener to be called when the rating changes.
     * 
     * @param listener The listener.
     */
    public void setOnRatingBarChangeListener(OnRatingBarChangeListener listener) {
        mOnRatingBarChangeListener = listener;
    }
    
    /**
     * @return The listener (may be null) that is listening for rating change
     *         events.
     */
    public OnRatingBarChangeListener getOnRatingBarChangeListener() {
        return mOnRatingBarChangeListener;
    }

    /**
     * Whether this rating bar should only be an indicator (thus non-changeable
     * by the user).
     * 
     * @param isIndicator Whether it should be an indicator.
     */
    public void setIsIndicator(boolean isIndicator) {
        mIsUserSeekable = !isIndicator;
        setFocusable(!isIndicator);
    }
    
    /**
     * @return Whether this rating bar is only an indicator.
     */
    public boolean isIndicator() {
        return !mIsUserSeekable;
    }
    
    /**
     * Sets the number of stars to show. In order for these to be shown
     * properly, it is recommended the layout width of this widget be wrap
     * content.
     * 
     * @param numStars The number of stars.
     */
    public void setNumStars(final int numStars) {
        if (numStars <= 0) {
            return;
        }
        
        mNumStars = numStars;
        
        // This causes the width to change, so re-layout
        requestLayout();
    }

    /**
     * Returns the number of stars shown.
     * @return The number of stars shown.
     */
    public int getNumStars() {
        return mNumStars;
    }
    
    /**
     * Sets the rating (the number of stars filled).
     * 
     * @param rating The rating to set.
     */
    public void setRating(float rating) {
        setProgress(Math.round(rating * getProgressPerStar()));
    }

    /**
     * Gets the current rating (number of stars filled).
     * 
     * @return The current rating.
     */
    public float getRating() {
        return getProgress() / getProgressPerStar();        
    }

    /**
     * Sets the step size (granularity) of this rating bar.
     * 
     * @param stepSize The step size of this rating bar. For example, if
     *            half-star granularity is wanted, this would be 0.5.
     */
    public void setStepSize(float stepSize) {
        if (stepSize <= 0) {
            return;
        }
        
        final float newMax = mNumStars / stepSize;
        final int newProgress = (int) (newMax / getMax() * getProgress());
        setMax((int) newMax);
        setProgress(newProgress);
    }

    /**
     * Gets the step size of this rating bar.
     * 
     * @return The step size.
     */
    public float getStepSize() {
        return (float) getNumStars() / getMax();
    }
    
    /**
     * @return The amount of progress that fits into a star
     */
    private float getProgressPerStar() {
        if (mNumStars > 0) {
            return 1f * getMax() / mNumStars;
        } else {
            return 1;
        }
    }

    @Override
    Shape getDrawableShape() {
        // TODO: Once ProgressBar's TODOs are fixed, this won't be needed
        return new RectShape();
    }

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

        // Keep secondary progress in sync with primary
        updateSecondaryProgress(getProgress());
        
        if (!fromUser) {
            // Callback for non-user rating changes
            dispatchRatingChange(false);
        }
    }

    /**
     * The secondary progress is used to differentiate the background of a
     * partially filled star. This method keeps the secondary progress in sync
     * with the progress.
     * 
     * @param progress The primary progress level.
     */
    private void updateSecondaryProgress(int progress) {
        final float ratio = getProgressPerStar();
        if (ratio > 0) {
            final float progressInStars = progress / ratio;
            final int secondaryProgress = (int) (Math.ceil(progressInStars) * ratio);
            setSecondaryProgress(secondaryProgress);
        }
    }
    
    @Override
    protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        
        if (mSampleTile != null) {
            // TODO: Once ProgressBar's TODOs are gone, this can be done more
            // cleanly than mSampleTile
            final int width = mSampleTile.getWidth() * mNumStars;
            setMeasuredDimension(resolveSize(width, widthMeasureSpec), mMeasuredHeight);
        }
    }

    @Override
    void onStartTrackingTouch() {
        mProgressOnStartTracking = getProgress();
        
        super.onStartTrackingTouch();
    }

    @Override
    void onStopTrackingTouch() {
        super.onStopTrackingTouch();

        if (getProgress() != mProgressOnStartTracking) {
            dispatchRatingChange(true);
        }
    }

    @Override
    void onKeyChange() {
        super.onKeyChange();
        dispatchRatingChange(true);
    }

    void dispatchRatingChange(boolean fromUser) {
        if (mOnRatingBarChangeListener != null) {
            mOnRatingBarChangeListener.onRatingChanged(this, getRating(),
                    fromUser);
        }
    }

    @Override
    public synchronized void setMax(int max) {
        // Disallow max progress = 0
        if (max <= 0) {
            return;
        }
        
        super.setMax(max);
    }
    
}

Other Android examples (source code examples)

Here is a short list of links related to this Android RatingBar.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.