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Android example source code file (LevelListDrawable.java)

This example Android source code file (LevelListDrawable.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, content, drawable, drawablecontainer, drawablecontainerstate, io, ioexception, levellistdrawable, levelliststate, override, resources, typedarray, util, utilities, utils, xmlpullparserexception

The LevelListDrawable.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.graphics.drawable;

import java.io.IOException;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;

import android.content.res.Resources;
import android.content.res.TypedArray;
import android.util.AttributeSet;

/**
 * A resource that manages a number of alternate Drawables, each assigned a maximum numerical value.
 * Setting the level value of the object with {@link #setLevel(int)} will load the image with the next
 * greater or equal value assigned to its max attribute.
 * A good example use of
 * a LevelListDrawable would be a battery level indicator icon, with different images to indicate the current
 * battery level.
 * <p>
 * It can be defined in an XML file with the <code><level-list> element.
 * Each Drawable level is defined in a nested <code><item>. For example:
 * </p>
 * <pre>
 * <level-list xmlns:android="http://schemas.android.com/apk/res/android">
 *  <item android:maxLevel="0" android:drawable="@drawable/ic_wifi_signal_1" />
 *  <item android:maxLevel="1" android:drawable="@drawable/ic_wifi_signal_2" />
 *  <item android:maxLevel="2" android:drawable="@drawable/ic_wifi_signal_3" />
 *  <item android:maxLevel="3" android:drawable="@drawable/ic_wifi_signal_4" />
 * </level-list>
 *</pre>
 * <p>With this XML saved into the res/drawable/ folder of the project, it can be referenced as
 * the drawable for an {@link android.widget.ImageView}. The default image is the first in the list.
 * It can then be changed to one of the other levels with
 * {@link android.widget.ImageView#setImageLevel(int)}.</p>
 * @attr ref android.R.styleable#LevelListDrawableItem_minLevel
 * @attr ref android.R.styleable#LevelListDrawableItem_maxLevel
 * @attr ref android.R.styleable#LevelListDrawableItem_drawable
 */
public class LevelListDrawable extends DrawableContainer {
    private final LevelListState mLevelListState;
    private boolean mMutated;

    public LevelListDrawable() {
        this(null, null);
    }

    public void addLevel(int low, int high, Drawable drawable) {
        if (drawable != null) {
            mLevelListState.addLevel(low, high, drawable);
            // in case the new state matches our current state...
            onLevelChange(getLevel());
        }
    }

    // overrides from Drawable

    @Override
    protected boolean onLevelChange(int level) {
        int idx = mLevelListState.indexOfLevel(level);
        if (selectDrawable(idx)) {
            return true;
        }
        return super.onLevelChange(level);
    }

    @Override
    public void inflate(Resources r, XmlPullParser parser, AttributeSet attrs)
            throws XmlPullParserException, IOException {

        super.inflate(r, parser, attrs);

        int type;

        int low = 0;

        final int innerDepth = parser.getDepth() + 1;
        int depth;
        while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
                && ((depth = parser.getDepth()) >= innerDepth
                || type != XmlPullParser.END_TAG)) {
            if (type != XmlPullParser.START_TAG) {
                continue;
            }

            if (depth > innerDepth || !parser.getName().equals("item")) {
                continue;
            }

            TypedArray a = r.obtainAttributes(attrs,
                    com.android.internal.R.styleable.LevelListDrawableItem);

            low = a.getInt(
                    com.android.internal.R.styleable.LevelListDrawableItem_minLevel, 0);
            int high = a.getInt(
                    com.android.internal.R.styleable.LevelListDrawableItem_maxLevel, 0);
            int drawableRes = a.getResourceId(
                    com.android.internal.R.styleable.LevelListDrawableItem_drawable, 0);

            a.recycle();

            if (high < 0) {
                throw new XmlPullParserException(parser.getPositionDescription()
                        + ": <item> tag requires a 'maxLevel' attribute");
            }

            Drawable dr;
            if (drawableRes != 0) {
                dr = r.getDrawable(drawableRes);
            } else {
                while ((type = parser.next()) == XmlPullParser.TEXT) {
                }
                if (type != XmlPullParser.START_TAG) {
                    throw new XmlPullParserException(
                            parser.getPositionDescription()
                                    + ": <item> tag requires a 'drawable' attribute or "
                                    + "child tag defining a drawable");
                }
                dr = Drawable.createFromXmlInner(r, parser, attrs);
            }

            mLevelListState.addLevel(low, high, dr);
        }

        onLevelChange(getLevel());
    }

    @Override
    public Drawable mutate() {
        if (!mMutated && super.mutate() == this) {
            mLevelListState.mLows = mLevelListState.mLows.clone();
            mLevelListState.mHighs = mLevelListState.mHighs.clone();
            mMutated = true;
        }
        return this;
    }

    private final static class LevelListState extends DrawableContainerState {
        private int[] mLows;
        private int[] mHighs;

        LevelListState(LevelListState orig, LevelListDrawable owner, Resources res) {
            super(orig, owner, res);

            if (orig != null) {
                mLows = orig.mLows;
                mHighs = orig.mHighs;
            } else {
                mLows = new int[getChildren().length];
                mHighs = new int[getChildren().length];
            }
        }

        public void addLevel(int low, int high, Drawable drawable) {
            int pos = addChild(drawable);
            mLows[pos] = low;
            mHighs[pos] = high;
        }

        public int indexOfLevel(int level) {
            final int[] lows = mLows;
            final int[] highs = mHighs;
            final int N = getChildCount();
            for (int i = 0; i < N; i++) {
                if (level >= lows[i] && level <= highs[i]) {
                    return i;
                }
            }
            return -1;
        }

        @Override
        public Drawable newDrawable() {
            return new LevelListDrawable(this, null);
        }

        @Override
        public Drawable newDrawable(Resources res) {
            return new LevelListDrawable(this, res);
        }

        @Override
        public void growArray(int oldSize, int newSize) {
            super.growArray(oldSize, newSize);
            int[] newInts = new int[newSize];
            System.arraycopy(mLows, 0, newInts, 0, oldSize);
            mLows = newInts;
            newInts = new int[newSize];
            System.arraycopy(mHighs, 0, newInts, 0, oldSize);
            mHighs = newInts;
        }
    }

    private LevelListDrawable(LevelListState state, Resources res) {
        LevelListState as = new LevelListState(state, this, res);
        mLevelListState = as;
        setConstantState(as);
        onLevelChange(getLevel());
    }
}

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