android_frameworks_base/graphics/java/android/graphics/LinearGradient.java

/*
 * 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.graphics;

public class LinearGradient extends Shader {

    private static final int TYPE_COLORS_AND_POSITIONS = 1;
    private static final int TYPE_COLOR_START_AND_COLOR_END = 2;

    /**
     * Type of the LinearGradient: can be either TYPE_COLORS_AND_POSITIONS or
     * TYPE_COLOR_START_AND_COLOR_END.
     */
    private int mType;

    private float mX0;
    private float mY0;
    private float mX1;
    private float mY1;
    private int[] mColors;
    private float[] mPositions;
    private int mColor0;
    private int mColor1;

    private TileMode mTileMode;

    /** Create a shader that draws a linear gradient along a line.
        @param x0           The x-coordinate for the start of the gradient line
        @param y0           The y-coordinate for the start of the gradient line
        @param x1           The x-coordinate for the end of the gradient line
        @param y1           The y-coordinate for the end of the gradient line
        @param  colors      The colors to be distributed along the gradient line
        @param  positions   May be null. The relative positions [0..1] of
                            each corresponding color in the colors array. If this is null,
                            the the colors are distributed evenly along the gradient line.
        @param  tile        The Shader tiling mode
    */
    public LinearGradient(float x0, float y0, float x1, float y1, int colors[], float positions[],
            TileMode tile) {
        if (colors.length < 2) {
            throw new IllegalArgumentException("needs >= 2 number of colors");
        }
        if (positions != null && colors.length != positions.length) {
            throw new IllegalArgumentException("color and position arrays must be of equal length");
        }
        mType = TYPE_COLORS_AND_POSITIONS;
        mX0 = x0;
        mY0 = y0;
        mX1 = x1;
        mY1 = y1;
        mColors = colors;
        mPositions = positions;
        mTileMode = tile;
        init(nativeCreate1(x0, y0, x1, y1, colors, positions, tile.nativeInt));
    }

    /** Create a shader that draws a linear gradient along a line.
        @param x0       The x-coordinate for the start of the gradient line
        @param y0       The y-coordinate for the start of the gradient line
        @param x1       The x-coordinate for the end of the gradient line
        @param y1       The y-coordinate for the end of the gradient line
        @param  color0  The color at the start of the gradient line.
        @param  color1  The color at the end of the gradient line.
        @param  tile    The Shader tiling mode
    */
    public LinearGradient(float x0, float y0, float x1, float y1, int color0, int color1,
            TileMode tile) {
        mType = TYPE_COLOR_START_AND_COLOR_END;
        mX0 = x0;
        mY0 = y0;
        mX1 = x1;
        mY1 = y1;
        mColor0 = color0;
        mColor1 = color1;
        mTileMode = tile;
        init(nativeCreate2(x0, y0, x1, y1, color0, color1, tile.nativeInt));
    }

    /**
     * @hide
     */
    @Override
    protected Shader copy() {
        final LinearGradient copy;
        switch (mType) {
            case TYPE_COLORS_AND_POSITIONS:
                copy = new LinearGradient(mX0, mY0, mX1, mY1, mColors.clone(),
                        mPositions != null ? mPositions.clone() : null, mTileMode);
                break;
            case TYPE_COLOR_START_AND_COLOR_END:
                copy = new LinearGradient(mX0, mY0, mX1, mY1, mColor0, mColor1, mTileMode);
                break;
            default:
                throw new IllegalArgumentException("LinearGradient should be created with either " +
                        "colors and positions or start color and end color");
        }
        copyLocalMatrix(copy);
        return copy;
    }

    private native long nativeCreate1(float x0, float y0, float x1, float y1,
            int colors[], float positions[], int tileMode);
    private native long nativeCreate2(float x0, float y0, float x1, float y1,
            int color0, int color1, int tileMode);
}