线性渲染:
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;
/**
* 线性渲染的类型:可以是TYPE_COLORS_AND_POSITIONS类型,
* 也可以是TYPE_COLOR_START_AND_COLOR_END类型。
*/
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;
/**
* 创建一个沿着直线绘制线性渐变的渲染器。
*
* @param x0 渐变线起点的x坐标
* @param y0 渐变线起点的y坐标
* @param x1 渐变线终点的x坐标
* @param y1 渐变线终点的y坐标
* @param colors 沿渐变线分布的颜色
* @param positions 可能为null。颜色数组中每个对应颜色的相对位置[0..1]。
* 如果为null,则颜色沿渐变线均匀分布。
* @param tile 渲染器拼接模式
*/
public LinearGradient(float x0, float y0, float x1, float y1, @NonNull @ColorInt int colors[],
@Nullable float positions[], @NonNull 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.clone();
mPositions = positions != null ? positions.clone() : null;
mTileMode = tile;
}
/**
* 创建一个沿着直线绘制线性渐变的渲染器。
*
* @param x0 渐变线起点的x坐标
* @param y0 渐变线起点的y坐标
* @param x1 渐变线终点的x坐标
* @param y1 渐变线终点的y坐标
* @param color0 渐变线起点的颜色
* @param color1 渐变线终点的颜色
* @param tile 渲染器拼接模式
*/
public LinearGradient(float x0, float y0, float x1, float y1,
@ColorInt int color0, @ColorInt int color1,
@NonNull TileMode tile) {
mType = TYPE_COLOR_START_AND_COLOR_END;
mX0 = x0;
mY0 = y0;
mX1 = x1;
mY1 = y1;
mColor0 = color0;
mColor1 = color1;
mColors = null;
mPositions = null;
mTileMode = tile;
}
@Override
long createNativeInstance(long nativeMatrix) {
if (mType == TYPE_COLORS_AND_POSITIONS) {
return nativeCreate1(nativeMatrix, mX0, mY0, mX1, mY1,
mColors, mPositions, mTileMode.nativeInt);
} else { // TYPE_COLOR_START_AND_COLOR_END
return nativeCreate2(nativeMatrix, mX0, mY0, mX1, mY1,
mColor0, mColor1, mTileMode.nativeInt);
}
}
/** @hide */
@Override
protected Shader copy() {
final LinearGradient copy;
if (mType == TYPE_COLORS_AND_POSITIONS) {
copy = new LinearGradient(mX0, mY0, mX1, mY1, mColors.clone(),
mPositions != null ? mPositions.clone() : null, mTileMode);
} else { // TYPE_COLOR_START_AND_COLOR_END
copy = new LinearGradient(mX0, mY0, mX1, mY1, mColor0, mColor1, mTileMode);
}
copyLocalMatrix(copy);
return copy;
}
private native long nativeCreate1(long matrix, float x0, float y0, float x1, float y1,
int colors[], float positions[], int tileMode);
private native long nativeCreate2(long matrix, float x0, float y0, float x1, float y1,
int color0, int color1, int tileMode);
}