How to change the color of the side view of the star in android?

问题

To see the below image,

Masking star

And the code is,

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Region;
import android.view.View;
import android.graphics.Bitmap;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.AttributeSet;

/**
 * Created by chozarajan.pandiyarajan on 11/3/2015.
*/

public class SfRatingItem extends View {

private int fillColor, minDim, topXPoint, topYPoint;
private double bigHypot, bigA, bigB, littleHypot, littleA, littleB, value;
private Paint starPaint;
private Path path;
private Bitmap starBitmap;
private Bitmap backBitmap;

public SfRatingItem(Context context, AttributeSet attrs) {
    super(context, attrs);
    initialize();
}

public SfRatingItem(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initialize();
}

public SfRatingItem(Context context) {
    super(context);
    initialize();
    this.setBackgroundColor(Color.GREEN);

}

@Override
protected void onDraw(Canvas canvas) {
    initialDraw();
    Paint q = new Paint(Paint.ANTI_ALIAS_FLAG);

    //canvas.saveLayer(0,0,canvas.getWidth(),canvas.getHeight(),q); // expensive call, instead set a hardware layer
    setLayerType(LAYER_TYPE_HARDWARE, q);

    canvas.drawBitmap(backBitmap, 0, 0, q);
    q.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
    canvas.drawBitmap(starBitmap, 0, 0, q);
    q.setXfermode(null);

    Paint p=new Paint();
    p.setColor(Color.RED);
    p.setStyle(Paint.Style.STROKE);
    p.setAntiAlias(true);
    canvas.drawPath(path,p);

}

private void initialDraw() {
    starPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    starPaint.setAntiAlias(true);

    minDim = Math.min(this.getWidth() - this.getPaddingLeft() - this.getPaddingRight(), this.getHeight() - this.getPaddingTop() - this.getPaddingBottom());

    bigHypot = (minDim / Math.cos(Math.toRadians(18)));
    bigB = minDim;
    bigA = Math.tan(Math.toRadians(18)) * bigB;

    littleHypot = bigHypot / (2 + Math.cos(Math.toRadians(72)) + Math.cos(Math.toRadians(72)));
    littleA = Math.cos(Math.toRadians(72)) * littleHypot;
    littleB = Math.sin(Math.toRadians(72)) * littleHypot;

    topXPoint = (this.getWidth() - this.getPaddingLeft() - this.getPaddingRight()) / 2;
    topYPoint = this.getPaddingTop();

    path.moveTo(topXPoint, topYPoint);
    path.lineTo((int) (topXPoint + bigA), (int) (topYPoint + bigB));
    path.lineTo((int) (topXPoint - littleA - littleB), (int) (topYPoint + littleB));
    path.lineTo((int) (topXPoint + littleA + littleB), (int) (topYPoint + littleB));
    path.lineTo((int) (topXPoint - bigA), (int) (topYPoint + bigB));
    path.lineTo(topXPoint, topYPoint);
    path.close();

    RectF bounds = new RectF();
    path.computeBounds(bounds, true);

    // Draw the background rectangle in a bitmap
    starPaint.setColor(Color.RED);
    backBitmap = Bitmap.createBitmap((int) bounds.width(), (int) bounds.height(), Bitmap.Config.ARGB_8888);
    Canvas backCanvas = new Canvas(backBitmap);
    final Rect backRect = new Rect(0, 0, 200, backBitmap.getHeight());

    // Draw the STAR mask in a bitmap

    starBitmap = Bitmap.createBitmap((int) bounds.width(), (int) bounds.height(), Bitmap.Config.ARGB_8888);
    Canvas starCanvas = new Canvas(starBitmap);
    starPaint.setColor(Color.RED);
    starCanvas.drawPath(path, starPaint);
    backCanvas.drawRect(backRect, starPaint);
}

private void initialize() {
    starPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    path = new Path();
 }
}

Please to see the above mentioned image.

In this code i am set the background of the window is green color.

And my question is, why the outside of the star is showing black color? and how to change that color?

回答1:

The reason this is not working is because the Hardware acceleration might be turned off and you need to turn it on. Refer this: http://developer.android.com/guide/topics/graphics/hardware-accel.html

But if you are not planning to do this via Hardware Acceleration, then use

canvas.saveLayer(0,0,canvas.getWidth(),canvas.getHeight(),q);

instead of this:

setLayerType(LAYER_TYPE_HARDWARE, q);

来源：https://stackoverflow.com/questions/33492847/how-to-change-the-color-of-the-side-view-of-the-star-in-android