将包含渐变的可绘制xml转换为位图

我想对位图应用渐变。到目前为止,我正在使用这种技术。 这是我在MainActivity的onCreate方法中的代码。班

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        double angle = Math.toRadians(135);
        double length = 100;
        int x = (int) (Math.cos(angle) * length);
        int y = (int) (Math.sin(angle) * length);


        int[] colors = new int[3];
        colors[0] = Color.parseColor("#FF4081");
        colors[1] = Color.parseColor("#3F51B5");

        Bitmap bitmap = Bitmap.createBitmap(1080, 1080, Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);

        LinearGradient linearGradient =
                new LinearGradient(0, 0, x, y, colors[1], colors[0], Shader.TileMode.CLAMP);

        Paint paint = new Paint();
        paint.setDither(true);
        paint.setShader(linearGradient);

        canvas.drawRect(new RectF(0, 0, 1080, 1080), paint);

        ImageView imageView = findViewById(R.id.iv);
        imageView.setImageBitmap(bitmap);
    }
}

这导致了

但我想得到这样的效果

图2的结果是通过使用以下代码创建一个可绘制的XML文件来实现的

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <gradient
        android:angle="45"
        android:endColor="@color/colorPrimary"
        android:startColor="@color/colorAccent" />
</shape>

并将其设置为ImageView的背景,但我希望对位图产生此效果,因为我希望将该位图本地保存为图像。我尝试在MainActivity中创建一个GradientDrawable实例,并在GradientDrawable上调用onDraw(canvas),如 post