与SweepGradient的布局背景

Question

我需要创建一个像图片中那样的多色背景。我知道所有的颜色和角度。

我尝试用SweepGradient做到这一点，但没有任何改变，我只看到白色背景。

我的布局

<RelativeLayout
    android:id="@+id/user_info_background"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

片段中的代码：

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    mRelativeLayout.setBackground(GraphicalUtils.addSweepGradientBackground(getResources().getDisplayMetrics().widthPixels, 
    getResources().getDisplayMetrics().heightPixels,getContext()));}

添加SweepGradient的方法：

 public static Drawable addSweepGradientBackground(int width, int height, Context context){
        Bitmap bitmap = Bitmap.createBitmap(width,height,Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas();

        SweepGradient sweepGradient = new SweepGradient(width/2,height/2,Color.RED, Color.BLUE);

        Paint paint = new Paint();
        paint.setShader(sweepGradient);
        paint.setStyle(Paint.Style.FILL);
        paint.setAntiAlias(true);
        canvas.drawBitmap(bitmap,0,0,paint);

        return new BitmapDrawable(context.getResources(), bitmap);

    }

Answer 1

试试这个：

public static Drawable addSweepGradientBackground(int width, int height, Context context){
    Bitmap bitmap = Bitmap.createBitmap(width,height,Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);

    SweepGradient sweepGradient = new SweepGradient(width/2,height/2,Color.RED, Color.BLUE);

    Paint paint = new Paint();
    paint.setShader(sweepGradient);
    paint.setStyle(Paint.Style.FILL);
    paint.setAntiAlias(true);
    canvas.drawBitmap(bitmap,0,0,null);
    canvas.drawCircle(width/2,height/2, width/2, paint)

    return new BitmapDrawable(context.getResources(), bitmap);

} 

画布应该用位图绑定，你需要在位图上绘制具有sweepGradient的paint的圆圈。