yinmeng-android/app/src/main/java/com/mango/moshen/treasurefairy/CustomDrawable.java

package com.mango.moshen.treasurefairy;

import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.drawable.Drawable;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

class CustomDrawable extends Drawable {
  private final Paint srcPaint;
  private final Drawable innerDrawable;
  /**
   * 使用时需要自定义path
   */
  private Path srcPath = new Path();
  private final PorterDuffXfermode xFermode =new PorterDuffXfermode(PorterDuff.Mode.CLEAR);

  public CustomDrawable(Drawable innerDrawable) {
    this.innerDrawable = innerDrawable;
    // path默认实现
    srcPath.addRect(100, 100, 200, 200, Path.Direction.CW);
    srcPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    srcPaint.setColor(0xffffffff);
  }

  /**
   * 设置内部透明的部分
   */
  public void setSrcPath(Path srcPath) {
    this.srcPath = srcPath;
  }

  @Override
  public void draw(@NonNull Canvas canvas) {
    innerDrawable.setBounds(getBounds());
    if (srcPath == null || srcPath.isEmpty()) {
      innerDrawable.draw(canvas);
    } else {
      // 将绘制操作保存到新的图层
      int saveCount = canvas.saveLayer(0, 0, getBounds().width(), getBounds().height(), srcPaint,
          Canvas.ALL_SAVE_FLAG);
      // 绘制目标图
      innerDrawable.draw(canvas);
      // 设置混合模式
      srcPaint.setXfermode(xFermode);
      // src 绘制源图
      canvas.drawPath(srcPath, srcPaint);
      // 清除混合模式
      srcPaint.setXfermode(null);
      // 还原画布
      canvas.restoreToCount(saveCount);
    }
  }

  @Override
  public void setAlpha(int alpha) {
    innerDrawable.setAlpha(alpha);
  }

  @Override
  public void setColorFilter(@Nullable ColorFilter colorFilter) {
    innerDrawable.setColorFilter(colorFilter);
  }

  @Override
  public int getOpacity() {
    return innerDrawable.getOpacity();
  }
}