解决方法如下：

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;

import androidx.annotation.Nullable;
import androidx.appcompat.widget.AppCompatTextView;

/**
 * 自定义加粗的TextView
 * https://www.jianshu.com/p/2ed23c25b095
 * tv.getPaint().setStyle(Paint.Style.FILL_AND_STROKRE)
 * tv.getPaint().setStrokeWidth(0.7)
 * 另外textStype="bold" 太粗
 */
public class BoldTextView extends AppCompatTextView {

    public BoldTextView(Context context) {
        super(context);
    }

    public BoldTextView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public BoldTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        getPaint().setStyle(Paint.Style.FILL_AND_STROKE);
        getPaint().setStrokeWidth(0.7f);
        super.onDraw(canvas);
    }
}

效果图如下：