源代码
源代码MainActivity
效果图32行需要修改，不修改会报错：需要常量表达式，我的代码已修改

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MainActivity

import static com.example.graphicverificationcode.RxCaptcha.TYPE.NUMBER;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
   
    TextView tvCode;
    ImageView ivCode;


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

        tvCode = findViewById(R.id.tv_code);
        ivCode = findViewById(R.id.iv_code);
        ivCode.setOnClickListener(this);
    }


    @Override
    public void onClick(View view) {
   
        if (view.getId() == R.id.iv_code) {
   
            RxCaptcha.build()
                    .backColor(0xffffff)
                    .codeLength(4)
                    .fontSize(60)
                    .lineNumber(2)
                    .size(200, 70)
                    .type(NUMBER)
                    .into(ivCode);
            tvCode.setText(RxCaptcha.build().getCode());
        }
    }
}

RxCaptcha

import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.widget.ImageView;

import java.util.Random;

/**
 * 随机生成验证码，使用方法：
 * <p>
 * 拿到验证码图片ImageView
 * mIvCode.setImageBitmap(RxCaptcha.getInstance().createBitmap());
 * int code=RxCaptcha.getInstance().getCode();
 * <p>
 * 只需生成验证码值 String
 *
 * <p/>
 * RxCaptcha
 *
 * @version 1.0.0
 */
public class RxCaptcha {
   

    public static RxCaptcha build() {
   
        if (rxCaptcha == null) {
   
            rxCaptcha = new RxCaptcha();
        }
        return rxCaptcha;
    }

    private static final char[] CHARS_NUMBER = {
   '0',