Android studio 入门实战——注册登录+验证功能的实现

1 注册

• 注册页面展示：
  

• 注册页面代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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"
    android:background="#ffffff"
    android:orientation="vertical"
    tools:context=".RegisterActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="253dp"
        android:scaleType="fitXY"
        android:src="@mipmap/a002"/>
    <ImageView
        android:id="@+id/iv_registeractivity_back"
        android:layout_width="17dp"
        android:layout_height="30dp"
        android:background="@drawable/ic_left_back"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="20dp"
        android:clickable="true"
        android:onClick="onClick"
        />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="210dp"
        android:orientation="vertical">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="300dp"
            android:layout_marginLeft="18dp"
            android:layout_marginRight="18dp"
            android:background="@drawable/shape_login_form"
            android:gravity="center"
            android:orientation="vertical"
            android:paddingLeft="43dp"
            android:paddingRight="31dp">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:orientation="horizontal">

                <ImageView
                    android:layout_width="25dp"
                    android:layout_height="25dp"
                    android:src="@mipmap/account" />

                <EditText
                    android:id="@+id/et_registeractivity_username"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="20dp"
                    android:background="@null"
                    android:hint="@string/account_hint"
                    android:textColor="#000000"
                    android:textColorHint="#bcbcbc"
                    android:textSize="18sp" />
            </LinearLayout>

            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:layout_marginTop="23dp"
                android:layout_marginBottom="23dp"
                android:background="@color/divider" />

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:orientation="horizontal">

                <ImageView
                    android:layout_width="25dp"
                    android:layout_height="25dp"
                    android:src="@mipmap/pwd" />

                <EditText
                    android:id="@+id/et_registeractivity_password1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="20dp"
                    android:background="@null"
                    android:hint="@string/pwd_hint1"
                    android:inputType="textPassword"
                    android:textColor="@color/black"
                    android:textColorHint="#bcbcbc"
                    android:textSize="18sp" />
            </LinearLayout>

            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:layout_marginTop="23dp"
                android:layout_marginBottom="23dp"
                android:background="@color/divider" />
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:orientation="horizontal">

                <ImageView
                    android:layout_width="25dp"
                    android:layout_height="25dp"
                    android:src="@mipmap/pwd" />

                <EditText
                    android:id="@+id/et_registeractivity_password2"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="20dp"
                    android:background="@null"
                    android:hint="@string/pwd_hint2"
                    android:inputType="textPassword"
                    android:textColor="@color/black"
                    android:textColorHint="#bcbcbc"
                    android:textSize="18sp" />
            </LinearLayout>
            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:layout_marginTop="23dp"
                android:layout_marginBottom="23dp"
                android:background="@color/divider" />

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="10dp"
                android:layout_marginRight="15dp"
                android:orientation="horizontal">
                <!-- 第四个文本编辑框  输入验证码 -->
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">

                    <EditText
                        android:id="@+id/et_registeractivity_phoneCodes"
                        android:layout_width="196dp"
                        android:layout_height="50dp"
                        android:layout_marginLeft="10dp"
                        android:layout_marginRight="10dp"
                        android:layout_weight="3"
                        android:hint="@string/code_hint"
                        android:textColor="#000000"
                        android:textColorHint="#bcbcbc" />

                    <ImageView
                        android:id="@+id/iv_registeractivity_showCode"
                        android:layout_width="95dp"
                        android:layout_height="63dp"
                        android:layout_marginTop="-10dp"
                        android:layout_weight="1.5"
                        android:clickable="true"
                        android:onClick="onClick" />
                </LinearLayout>
            </LinearLayout>
        </LinearLayout>

        <Button
            android:id="@+id/bt_registeractivity_register"
            android:layout_width="match_parent"
            android:layout_height="55dp"
            android:layout_marginLeft="18dp"
            android:layout_marginTop="40dp"
            android:layout_marginRight="18dp"
            android:background="@drawable/shape_big_register_btn"
            android:text="@string/register"
            android:textColor="@color/white"
            android:textSize="24sp" />
    </LinearLayout>

</RelativeLayout>

• 注册按钮
  

这里注册按钮的格式是通过xml代码设计的，代码文件放在drawable文件夹下：

shape_big_register_btn.xml：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners android:radius="9dp" />
    <solid android:color="#EA9F44" />
</shape>

• 注册框以及登录框的设计：
  

以下xml文件也是在drawable文件夹下新建

shape_login_form.xml：

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- 边 -->
    <item>
        <shape android:shape="rectangle">
            <padding
                android:bottom="2dp"
                android:left="1.5dp"
                android:right="2dp"
                android:top="1.5dp" />
            <solid android:color="#F2F2F2" />
            <corners android:radius="8dp" />
        </shape>
    </item>
    <!-- 中心背景 -->
    <item>
        <shape
            android:shape="rectangle"
            android:useLevel="false">
            <!-- 实心 -->
            <solid android:color="#ffffff" />
            <corners android:radius="10dp" />
            <padding
                android:bottom="10dp"
                android:left="10dp"
                android:right="10dp"
                android:top="10dp" />
        </shape>
    </item>
</layer-list>

• 注册功能实现代码

import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class RegisterActivity extends AppCompatActivity implements View.OnClickListener {

    private String realCode;
    private DBOpenHelper mDBOpenHelper;
    private Button mBtRegisteractivityRegister;
    private ImageView mIvRegisteractivityBack;
    private EditText mEtRegisteractivityUsername;
    private EditText mEtRegisteractivityPassword1;
    private EditText mEtRegisteractivityPassword2;
    private EditText mEtRegisteractivityPhonecodes;
    private ImageView mIvRegisteractivityShowcode;

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

        initView();

        mDBOpenHelper = new DBOpenHelper(this);

        //将验证码用图片的形式显示出来
        mIvRegisteractivityShowcode.setImageBitmap(Code.getInstance().createBitmap());
        realCode = Code.getInstance().getCode().toLowerCase();
    }

    private void initView(){
        mBtRegisteractivityRegister = findViewById(R.id.bt_registeractivity_register);
        mIvRegisteractivityBack = findViewById(R.id.iv_registeractivity_back);
        mEtRegisteractivityUsername = findViewById(R.id.et_registeractivity_username);
        mEtRegisteractivityPassword1 = findViewById(R.id.et_registeractivity_password1);
        mEtRegisteractivityPassword2 = findViewById(R.id.et_registeractivity_password2);
        mEtRegisteractivityPhonecodes = findViewById(R.id.et_registeractivity_phoneCodes);
        mIvRegisteractivityShowcode = findViewById(R.id.iv_registeractivity_showCode);

        /**
         * 注册页面能点击的就三个地方
         * top处返回箭头、刷新验证码图片、注册按钮
         */
        mIvRegisteractivityBack.setOnClickListener(this);
        mIvRegisteractivityShowcode.setOnClickListener(this);
        mBtRegisteractivityRegister.setOnClickListener(this);
    }

    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.iv_registeractivity_back: //返回登录页面
                Intent intent1 = new Intent(this, LoginActivity.class);
                startActivity(intent1);
                finish();
                break;
            case R.id.iv_registeractivity_showCode:    //改变随机验证码的生成
                mIvRegisteractivityShowcode.setImageBitmap(Code.getInstance().createBitmap());
                realCode = Code.getInstance().getCode().toLowerCase();
                break;
            case R.id.bt_registeractivity_register:    //注册按钮
                //获取用户输入的用户名、密码、验证码
                String username = mEtRegisteractivityUsername.getText().toString().trim();
                String password1 = mEtRegisteractivityPassword1.getText().toString().trim();
                String password2 = mEtRegisteractivityPassword2.getText().toString().trim();
                String phoneCode = mEtRegisteractivityPhonecodes.getText().toString().toLowerCase();
                //注册验证
                if (!TextUtils.isEmpty(username) && !TextUtils.isEmpty(password1)&& !TextUtils.isEmpty(password2) && !TextUtils.isEmpty(phoneCode) ) {
                    if (phoneCode.equals(realCode)) {
                        if (!(password1==password2)) {
                            //将用户名和密码加入到数据库中
                            mDBOpenHelper.add(username, password2);
                            Intent intent2 = new Intent(this, MainActivity.class);
                            startActivity(intent2);
                            finish();
                            Toast.makeText(this, "验证通过，注册成功", Toast.LENGTH_SHORT).show();
                        }else
                        {
                            Toast.makeText(this, "密码输入不一致,请重新输入", Toast.LENGTH_SHORT).show();
                        }
                    } else {
                        Toast.makeText(this, "验证码错误,注册失败", Toast.LENGTH_SHORT).show();
                    }
                }else {
                    Toast.makeText(this, "未完善信息，注册失败", Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }
}

2 登录

• 登录界面展示：
  
• 登录页面代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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"
    android:background="#ffffff"
    tools:context=".RegisterActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="253dp"
        android:scaleType="fitXY"
        android:src="@mipmap/a001" />

    <Button
        android:id="@+id/tv_loginactivity_register"
        android:layout_width="55dp"
        android:layout_height="70dp"
        android:layout_marginLeft="280dp"
        android:background="@android:color/transparent"
        android:text="@string/register"
        android:textColor="#85FFFFFF"
        android:textColorHint="#bcbcbc"
        android:textSize="22sp"
        android:onClick="onClick"/>
    <ImageView
        android:layout_width="17dp"
        android:layout_height="30dp"
        android:layout_marginLeft="335dp"
        android:layout_marginTop="20dp"
        android:src="@drawable/right"
        />
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="240dp"
        android:orientation="vertical">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="260dp"
            android:layout_marginLeft="18dp"
            android:layout_marginRight="18dp"
            android:background="@drawable/shape_login_form"
            android:gravity="center"
            android:orientation="vertical"
            android:paddingLeft="43dp"
            android:paddingRight="31dp">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:orientation="horizontal">

                <ImageView
                    android:layout_width="25dp"
                    android:layout_height="25dp"
                    android:src="@mipmap/account" />

                <EditText
                    android:id="@+id/et_loginactivity_username"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="20dp"
                    android:background="@null"
                    android:hint="@string/account_hint"
                    android:textColor="#000000"
                    android:textColorHint="#bcbcbc"
                    android:textSize="18sp" />
            </LinearLayout>

            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:layout_marginTop="23dp"
                android:layout_marginBottom="23dp"
                android:background="#e8e7e7" />

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="center_vertical"
                android:orientation="horizontal">

                <ImageView
                    android:layout_width="25dp"
                    android:layout_height="25dp"
                    android:src="@mipmap/pwd" />

                <EditText
                    android:id="@+id/et_loginactivity_password"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="20dp"
                    android:background="@null"
                    android:hint="@string/pwd_hint1"
                    android:inputType="textPassword"
                    android:textColor="#000000"
                    android:textColorHint="#bcbcbc"
                    android:textSize="18sp" />
            </LinearLayout>

            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:layout_marginTop="23dp"
                android:layout_marginBottom="23dp"
                android:background="@color/divider" />

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="10dp"
                android:layout_marginRight="15dp"
                android:orientation="horizontal">
                <!-- 第四个文本编辑框  输入验证码 -->
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="horizontal">

                    <EditText
                        android:id="@+id/et_loginactivity_phoneCodes"
                        android:layout_width="196dp"
                        android:layout_height="50dp"
                        android:layout_marginLeft="10dp"
                        android:layout_marginRight="10dp"
                        android:layout_weight="3"
                        android:hint="@string/code_hint"
                        android:textColor="#000000"
                        android:textColorHint="#bcbcbc" />

                    <ImageView
                        android:id="@+id/iv_loginactivity_showCode"
                        android:layout_width="95dp"
                        android:layout_height="63dp"
                        android:layout_marginTop="-10dp"
                        android:layout_weight="1.5"
                        android:clickable="true"
                        android:onClick="onClick" />
                </LinearLayout>
            </LinearLayout>

        </LinearLayout>

        <Button
            android:id="@+id/bt_loginactivity_login"
            android:layout_width="match_parent"
            android:layout_height="55dp"
            android:layout_marginLeft="18dp"
            android:layout_marginTop="50dp"
            android:layout_marginRight="18dp"
            android:background="@drawable/shape_big_login_btn"
            android:text="@string/login"
            android:textColor="#ffffff"
            android:textSize="24sp" />
    </LinearLayout>
</RelativeLayout>

• 登录按钮
  

shape_big_login_btn.xml：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners android:radius="9dp" />
    <solid android:color="#A440B5" />
</shape>

• 登录功能实现代码：

import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import java.util.ArrayList;

public class LoginActivity extends AppCompatActivity implements View.OnClickListener {

    private String realCode;
    private DBOpenHelper mDBOpenHelper;
    private TextView mTvLoginactivityRegister;
    private EditText mEtLoginactivityUsername;
    private EditText mEtLoginactivityPassword;
    private Button mBtLoginactivityLogin;
    private EditText mEtloginactivityPhonecodes;
    private ImageView mIvloginactivityShowcode;


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

        initView();

        mDBOpenHelper = new DBOpenHelper(this);

        //将验证码用图片的形式显示出来
        mIvloginactivityShowcode.setImageBitmap(Code.getInstance().createBitmap());
        realCode = Code.getInstance().getCode().toLowerCase();


    }

    private void initView() {
        // 初始化控件
        mBtLoginactivityLogin = findViewById(R.id.bt_loginactivity_login);
        mTvLoginactivityRegister = findViewById(R.id.tv_loginactivity_register);
        mEtLoginactivityUsername = findViewById(R.id.et_loginactivity_username);
        mEtLoginactivityPassword = findViewById(R.id.et_loginactivity_password);
        mEtloginactivityPhonecodes = findViewById(R.id.et_loginactivity_phoneCodes);
        mIvloginactivityShowcode = findViewById(R.id.iv_loginactivity_showCode);

        // 设置点击事件监听器
        mBtLoginactivityLogin.setOnClickListener(this);
        mIvloginactivityShowcode.setOnClickListener(this);

    }

    public void onClick(View view) {
        switch (view.getId()) {
            // 跳转到注册界面
            case R.id.tv_loginactivity_register:
                startActivity(new Intent(this, RegisterActivity.class));
                finish();
                break;

            case R.id.iv_loginactivity_showCode:    //改变随机验证码的生成
                mIvloginactivityShowcode.setImageBitmap(Code.getInstance().createBitmap());
                realCode = Code.getInstance().getCode().toLowerCase();
                break;
            case R.id.bt_loginactivity_login:
                String name = mEtLoginactivityUsername.getText().toString().trim();
                String password = mEtLoginactivityPassword.getText().toString().trim();
                String phoneCode = mEtloginactivityPhonecodes.getText().toString().toLowerCase();

                if (!TextUtils.isEmpty(name) && !TextUtils.isEmpty(password)&&!TextUtils.isEmpty(phoneCode)) {
                    if (phoneCode.equals(realCode)) {
                        ArrayList<User> data = mDBOpenHelper.getAllData();
                        boolean match = false;
                        for (int i = 0; i < data.size(); i++) {
                            User user = data.get(i);
                            if (name.equals(user.getName()) && password.equals(user.getPassword())/*&&phoneCode.equals(realCode)*/) {
                                match = true;
                                break;
                            } else {
                                match = false;
                            }
                        }

                        if (match) {
                            Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();
                            Intent intent = new Intent(this, MainActivity.class);
                            startActivity(intent);
                            finish();//销毁此Activity
                        } else {
                            Toast.makeText(this, "用户名或密码不正确，请重新输入", Toast.LENGTH_SHORT).show();
                        }
                    }else {
                        Toast.makeText(this, "验证码错误,注册失败", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    Toast.makeText(this, "请输入你的用户名或密码", Toast.LENGTH_SHORT).show();
                }break;


        }


    }
}

3 验证码实现

• 验证码生成

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;

import java.util.Random;

public class Code {
    /**
     * 随机数数组
     * 去除了易混淆的 数字 0 和 字母 o O
     *                数字 1 和 字母 i I l L
     *                数字 6 和 字母 b
     *                数字 9 和 字母 q
     *                字母 c C 和 G
     *                字母 t （经常和随机线混在一起看不清）
     */
    private static final char[] CHARS = {
            '2', '3', '4', '5',  '7', '8',
            'a',  'd', 'e', 'f', 'g', 'h', 'j', 'k', 'm',
            'n', 'p',  'r', 's',  'u', 'v', 'w', 'x', 'y', 'z',
            'A', 'B',  'D', 'E', 'F',  'H',  'J', 'K', 'M',
            'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
    };

    private static Code bmpCode;

    public static Code getInstance() {
        if(bmpCode == null)
            bmpCode = new Code();
        return bmpCode;
    }

    //default settings
    //验证码默认随机数的个数
    private static final int DEFAULT_CODE_LENGTH = 4;
    //默认字体大小
    private static final int DEFAULT_FONT_SIZE = 25;
    //默认线条的条数
    private static final int DEFAULT_LINE_NUMBER = 5;
    //padding值
    private static final int BASE_PADDING_LEFT = 10, RANGE_PADDING_LEFT = 15, BASE_PADDING_TOP = 15, RANGE_PADDING_TOP = 20;
    //验证码的默认宽高
    private static final int DEFAULT_WIDTH = 100, DEFAULT_HEIGHT = 40;

    //settings decided by the layout xml
    //canvas width and height
    private int width = DEFAULT_WIDTH, height = DEFAULT_HEIGHT;

    //random word space and pading_top
    private int base_padding_left = BASE_PADDING_LEFT, range_padding_left = RANGE_PADDING_LEFT,
            base_padding_top = BASE_PADDING_TOP, range_padding_top = RANGE_PADDING_TOP;

    //number of chars, lines; font size
    private int codeLength = DEFAULT_CODE_LENGTH, line_number = DEFAULT_LINE_NUMBER, font_size = DEFAULT_FONT_SIZE;

    //variables
    private String code;
    private int padding_left, padding_top;
    private Random random = new Random();
    //验证码图片
    public Bitmap createBitmap() {
        padding_left = 0;

        Bitmap bp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        Canvas c = new Canvas(bp);

        code = createCode();

        c.drawColor(Color.WHITE);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setTextSize(font_size);
        //画验证码
        for (int i = 0; i < code.length(); i++) {
            randomTextStyle(paint);
            randomPadding();
            c.drawText(code.charAt(i) + "", padding_left, padding_top, paint);
        }
        //画线条
        for (int i = 0; i < line_number; i++) {
            drawLine(c, paint);
        }

//        c.save( Canvas.ALL_SAVE_FLAG );//保存
        c.save();//保存
        c.restore();//
        return bp;
    }

    public String getCode() {
        return code;
    }

    //生成验证码
    private String createCode() {
        StringBuilder buffer = new StringBuilder();
        for (int i = 0; i < codeLength; i++) {
            buffer.append(CHARS[random.nextInt(CHARS.length)]);
        }
        return buffer.toString();
    }
    //画干扰线
    private void drawLine(Canvas canvas, Paint paint) {
        int color = randomColor();
        int startX = random.nextInt(width);
        int startY = random.nextInt(height);
        int stopX = random.nextInt(width);
        int stopY = random.nextInt(height);
        paint.setStrokeWidth(1);
        paint.setColor(color);
        canvas.drawLine(startX, startY, stopX, stopY, paint);
    }
    //生成随机颜色
    private int randomColor() {
        return randomColor(1);
    }

    private int randomColor(int rate) {
        int red = random.nextInt(256) / rate;
        int green = random.nextInt(256) / rate;
        int blue = random.nextInt(256) / rate;
        return Color.rgb(red, green, blue);
    }
    //随机生成文字样式，颜色，粗细，倾斜度
    private void randomTextStyle(Paint paint) {
        int color = randomColor();
        paint.setColor(color);
        paint.setFakeBoldText(random.nextBoolean());  //true为粗体，false为非粗体
        float skewX = random.nextInt(11) / 10;
        skewX = random.nextBoolean() ? skewX : -skewX;
        paint.setTextSkewX(skewX); //float类型参数，负数表示右斜，整数左斜
        //paint.setUnderlineText(true); //true为下划线，false为非下划线
        //paint.setStrikeThruText(true); //true为删除线，false为非删除线
    }
    //随机生成padding值
    private void randomPadding() {
        padding_left += base_padding_left + random.nextInt(range_padding_left);
        padding_top = base_padding_top + random.nextInt(range_padding_top);
    }
}

4 数据库

• 相关代码：

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import java.util.ArrayList;

public class DBOpenHelper extends SQLiteOpenHelper {
    private SQLiteDatabase db;

    public DBOpenHelper(Context context){
        super(context,"db_map",null,1);
        db = getReadableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL("CREATE TABLE IF NOT EXISTS user(" +
                "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
                "name TEXT," +
                "password TEXT)");
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        db.execSQL("DROP TABLE IF EXISTS user");
        onCreate(db);
    }
    
    public void add(String name,String password){
        db.execSQL("INSERT INTO user (name,password) VALUES(?,?)",new Object[]{name,password});
    }
    public void delete(String name,String password){
        db.execSQL("DELETE FROM user WHERE name = AND password ="+name+password);
    }
    public void updata(String password){
        db.execSQL("UPDATE user SET password = ?",new Object[]{password});
    }

  
    public ArrayList<User> getAllData(){

        ArrayList<User> list = new ArrayList<User>();
        Cursor cursor = db.query("user",null,null,null,null,null,"name DESC");
        while(cursor.moveToNext()){
            String name = cursor.getString(cursor.getColumnIndex("name"));
            String password = cursor.getString(cursor.getColumnIndex("password"));
            list.add(new User(name,password));
        }
        return list;
    }
}

public class User {
    private String name;            //用户名
    private String password;        //密码
    public User(String name, String password) {
        this.name = name;
        this.password = password;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

本文地址：https://blog.csdn.net/dawn_1108/article/details/108123041