第5天~

2021/1/25再更新:

因为每个电脑配置都不同，所以要移动时就是要用java和xml档COPY

和

用的方法-
1.开新空专案跑完
2.找到对应的档案CTRL C+CTRL V
3.要.java和.xml档都贴完才可以消失红

和

觉得最麻烦的就是不断更新的模拟器debug

记得老师有交代自己写的APP不要用自己在用的手机测..
但是TOAST模拟器真的不能....
https://www.google.com/search?sxsrf=AOaemvJ4BLMRazL6ZIXVhmwWDU1yQ6LJ9Q%3A1642918325626&lei=tfHsYazlJYv30AT2_YLwCQ&q=Android%20studio%20Toast%20%E9%A1%AF%E7%A4%BA%20%E4%B8%8D%20%E5%87%BA%E4%BE%86&ved=2ahUKEwjsk8bZm8f1AhWLO5QKHfa-AJ4QsKwBKAB6BAg0EAE&biw=1536&bih=722&dpr=1.25

虽然做久了就习惯

要全部有id也可以但是下面一定要有

调字大小.字的大小单位是sp:

要先用RadioGroup 再用 RadioButton

要先用RadioGroup-不好绑要放大点

再用 RadioButton-一定有缩排-用RadioGroup只能选定一个

ConstraintLayout-是预设一个一个排的-没有缩排

所以下面容器用LinearLayout 来选要直着排..还是横着排..
先拉好在下面(不好调~><)

用旁边的Layout-Constraint Widget去调旁边的距离是最好的

RadioButton单选-要有id-拉到旁边

再加入button

再加入textview

用radioGroup去管理radioButton
所以要先按radioGroup-一定要有id

重构-ok才能变

再来是radioButton的id

从code来改

新增一个按钮-一个完整xml

<RadioButton
            android:id="@+id/r2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="女士" />

看面板

要改方向-orientation

改完的样子

CheckBox复选-要有id

linearlayout 设定宽度

wrap_content设定高度

wrap_content

wrap 翻译过来是包裹,conten是内容。那麽这个就是包裹内容的意思,也就是说你的控制元件里面的内容有多大,这个控制元件就有多大。

linearLayout设定内距Padding 让他留边边-左/右

开始写里面的id

button-确认送出

改字的大小

制定 onClick

开始绑定 onClick

程序码变

有时候刚改完红色不会马上变黄色

最後显示的TextView-要有id

目前显示

模拟器再重动

改字的大小

要注意import开始写

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void onClick(View view) {
    }
}

JAVA 档-照顺序id

反红就是要ALT+ENTER按import class

宣告变数:

用字串string让显示的显现出来~

String all="";

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.RadioGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";


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

    public void onClick(View view) {
    }
}

再来要初始化-在onCreate

用 findViewById 找出 sex

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.RadioGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);

        //初始化CheckBox按钮


    }

    public void onClick(View view) {
    }
}

里面管3个~
当要预设选项"预设"被V时-只能选一个

Common Attributes-checked要V

clickable要预设为true 就是可以让"使用者"可以选

从程序码来看:

再回到java档

加入侦听器-RadioGroup有自家的要选

选择OnCheckChangeListener

原来的 int i

改成 int checkedId就是指int的r1,r2,r3的哪个id被点到了

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.RadioGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";

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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

            }
        });



        //初始化CheckBox按钮


    }

    public void onClick(View view) {
    }
}

用switch去写int checkedId到底选到哪一个

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.RadioGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";

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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                }

            }
        });



        //初始化CheckBox按钮


    }

    public void onClick(View view) {
    }
}

蒐集文字要宣告字串
RadioGroup是s1
CheckBox 是s2

如果是r1被点到就内容"先生"显示使用Toast模拟器显示不出来建议使用手机
switch後面一定要有break;

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this,
                                s1,
                                Toast.LENGTH_SHORT).show();
                        break;


                }

後面依序r2和r3

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });



        //初始化CheckBox按钮


    }

    public void onClick(View view) {
    }
}

初始化CheckBox按钮

//初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

加加入侦听器-比较麻烦-一个一个去看有没有被点选

c1.setOnCheckedChangeListener(new MM());
中new MM()目前是假设

初始化TextView

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        c1.setOnCheckedChangeListener(new MM());
        c2.setOnCheckedChangeListener(new MM());
        c3.setOnCheckedChangeListener(new MM());


        show = findViewById(R.id.show);


    }

    public void onClick(View view) {
    }
}

离开了 onCreate
CheckBox的侦听器:内部类

类所以是class

使用alt+enter让他跳出提示解决方

CheckBox的侦听器:内部类

按下变这样

再移上去

implements的3种显示方法:
1-红色灯泡implements

2-Alt+Insert -->implements

3-右键-->Generate -->implements这里选这种

extends与implements的区别：

extends 是继承父类，只要那个类不是宣告为final或者那个类定义为abstract的就能继承，JAVA中不支援多重继承，但是可以用介面来实现，这样就用到了implements，继承只能继承一个类，但implements可以实现多个介面，用逗号分开就行了。

改写 compoundButton, boolean b变成CompoundButton buttonView, boolean isChecked

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        c1.setOnCheckedChangeListener(new MM());
        c2.setOnCheckedChangeListener(new MM());
        c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

        }
    }

    public void onClick(View view) {
    }


}

CheckBox的侦听器:内部类

1.一般父类->判断元件
2.取出元件名称
3.再用if去判断 +判断点选状态

里面也是加入toast用手机测

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        c1.setOnCheckedChangeListener(new MM());
        c2.setOnCheckedChangeListener(new MM());
        c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    public void onClick(View view) {
    }


}

也是要用手机测不然TOAST模拟器不能

太长收起来

按钮收集资料，显示在show-常用

使用for each的语法:
for-each 回圈

当我们想要存取一个阵列或集合里面的元素时，for-each回圈是个简单且有效率的方法

for-each回圈的格式如下:

for(元素型态回圈控制变数 : 集合或阵列名称)

//回圈主体;

for-each有几项注意要点

1.只能从头开始走访每个元素，不能从集合或阵列的尾端向前走访

2.只能取出集合或阵列里的元素不能置换

3.foe-each回圈里面的变数是区域变数

下面这个范例在示范传统for回圈和for-each回圈读取阵列元素

你会发现for-each简洁许多

public class HelloDate {
    public static void main(String args[]) {
        int arr[]={5,3,8};
       
        //传统for回圈
        for(int i=0;i<arr.length;i++){
            System.out.print(arr[i]+" ");
        }
        System.out.println();
       
        //for-each loop
        for(int i:arr){
            System.out.print(i+" ");
        }
    }
}

这里写的-

public void onClick(View view) {
        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        all = s1+"\n"+s2;
    }

目前显示的全部:

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        c1.setOnCheckedChangeListener(new MM());
        c2.setOnCheckedChangeListener(new MM());
        c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    //按钮收集资料，显示在show
    public void onClick(View view) {
        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        all = s1+"\n"+s2;
    }


}

要显示要写show

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        c1.setOnCheckedChangeListener(new MM());
        c2.setOnCheckedChangeListener(new MM());
        c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    //按钮收集资料，显示在show
    public void onClick(View view) {
        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        all = s1+"\n"+s2;
        show.setText(all);
    }


}

如果不要按钮直接空按是空白
要改-s1

累积经验越写越完美

如果不要按钮直接空按是空白
要改-s2

下面多判断式:

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1="先生",s2="没有点选";


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        //c1.setOnCheckedChangeListener(new MM());
        //c2.setOnCheckedChangeListener(new MM());
        //c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    //按钮收集资料，显示在show
    public void onClick(View view) {
        //先清空s2
        s2="";

        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            //CheckBox cc =findViewById(i);

            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        //判断文字栏位是否为空

        if(TextUtils.isEmpty(s2)){
            s2="没有点选";
        }

        all = s1+"\n"+s2;
        show.setText(all);
    }


}

TextUtils.isEmpty的方法。但其实TextUtils不止有这一个方法。这里我列举出TextUtils中常用的四个方法，供大家需要时查阅。

isEmpty:判断字串是否为空值。
getTrimmedLength:获取字串去除头尾空格之後的长度。
isDigitsOnly:判断字串是否全部由数字组成。
ellipsize:如果字串超长，则返回按规则截断并新增省略号的字串。

延续上一篇因为太长了
目前的程序码:

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1,s2;


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        c1.setOnCheckedChangeListener(new MM());
        c2.setOnCheckedChangeListener(new MM());
        c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    //按钮收集资料，显示在show
    public void onClick(View view) {
        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        all = s1+"\n"+s2;
        show.setText(all);
    }


}

手机显示:

c1,c2,c3也可以比较简单的写法:

setOnCheckedChangeListener侦听器关掉也是可以

下面配合上面

private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

目前会有null是因为没有初始化完成

要改 String s1,s2;这句

要变成String s1="",s2="";

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1="",s2="";


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        //c1.setOnCheckedChangeListener(new MM());
        //c2.setOnCheckedChangeListener(new MM());
        //c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    //按钮收集资料，显示在show
    public void onClick(View view) {
        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            //CheckBox cc =findViewById(i);

            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        all = s1+"\n"+s2;
        show.setText(all);
    }


}

当使用者反覆操作.下面有累积的感觉

就是s2先清空再收集s2="";

package com.huang.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    //宣告变数
    RadioGroup sex;
    CheckBox c1,c2,c3;
    TextView show;
    String all="";
    String s1="",s2="";


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

        //初始化RadioGroup按钮

        sex = findViewById(R.id.sex);
        sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {

                switch (checkedId){
                    case R.id.r1:
                        s1 = "先生";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r2:
                        s1 = "女士";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;

                    case R.id.r3:
                        s1 = "不显示";
                        Toast.makeText(MainActivity.this, s1,Toast.LENGTH_SHORT).show();
                        break;


                }

            }
        });

        //初始化CheckBox按钮
        c1 =findViewById(R.id.c1);
        c2 =findViewById(R.id.c2);
        c3 =findViewById(R.id.c3);

        //c1.setOnCheckedChangeListener(new MM());
        //c2.setOnCheckedChangeListener(new MM());
        //c3.setOnCheckedChangeListener(new MM());

        show = findViewById(R.id.show);
            }

    //CheckBox的侦听器:内部类

    private class MM implements CompoundButton.OnCheckedChangeListener {

        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            //判断元件
            CheckBox box=(CheckBox) buttonView;

            //取出元件的名称
            String name = box.getText().toString();

            //判断点选状态

            if(isChecked){
                Toast.makeText(MainActivity.this,name+"被选中",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(MainActivity.this,name+"被取消",Toast.LENGTH_SHORT).show();
            }

        }
    }

    //按钮收集资料，显示在show
    public void onClick(View view) {
        //先清空s2
        s2="";

        //收集checkBox的结果
        int[] cbs ={R.id.c1,R.id.c2,R.id.c3};
        CheckBox cc;
        for(int i:cbs){
            //CheckBox cc =findViewById(i);

            cc =findViewById(i);
            if(cc.isChecked()){
                s2 += cc.getText()+"\t";
            }
        }

        all = s1+"\n"+s2;
        show.setText(all);
    }


}