布局界面:

布局界面的代码：

java代码：

　　点击按钮答案时显示答案：

public class MainActivity extends AppCompatActivity {
    private int a,b,c,ty;
    private TextView tv;
    private Button show,next;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv=(TextView)findViewById(R.id.textView2);
        show = (Button)findViewById(R.id.button1);
        next = (Button)findViewById(R.id.button2);
        sz();
        sw();
        //点击答案按钮时显示答案
        show.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                switch (ty) {
                    case 0:
                        tv.setText(a + "+" + b + "=" + (a + b));
                        break;
                    case 1:
                        tv.setText(a + "-" + b + "=" + (a - b));
                        break;
                    case 2:
                        tv.setText(a + "+" + b +"*"+ c + "="+ (a+b*c));
                        break;
                    case 3:
                        tv.setText(a + "+" + b +"/"+ c + "="+(a+b/c));
                        break;
                    case 4:
                        tv.setText(a + "-" + b +"*"+ c + "="+(a-b*c));
                        break;
                    case 5:
                        tv.setText(a + "-" + b +"/"+ c + "="+(a-b/c));
                        break;
                    case 6:
                        tv.setText(a + "*" + b + "=" + (a*b));
                        break;
                    case 7:
                        tv.setText(a + "/" + b + "=" + (a/b));
                        break;
                }
            }
        });

　　点击显示下一题：

//点击下题
    next.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            sz();
            sw();
        }
    });
}

　　生成随机数：

//生成随机数
private void sz(){
    Random random = new Random();
    random.nextInt();
    a = random.nextInt(100);
    b = random.nextInt(100);
    c = random.nextInt(100);
    ty = random.nextInt(8);
}

　　显示题目：

 //显示题目
    private void sw(){
        switch (ty) {
            case 0:
                tv.setText(a + "+" + b + "=" + "?");
                break;
            case 1:
                tv.setText(a + "-" + b + "=" + "?");
                break;
            case 2:
                tv.setText(a + "+" + b +"*"+ c + "=" + "?");
                break;
            case 3:
                tv.setText(a + "+" + b +"/"+ c + "=" + "?");
                break;
            case 4:
                tv.setText(a + "-" + b +"*"+ c + "=" + "?");
                break;
            case 5:
                tv.setText(a + "-" + b +"/"+ c + "=" + "?");
                break;
            case 6:
                tv.setText(a + "*" + b + "=" + "?");
                break;
            case 7:
                tv.setText(a + "/" + b + "=" + "?");
                break;
        }
    }
}

简单的Android四则运算