Android studio中string和char的转换

在 Android Studio 中，可以使用以下代码将字符串转换为字符数组：

String str = "Hello";
char[] charArray = str.toCharArray();

同样地，也可以使用以下代码将字符数组转换为字符串：

char[] charArray = {'H', 'e', 'l', 'l', 'o'};
String str = new String(charArray);

注意，在将字符数组转换为字符串时，需要使用 `new String()` 的方式来创建字符串对象。

相关问题

Android Studio 16进制数据转换成ASCII

很抱歉，提供的引用内容中没有关于Android Studio 16进制数据转换成ASCII的信息。但是，你可以使用Java语言中的方法将16进制数据转换成ASCII码。可以使用以下代码实现：

public static String hexToAscii(String hexStr) {
    StringBuilder output = new StringBuilder("");
    for (int i = 0; i < hexStr.length(); i += 2) {
        String str = hexStr.substring(i, i + 2);
        output.append((char) Integer.parseInt(str, 16));
    }
    return output.toString();
}

这个方法将输入的16进制字符串转换成ASCII码并返回一个字符串。你可以在Android Studio中使用这个方法。

android studio计算器能同时输出表达式和结果的代码

下面是一个简单的 Android Studio 计算器应用程序的代码，它可以同时输出表达式和结果：

布局文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/output"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:textSize="30sp" />

    <GridLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:columnCount="4"
        android:rowCount="5"
        android:padding="16dp">

        <Button
            android:id="@+id/button_clear"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="C" />

        <Button
            android:id="@+id/button_divide"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="/" />

        <Button
            android:id="@+id/button_multiply"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="*" />

        <Button
            android:id="@+id/button_subtract"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="-" />

        <Button
            android:id="@+id/button_7"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="7" />

        <Button
            android:id="@+id/button_8"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="8" />

        <Button
            android:id="@+id/button_9"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="9" />

        <Button
            android:id="@+id/button_add"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="+" />

        <Button
            android:id="@+id/button_4"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="4" />

        <Button
            android:id="@+id/button_5"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="5" />

        <Button
            android:id="@+id/button_6"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="6" />

        <Button
            android:id="@+id/button_equals"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="2"
            android:text="=" />

        <Button
            android:id="@+id/button_1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="1" />

        <Button
            android:id="@+id/button_2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="2" />

        <Button
            android:id="@+id/button_3"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="3" />

        <Button
            android:id="@+id/button_0"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="2"
            android:layout_rowWeight="1"
            android:text="0" />

        <Button
            android:id="@+id/button_decimal"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_columnWeight="1"
            android:layout_rowWeight="1"
            android:text="." />

    </GridLayout>

</LinearLayout>

Java 代码：

import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import java.util.Stack;

public class MainActivity extends AppCompatActivity {

    private TextView output;
    private Button button_clear, button_divide, button_multiply, button_subtract, button_add,
            button_7, button_8, button_9, button_4, button_5, button_6, button_1, button_2,
            button_3, button_0, button_decimal, button_equals;

    private StringBuilder expression = new StringBuilder(); // 存储表达式
    private Stack<Double> numbers = new Stack<>(); // 存储数字
    private Stack<Character> operators = new Stack<>(); // 存储运算符

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

        output = findViewById(R.id.output);

        button_clear = findViewById(R.id.button_clear);
        button_divide = findViewById(R.id.button_divide);
        button_multiply = findViewById(R.id.button_multiply);
        button_subtract = findViewById(R.id.button_subtract);
        button_add = findViewById(R.id.button_add);
        button_7 = findViewById(R.id.button_7);
        button_8 = findViewById(R.id.button_8);
        button_9 = findViewById(R.id.button_9);
        button_4 = findViewById(R.id.button_4);
        button_5 = findViewById(R.id.button_5);
        button_6 = findViewById(R.id.button_6);
        button_1 = findViewById(R.id.button_1);
        button_2 = findViewById(R.id.button_2);
        button_3 = findViewById(R.id.button_3);
        button_0 = findViewById(R.id.button_0);
        button_decimal = findViewById(R.id.button_decimal);
        button_equals = findViewById(R.id.button_equals);

        // 添加清除按钮的点击事件
        button_clear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression = new StringBuilder();
                numbers.clear();
                operators.clear();
                output.setText("");
            }
        });

        // 添加运算符按钮的点击事件
        button_divide.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (expression.length() == 0) {
                    expression.append("0");
                }
                char lastChar = expression.charAt(expression.length() - 1);
                if (lastChar == '+' || lastChar == '-' || lastChar == '*' || lastChar == '/') {
                    expression.deleteCharAt(expression.length() - 1);
                }
                expression.append("/");
                output.setText(expression.toString());
            }
        });

        button_multiply.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (expression.length() == 0) {
                    expression.append("0");
                }
                char lastChar = expression.charAt(expression.length() - 1);
                if (lastChar == '+' || lastChar == '-' || lastChar == '*' || lastChar == '/') {
                    expression.deleteCharAt(expression.length() - 1);
                }
                expression.append("*");
                output.setText(expression.toString());
            }
        });

        button_subtract.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (expression.length() == 0) {
                    expression.append("0");
                }
                char lastChar = expression.charAt(expression.length() - 1);
                if (lastChar == '+' || lastChar == '-' || lastChar == '*' || lastChar == '/') {
                    expression.deleteCharAt(expression.length() - 1);
                }
                expression.append("-");
                output.setText(expression.toString());
            }
        });

        button_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (expression.length() == 0) {
                    expression.append("0");
                }
                char lastChar = expression.charAt(expression.length() - 1);
                if (lastChar == '+' || lastChar == '-' || lastChar == '*' || lastChar == '/') {
                    expression.deleteCharAt(expression.length() - 1);
                }
                expression.append("+");
                output.setText(expression.toString());
            }
        });

        // 添加数字按钮的点击事件
        button_0.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("0");
                output.setText(expression.toString());
            }
        });

        button_1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("1");
                output.setText(expression.toString());
            }
        });

        button_2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("2");
                output.setText(expression.toString());
            }
        });

        button_3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("3");
                output.setText(expression.toString());
            }
        });

        button_4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("4");
                output.setText(expression.toString());
            }
        });

        button_5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("5");
                output.setText(expression.toString());
            }
        });

        button_6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("6");
                output.setText(expression.toString());
            }
        });

        button_7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("7");
                output.setText(expression.toString());
            }
        });

        button_8.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("8");
                output.setText(expression.toString());
            }
        });

        button_9.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                expression.append("9");
                output.setText(expression.toString());
            }
        });

        button_decimal.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (expression.length() == 0) {
                    expression.append("0");
                }
                char lastChar = expression.charAt(expression.length() - 1);
                if (lastChar == '+' || lastChar == '-' || lastChar == '*' || lastChar == '/') {
                    expression.append("0");
                }
                expression.append(".");
                output.setText(expression.toString());
            }
        });

        // 添加等于按钮的点击事件
        button_equals.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String exp = expression.toString();
                if (TextUtils.isEmpty(exp)) {
                    return;
                }
                // 处理负数
                exp = exp.replaceAll("\\(-", "(0-");
                // 将表达式转换为后缀表达式
                String[] tokens = exp.split("(?<=[-+*/()])|(?=[-+*/()])");
                for (String token : tokens) {
                    if (TextUtils.isEmpty(token)) {
                        continue;
                    }
                    if (Character.isDigit(token.charAt(0))) {
                        double num = Double.parseDouble(token);
                        numbers.push(num);
                    } else if (token.charAt(0) == '(') {
                        operators.push('(');
                    } else if (token.charAt(0) == ')') {
                        while (operators.peek() != '(') {
                            double num2 = numbers.pop();
                            double num1 = numbers.pop();
                            char opr = operators.pop();
                            double res = evaluate(num1, num2, opr);
                            numbers.push(res);
                        }
                        operators.pop();
                    } else {
                        while (!operators.isEmpty() && precedence(operators.peek(), token.charAt(0))) {
                            double num2 = numbers.pop();
                            double num1 = numbers.pop();
                            char opr = operators.pop();
                            double res = evaluate(num1, num2, opr);
                            numbers.push(res);
                        }
                        operators.push(token.charAt(0));
                    }
                }
                while (!operators.isEmpty()) {
                    double num2 = numbers.pop();
                    double num1 = numbers.pop();
                    char opr = operators.pop();
                    double res = evaluate(num1, num2, opr);
                    numbers.push(res);
                }
                double result = numbers.pop();
                expression = new StringBuilder();
                numbers.clear();
                operators.clear();
                expression.append(exp);
                expression.append("=");
                expression.append(result);
                output.setText(expression.toString());
            }
        });
    }

    // 计算两个数字之间的运算结果
    private double evaluate(double num1, double num2, char opr) {
        switch (opr) {
            case '+':
                return num1 + num2;
            case '-':
                return num1 - num2;
            case '*':
                return num1 * num2;
            case '/':
                if (num2 == 0) {
                    throw new ArithmeticException("除数不能为零");
                }
                return num1 / num2;
            default:
                return 0;
        }
    }

    // 比较两个运算符的优先级
    private boolean precedence(char opr1, char opr2) {
        if (opr1 == '(' || opr1 == ')') {
            return false;
        }
        if ((opr1 == '+' || opr1 == '-') && (opr2 == '*' || opr2 == '/')) {
            return false;
        }
        return true;
    }

}

这个计算器应用程序使用逆波兰表达式算法来计算表达式的结果，并将表达式和结果一起输出到 TextView 控件中。