程序一 | Android studio 实现简易计算器

一、首先编写layout界面框架

整体采用LinearLayout布局；Button实现按键功能，为其设置id，以便进行触发事件的控制，设置文本大小/宽高以及颜色；

例如为“1”按钮进行布局：

Ps:Input输入框采用Text view文本框

 

二、Java程序编写

为每个功能按钮绑定触发事件，以按钮“1”为例
btn_1 = (Button) findViewById(R.id.btn_1);
btn_1.setOnClickListener(this);

运算逻辑的程序实现：

public void onClick(View v) {
    int last = 0;
    if (pending.length() != 0) {
        last = pending.codePointAt(pending.length() - 1);
    }
    switch (v.getId()) {
        case R.id.btn_0:
            pending = pending.append("0");
            et_input.setText(pending);
            break;
        case R.id.btn_1:
            pending = pending.append("1");
            et_input.setText(pending);
            break;
        case R.id.btn_2:
            pending = pending.append("2");
            et_input.setText(pending);
            break;
        case R.id.btn_3:
            pending = pending.append("3");
            et_input.setText(pending);
            break;
        case R.id.btn_4:
            pending = pending.append("4");
            et_input.setText(pending);
            break;
        case R.id.btn_5:
            pending = pending.append("5");
            et_input.setText(pending);
            break;
        case R.id.btn_6:
            pending = pending.append("6");
            et_input.setText(pending);
            break;
        case R.id.btn_7:
            pending = pending.append("7");
            et_input.setText(pending);
            break;
        case R.id.btn_8:
            pending = pending.append("8");
            et_input.setText(pending);
            break;
        case R.id.btn_9:
            pending = pending.append("9");
            et_input.setText(pending);
            break;
        case R.id.btn_plus:
            //if (last >= '0' && last <= '9' ) {
            pending = pending.append("+");
            // }
            et_input.setText(pending);
            break;
        case R.id.btn_minus:
            //if (last >= '0' && last <= '9') {
            pending = pending.append("-");
            //  }
            et_input.setText(pending);
            break;
        case R.id.btn_multiply:
            // if (last >= '0' && last <= '9' ) {
            pending = pending.append("*");
            // }
            et_input.setText(pending);
            break;
        case R.id.btn_divide:
            // if (last >= '0' && last <= '9' ) {
            pending = pending.append("/");
            // }
            et_input.setText(pending);
            break;
        case R.id.btn_point:
            if (judje1()) {
                pending = pending.append(".");
                et_input.setText(pending);
            }
            break;
        case R.id.btn_clear: //清空
            pending = pending.delete(0, pending.length());
            et_input.setText(pending);
            break;
        case R.id.btn_equal: // =等于
            if ((pending.length() > 1)) {
                InfixInToDuffix inf = new InfixInToDuffix();
                String jieguo;
                try {
                    String a = inf.toSuffix(pending);
                    jieguo = inf.dealEquation(a);

                } catch (Exception ex) {
                    jieguo = "出错";
                }
                et_input.setText(pending + "=" + jieguo);
                pending = pending.delete(0, pending.length());
                if (Character.isDigit(jieguo.charAt(0))) {
                    pending = pending.append(jieguo);
                }
            }
            break;
        default:
            break;
    }
}

private boolean judje1() {
    String a = "+-*/.";
    int[] b = new int[a.length()];
    int max;
    for (int i = 0; i < a.length(); i++) {
        String c = "" + a.charAt(i);
        b[i] = pending.lastIndexOf(c);
    }
    Arrays.sort(b);
    if (b[a.length() - 1] == -1) {
        max = 0;
    } else {
        max = b[a.length() - 1];
    }
    if (pending.indexOf(".", max) == -1) {
        return true;
    } else {
        return false;
    }
}

private int judje2() {
    int a = 0, b = 0;
    for (int i = 0; i < pending.length(); i++) {
        if (pending.charAt(i) == '(') {
            a++;
        }
        if (pending.charAt(i) == ')') {
            b++;
        }
    }
    if (a == b)
        return 0;
    if (a > b)
        return 1;
    return 2;
}

PS：运算逻辑程序实现比较复杂，因此参考了网上的代码实现；增加多了一个JAVA文件 InfixInToDuffix 以维持正常运算；

 

三、最后运行界面样例

心得：对布局有了更深层次的理解和运用。熟悉了Layout代码和Androidstudio软件的运行；