初学编程 第一个小程序Android studio实现计算器功能

源代码下载：/zha-yingying/calculator.git

1.建立一个新的Layout，我这里使用的是GridLayout（网格布局），提取屏幕宽度（方便后面设置子控件的宽度）GridLayout的特点是自定义网格布局有几行几列，我们可以将自控件自定义放在第几行第几列。

2.建立一个新的textview（文本框）作为我们计算器输入数字运算符号的界面，将textview放在第一行第一列，设置宽度为屏幕的宽度，这边我们需要提取一下屏幕的宽度。

3.添加子控件 添加按钮到布局上（数字+运算符号+等于符号）分别设置它们的位置，我这里的GridLayout设置的是八行四列，宽度为屏幕宽度的四分之一。

4.给每个控件都加上点击事件，给按钮设置监听器。在MainaActivity中使用enum（枚举）方法，分为四种情况（1）无按钮操作（2）上一次按钮为数字（3）上一次按钮为运算符号（4）上一次按钮为等于，分别写出其操作内容，需要在点击事件中添加状态。

提取屏幕宽度：

WindowManager wm = (WindowManager) this.getSystemService(this.WINDOW_SERVICE);

int width = wm.getDefaultDisplay().getWidth();

添加按钮：

（1）添加数字按钮（依次添加0-9和"."按钮）

Button button1 = new Button(this);layout1.addView(button1);GridLayout.LayoutParams bt1 = (GridLayout.LayoutParams) button1.getLayoutParams();bt1.rowSpec = GridLayout.spec(6,1,GridLayout.CENTER,1);bt1.columnSpec = GridLayout.spec(0,1,GridLayout.CENTER,1);bt1.width = width/4;button1.setText("1");button1.setLayoutParams(bt1);

（2）添加运算符号按钮（加减乘除这一类）

减号为例：

Button buttonminus = new Button(this);layout1.addView(buttonminus);buttonminus.setText("-");GridLayout.LayoutParams btjian = (GridLayout.LayoutParams) buttonminus.getLayoutParams();btjian.rowSpec = GridLayout.spec(6, 1, GridLayout.CENTER, 1);btjian.columnSpec = GridLayout.spec(3, 1, GridLayout.CENTER, 1);btjian.width = width / 4;buttonminus.setLayoutParams(btjian);

（3）添加等号按钮

Button buttonequal = new Button(this);layout1.addView(buttonequal);buttonequal.setText("=");GridLayout.LayoutParams btdy = (GridLayout.LayoutParams) buttonequal.getLayoutParams();btdy.rowSpec = GridLayout.spec(7, 1, GridLayout.CENTER, 1);btdy.columnSpec = GridLayout.spec(3, 1, GridLayout.CENTER, 1);btdy.width = width / 4;buttonequal.setLayoutParams(btdy);

给按钮添加点击事件，设置状态：

（1）数字按钮

button1.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {NumberClick("1");}});

（2）运算符号按钮（减号为例子）

buttonminus.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {OperationClick("-");operationType = OperationType.Minus;}});

（3）等号按钮

buttonequal.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {EqualClick("=");}});}

枚举法举例

新建两个enum的类

ClickType判断上一次按钮是数字/运算符号/等于符号

public enum ClickType {None,Number,Operation,Equqal,}

OperationType判断上一次的运算符号是加/减/乘/除

public enum OperationType {None,Plus,Minus,Multiply,Divide,}

在MainActivity里：

private ClickType clickType = ClickType.None;

private OperationType operationType = OperationType.None;

//按下数字键时

private void NumberClick(String n){switch (clickType){case None:textView.setText(n);break;case Number:String an = textView.getText().toString();textView.setText(an+n);break;case Operation:textView.setText(n);break;case Equqal:textView.setText(n);break;}clickType = ClickType.Number;}

//按下操作符号时

private void OperationClick(String n1){switch ((clickType)){case None:textView.setText("mistake");break;case Number:

switch ((operationType)){case None:String an2 = textView.getText().toString();a = Double.valueOf(an2);textView.setText(an2+n1);break;case Plus:String an3 = textView.getText().toString();b = Double.valueOf(an3);a = a + b;textView.setText(an3+n1);textView.setText(""+a);break;

case Minus:String an4 = textView.getText().toString();b = Double.valueOf(an4);a = a - b;textView.setText(an4+"-");textView.setText(""+a);break;case Divide:String an5 = textView.getText().toString();b = Double.valueOf(an5);a = a / b;textView.setText(an5+n1);textView.setText(""+a);break;case Multiply:String an6 = textView.getText().toString();b = Double.valueOf(an6);a = a * b;textView.setText(an6+n1);textView.setText(""+a);break;}break;case Operation:textView.setText("mistake");break;

case Equqal:String an1 = textView.getText().toString();a = Double.valueOf(an1);break;}clickType = ClickType.Operation;}

//按下等于号时

private void EqualClick(String n2){switch ((clickType)){case None:textView.setText("mistake");break;case Number:switch ((operationType)){case None:textView.setText(""+a);case Plus:String bn = textView.getText().toString();b = Double.valueOf(bn);b = a + b;textView.setText(""+b);a = 0;break;

case Minus:String bn1 = textView.getText().toString();b = Double.valueOf(bn1);b = a - b;textView.setText(""+b);a = 0;break;case Multiply:String bn2 = textView.getText().toString();b = Double.valueOf(bn2);b = a * b;textView.setText(""+b);a = 0;break;case Divide:String bn3 = textView.getText().toString();b = Double.valueOf(bn3);b = a / b;textView.setText(""+b);a = 0;break;}break;case Operation:textView.setText("mistake");break;case Equqal:textView.setText("mistake");break;}clickType = ClickType.Equqal;}