简单乘法运算功能的实现

/*
* 1.在MainActivity中，声明四个控件
* 2.位其中两个控件设置显示的值
* 3. 创建一个监听器类，监听按钮按下的动作
* 4.将监听器类的对象，绑定在按钮对象上
* */

private EditText factorOne;
private EditText factorTwo;
private TextView symbol;
private Button calculate;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//根据控件的ID来取得代表控件的对象
factorOne = (EditText) findViewById(R.id.factorOne);
factorTwo = (EditText) findViewById(R.id.factorTwo);
symbol = (TextView) findViewById(R.id.symbol);
calculate = (Button) findViewById(R.id.calculate);
//为synbol和calculate设置显示的值
//                    symbol.setText("乘以");
//                    calculate.setText("计算");
symbol.setText(R.string.symbol);
calculate.setText(R.string.calculate);
//将监听器绑定到按钮对象上面
calculate.setOnClickListener(new CalculateListener());
}

class CalculateListener implements View.OnClickListener {
//编写监听器
@Override
public void onClick(View v) {
/*
* 取得两个EditText控件的值
* 将这两个值存放到Intent对象当中
* 使用这个Intent对象来启动ResultActivity
* */
String factorOneStr = factorOne.getText().toString();
String factorTwoStr = factorTwo.getText().toString();
Intent intent = new Intent();
intent.putExtra("one", factorOneStr);
intent.putExtra("two", factorTwoStr);
intent.setClass(MainActivity.this, ResultActivity.class);
MainActivity.this.startActivity(intent);
}
}

/*
* 1.接收从MainActivity中传递的值
* 2.计算两个值得积
* 3.将计算结果显示
* */
private TextView resultView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_result);
resultView=(TextView)findViewById(R.id.result);
//得到Intent对象中的值
Intent intent=getIntent();
String factorOneStr=intent.getStringExtra("one");
String factorTwoStr=intent.getStringExtra("two");
int factorOneInt=Integer.parseInt(factorOneStr);
int factorTwoInt=Integer.parseInt(factorTwoStr);
//计算两个值的积
int result=factorOneInt*factorTwoInt;
resultView.setText(result+"");
}

<string name="symbol">乘以</string>
<string name="calculate">计算</string>
<string name="exit">退出</string>
<string name="about">关于</string>

//当客户点击MENU按钮的时候，调用该方法
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
// getMenuInflater().inflate(R.menu.menu_main, menu);
menu.add(0,1,1,R.string.exit);
menu.add(0, 2, 2, R.string.about);
return super.onCreateOptionsMenu(menu);
}

//当客户点击菜单中的某个选项是，会调用该方法
@Override
public boolean onOptionsItemSelected(MenuItem item) {//菜单点击响应
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();

//noinspection SimplifiableIfStatement
if (id ==1) {
finish();
}

return super.onOptionsItemSelected(item);
}