【Android开发学习21】写一个简单的乘法计算器，并添加退出菜单
一、目标和即将学到的知识:
1.目标:
写一个简单的乘法计算器，并添加退出菜单
2.即将需要或者学习到的知识:
①.TextView显示文本
②.EditText编辑框
③.Button按钮
④.Menu菜单
3.基础知识:
① setText函数中，连接符两端，有一个端是字符串，则另外一端也会被转为字符串。
private TextView resultView;private int result;...resultView.setText(result + "");
② 判断某字符串是否为空:
if(factorOneStr.equals(""))
③ 字符串转整数:
int factorOneInt = Integer.parseInt(factorOneStr);
④ 添加菜单:
为主程序添加菜单显示: onCreateOptionsMenu(重载函数)
为菜单添加响应事件: onOptionsItemSelected(重载函数)
@Overridepublic boolean onOptionsItemSelected(MenuItem item) {// TODO Auto-generated method stubif(item.getItemId()==1){finish();// 结束当前Activity.}return super.onOptionsItemSelected(item);}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// TODO Auto-generated method stubmenu.add(0,1,1,R.string.exit);menu.add(0,2,2,R.string.about);return super.onCreateOptionsMenu(menu);}3.用到的快捷键:
添加导入库 Ctrl+Shift+M
二、代码展示:
1."Activity_03\src\yan\activity_02\Activity_03.java"
package yan.activity_03;import android.os.Bundle;import android.app.Activity;import android.content.Intent;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;/* * 1.在Activity_03当中，要声明四个控件 * 2.要为其中的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 * */public class Activity_03 extends Activity {private EditText factorOne;private EditText factorTwo;private TextView symbol;private Button calculate;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_03);//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symbol和calculate设置显示的值symbol.setText(R.string.symbol);calculate.setText(R.string.calculate);// 将监听器的对象绑定到按钮对象上面calculate.setOnClickListener(new CalculateListener());}@Overridepublic boolean onOptionsItemSelected(MenuItem item) {// TODO Auto-generated method stubif(item.getItemId()==1){finish();// 结束当前Activity.}return super.onOptionsItemSelected(item);}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// TODO Auto-generated method stubmenu.add(0,1,1,R.string.exit);menu.add(0,2,2,R.string.about);return super.onCreateOptionsMenu(menu);}class CalculateListener implements OnClickListener{@Overridepublic void onClick(View v) {// TODO Auto-generated method stub// 取得两个EditText控件的值String factorOneStr = factorOne.getText().toString();String factorTwoStr = factorTwo.getText().toString();// 将这两个值存放到Intent对象中Intent intent = new Intent();intent.putExtra("one", factorOneStr);intent.putExtra("two", factorTwoStr);intent.setClass(Activity_03.this, ResultActivity.class);// 使用这个Intent对象来启动ResultActivityActivity_03.this.startActivity(intent);}}}package yan.activity_03;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.widget.TextView;// 1.接收从Activity_03当中传递过来的值// 2.计算两个值的积// 3.将计算的结果显示在Activity上public class ResultActivity extends Activity{private TextView resultView;private int result;@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);setContentView(R.layout.result);resultView = (TextView)findViewById(R.id.result);// 得到Intent对象当中的值Intent intent = getIntent();String factorOneStr = intent.getStringExtra("one");String factorTwoStr = intent.getStringExtra("two");System.out.println(" 225 === ");// 判断输入是否为空.if(factorOneStr.equals("") || factorTwoStr.equals(""))result=0;else{int factorOneInt = Integer.parseInt(factorOneStr);int factorTwoInt = Integer.parseInt(factorTwoStr);// 计算两个值的积result = factorOneInt * factorTwoInt;}// 显示结果到界面resultView.setText(result + "");}}<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <EditText android:id="@+id/factorOne" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/symbol" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@+string/hello_world" /> <EditText android:id="@+id/factorTwo" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <Button android:id="@+id/calculate" android:layout_width="fill_parent" android:layout_height="wrap_content" /></LinearLayout>
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/result" android:layout_width="fill_parent" android:layout_height="wrap_content" /></LinearLayout>
<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="yan.activity_03" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="4" android:targetSdkVersion="4" /> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="yan.activity_03.Activity_03" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="yan.activity_03.ResultActivity" android:label="@string/result" > </activity> </application></manifest>
<?xml version="1.0" encoding="utf-8"?><resources> <string name="app_name">Activity_03</string> <string name="hello_world">Hello world!</string> <string name="menu_settings">Settings</string><string name="symbol">乘以</string><string name="calculate">计算</string><string name="result">结果</string><string name="exit">退出</string><string name="about">关于</string></resources>
三、效果展示:
点击"计算"按钮，之后，跳转到ResultActivity-->>
当返回之后，按手机的"菜单"键，显示如下 -->>
其中的"退出"和“关于”就是我们自己添加进去的菜单了。
本文完整代码下载地址:http://download.csdn.net/detail/ypist/5138073
本文博客源地址:http://blog.csdn.net/ypist