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)
@Override public boolean onOptionsItemSelected(MenuItem item) { // TODO Auto-generated method stub if(item.getItemId()==1){ finish(); // 结束当前Activity. } return super.onOptionsItemSelected(item); } @Override public boolean onCreateOptionsMenu(Menu menu) { // TODO Auto-generated method stub menu.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; @Override protected 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()); } @Override public boolean onOptionsItemSelected(MenuItem item) { // TODO Auto-generated method stub if(item.getItemId()==1){ finish(); // 结束当前Activity. } return super.onOptionsItemSelected(item); } @Override public boolean onCreateOptionsMenu(Menu menu) { // TODO Auto-generated method stub menu.add(0,1,1,R.string.exit); menu.add(0,2,2,R.string.about); return super.onCreateOptionsMenu(menu); } class CalculateListener implements OnClickListener{ @Override public 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ResultActivity Activity_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; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.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