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。
[java]
private TextView resultView;
private int result;
...
resultView.setText(result + "");
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)
[java]
@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);
}
@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_03srcyanactivity_02Activity_03.java"
[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.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);
}
}
}
2."Activity_03srcyanactivity_02ResultActivity.java"
[java]
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 + "");
}
}
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 + "");
}
}
3."Activity_03reslayoutactivity_03.xml"
[java]
<?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"
>
<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>
4."Activity_03reslayoutresult.xml"
[html]
<?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"?>
<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>
5."Activity_03AndroidManifest.xml"
[java]
<?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"?>
<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>
6."Activity_03resvaluesstrings.xml"
[html]
<?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>
<?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-->>
