Android加法计算器

一个加法计算器的实现

1. 创建两个Activity
2. 向AndroidManifest.xml添加Activity

<application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".ComputeActivity"
                  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=".ResultActivity"
                  android:label="@string/app_name">
        </activity>
</application>

3. 向main.xml中添加控件

<EditText 
	android:id="@+id/input1" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/input1"
    />
<TextView 
	android:id="@+id/symbol" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/symbol"
    />
<EditText 
	android:id="@+id/input2" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/input2"
    />
<Button
	android:id="@+id/myButton"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/myButton"
	/>

  为第二个Activity创建layout xml, 对于这个现实结果的TextView android:text要省略,在程序里赋动态值

<?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/sum" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    />

</LinearLayout>

4. 在string.xml中添加必要键值对, 这里的值通常为控件设定默认值,但如果控件在layout里指定了android:text,就会覆盖程序中的动态赋值

5. 实现这两个Activity

ComputeActivity.java

public class ComputeActivity extends Activity {
	
	private EditText et1 = null;
	private EditText et2 = null;
	private TextView tv = null;
	private Button btn = null;
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //取出所有控件,使用R.id
        et1 = (EditText)findViewById(R.id.input1);
        et2 = (EditText)findViewById(R.id.input2);
        tv = (TextView)findViewById(R.id.symbol);
        btn = (Button)findViewById(R.id.myButton);
        //给控件的显示标识赋值,使用R.string,这里如果使用R.id,Text会显示"false"
        tv.setText(R.string.symbol);
        btn.setText(R.string.myButton);
        //为控件绑定监听器
        btn.setOnClickListener(new ButtonListener());
    }
    
    class ButtonListener implements OnClickListener{

		@Override
		public void onClick(View arg0) {
			String str1 = et1.getText().toString();
			String str2 = et2.getText().toString();
			int v1 = Integer.parseInt(str1);
			int v2 = Integer.parseInt(str2);
			int sum = v1 + v2;
			System.out.println("------------>"+sum);
                        //创建一个新的intent
			Intent intent = new Intent();
			intent.putExtra("result",sum+"");
			intent.setClass(ComputeActivity.this, ResultActivity.class);
                        //传递这个intent
			ComputeActivity.this.startActivity(intent);
		}
    }
}

ResultActivity.java

public class ResultActivity extends Activity {

	public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.result);
        TextView tv = (TextView)findViewById(R.id.sum);
        //获取intent
        Intent intent = getIntent();
        //取出不同类型的Extra, 键值要和前面一致,包括大小写
        String str = intent.getStringExtra("result");
        tv.setText(str);

	}
}