Activity 的onActivityResult使用之旅

package com.example.helloworld2;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class A_Activity extends Activity {
    private TextView text;
    private final static int REQUESTCODE = 1;
    private final static int RESULTCODE = 2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        text = (TextView) findViewById(R.id.text);
    }
    public void go(View v){
        Intent intent = new Intent(A_Activity.this,B_Activity.class);
        startActivityForResult(intent, REQUESTCODE);
    }
    
    @Override
    protected void onActivityResult(int requsetCode, int resultCode, Intent intent) {
        // TODO Auto-generated method stub
        super.onActivityResult(requsetCode, resultCode, intent);
        if(resultCode==RESULTCODE){
            Bundle bundle = intent.getExtras();
            String result = bundle.getString("result");
            text.setText("返回的值："+result+"");
        }
        
    }
}

public class B_Activity extends Activity {
    private EditText text2;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_b);
        text2 = (EditText) findViewById(R.id.text2);
    }
    /**
     * 返回
     * @param v
     */
    public void go(View v){
        Intent intent = new Intent();
        intent.putExtra("result", text2.getText().toString().trim());
        setResult(2, intent); //将结果出给A 
        finish();//此处一定要调用finish()方法
    }
    
} 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.helloworld.MainActivity" >
    <Button 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="go"
        android:text="跳转"/>
    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
</LinearLayout>  

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.helloworld.MainActivity" >
    <Button 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="go"
        android:text="返回"/>
    <EditText
        android:id="@+id/text2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="100" />
</LinearLayout>