使用Intent返回数据（返回到上一Activity）

MainActivity.java

package com.example.returnresult;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.app.Activity;
import android.content.Intent;

public class MainActivity extends Activity {

    private EditText num1, num2, result;
    private Button button;
    private final static int REQUESTCODE = 1;// 返回的结果码

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        num1 = (EditText) this.findViewById(R.id.num1);
        num2 = (EditText) this.findViewById(R.id.num2);
        result = (EditText) this.findViewById(R.id.result);
        button = (Button) this.findViewById(R.id.count);

        button.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                int i1 = Integer.parseInt(num1.getText().toString());
                int i2 = Integer.parseInt(num2.getText().toString());
                Intent intent = new Intent(MainActivity.this, Other.class);
                intent.putExtra("i1", i1);
                intent.putExtra("i2", i2);
                startActivityForResult(intent, REQUESTCODE);// 表示可以返回结果

            }
        });
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == 2) {
            if (requestCode == REQUESTCODE) {
                int three = data.getIntExtra("three", 0);
                result.setText(String.valueOf(three));
            }
        }
    }
}

Other.java

package com.example.returnresult;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Other extends Activity {

    private Button button;
    private TextView textView;
    private EditText editText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);
        button = (Button)this.findViewById(R.id.rt);
        textView = (TextView)this.findViewById(R.id.msg);
        editText = (EditText)this.findViewById(R.id.three);
        Intent intent = getIntent();
        int a = intent.getIntExtra("i1", 0);
        int b = intent.getIntExtra("i2", 0);
        textView.setText(a+" + "+b+" = "+" ? ");
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
               Intent intent = new Intent();
               int three = Integer.parseInt(editText.getText().toString());
               intent.putExtra("three", three);
               //通过Intent对象返回结果，setResult方法，
               setResult(2, intent);
               finish();//结束当前的Activity的生命周期。
            }
        });
    }
}

MainActivity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <LinearLayout
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <EditText
            android:id="@+id/num1"
            android:layout_width="95dp"
            android:layout_height="wrap_content"
            android:inputType="number" />

        <TextView
            android:id="@+id/plus"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/plus" />

        <EditText
            android:id="@+id/num2"
            android:layout_width="95dp"
            android:layout_height="wrap_content"
            android:inputType="number" />

        <TextView
            android:id="@+id/equal"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/equal" />
        <EditText
            android:id="@+id/result"
            android:layout_width="95dp" 
            android:layout_height="wrap_content"
            android:inputType="number"
            />
    </LinearLayout>

    <Button
        android:id="@+id/count"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/计算结果" >
    </Button>

</LinearLayout>

Other.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/msg"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >
        </TextView>

        <EditText
            android:id="@+id/three"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:inputType="number" >
        </EditText>
    </LinearLayout>

    <Button
        android:id="@+id/rt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/rt" >
    </Button>

</LinearLayout>