兩個Activity通過Intent相互交換資料，在Activity中用一個Button 選擇是否接受資料，不能直接寫在onCreate中否則在Activity1 中獲取從Activity2傳送的資料時會崩潰，原因是因為在Activity中會通過Intent再建立一個Activity1的介面 而Activity1在記憶體中是存在的。

package com.example.he.text2;

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

/**
 * Created by he on 2016/3/19.
 */
public class FirstActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.firstlayout);
        Button first_button =(Button)findViewById(R.id.first_button);
        Button second_button=(Button)findViewById(R.id.second_button);

        //向SecondActivity傳資料的按鈕
        first_button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent =new Intent(FirstActivity.this,SecondActivity.class);
                intent.putExtra("first_action","hello secondActivity");
                startActivity(intent);
            }
        });

        //從SecondActivity得到資料的按鈕
        second_button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent =new Intent(FirstActivity.this,SecondActivity.class);
                startActivityForResult(intent,1);
            }
        });


    }



    //讀取返回資訊
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (requestCode){
            case  1:
                if (resultCode==RESULT_OK){
                    String s=data.getStringExtra("data_return");
                    Toast.makeText(FirstActivity.this, s, Toast.LENGTH_SHORT).show();
//                    Log.i("FirstActivity",s);
                }
                break;
        }
    }
}
 

package com.example.he.text2;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
/**
 * Created by he on 2016/3/19.
 */
public class SecondActivity extends Activity {
    @Override
 
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
setContentView(R.layout.secondlayout);
Button button1 = (Button) findViewById(R.id.button1);
Button button2 = (Button) findViewById(R.id.button2);
button1.setOnClickListener(new View.OnClickListener() {
            @Override
 
public void onClick(View v) {
                Intent intent2 = new Intent();
intent2.putExtra("data_return", "hello firstActivity");
setResult(RESULT_OK, intent2);
finish();
}
        });
button2.setOnClickListener(new View.OnClickListener() {
            @Override
public void onClick(View v) {
                Intent intent1 = getIntent();
String data = intent1.getStringExtra("first_action");
Toast.makeText(SecondActivity.this, data, Toast.LENGTH_SHORT).show();
//                Log.i("SecondActivity", data);
}
        });
}


    @Override
public void onBackPressed() {
        Intent intent2 = new Intent();
intent2.putExtra("data_return", "hello firstActivity");
setResult(RESULT_OK, intent2);
finish();
}
}