向上一个活动传输数据需要的内容
1.一个主页文件和一个子文件
MainActivity.java和IntentActivity.Java
2.文件对应的布局文件。
3.intent 的开启和传递数据

activity_main.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
<Button
   android:text="button";
   android:id="@+id/button";
   android:layout_width="match_parent"
   android:layout_height="match_parent"/>
</LinearLayout>

activity_intent.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".IntentActivity">
<button
     android:text="button1"；
     android:id="@+id/buton1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>
</LinearLayout>

MainActivity.java

package com.example.toast;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.content.Intent;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
   Button button=(Button)findViewById(R.id.button);
  button.setOnClickListener(new View.setOnClickListener(){
@Override
public void onClick(View v){
String data="hello sy";
Intent intent=new intent(MainActivity.this,IntentActivity.class);
intent.putExtra("name",data);
startActivity(intent);
}
});
}
}

IntentActivity.java

package com.example.toast;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class IntentActivity extends AppCompatActivity {

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_intent);
   Intent intent=getIntent();
   String data=intent.getStringExtra("name");
   Log.d("IntentActivity",data);
}
}

返回数据给上一个活动需要的内容
1.一个主文件和一个子文件。
2.布局文件不变，不写了

mainActivity.java文件

package com.example.toast;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.content.Intent;
import java.lang.String;

public class MainActivity extends AppCompatActivity {



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
Button button=(Button)findViewById(R.id.button);
button.setOnClickListener(new View OnClickListener(){
@Override
public void onClick(View v){
Intent intent=new intent(MainActivity.this,IntentActivity.class);
startActivityForResult(intent,1)；
}
});
}
@Override
orotected void onActivityResult(int requestCode,int resultCode,Intent data){
switch(requestCode){
case 1:
if(resultCode ==RESULT_OK){
String returnedData=data.getStringExtra("name");
Log.d("MainActivity",returnedData);
}
break;
default;
}
}
}

IntentActivity.java文件

package com.example.toast;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class IntentActivity extends AppCompatActivity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_intent);
 Button button=(Button)findViewById(R.id.button2);
 button.setOnColickListener(new View.OnColickListener(){
   @Override
public void onClick(View v){
Intent intent=new Intent();
intent.putExtra("name","hello sy");
setResult(RESULT_OK,intent);
finish();
}
});
}
}