startActivityForResult

 1、 startActivityForResult（）和startActivity（）

startActivity()仅仅只是页面的跳转，如果想跳转回到原页面，还需要再使用一次startActivity().

 startActivityForResult（）可以直接完成上述任务，例如从A1
Activity跳转到A2 Activity，当A2
Activity调用了finish()方法以后，程序就会自动跳回A1 Activity并调用A1
Activity中的onActivityResult( )方法

2、主要函数

startActivityForResult(Intent
intent, Int requestCode) A1
setResut(int resultCode, Intent intent) A2
onActivityResult(int requestCode, int resultCode, Intent intent) A1

A1
Activity中的startActivityForResult

toSec
4000
ondButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent();
intent.setClass(FirstActivity.this, SecondActivity.class);
intent.putExtra("str", "I'm back");
startActivityForResult(intent, BACK1);   //此处BACK1为1，也可以为其他值，但一定大于等于0

}
});

A1
Activity中重写onActivityResult方法（从A2返回后执行）

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode){
case BACK1:
Bundle bundle=data.getExtras();
String string=bundle.getString("back1");
Toast.makeText(FirstActivity.this,string,Toast.LENGTH_SHORT).show();
break;
case BACK2 :
Bundle bundle2=data.getExtras();
String string2=bundle2.getString("back2");
Toast.makeText(FirstActivity.this,string2,Toast.LENGTH_SHORT).show();
break;
case BACK3:
Bundle bundle3=data.getExtras();
String string3=bundle3.getString("ID");
textView.setText(string3);
Toast.makeText(FirstActivity.this,string3,Toast.LENGTH_SHORT).show();
break;
default:
break;
}
}

A2 Activity中的setResut

back1.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent();
intent.putExtra("back1","back button1");      //back button1"为传递的内容

setResult(BACK1, intent);               //BACK1为resultcode
intent.setClass(SecondActivity.this,FirstActivity.class);
finish();                                //一定要有
}
});