带值跳转startActivityForResult

1.MainActivity主函数中：

Intent it = new Intent(MainActivity.this, CityActivity.class);

startActivityForResult(it, 100);

2.  另一个Activity的主函数中

Intent it=new Intent(CityActivity.this, MainActivity.class);
it.putExtra("value", "中国");
setResult(200,it);
finish();

3.回到MainActivity主函数中：需要重写onActivityResult(int arg0, int arg1, Intent arg2)

// arg0 请求码

// arg1 结果码

if (arg0 == 100 && arg1 == 200) {
String new_city=arg2.getStringExtra("value");//取值
city.setText(new_city);//控件赋值
}