返回上一个activity时如何带数据

从activity1 进入 activity2，从activity2 返回到 activity1

activity1中调用 startActivityForResult(Intent intent, int requestCode)

Intent intent = new Intent(MainActivity.this,Main2Activity.class);
startActivityForResult(intent,200);

activity2中调用 setResult(int resultCode, Intent data)

setResult(300);
finish();

activity1中重写 onActivityResult

只有在activity2中调用 finish()，activity1中的onActivityResult才会被执行，finish()之前不用必须调用setResult

@Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        // TODO 处理数据，通常要判断
    }