向下一个活动传递数据

MainActivity1传递数据给MainActivity2
通过extra_data来进行数据传递

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String data = "Hello MainActivity2";
                Intent intent = new Intent(MainActivity.this, Main2Activity.class);
                intent.putExtra("extra_data", data);
                startActivity(intent);
                startActivityForResult(intent, 1);
            }
        });

MainActivity2接收数据

        Intent intent=getIntent();
        String data=intent.getStringExtra("extra_data");
        Log.d("onCreate: ",data);

向上一个活动接收数据

MainActivity2返回数据

 button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent1=new Intent();
                intent1.putExtra("data_return","Hello MainActivity");
                setResult(RESULT_OK,intent1);
                finish();
            }
        });

MainActivity1接收数据

startActivityForResult(intent, 1);

    @Override
    protected void onActivityResult(int requestCode, int resultCode,Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case 1:
                if (resultCode == RESULT_OK) {
                    String returnData = data.getStringExtra("data_return");
                    Log.d("onActivityResult: ", returnData);
                }
                break;
            default:
        }
    }