Intent返回数据

一、发起页面跳转时：

                Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                startActivityForResult(intent, 1);

二、被调用页面：

        Intent intent = new Intent();
        intent.putExtra("data_return", "Hello MainActivity");
        setResult(RESULT_OK, intent);
        finish();

三、发起调用页面需要再获取数据：

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        switch (requestCode){
            case 1:
                if(resultCode == RESULT_OK){
                    String returnedData = data.getStringExtra("data_return");
                    Toast.makeText(this, returnedData, Toast.LENGTH_SHORT).show();
                }
                break;
            default:
        }
    }

 四、可以通过重写被调用页面的onBackPressed()方法，使页面在通过返回键返回时也能回传数据：

    @Override
    public void onBackPressed() {
        Intent intent = new Intent();
        intent.putExtra("data_return", "Hello MainActivity");
        setResult(RESULT_OK, intent);
        finish();
    }