重写返回键(intent 带返回值的)

通过返回键往上个活动里传值

@Override
public void onBackPressed() {
    Intent intent = new Intent();
    intent.putExtra("data_return","HelloFirstActivity");
    setResult(RESULT_OK,intent);
    Toast.makeText(this,"你点击了返回键",Toast.LENGTH_SHORT).show();
    finish();
}