使用Intent在活动之间穿梭（《第一行代码》读书笔记）

Intent intent = new Intent(A.this, B.class);

startActivity(intent);

A
---
Intent intent = new Intent(A.this, B.class);

intent.putExtra(  "这里是参数的键" , "这里是参数，本样例是字符串，也可以是其他的类型"  ); // 传参

startActivity(intent);


B
---
Intent intent = getIntent();

String data = intent.getStringExtra("这里是参数的键");　　//取出参数

A
---
Intent intent = new Intent(A.this, B.class);
startActivity(intent, 1); //1是请求码，要求唯一

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {　　// 接收返回的值
    switch(requestCode) { //请求码是唯一的
    case 1:
        if (resultCode == RESULT_OK) {
            String returnData = data.getStringExtra("data_return");
        }
        break;
    dafault:
    }
}


B
---
Intent intent = getIntent();
intent.putExtra("data_return", "hey~");
setResult(RESULT_OK/RESULT_CANCELED, intent);