//  How to send value using intent from one class to another class
//  class A(which will send data)
    Intent theIntent = new Intent(this, B.class);
    theIntent.putExtra("name", john);
    startActivity(theIntent);
//  How to get these values in another class
//  Class B
    Intent i= getIntent();
    i.getStringExtra("name");
//  if you log here i than you will get the value of i i.e. john

在接收活动中

Bundle extras = getIntent().getExtras(); 
String userName;

if (extras != null) {
    userName = extras.getString("name");
    // and get whatever type user account id is
}

加起来

设置数据

String value = "Hello World!";
Intent intent = new Intent(getApplicationContext(), NewActivity.class);
intent.putExtra("sample_name", value);
startActivity(intent);

获取数据

String value;
Bundle bundle = getIntent().getExtras();
if (bundle != null) {
    value = bundle.getString("sample_name");
}

你也可以这样做//将价值放在意图上

    Intent in = new Intent(MainActivity.this, Booked.class);
    in.putExtra("filter", "Booked");
    startActivity(in);

//从意图中获得价值

    Intent intent = getIntent();
    Bundle bundle = intent.getExtras();
    String filter = bundle.getString("filter");

不要初始化另一个新的Intent来接收数据，只需执行以下操作：

String id = getIntent().getStringExtra("id");

科特林

第一项活动

val intent = Intent(this, SecondActivity::class.java)
intent.putExtra("key", "value")
startActivity(intent)

第二项活动

val value = getIntent().getStringExtra("key")

建议

始终将密钥放在常量文件中，以便于管理。

companion object {
    val PUT_EXTRA_USER = "PUT_EXTRA_USER"
}