Android Studio：通过另一个变量传递变量不起作用

Question

I created a Method for my MainActivity to pass a String to my SecondActivity.

public void convertCurrency(View view)
{
   intent.putExtra("NO", "My String");
   startActivity(intent);
}

But in my SecondActivity in my OnCreate Method

    Button back = (Button) findViewById(R.id.back);
    TextView t = (TextView) findViewById(R.id.first_text);

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

    String g = intent.getStringExtra("NO");
    t.setText(g);

Nothing happens. But Why?

Answer 1

get Your variable in this way:

String yourVriable = getIntent().getStringExtra("NO")

don't new Your intent

Answer 2

Your are creating new intent.

In onCreate method call

String data = getIntent().getStringExtra(key);

Answer 3

replace Intent intent = new Intent(this, MainActivity.class); by Intent intent = getIntent();

When you do intent.getStringExtra("NO"); your intent Object is new, so his Extra is empty.

Answer 4

You need to change the code in both the activities . You need to create intent and put your string into it, so your code will be.

public void convertCurrency(View view) { 
     Intent intent = new Intent(this, Main2Activity.class);
     intent.putExtra("NO","My String");                  
     startActivity(intent);
 }

Note that in the intent constructor the first argument is the current activity and the second argument will be the activity that you are starting.So in the second activity you need to recieve the string. Code for that will be,

Button back = (Button) findViewById(R.id.back); 
TextView t = (TextView) findViewById(R.id.first_text); 
String g = getIntent().getStringExtra("NO")
t.setText(g);

Answer 5

I resolve the problem myself. There occurs an error if you have two Intent objects with the same name even if they are within separate methods.