如何检查是否有意图发送的捆绑包？

Question

I have an Android application in which there are two activities. The start-up activity is where the user chooses category, and the second activity is where the user plays a game and gets a result. This result is then passed back to the first activity to be posted on facebook.

To pass data between activities I use this code:

Bundle extras = new Bundle();
                extras.putInt("categoryid", categoryid);
                Intent i = new Intent(MenuView.this, CreateTestView.class);
                i.putExtras(extras);
                startActivity(i);

This goes both ways. Now to my problem: The first time I start the MenuActivity there is no bundle being passed, and therefore I get a nullpointer exception when I try to retreive the extras. How can I use a check at start-up to see if there is a bundle beeing passed or not?

I tried it this way:

Bundle b = this.getIntent().getExtras();
       if(b==null){}
       else{
          noqs = b.getInt("noqs");
           point = b.getInt("point");

But this goes as b==null every time, even after finished game and the bundle is sent from the GameActivity.

Answer 1

From your MainActivity you could start sub- GameActivity via startActivityForResult and once it is finished, then you could receive your game results back via onActivityResult .

Something like this:

MainActivity:

private void startGameActivity() {
    Intent i = new Intent(getApplicationContext(), GameActivity.class);
    i.putExtra("some.key.here", "value");
    startActivityForResult(i, 0);
}

@Override protected void onActivityResult( int req, int resp, Intent data ) {
    super.onActivityResult(req, resp, data);
    // process your received "data" from GameActivity ...
}

GameActivity:

public void onCreate( Bundle savedInstanceState ) {
    // ...
    Bundle b = getIntent().getExtras();
    // ... process your extras from MainActivity
}

public void finishMySubActivity() {
    Intent data = new Intent();
    data.putExtra("some.other.key", GameResultsHere);
    setResult(RESULT_OK, data);
    finish();
 }