getBooleanExtra() using only the default argument

问题:

Here's the code. In this part, the answerIsTrue variable should be initialized to true, which it rightly does (I debugged and checked) and is rightly also passed into putExtra() (again, I debugged and checked).

mCheatButton.setOnClickListener(new View.OnClickListener(){
        public void onClick(View v){
            Intent i = new Intent(QuizActivity.this, CheatActivity.class);
            boolean answerIsTrue = mQuestionBank[mCurrentIndex].isTrueQuestion();
            i.putExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE, answerIsTrue);
            startActivity(i);
        }
    });

But coming to a different class, the variable mAnswerIsTrue gets assigned to false (probably due to the default argument) despite the argument being passed by putExtra() is true. Here's the code.

mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);

I debugged this line as well, and it does get assigned to false. What could be wrong?

Here's the complete CheatActivity class:

public class CheatActivity extends Activity {
public static final String EXTRA_ANSWER_IS_TRUE = "com.bignerdranch.android.geoquiz.answer_is_true";
private Button mShowAnswerButton;
private boolean mAnswerIsTrue;
private TextView mAnswerTextView;
@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_cheat);
    mAnswerIsTrue = getIntent().getBooleanExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE, false);
    mAnswerTextView = (TextView)findViewById(R.id.answerTextView);
    mShowAnswerButton = (Button)findViewById(R.id.showAnswerButton);
    mShowAnswerButton.setOnClickListener(new View.OnClickListener(){
        public void onClick(View v){
            if (mAnswerIsTrue){
                mAnswerTextView.setText(R.id.true_button);
            }else{
                mAnswerTextView.setText(R.id.false_button);
            }
        }
    });
}

}

Note: I'm a complete beginner, who just learnt debugging.

回答1:

I cannot be sure, but my best guess that, getBooleanExtra() is not good. I suggest using simple getExtras and then getting your value.

 i.putExtra(EXTRA_ANSWER_IS_TRUE, value);

 Bundle args = MyActivity.getIntent().getExtras();
 boolean istrue= args.getBoolean(EXTRA_ANSWER_IS_TRUE, false);

回答2:

In your CheatActivity initialize mAnswerIsTrue in onCreate() like this:

private boolean mAnswerIsTrue = false; // default value

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, false);
}

回答3:

for getting the data use the code

Boolean answertrue =getIntent().getExtras().getBoolean(CheatActivity.EXTRA_ANSWER_IS_TRUE);

in button click use the code

Intent i = new Intent(QuizActivity.this, CheatActivity.class);
 boolean answerIsTrue = true; 
i.putExtra(CheatActivity.EXTRA_ANSWER_IS_TRUE, answerIsTrue); 
startActivity(i);

回答4:

" Ctrl + B " to get in method in API. (android studio)

public boolean getBooleanExtra(String name, boolean defaultValue) {

        return mExtras == null ? defaultValue :
            mExtras.getBoolean(name, defaultValue);

    }

defaultValue the value to be returned if no value of the desired type is stored with the given name.

回答5:

Every time you rotate your screen, you should call pullExtra method. I am learning Android as well, but it seems to me that everytime onCreate method is called, Android app forgets all information about intend.

My code for that parts looks like this:

protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cheat);


        mAnswerIsTrue = getIntent().getBooleanExtra(EXTRA_ANSWER_IS_TRUE, true );

        if(savedInstanceState != null ){

            mShownAnswer = savedInstanceState.getBoolean(KEY_IS_CHEATER, false);
            setAnswerShownResult(mShownAnswer);

            Log.i(TAG, String.format("IsACheater: %b", mShownAnswer) );
        }
        else{
            setAnswerShownResult(false);
        }

...

回答6:

Use instead of .getBooleanExtra() the intent.extras.get(). So your code will same like this:

val mAnswerIsTrue = ((intent.extras.get("EXTRA_ANSWER_IS_TRUE")).toString()).toBoolean()

You need to cast, if you want to use the variable as an boolean.

If you want to put more extra, you need make a Bundle:

val extras = Bundle()
extras.putString("KEY_string", someString)
extras.putBoolean("KEY_boolean", someBoolean)

var intent = Intent(context,StartingActivity::class.java)
intent.putExtras(extras)