如何从 ArrayList 检索值并将它们放在 Android Studio 中的不同 TextViews 中？

Question

I have the following ArrayList: ArrayList<Integer> counters; , with 3 values in it.

I made an Intent to move this ArrayList from Main.class , to a new class, callesd: two.class . And I want to get each value from the ArrayList, and put them in three TextViews, tv1, tv2, tv3 , like this: tv1 = value1, tv2 = value2, tv3 = value3 . Here is my code:

Main.class:

public void moveToAns(View view) {

counters.add(countCorrect);
counters.add(countWrong);
counters.add(countTotal);

seeAns = new Intent(this, two.class);

seeAns.putExtra("seeAnswers", counters);

startActivity(seeAns);

}

two.class:

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

        tv1 = (TextView) findViewById(R.id.tv1);
        tv2 = (TextView) findViewById(R.id.tv2);
        tv3 = (TextView) findViewById(R.id.tv3);

        intentSee = getIntent();

        seeAnsC = intentSee.getIntegerArrayListExtra("seeAnswers");

    }

so, what I need to do to get each value from the ArrayList into three different TextViews?

Answer 1

In your Main.class do this

public void moveToAns(View view) {
ArrayList<Integer> counters = new ArrayList();// you can declare it globally
counters.add(countCorrect);
counters.add(countWrong);
counters.add(countTotal);

seeAns = new Intent(this, two.class);

seeAns.putIntegerArrayListExtra("seeAnswers", counters);

startActivity(seeAns);

And in Two.class

 ArrayList<Integer> counters = getIntent().getIntegerArrayListExtra("seeAnswers");
 tv1 = (TextView) findViewById(R.id.tv1);
 tv2 = (TextView) findViewById(R.id.tv2);
 tv3 = (TextView) findViewById(R.id.tv3);

 tv1.setText("Correct answers: " + seeAnsC.get(0));
 tv2.setText("Wrong answers: " + seeAnsC.get(1));
 tv3.setText("Total answers: " + seeAnsC.get(2));

Answer 2

If I understand correctly, this should be what you're looking for. Let me know if it works :D

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

    tv1 = (TextView) findViewById(R.id.tv1);
    tv2 = (TextView) findViewById(R.id.tv2);
    tv3 = (TextView) findViewById(R.id.tv3);

    intentSee = getIntent();

    seeAnsC = intentSee.getIntegerArrayListExtra("seeAnswers");

    tv1.setText("Correct answers: " + seeAnsC.get(0));
    tv2.setText("Wrong answers: " + seeAnsC.get(1));
    tv3.setText("Total answers: " + seeAnsC.get(2));
}

Answer 3

you should use:

seeAns.putIntegerArrayListExtra("seeAnswers", counters);

instead of:

seeAns.putExtra("seeAnswers", counters);

Update:

Move the TextView code to onStart():

private ArrayList<Integer> seeAnsC;

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

    intentSee = getIntent();
    seeAnsC = intentSee.getIntegerArrayListExtra("seeAnswers");

}

protected void onStart() {
   tv1 = (TextView) findViewById(R.id.tv1);
   tv2 = (TextView) findViewById(R.id.tv2);
   tv3 = (TextView) findViewById(R.id.tv3);

   tv1.setText("Correct answers: " + seeAnsC.get(0));
   tv2.setText("Wrong answers: " + seeAnsC.get(1));
   tv3.setText("Total answers: " + seeAnsC.get(2));
}

Answer 4

Please post your code, so we can help you. According to what your posted on pastebin, you have an error in your OnClick and a NullPointerException :

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.add(java.lang.Object)' on a null object reference
                                                                              at com.example.user.thordrandom.Main.moveToAns(Main.java:108)

The NullPointerException is probably because the list is null.

Answer 5

Try this .

• initialize ArrayList<Integer> counters; and ArrayList<Integer> seeAnsC;

• change method to seeAns.putIntegerArrayListExtra("seeAnswers", counters);

Main.class

ArrayList<Integer> counters;

public void moveToAns(View view) {
    // Initialization
    counters = new ArrayList<>();

    counters.add(countCorrect);
    counters.add(countWrong);
    counters.add(countTotal);

    seeAns = new Intent(this, two.class);

    // change method to putIntegerArrayListExtra
    seeAns.putIntegerArrayListExtra("seeAnswers", counters);
    startActivity(seeAns);
}

Two.class

ArrayList<Integer> seeAnsC;

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

    tv1 = (TextView) findViewById(R.id.tv1);
    tv2 = (TextView) findViewById(R.id.tv2);
    tv3 = (TextView) findViewById(R.id.tv3);

    intentSee = getIntent();
    // init
    seeAnsC = new ArrayList<>();
    seeAnsC = intentSee.getIntegerArrayListExtra("seeAnswers");
}