EditText and using buttons to submit them

问题:

So basically I would like this to allow the user to input text (their name). Then to click the submit button which will store that name into an array and erase the writing in the EditText (as well as make a counter for players). After they are done submitting players names I want them to be able to click the play button (titled done i believe) and continue to the next page with all the information being sent over.

My problem currently is when i enter in a name and click submit it force closes. If i click the play button it force closes. Think you could help me out? Thanks

Class 1:

public class Class1 extends Activity
{  
int players=0;
String names[];

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.class1);

    final EditText input = (EditText) findViewById(R.id.nameinput);


    Button submitButton = (Button) findViewById(R.id.submit_btn);
    submitButton.setOnClickListener(new View.OnClickListener()
    {
        public void onClick(View submit1)
        {
            players++;
            for(int i=0; i < players; i++)
            {
                names[i] = input.getText().toString();
                input.setText("");
            }
        }
    });

    Button doneButton = (Button) findViewById(R.id.done_btn);
    doneButton.setOnClickListener(new View.OnClickListener()
    {
        public void onClick(View done1)
        {
            Intent done = new Intent(Class1.this, Class2.class);
            done.putExtra("players", players);
            done.putExtra("names", names[players]);
            startActivity(done);
        }
    });
}

回答1:

You're not allocating for variable names anywhere. You should do this:

names = new String[NO_OF_PLAYERS];

If you're not sure about NO_OF_PLAYERS, then use

ArrayList<String> names = new ArrayList<String>();

and use it:

names.add(input.getText().toString());

回答2:

Your program crashes because you're trying to access non-initialized array. You must create array object using String names[] = new String[MAX_COUNT].

回答3:

I'm not sure this could be the reason but needs attention:

your onclick method of submit button:

  public void onClick(View submit1)
    {
        players++;
        for(int i=0; i < players; i++)
        {
            names[i] = input.getText().toString();
            input.setText("");
        }
    }

Here you increase players counter. Then loop from 0 to players counter. In loop you assign the input text in names array. Finally you clear the input.

This is not the right way to do. You have not initialized names array. Also you should not loop every time. It will override the old values in names array. And next time in loop input.getText() will return blank cause you have erased text from input already in first time you entered the loop.

It should be

public void onClick(View submit1)
{
    names[players++] = input.getText().toString();
    input.setText("");
}

if you debug your code you will better understand what I'm trying to say.

回答4:

Please try this edited code,

  public class Class1 extends Activity
    {  
    static int players;
    static String names[];
    static  //this is called once when class is first time used.
   {
     players=-1;
   }

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.class1);

        final EditText input = (EditText) findViewById(R.id.nameinput);


        Button submitButton = (Button) findViewById(R.id.submit_btn);
        submitButton.setOnClickListener(new View.OnClickListener()
        {
            public void onClick(View submit1)
            {
                players++;
                names[players] = input.getText().toString();
                input.setText("");
            }
        });

        Button doneButton = (Button) findViewById(R.id.done_btn);
        doneButton.setOnClickListener(new View.OnClickListener()
        {
            public void onClick(View done1)
            {
                Intent done = new Intent(Class1.this, Class2.class);
                done.putExtra("players", players);
                done.putExtra("names", names[players]);
                startActivity(done);
            }
        });
    }