Develop Reference

App crashing at the end of array

My app is crashing at the end of the array in bluestacks. I have no idea why.
When I click the next button at the end of the array, the app crashes. I also tested it on my phone, same result. The rest of the app functions as intended.
From what I know "i %= image_elements.length;" is supposed to be the function that loops the array.
I am pretty sure this is where the crash is coming from.
i++;
element.setImageResource(image_elements[i]);
name.setImageResource(image_names[i]);
i %= image_elements.length;
Full code below
public class Practice extends MainMenuActivity {
int i = 0;
final int[] image_elements = {
R.drawable.spr_elements_0,
R.drawable.spr_elements_1,
[...]
R.drawable.spr_elements_86,
R.drawable.spr_elements_87,
};
final int[] image_names = {
R.drawable.spr_name_0,
R.drawable.spr_name_1,
[...]
R.drawable.spr_name_86,
R.drawable.spr_name_87,
};
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.practice);
final ImageView element = (ImageView) findViewById(R.id.element);
final ImageView name = (ImageView) findViewById(R.id.name);
Button nextButton = (Button) findViewById(R.id.buttonNext);
nextButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
i++;
element.setImageResource(image_elements[i]);
name.setImageResource(image_names[i]);
i %= image_elements.length;
}
});
}
public void backButton(View view) {
Intent z = new Intent(this, MainMenuActivity.class);
startActivity(z);
}
}

You'll need to rearrange your code from this:
i++;
element.setImageResource(image_elements[i]);
name.setImageResource(image_names[i]);
i %= image_elements.length;
to this:
i++;
i %= image_elements.length;
element.setImageResource(image_elements[i]);
name.setImageResource(image_names[i]);
What happens otherwise is that the index is incremented beyond the boundaries of the array, and that is corrected afterwards with the modulus operator. You'll need to the the correction before you use the index.
i %= image_elements.length in this particular case, is essentially the same as
if( i == image_elements.length ) {
i = 0;
}
Arrays indices go from 0 to length-1.
You could get rid of the arrays entirely by looking up the resources by name, such as this:
final static int MAX_ELEMENTS = 88; // this includes 0..87
private int index = 0;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.practice);
final ImageView element = (ImageView) findViewById(R.id.element);
final ImageView name = (ImageView) findViewById(R.id.name);
final Resources res = this.getResources();
final String pkgName = this.getPackageName();
Button nextButton = (Button) findViewById(R.id.buttonNext);
nextButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
final int imgId = res.getIdentifier( "spr_elements_" + index, "drawable", pkgName );
final int nameId = res.getIdentifier( "spr_name_" + index, "drawable", pkgName );
element.setImageResource( imgId );
name.setImageResource( nameId );
index = (index+1) % MAX_ELEMENTS;
}
});
}

How to generate random order for a strings list?

Every time an user click on the button it has to show "John - Sue" or "Sue - John".
I tried with this code:
public class MyActivity extends Activity {
ArrayList<String> names = new ArrayList<String>();
int p1, p2;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.myactivity);
names.add("John");
names.add("Sue");
Button b = (Button) findViewById(R.id.mybutton);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
p1 = (int)Math.random();
if (p1 == 0)
p2 = 1;
else
p2 = 0;
String msg = names.get(p1) + " - " + names.get(p2);
AlertDialog msgbox = new AlertDialog.Builder(About.this).setTitle("Click here").setMessage(msg).create();
//msgbox.setPositiveButton("OK", null);
msgbox.setCancelable(true);
msgbox.show();
TextView textView = (TextView) msgbox.findViewById(android.R.id.message);
textView.setTextSize(16);
}
});
}
}
But i get always the same order, even i close and run again the app. How to do that?

If you want shuffle list:
Collections.shuffle(names)
If you want random int between 0 or 1 (nextInt(int) javadoc):
Random random = new Random();
int randomInt = random.nextInt(2);

Math.random() returns a number between 0 and 1. So when you cast it to int it will always be 0.
Try this:
p1 = (int)(Math.random()*2);

It happens because
p1 = (int)Math.random();
always gives you zero.

Android: new random sum after each click?

In an android app I intend to allow users to answer a random sum then a new one appears on screen. This is repeated 10 times and then a final score will then be given. However I am unsure how to update the sum so that after each each a new random is shown on screen.
Below is my current code:
public class Test extends Activity {
//declare vars
TextView text;
EditText answer;
Button submit;
int random1;
int random2;
String question;
int correctAnswer;#
Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test);
// initialising variables
initialiseVars();
//set up random
setUpRandom();
//Set text view equal to question
text.setText(question);
//updateQuestion?
}
public void initialiseVars() {
text = (TextView) findViewById(R.id.tvTopRandomTest);
answer = (EditText) findViewById(R.id.etEnterAnswerRandomTest);
submit = (Button) findViewById(R.id.btnSubmitRandomTest);
}
public void setUpRandom() {
//setting up randoms
Random random = new Random();
// Generating random number between 1 and 12
random1 = random.nextInt(12) + 1;
// Generating another random number between 1 and 12
random2 = random.nextInt(12) + 1;
question = random1 + " x " + random2 + " = ";
correctAnswer = random1 * random2;
}
public void updateQuestion() {
//CODE TO UPDATE QUESTION
}
}

Add Button ClickListener so that when user press submit button it will update question and clean all previous values
submit = (Button) findViewById(R.id.btnSubmitRandomTest);
submit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
updateQuestion();
}
}
Maintain a count in your activity and increase it in updateQuestion
public void updateQuestion() {
if (Int.parseString(answer.getText().toString()) != correctAnswer) {
// Show toast or something
return;
}
tries++;
if (tries == 10) return; // or do something else;
answer.setText("");
setUpRandom();
text.setText(question); // add this line in your setUpRandom();
}
To generate random integers look at this. Hopefully this will help you out.

How to change object button to integer

I have 6 object button
kartu1 = (Button)findViewById(R.id.kartu1);
kartu2 = (Button)findViewById(R.id.kartu2);
kartu3 = (Button)findViewById(R.id.kartu3);
kartu4 = (Button)findViewById(R.id.kartu4);
kartu5 = (Button)findViewById(R.id.kartu5);
kartu6 = (Button)findViewById(R.id.kartu6);
All this object set to OnclickListener
kartu1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
r = new Random();
int i = r.nextInt(gamb.size());
v.setBackgroundDrawable(gamb.get(i));
}
});
I want to make all the object as an integer, cause there is a condition to count all the object. I have a condition.
if (kartu1 >= 5){
}
How to change kartu1 to integer?

try this
int[] ids={R.id.kartu1 ,R.id.kartu2, R.id.kartu3, R.id.kartu4, R.id.kartu5,R.id.kartu6 };
int clicks=0;
for(int i=0;i<ids.length;i++)
{
Button b=(Button)findViewById(R.id.kartu1);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
r = new Random();
int i = r.nextInt(gamb.size());
v.setBackgroundDrawable(gamb.get(i));
// set the click count in variable
clicks+=1;
if(clicks>=5){
// do stuff here
}
}
});
}
Second Case.
Above assumes that Total clicks on all images 5
if you want to set individual button click count of 5 do like this
public void onClick(View v) {
r = new Random();
int i = r.nextInt(gamb.size());
v.setBackgroundDrawable(gamb.get(i));
// set the click count in variable
String count=b.getContentDescription();
if(count!=null && count.length()!=0)
{
int cnt=Integer.parseInt(count);
cnt+=1;
button.setContentDescription(String.valueOf(cnt));
if(cnt>=5)
{
// do stuff here
}
}
else
{
button.setContentDescription(String.valueOf(1));
}
}

Seekbar creating EditTexts and then getting entries for further use

This code creates a seekbar and makes the seekbar create as many EditText fields as the slider is at / remove ones that would be too much. This code is in OnActivityCreated
final LinearLayout linearLayout = (LinearLayout) getActivity()
.findViewById(R.id.npv_calcfields);
EditText editText = new EditText(getActivity());
editText.setId(i);
editText.setLayoutParams(new LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
SeekBar bar = (SeekBar) getActivity().findViewById(R.id.npv_seekbar);
final TextView selection = (TextView) getActivity()
.findViewById(R.id.npv_selected);
bar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
public void onProgressChanged(SeekBar seekbar, int progress,
boolean fromUser) {
selection.setText("You have selected " + progress + " periods.");
if (progress == 0) {
String normalstring = getActivity().getResources()
.getString(R.string.npv1);
selection.setText(normalstring);
}
if (i > progress) {
while (i > progress) {
i--;
EditText editText = (EditText) getActivity()
.findViewById(i);
linearLayout.removeView(editText);
}
} else {
while (i < progress) {
EditText editText = new EditText(getActivity());
editText.setId(i);
editText.setLayoutParams(new LayoutParams(
LayoutParams.FILL_PARENT,
LayoutParams.WRAP_CONTENT));
linearLayout.addView(editText);
editText.setHint("Cash Flow " + i);
i++;
}
}
}
public void onStopTrackingTouch(SeekBar arg0) {
}
public void onStartTrackingTouch(SeekBar arg0) {
}
});
This code is in the general class area:
int i = 0;
EditText r = (EditText) getActivity().findViewById(R.id.npv_rate);
Button calc = (Button) getActivity().findViewById(R.id.npv_calc);
EditText[] DynamicField = new EditText[16];
Now I want users to input numbers into those edittext fields and then I want to do some math on them: Entry / (Math.pow(1+r, i) with i beeing the id of the field. The first entry should therefore be calculated as this: entry/(1+r)^0. This is what I tried but it doesn't work. It just crashes on startup.
calc.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
Double r1 = Double.parseDouble(r.getText().toString());
EditText editText = (EditText) getActivity().findViewById(i);
TextView answer = (TextView) getActivity().findViewById(R.id.npv_answer);
double[] CashFlows;
CashFlows = new double[i];
double result = 0;
CashFlows[i] = (Double.parseDouble(editText.getText()
.toString())) / (Math.pow(1 + r1, i));
for (double d : CashFlows) {
result += d;
}
answer.setText("answer is " + result);
}
});
What did I do wrong? by the way only the last code segment isnt working. if i comment that out it all works fine i tested it :) just dosent do anything obviuosly :)
ok a little background on the errorlog that you can see here: http://pastebin.com/G8iX6Pkm
EDIT: the entire class file can be seen here: http://pastebin.com/dxA91dst, the entire project can be found here: https://github.com/killerpixler/Android-Financial-Calculator.git
the class file is a fragment that gets loaded in a DetailsActivity when somebody clicks on a listitem from the Main activity. Like i said the error has to be in the button listener because it was working before i added it.

That NullPointerException comes from the fact that you initialize your Views using the getActivity() method where you declare them as fields in the F_NPV class. The method getActivity() method will return a valid Activity reference after the callback onAttach() is called, so the way you initialize the views will not work as, at that moment(when the fields of the Fragment class are initialized) the method getActivity will return null, no valid reference. The correct way to do that initialization is doing it in the onActivityCreated callback:
EditText r;
Button calc;
//...
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
r = (EditText) getActivity().findViewById(R.id.npv_rate);
calc = (Button) getActivity().findViewById(R.id.npv_calc);
//...
Also, if I may, some suggestions regarding your code:
You're doing some double's parsing from Strings and it may be a good idea to check the input so you don't throw a NumberFormatException. For example, if the user creates some EditTexts and then clicks the calculate Button(I know, it sounds silly, but there are chances the user will do it(I did it for example)), you'll throw a NumberFormatException as you try to parse an empty String. Instead make a little check:
public void onClick(View arg0) {
Double r1 = Double.parseDouble((r.getText().toString())
.equals("") ? "0" : r.getText().toString());
EditText editText = (EditText) getActivity().findViewById(i);
TextView answer = (TextView) getActivity().findViewById(R.id.npv_answer);
double[] CashFlows;
CashFlows = new double[i];
double result = 0;
String tmp = editText.getText().toString();
CashFlows[i] = (Double.parseDouble(tmp.equals("") ? "0" : tmp))
/ (Math.pow(1 + r1, i));
//...
Also, even if you have correct values in the EditText the above code will throw a NullPointerException, as the editText variable will be null. The reason for this is in the while loops that you used to create the fields. For example, if the user moves the SeekBar to 3 than the while loop will run 3 times, each time incrementing the i value. So i will be 0, 1, 2, so far correct but because you increment i each time the final i will be 4. Now in the onClick method you'll look for an EditText with the id i, but as there is no EditText in the layout with the id 4, the view will be null.
Also, try to give your classes better names, you may know very well what they mean but you could be making things worse for someone that reads your code(like F_PNV, F_PV etc).
Code for the onActivityCreated method. This should solve what you're trying to do(if I understand what you want):
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
r = (EditText) getActivity().findViewById(R.id.npv_rate);
calc = (Button) getActivity().findViewById(R.id.npv_calc);
final LinearLayout linearLayout = (LinearLayout) getActivity()
.findViewById(R.id.npv_calcfields);
SeekBar bar = (SeekBar) getActivity().findViewById(R.id.npv_seekbar);
final TextView selection = (TextView) getActivity().findViewById(
R.id.npv_selected);
bar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
public void onProgressChanged(SeekBar seekbar, int progress,
boolean fromUser) {
selection
.setText("You have selected " + progress + " periods.");
if (progress == 0) {
String normalstring = getActivity().getResources()
.getString(R.string.npv1);
selection.setText(normalstring);
linearLayout.removeAllViews(); // the progress is 0 so
// remove all the views that
// are currently present
} else {
int currentChilds = linearLayout.getChildCount();
if (currentChilds < progress) {
while (currentChilds != progress) {
EditText editText = new EditText(getActivity());
editText.setLayoutParams(new LayoutParams(
LayoutParams.FILL_PARENT,
LayoutParams.WRAP_CONTENT));
linearLayout.addView(editText);
currentChilds++;
}
} else if (currentChilds > progress) {
while (currentChilds != progress) {
linearLayout.removeViewAt(linearLayout
.getChildCount() - 1);
currentChilds--;
}
}
}
}
public void onStopTrackingTouch(SeekBar arg0) {
}
public void onStartTrackingTouch(SeekBar arg0) {
}
});
calc.setOnClickListener(new OnClickListener() {
public void onClick(View view) {
Double r1 = Double.parseDouble((r.getText().toString())
.equals("") ? "0" : r.getText().toString());
TextView answer = (TextView) getActivity().findViewById(
R.id.npv_answer);
final LinearLayout linearLayout = (LinearLayout) getActivity()
.findViewById(R.id.npv_calcfields);
int size = linearLayout.getChildCount();
double[] CashFlows = new double[size];
double result = 0;
for (int i = 0; i < size; i++) {
EditText editText = (EditText) linearLayout.getChildAt(i);
String tmp = editText.getText().toString();
CashFlows[i] = (Double.parseDouble(tmp.equals("") ? "0"
: tmp)) / (Math.pow(1 + r1, i));
}
for (double d : CashFlows) {
result += d;
}
answer.setText("answer is " + result);
}
});
}