Develop Reference

how to call the output of a method in another Activity 's textview?

im programming an app to sort numbers and display the sorting process
after the input is sorted , a new button will be showen to display the selection sort steps in a new activity
[SelectionSort activity 1
I want the output of the function SelectionSortMethod in SelectionSortclass to be displayed in a new activity activity_Ssteps
SelectionSort.java :
public class SelectionSort extends AppCompatActivity {
EditText input;
EditText output;
Button Ssteps ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_selection_sort);
input=findViewById(R.id.input);
output=findViewById(R.id.output);
Ssteps = findViewById(R.id.steps);
Ssteps.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
Intent s = new Intent(SelectionSort.this, com.example.sorted.Ssteps.class);
startActivityForResult(s, 1);
}
});}
public void sortButtonPressed(View view){
String[] numberList = input.getText().toString().split(",");
Integer[] numbers = new Integer[numberList.length];
for (int i = 0; i < numberList.length; i++) {
numbers[i] = Integer.parseInt(numberList[i]);
}
SelectionSortmethod(numbers);
output.setText(Arrays.toString(numbers));
// if button "sort " is pressed , the button "view steps "will be displayed
Ssteps.setVisibility(View.VISIBLE);
}
}
public static void SelectionSortmethod (Integer[] arr)
{
// some code for sorting and showing the steps
}
Ssteps.java :
public class Ssteps extends AppCompatActivity {
TextView steps_text ;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ssteps);
setTitle("selection sort steps ");
steps_text =findViewById(R.id.Stepstextview);
}
}

You can just use intent.extras like so:
Intent s = new Intent(SelectionSort.this, com.example.sorted.Ssteps.class);
s.putExtra("AnyID",YOURDATA);
startActivity(s);
And then in your Ssteps.class you can get the data using
the id like this:
String ss = getIntent.getExtra("AnyID"); //the id is the same as the other one above
steps_text.settext(ss);

Working with Intents like Youssof described is the way to go for small applications like yours. However as you progress in Android programming, you should definitely have a look at splitting your application in Fragments rather than Activities. They can use a Viewmodel, which makes sharing lots of data between screens much easier. Also Fragments can be use in androidx Navigation component, whos changing Fragments can be beautifully arranged in a UI. Very convenient for product reviews.

Java class extends MainActivity but findViewById comes back null?

This class extends my main Activity.
public class Numbers extends MainActivity{
public ArrayList<ImageView> getNumbers () {
ArrayList<ImageView> numbers = new ArrayList<>();
ImageView one = (ImageView) findViewById(R.id.one);
numbers.add(one);
return numbers;
}
And I've done some digging but can figure out why my variable "one" is coming back null.
My MainActivity has a ContentView set.
This is the content of my onCreate in MainActivity
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageView start = (ImageView) findViewById(R.id.start);
sceneRoot = (ViewGroup) findViewById(R.id.scene_root);
questionView = findViewById(R.id.questionView);
startView = findViewById(R.id.startView);
gameOverView = findViewById(R.id.gameOver);
animSlide = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.slide);
animSlide.setAnimationListener(this);
animZoom = AnimationUtils.loadAnimation(getApplicationContext(), R.anim.zoom_fade);
animZoom.setAnimationListener(this);
set.addTransition(new Fade())
.addTransition(new Slide(Gravity.RIGHT));
start.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
getQuestion();
TransitionManager.beginDelayedTransition(sceneRoot, set);
startView.setVisibility(View.GONE);
questionView.setVisibility(View.VISIBLE);
}
});
}
public void getQuestion (){
time = (TextView) findViewById(R.id.timeBar);
time.startAnimation(animSlide);
}
I don't call getNumbers() until after start has been clicked and the animation has started.
public void onAnimationStart(Animation animation){
if(animation == animSlide) {
final Questions questions = new Questions();
Numbers n = new Numbers();
for (int i = 0; i < n.getNumbers().size(); i++) {
n.getNumbers().get(i).setVisibility(View.GONE);
n.getNumbersTen().get(i).setVisibility(View.GONE);
}
n.getNumbers().get(0).setVisibility(View.VISIBLE);
EDIT:
If anyone was wondering, I got it to work by extending the class as a Fragment instead of my MainActivity. Then I just used the fragment in my xml.

Because you extended an Activity class doesn't mean setContentView gets called for that class also. It will only do so if properly started and you call super.onCreate(bundle) from your own implementation of onCreate within Numbers
Basically, you should never new any Activity. It has no life-cycle, and therefore no content view, so findViewById just won't work.
Numbers n = new Numbers();
You could not extend anything and have a data-only class around your list of images.
public class Numbers {
private List<ImageView> numbers = new ArrayList<ImageView>();
public Numbers() {}
public void addNumber(ImageView v) { numbers.add(v); }
public List<ImageView> getNumbers() { return numbers; }
}
And from MainActivity you can find and add as you want.
Number n = new Numbers();
n.addNumber((ImageView) findViewById(R.id.one));
However, I don't know if that is useful, really...
Maybe a Fragment would serve a better purpose if you want a "sub-view" of your Activity, but it's hard to tell.

Class variable random number... always the same? Android.

I am working through a Udemy course and we're building a basic "Higher or Lower" app. My app essentially works, however the random number it chooses for us to guess is always the same no matter how many times I destroy and relaunch the activity.
My MainActivity.java:
//mad import statements here
public class MainActivity extends AppCompatActivity {
int correctNumber;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int correctNumber = generateNum();
}
protected int generateNum(){
Random rand = new Random();
int randNum = rand.nextInt(100);
return randNum;
}
protected void numberEval(View view) {
EditText enteredNumber = (EditText) findViewById(R.id.numberEntry);
String numberString = enteredNumber.getText().toString();
Button pressMe = (Button) findViewById(R.id.button);
int numToEval = Integer.parseInt(numberString);
String result;
TextView showWinLose = (TextView) findViewById(R.id.winLoseText);
if (numToEval > correctNumber) {
result = "Too high!";
} else if (numToEval < correctNumber) {
result = "Too Low!";
}else {
result = "You guessed it!";
}
showWinLose.setText(result);
}
}
Super super basic, yes? Originally, my numberEval() method called generateNum(), but then I realized it was generating a new number to guess every time I pressed the button. So I set it the way it was here, where onCreate() generates correctNumber only once and correctNumber is now a class variable. Now it doesn't generate a new number every button click, but it won't seem to generate a new number at all. It's stuck at 0 no matter how any times I launch, close, relaunch, etc. the app.
How can I fix this? Thanks in advance.

public class MainActivity extends AppCompatActivity {
int correctNumber;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int correctNumber = generateNum();
}
// ...
}
The last line in onCreate() declares a local variable named correctNumber. This hides the class field with the same name and is only available inside onCreate(). To fix the problem, remove int from this line so that you use the class field instead.

Displaying list values with each button click

How can i display list items on each button click. Lets say there are 4 names in the list. When I press next it displays the first name. Then when you press next it displays the second name and so on.
The only way I think is using the list.get() method. however I dont know how to use the method so that it knows how many values there are in the list and displaying then on each button hit. I think i need to use for method however I hadnt had any luck with it.
public class ZaidimasActivity extends ZaidejaiActivity {
public TextView mPlayer;
public TextView mKlausimas;
public Button mNext;
public Button mBack;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_zaidimas);
/** //get the player list from ZaidejaiActivity
Bundle recdData = getIntent().getExtras();
String myVal = recdData.getString("playerList"); */
Intent zaidejuInfo = getIntent();
Bundle extrasBundle = zaidejuInfo.getExtras();
final ArrayList<String> players = extrasBundle.getStringArrayList("playerList");
//show the first players name
mPlayer = (TextView)findViewById(R.id.ZaidejoVardas);
players.size();
mPlayer.setText(players.get(0));
mNext = (Button)findViewById(R.id.KitasBtn);
mNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mPlayer.setText(players.get(1));
}
});
mBack = (Button)findViewById(R.id.GryztiMeniuBtn);
mBack.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent gryztiMeniu = new Intent(ZaidimasActivity.this, ZaidejaiActivity.class);
startActivity(gryztiMeniu);
}
});
}

Here you go, maintain a variable for storing the global array index and increment it every time the button is clicked.
private int count = 0; // Global array index. Make it as class field
final ArrayList<String> players = extrasBundle.getStringArrayList("playerList");
mPlayer = (TextView)findViewById(R.id.ZaidejoVardas);
players.size();
mPlayer.setText(players.get(0));
mNext = (Button)findViewById(R.id.KitasBtn);
mNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
count++;
mPlayer.setText(players.get((count)%players.size())); //Incrementing global count and making sure it never exceeds the players list size
}
});

Android tableview with dynamic numbers columns and rows

This is actually a memory training app, with matrix of squares wich flips to their other side and than back to first side. And user need to click on squares that flipped. You know what I mean?
Something like that.
What I need is that sizes of the matrix would change dynamically. If user have been passed one level of complexity (matrix size is 4x4 for example), then matrix size would grow (5x5 for example), and if not then matrix size would get smaller (3x3 for example). I hope that's clear, and if not - sorry, English is not my native language =)
So if I would do it from code this would not be a problem. I would use ViewFlipper with some transition animation and create TableView with sizes that I want with inflater or something like that (or directly from code without using xml at all). And then adding it to ViewFlipper from code.
But somehow I don't like that idea.
Then next idea come into my mind. To do ViewFlipper with all possible tableviews in it and then just showNext(); or showPrevious(); depending on what user have done. But in this case XML would be of very great size.
So maybe someone knows the another way to do it?

i suggest you to look view-pager-example,
using viewflipper showNext(); or showPrevious(); you had to download all data at the same time, but using fragmen, you can load only specific data assoiated with fragment.
you can change the view on every fragment like below
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new DetailFragment();
case 1:
return new ImageFragment(R.drawable.ic_launcher);
case 2:
return new ImageFragment(R.drawable.thumb);
default:
return null;
}
}
[EDIT - For checking view in listener]
public class LoginExampleImplements extends Activity implements OnClickListener {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
btn1.setOnClickListener(this);
btn2.setOnClickListener(this);
btn3.setOnClickListener(this);
btn4.setOnClickListener(this);
}
#Override
public void onClick(View v) {
if(v==btn1) {
} else if(v==btn2) {
} else if(v==btn3) {
} else if(v==btn4) {
}
}
}
[EDIT 2]
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
LinearLayout1 = (LinearLayout) findViewById(R.id.LinearLayout1);
for (int i = 0; i < 30; i++) {
button = new Button(getApplicationContext());
button.setId(i);
button.setOnClickListener(this);
LinearLayout1.addView(button);
}
}
#Override
public void onClick(View v) {
Button b = (Button)v;
b.getId()
// check clikedId
}
[EDIT 3]
public class MainActivity extends Activity implements OnClickListener{
ImageView img;
LinearLayout LinearLayout1;
LinearLayout.LayoutParams layoutParams;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout1 = (LinearLayout) findViewById(R.id.ln1);
layoutParams = new LinearLayout.LayoutParams(100, 100);
for (int i = 0; i < 30; i++) {
img = new ImageView(getApplicationContext());
img.setId(i);
img.setTag(i);
layoutParams.setMargins(10, 10, 10, 10);
img.setLayoutParams(layoutParams);
img.setBackgroundColor(Color.RED);
img.setPadding(10, 10, 10, 10);
img.setOnClickListener(this);
LinearLayout1.addView(img);
}
}
#Override
public void onClick(View v) {
ImageView b = (ImageView)v;
b.setBackgroundColor(Color.BLUE);
b.setImageLevel(Integer.valueOf(String.valueOf(b.getTag())));
}
}