Develop Reference

Random activity when button pressed

I would like to make a game, if i press play button, random level (activity) will open. I got code for this: https://stackoverflow.com/a/29579373/13101103
This is working, but i would like to edit, example, all levels have 2 different answer, answer1 is fail, answer2 is pass the level, if user pass level1, and in level2 fail, than go back to mainactivity, and if start again, then the passed levels will not show again.
Example:
There are 5 levels, user start random level, example level3, it passed, go to next random level, example level2, it pass, go to next... level4, it failed, go back to mainactivity, user start again, but the already passed levels will not show, only unpassed... example start level3... if passed then go to level1....
How can i edit this code for my solution? Can somebody give me some tips? Because in this if i go back to mainactivity and start again, then it start with all levels... I tried to edit, but i'm stucked and not works...
Plus i would like to save progress when user leave the app. In sharedpreferences how can i save the passed levels (arraylist)....?
MainActivity:
enter code here
Button level1Button = findViewById(R.id.level1Button);
level1Button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// We are creating a list, which will store the activities that haven't been opened yet
ArrayList<Class> activityList = new ArrayList<>();
activityList.add(Level1Activity.class);
activityList.add(Level2Activity.class);
activityList.add(Level3Activity.class);
activityList.add(Level4Activity.class);
activityList.add(Level5Activity.class);
Random generator = new Random();
int number = generator.nextInt(5) + 1;
Class activity = null;
// Here, we are checking to see what the output of the random was
switch(number) {
case 1:
activity = Level1Activity.class;
// We are adding the number of the activity to the list
activityList.remove(Level1Activity.class);
break;
case 2:
activity = Level2Activity.class;
activityList.remove(Level2Activity.class);
break;
case 3:
activity = Level3Activity.class;
activityList.remove(Level3Activity.class);
break;
case 4:
activity = Level4Activity.class;
activityList.remove(Level4Activity.class);
break;
default:
activity = Level5Activity.class;
activityList.remove(Level5Activity.class);
break;
}
// We use intents to start activities
Intent intent = new Intent(getBaseContext(), activity);
// `intent.putExtra(...)` is used to pass on extra information to the next activity
intent.putExtra("ACTIVITY_LIST", activityList);
startActivity(intent);
}
});
Level1Activity:
enter code here
failbutton1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v){
ArrayList<Class> activityList = new ArrayList<>();
activityList.add(Level1Activity.class);
Bundle extras = getIntent().getExtras();
activityList = (ArrayList<Class>) extras.get("ACTIVITY_LIST");
//Class activity = null;
Intent intent = new Intent(Level1Activity.this, Main2Activity.class);
intent.putExtra("ACTIVITY_LIST", activityList);
startActivity(intent);
}
});
buttonlevel1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ArrayList<Class> activityList = new ArrayList<>();
Bundle extras = getIntent().getExtras();
activityList = (ArrayList<Class>) extras.get("ACTIVITY_LIST");
if(activityList.size() == 0) {
// Do something when after all activities have been opened
//startActivity(new Intent(Level1Activity.this, Main2Activity.class));
//Intent intent = new Intent(Level1Activity.this, Main2Activity.class);
//intent.putExtra("ACTIVITY_LIST", activityList);
//startActivity(intent);
} else {
// Now, the random number is generated between 1 and however many
// activities we have remaining
Random generator = new Random();
int number = generator.nextInt(activityList.size()) + 1;
Class activity = null;
// Here, we are checking to see what the output of the random was
switch(number) {
case 1:
// We will open the first remaining activity of the list
activity = activityList.get(0);
// We will now remove that activity from the list
activityList.remove(0);
break;
case 2:
// We will open the second remaining activity of the list
activity = activityList.get(1);
activityList.remove(1);
break;
case 3:
// We will open the third remaining activity of the list
activity = activityList.get(2);
activityList.remove(2);
break;
case 4:
// We will open the fourth remaining activity of the list
activity = activityList.get(3);
activityList.remove(3);
break;
default:
// We will open the fifth remaining activity of the list
activity = activityList.get(4);
activityList.remove(4);
break;
}
// Note: in the above, we might not have 3 remaining activities, for example,
// but it doesn't matter because that case wouldn't be called anyway,
// as we have already decided that the number would be between 1 and the number of
// activities left.
// Starting the activity, and passing on the remaining number of activities
// to the next one that is opened
Intent intent = new Intent(getBaseContext(), activity);
intent.putExtra("ACTIVITY_LIST", activityList);
startActivity(intent);
}
}
});
level2, level3.... is same just different id-s

I'd suggest using the Singleton pattern to handle passing data between activities.
You can pass the list by intent's putExtra() or by SharedPreferences but with a Singleton class, it looks much better and easier to manipulate your data because they are encapsulated. So much so in your situation where you want to save your levels' states (e.g. when they are already completed).
However, if you really insist on using SharedPreferences to save the list then I suggest converting it to Json by using Gson. (Check below my answer on how to implement this.)
As I said, I'd use the Singleton pattern to avoid creating unnecessary boilerplate code and to encapsulate the levels' states.
LevelManager class (the singleton)
final class LevelManager {
// constants
private static final String LEVELS_SHARED_PREFERENCES_NAME = "app_name.LEVELS";
// variables
private static LevelManager instance;
private List<Class> levels;
private SharedPreferences sharedPreferences;
private LevelManager(Context context) {
sharedPreferences =
context.getSharedPreferences(LEVELS_SHARED_PREFERENCES_NAME, Context.MODE_PRIVATE);
levels = new ArrayList<>();
initializeList();
}
private void initializeList() {
// Initialize levels, ie. add levels that are not yet completed/passed
// Check in SharedPreferences if level has already been completed
boolean alreadyPassed;
alreadyPassed = sharedPreferences.getBoolean(Level1Activity.class.getSimpleName(), false);
if (!alreadyPassed) levels.add(Level1Activity.class);
alreadyPassed = sharedPreferences.getBoolean(Level2Activity.class.getSimpleName(), false);
if (!alreadyPassed) levels.add(Level2Activity.class);
alreadyPassed = sharedPreferences.getBoolean(Level3Activity.class.getSimpleName(), false);
if (!alreadyPassed) levels.add(Level3Activity.class);
alreadyPassed = sharedPreferences.getBoolean(Level4Activity.class.getSimpleName(), false);
if (!alreadyPassed) levels.add(Level4Activity.class);
alreadyPassed = sharedPreferences.getBoolean(Level5Activity.class.getSimpleName(), false);
if (!alreadyPassed) levels.add(Level5Activity.class);
}
static LevelManager getInstance(Context context) {
if (instance == null) {
instance = new LevelManager(context);
}
return instance;
}
Class getRandomLevel() {
if (levels.isEmpty()) {
return null; // Return null if all levels are already completed
}
Collections.shuffle(levels);
return levels.get(0);
}
void saveLevelState(Class levelClass, boolean passed) {
sharedPreferences.edit().putBoolean(levelClass.getSimpleName(), passed).apply();
if (passed) {
// Remove level from list if user passed it so that it won't
// be included in next levels
levels.remove(levelClass);
}
}
void reset() {
// Clears all entries in SharedPreferences and re-initialize list
sharedPreferences.edit().clear().apply();
initializeList();
}
}
Inside onCreate in MainActivity
// Get LevelManager singleton instance
final LevelManager levelManager = LevelManager.getInstance(this);
Button startButton = findViewById(R.id.startButton);
startButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// Get next random level
Class levelToStart = levelManager.getRandomLevel();
// If all levels are already completed
if (levelToStart == null) {
Toast.makeText(MainActivity.this, "All levels are completed!",
Toast.LENGTH_LONG).show();
return;
}
Intent intent = new Intent(MainActivity.this, levelToStart);
startActivity(intent);
}
});
// I added a new button to reset all levels
Button resetButton = findViewById(R.id.resetButton);
resetButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// Use the method reset() from LevelManager to restart everything
levelManager.reset();
Toast.makeText(MainActivity.this, "All levels have been reset!",
Toast.LENGTH_LONG).show();
}
});
Inside of onCreate on each Level Activity
// Get LevelManager
final LevelManager levelManager = LevelManager.getInstance(this);
// I created two buttons to simulate pass and fail
Button pass = findViewById(R.id.passButton);
Button fail = findViewById(R.id.failButton);
pass.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// Save state (Don't forget to change 'N' below)
levelManager.saveLevelState(LevelNActivity.class, true);
// Get next level
Class levelToStart = levelManager.getRandomLevel();
// Check if all are levels already completed
if (levelToStart == null) {
Toast.makeText(LevelNActivity.this, "Completed all levels",
Toast.LENGTH_LONG).show();
finish(); // Must implement to avoid going back to previous level (ie. Activity)
return;
}
Intent intent = new Intent(LevelNActivity.this, levelToStart);
startActivity(intent);
finish();
}
});
fail.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
finish();
}
});
As you can see, you can simply use the finish() method if the user failed the level whereas you use the code below to proceed to the next level:
// Get LevelManager
LevelManager levelManager = LevelManager.getInstance(this);
// Set that the user passed this level (Change 'N' to the current level we are in)
levelManager.saveLevelState(LevelNActivity.class, true);
// Get next level
Class nextLevel = levelManager.getRandomLevel();
// If all levels are completed then 'nextLevel' will be null
if (nextLevel == null) {
// ...
}
// Start next level and finish current
Intent intent = new Intent(this, nextLevel);
startActivity(intent);
finish();
Note: To avoid calling finish() explicitly when starting the next level, you can put android:noHistory="true" in your levels' activity tag inside your manifest file.
How to save list to SharedPreferences by converting it to Json using Gson
To actually use Gson, you'll have to add implementation 'com.google.code.gson:gson:2.8.6' inside your app gradle dependencies.
Also, there's a problem on Gson when parsing Class objects to Json: You need to create your own serializer and deserializer for these objects and register it to your GsonBuilder.
ClassAdapter class (this is where we create our own custom serializer and deserializer for Class objects)
public class ClassAdapter implements JsonSerializer<Class>, JsonDeserializer<Class> {
#Override
public JsonElement serialize(Class src, Type typeOfSrc, JsonSerializationContext context) {
// Get our class 'src' name
return new JsonPrimitive(src.getName());
}
#Override
public Class deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
try {
// Get class
return Class.forName(json.getAsString());
} catch (ClassNotFoundException e) {
// If class could not be found or did not exists, handle error here...
e.printStackTrace();
}
return null;
}
}
Here's a sample usage of saving a list to SharedPreferences by Json using Gson:
// Create new GsonBuilder and register our adapter for Class objects
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(Class.class, new ClassAdapter());
// Initialize our list of levels (ie. classes)
List<Class> classes = new ArrayList<>();
classes.add(Level1Activity.class);
classes.add(Level2Activity.class);
classes.add(Level3Activity.class);
classes.add(Level4Activity.class);
classes.add(Level5Activity.class);
// Create Gson from GsonBuilder and convert list to json
Gson gson = gsonBuilder.create();
String json = gson.toJson(classes);
// Save json to SharedPreferences
SharedPreferences sharedPreferences = getSharedPreferences("app_name", MODE_PRIVATE);
sharedPreferences.edit().putString("levels", json).apply();
And to retrieve the list back:
// Retrieve json from SharedPreferences
SharedPreferences sharedPreferences = getSharedPreferences("app_name", MODE_PRIVATE);
String json = sharedPreferences.getString("levels", null);
// Handle here if json doesn't exist yet
if (json == null) {
// ...
}
// Create new GsonBuilder and register our adapter for Class objects
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(Class.class, new ClassAdapter());
// Create Gson from GsonBuilder and specify type of list
Gson gson = gsonBuilder.create();
Type type = new TypeToken<ArrayList<Class>>(){}.getType();
// Convert json to list
List<Class> classes = gson.fromJson(json, type);
I hope you gained valuable tips to tackle this problem! And as always, happy coding!

How to show income in intent string array at recyclerview android?

In my application I have draft messages which I can edit. Some of my drafts include attachments which I try to send to my edit activity and show it at recyclerview. In general I have managed to send my string arraylist and get it at my activity. But I can't show my attached files, especially their names at the recyclerview. I tried to make smth like that:
adapter.notifyDataSetChanged();
but it didn't help me.
So, firstly I get from my message names of attached files:
file_name = Objects.requireNonNull(response.body()).getAttachesNames();
then put this names into arraylist:
nameList = new ArrayList<>(Arrays.asList(file_name));
such result I can see in my logs:
W: [eZV9f.jpg, index.html]
and then I send my list via intent to another activity:
intent2.putStringArrayListExtra("attached_files", (ArrayList<String>) nameList);
receiving data from intent:
Intent intent = getIntent();
extras = intent.getExtras();
if (extras != null) {
if (extras.containsKey("attached_files")) {
draft_files = getIntent().getStringArrayListExtra("attached_files");
Log.w("MY_TAG", String.valueOf(draft_files));
}
}
results from logcat:
W: [eZV9f.jpg, index.html]
initialising of my adapter and recyclerview:
adapter = new AttachedFileAdapter(mNames);
recyclerView = findViewById(R.id.recyclerView);
recyclerView.setLayoutManager(new LinearLayoutManager(WriteResponseMess.this, LinearLayoutManager.VERTICAL, false));
and then I try to get single element from this list and add to my ArrayList<>:
for (int i = 0; i < draft_files.size(); i++) {
mNames.addAll(Collections.singleton(draft_files.get(i)));
adapter.notifyDataSetChanged();
recyclerView.setAdapter(adapter);
Log.w("MY_TAG", draft_files.get(i));
Log.w("MY_TAG", String.valueOf(mNames));
}
all previous pieces of code are used at my onCreate() method and as a result of all these actions I would like to see income data from another activity. Sometimes I managed to do it, but one element contained all income data and looked like this:
[eZV9f.jpg, index.html]
and it was wrong for me. I try to create the list which will contain all elements separately. I also tried to use some info from this link which is connected with Collections, but I didn't manage to reach the goal of my task. In general I'm sure that the solution is very simple but I can't see it.
update
all my activity class has more than 1000 lines and I will share all code which is connected with adding attachments and show attached data at my writing form:
Here is my dialog for getting directory list and choosing some files:
#Override
protected Dialog onCreateDialog(int id) {
Dialog dialog = null;
switch (id) {
case CUSTOM_DIALOG_ID:
dialog = new Dialog(WriteResponseMess.this, android.R.style.Theme_DeviceDefault_Light_NoActionBar_Fullscreen);
dialog.setContentView(R.layout.dialog_layout);
dialog.setCanceledOnTouchOutside(true);
Toolbar toolbar = dialog.findViewById(R.id.toolbar_d);
toolbar.setTitle("Add a new file.");
textFolder = dialog.findViewById(R.id.folder);
buttonUp = dialog.findViewById(R.id.up);
buttonUp.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
ListDir(curFolder.getParentFile());
}
});
dialog_ListView = dialog.findViewById(R.id.dialoglist);
final Dialog finalDialog1 = dialog;
dialog_ListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#RequiresApi(api = Build.VERSION_CODES.O)
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
File selected = new File(curFolder, fileList.get(position));
if (selected.isDirectory()) {
ListDir(selected);
}
if (selected.isFile()) {
if (array.size() == 0) {
array = uploadFiles(array, selected.getName(), convertFileToString(selected.getPath()));
adapter.notifyDataSetChanged();
getImages();
} else {
if (array.toString().contains(selected.getName())) {
Toast.makeText(WriteResponseMess.this, R.string.attaching_message, Toast.LENGTH_SHORT).show();
adapter.notifyDataSetChanged();
getImages();
} else {
array = uploadFiles(array, selected.getName(), convertFileToString(selected.getPath()));
adapter.notifyDataSetChanged();
getImages();
}
}
finalDialog1.dismiss();
ms.setArray(array);
}
}
});
break;
}
return dialog;
}
and method for showing attached list, and in general this method works when I create a new message and attach a new file, it works fine:
private void getImages() {
mNames.clear();
adapter.notifyDataSetChanged();
for (int i = 0; i < array.size(); i++) {
JsonObject object = array.get(i).getAsJsonObject();
if (extras != null) {
if (extras.containsKey("attached_files")) {
for (int j = 0; j < draft_files.size(); j++) {
mNames.clear();
mNames.add(draft_files.get(j));
adapter.notifyDataSetChanged();
//Log.w("MY_TAG", draft_files.get(i));
Log.w("MY_TAG", String.valueOf(mNames));
}
mNames.add(object.get("filename").toString().substring(1, object.get("filename").toString().length() - 1));
adapter.notifyDataSetChanged();
//Log.w("MY_TAG", Arrays.toString(draft_files));
Log.w("MY_TAG", Arrays.toString(new ArrayList[]{mNames}));
} else {
mNames.add(object.get("filename").toString().substring(1, object.get("filename").toString().length() - 1));
adapter.notifyDataSetChanged();
Log.w("MY_TAG", String.valueOf(mNames));
}
}
}
}

no need to set Adapter twice . remove this line
recyclerView.setAdapter(adapter);
From
for (int i = 0; i < draft_files.size(); i++) {
mNames.addAll(Collections.singleton(draft_files.get(i)));
adapter.notifyDataSetChanged();
//recyclerView.setAdapter(adapter); no need
Log.w("MY_TAG", draft_files.get(i));
Log.w("MY_TAG", String.valueOf(mNames));
}

how to save the state of those items which have been selected in recyler view even after the app is closed

What I want to do is to show the same selected items on a recycler view even after the activity has been closed and only change items color when I again click on it. For now I have achieved changing the color on click but the state doesn't get saved?
This is my adapter:
public class LightsRecyclerViewAdapter extends
RecyclerView.Adapter<LightsRecyclerViewAdapter.ViewHolder> {
// private List<Integer> mViewColors;
private List<String> mAnimals;
private LayoutInflater mInflater;
private ItemClickListener mClickListener;
// data is passed into the constructor
LightsRecyclerViewAdapter(Context context, List<String>
animals) {
this.mInflater = LayoutInflater.from(context);
this.mAnimals = animals;
}
// inflates the row layout from xml when needed
#Override
#NonNull
public ViewHolder onCreateViewHolder(#NonNull ViewGroup
parent, int viewType) {
View view = mInflater.inflate(R.layout.item, parent,
false);
return new ViewHolder(view);
}
// binds the data to the view and textview in each row
#Override
public void onBindViewHolder(#NonNull ViewHolder holder, int
position) {
// int color = mViewColors.get(position);
String animal = mAnimals.get(position);
// holder.myView.setBackgroundColor(color);
holder.myTextView.setText(animal);
}
// total number of rows
#Override
public int getItemCount() {
return mAnimals.size();
}
// stores and recycles views as they are scrolled off screen
public class ViewHolder extends RecyclerView.ViewHolder
implements View.OnClickListener {
View myView;
TextView myTextView;
ViewHolder(View itemView) {
super(itemView);
// myView = itemView.findViewById(R.id.colorView);
myTextView =
itemView.findViewById(R.id.tvAnimalName);
itemView.setOnClickListener(this);
}
#Override
public void onClick(View view) {
if (mClickListener != null)
mClickListener.onItemClick(view, getAdapterPosition());
}
}
// convenience method for getting data at click position
public String getItem(int id) {
return mAnimals.get(id);
}
// allows clicks events to be caught
public void setClickListener(ItemClickListener
itemClickListener) {
this.mClickListener = itemClickListener;
}
// parent activity will implement this method to respond to click events
public interface ItemClickListener {
void onItemClick(View view, int position);
}
}
And this is my activity:
public class DevicesList extends AppCompatActivity implements
LightsRecyclerViewAdapter.ItemClickListener{
private LightsRecyclerViewAdapter adapter,adapter1;
TextView title;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_devices_list);
title = (TextView)findViewById(R.id.textGrid);
// data to populate the RecyclerView with
ArrayList<Integer> viewColors = new ArrayList<>();
viewColors.add(Color.BLUE);
viewColors.add(Color.YELLOW);
viewColors.add(Color.MAGENTA);
viewColors.add(Color.RED);
viewColors.add(Color.BLACK);
ArrayList<String> Lab1LightsList = new ArrayList<>();
Lab1LightsList.add("Light 1");
Lab1LightsList.add("Light 2");
Lab1LightsList.add("Light 3");
Lab1LightsList.add("Light 4");
Lab1LightsList.add("Light 5");
ArrayList<String> Lab1ACList = new ArrayList<>();
Lab1ACList.add("AC 1");
Lab1ACList.add("AC 2");
Lab1ACList.add("AC 3");
Lab1ACList.add("AC 4");
Lab1ACList.add("AC 5");
ArrayList<String> Lab2LightsList = new ArrayList<>();
Lab2LightsList.add("Light 1");
Lab2LightsList.add("Light 2");
Lab2LightsList.add("Light 3");
Lab2LightsList.add("Light 4");
Lab2LightsList.add("Light 5");
Lab2LightsList.add("Light 6");
ArrayList<String> Lab2ACList = new ArrayList<>();
Lab2ACList.add("AC 1");
Lab2ACList.add("AC 2");
Lab2ACList.add("AC 3");
Lab2ACList.add("AC 4");
// set up the RecyclerView
RecyclerView recyclerView = findViewById(R.id.list1);
RecyclerView recyclerView1 =findViewById(R.id.list2);
LinearLayoutManager horizontalLayoutManagaer
= new LinearLayoutManager(DevicesList.this, LinearLayoutManager.HORIZONTAL, false);
LinearLayoutManager horizontalLayoutManager
= new LinearLayoutManager(DevicesList.this, LinearLayoutManager.HORIZONTAL, false);
recyclerView.setLayoutManager(horizontalLayoutManagaer);
recyclerView1.setLayoutManager(horizontalLayoutManager);
Intent mIntent = getIntent();
int intValue = mIntent.getIntExtra("labno", 0);
if(intValue==0) {
adapter = new LightsRecyclerViewAdapter(this, Lab1LightsList);
adapter1 = new LightsRecyclerViewAdapter(this, Lab1ACList);
adapter.setClickListener(this);
adapter1.setClickListener(this);
recyclerView.setAdapter(adapter);
recyclerView1.setAdapter(adapter1);
}
if(intValue==1) {
adapter = new LightsRecyclerViewAdapter(this, Lab2LightsList);
adapter1 = new LightsRecyclerViewAdapter(this, Lab2ACList);
adapter.setClickListener(this);
adapter1.setClickListener(this);
recyclerView.setAdapter(adapter);
recyclerView1.setAdapter(adapter1);
}
}
#Override
public void onItemClick(View view, int position) {
Toast.makeText(this, "You clicked " +
adapter.getItem(position) + " on item position " + position,
Toast.LENGTH_SHORT).show();
view.setBackgroundColor(getResources().getColor(R.color.colorPrimaryDark));
}
}
Please help on this.

Create one selected item position list and store it in prefs when an app goes to background or closed. Load that list when launching an app and compare that list in an adapter's onBindViewHolder's position parameter and marks it selected/unselected based on a comparison.

As per my understandings about your question, you want to save the state of the selected items even after the app is closed, and then you want to reload it whenever the app is launched again. You need to refer to this link Android Save Data
For the above solution, there can be various ways to save state, I am mentioning a few below:
Use SQLite Database to save the selected items. Then, whenever the app is loaded, fetch all the selected data from the DB and then mark them selected with whatever colour you want on the list.
You can also use Shared Preferences, to store the selection. And, same as above, you can reload the data when the app is launched.
You can also store the data in a specific format, maybe CSV, JSON, XML etc., in a file and save it either in Internal Storage or External Storage of the device. And when the app is launched, fetch all the selected values from the file and process accordingly.
You can also use a web server, Firebase Storage, or other cloud storage services to save the data and then fetch the data on new app launch.
Do note: All these techniques require you to save the state before the app is closed. So it is better to store the states, either on click of the item, or onPause method of the activity.
If you face any problems with these solutions, you can post another comment and I will give it a look.

Save these clicked item position in a hashmap in Shareprefence. suppose u close the activity after u coming back the activity just pass the saved list with ur data in adapter and compare the shareprefence list with ur data list if position or data match than make the itemview layout colored.
// save clicked item is a list and save it sharePreference.
List<Integer> clikedList = new ArrayList<>();
if (clicked item){
ClikedList.add(position)
}
String value = gson.toJson(list);
SharedPreferences prefs = context.getSharedPreferences("mylist",
Context.MODE_PRIVATE);
Editor e = prefs.edit();
e.putString("list", value);
e.commit();
// for getting cliked position list from SharePreference
SharedPreferences prefs = context.getSharedPreferences("mylist",
Context.MODE_PRIVATE);
String value = prefs.getString("list", null);
GsonBuilder gsonb = new GsonBuilder();
Gson gson = gsonb.create();
MyObject[] list = gson.fromJson(value, MyObject[].class);
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
// suppose clicked position 4 u get from shaved cliked list
in here u neddd to retreive cliked list position and clored those item
int select = 4;
if (select == position) {
holder.itemView.setBackgroundColor(Color.BLUE);
Toast.makeText(context, "" + position, Toast.LENGTH_SHORT).show();
} else {
holder.itemView.setBackgroundColor(Color.parseColor("#214F4B"));
Toast.makeText(context, "" + position, Toast.LENGTH_SHORT).show();
}
holder.tv_title.setText(data.get(position));
}

Add values to ArrayList from different activity

I'm trying to create an app like shopping cart
Using this to access my database http://www.tutecentral.com/restful-api-for-android-part-2/
And i'm stuck at adding products to cart, so far I understand that the selected products go to arraylist in a few tutorials. In the code below I have two Activities, the MaterialView (this shows the details of the materials and has the option to add to cart), and the MaterialCart (shows the list of selected products.)
this is the block of code in MaterialView to send the values to MaterialCart
ButtonAdd.setOnClickListener(new View.OnClickListener(){
public void onClick (View view){
Intent i=new Intent(MaterialView.this, MaterialCart.class);
i.putExtra("mID", mid);
i.putExtra("name", Name.getText().toString());
i.putExtra("qty", Qty.getText().toString());
i.putExtra("price", Price.getText().toString());
i.putExtra("stock", Stock.getText().toString());
i.putExtra("rqQty", RqQty.getText().toString());
startActivity(i);
Toast.makeText(MaterialView.this, "Added Succesfully.", Toast.LENGTH_LONG).show();
}
} );
I have used Intent to pass the values (I'm pretty sure this method is wrong, I also tried calling the MaterialCart class itself to access the arrayList so I can add values and it didn't work)
This is the block of codes in my MaterialCart to receive the values
public class MaterialCart extends Activity {
final ArrayList<PropertyCartTable> materialProperties = new ArrayList<>();
#SuppressLint("LongLogTag")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_material_cart);
Intent i = new Intent();
Bundle extras = getIntent().getExtras();
try{
String Name = extras.getString("name");
String Qty = extras.getString("qty");
String Price = extras.getString("price");
String Stock = extras.getString("stock");
String RqQty = extras.getString("rqQty");
String ID = extras.getString("mID");
Log.d("EXTRAS:", Name + " " + Qty + " " + ID);
materialProperties.add(new PropertyCartTable( ID,Name,Qty,Price,Stock,RqQty));
getIntent().removeExtra("Name");
getIntent().removeExtra("Qty");
getIntent().removeExtra("Price");
getIntent().removeExtra("Stock");
getIntent().removeExtra("RqQty");
getIntent().removeExtra("MID");
}
catch (Exception h){
Log.d("Exception!",h.toString());
}
// materialProperties.add(array);
Log.d("MaterialView.Cart isEmpty", String.valueOf(materialProperties.isEmpty()));
if(materialProperties.isEmpty()) {
Toast.makeText(this, "You have no materials to request.", Toast.LENGTH_LONG).show();
i = new Intent(MaterialCart.this, ProductDetails.class);
startActivity(i);
}else{
ArrayAdapter<PropertyCartTable> adapter = new propertyArrayAdapter(this, 0, materialProperties);
ListView listView = (ListView) findViewById(R.id.lv_materialcart);
listView.setAdapter(adapter);
}
}
The codes work for receiving the values, but when I go back to the materialView (or choose another product) the ArrayList doesn't append the values.
What I'm trying to achieve here is to add the values from the MaterialView (even if the user adds many prodducts) to MaterialCart's ArrayList.

You can let your Application contain the data:
public class MyApp extends Application {
private static List<String> data = new ArrayList<>();
public static void addItem(String item) {
data.add(item);
}
public static List<String> getData() {
return data;
}
}
And when button is clicked:
ButtonAdd.setOnClickListener(new View.OnClickListener(){
public void onClick (View view){
MyApp.addItem(your item);
Intent i=new Intent(MaterialView.this, MaterialCart.class);
startActivity(i);
}
} );
And in MaterialCart.class:
List<String> data = MyApp.getData();
But remember:data will be clear when app is closed.And if you want save it locally,you need to use SharedPreferences

Android: Java: TextView Won't Change Color

I can't seem to figure out why my list row item won't change color:
/** Populate the Views in act_alliances.xml with data from the database */
private void loadAllianceData() {
TblAlliances mTAlliances = new TblAlliances(this);
mTAlliances.openRead();
Cursor mCursor = mTAlliances.selectSectorData(mSector);
// load Sector Name into act_alliance_detail.xml
TextView mTxtSctName = (TextView) findViewById(R.id.allc_sname);
mTxtSctName.setText("Sector: "+mSector);
// load the "Number of Alliances" field with the count from the cursor
TextView mTxtNumAllcs = (TextView) findViewById(R.id.allc_textView2);
mTxtNumAllcs.setText(String.valueOf(mCursor.getCount()));
String[] cols = new String[] {
mTAlliances.C_FID,
mTAlliances.C_FANAME,
mTAlliances.C_FPLTC,
mTAlliances.C_FSPWER
};
int[] to = new int[] {
R.id.allc_lstRow_textView1,
R.id.allc_lstRow_textView2,
R.id.allc_lstRow_invisible,
R.id.allc_lstRow_textView3
};
// connect to the ListView and clear it just in case this isnt the first time
ListView mListView = (ListView) findViewById(R.id.allc_listView);
mListView.destroyDrawingCache();
mListView.setVisibility(ListView.INVISIBLE);
mListView.setVisibility(ListView.VISIBLE);
// create the adapter using the cursor pointing to the desired data
//as well as the layout information
SimpleCursorAdapter dataAdapter = new SimpleCursorAdapter(
this,
R.layout.act_alliances_list_row,
mCursor,
cols,
to,
0);
dataAdapter.setViewBinder(new SimpleCursorAdapter.ViewBinder() {
#Override
public boolean setViewValue(View view, Cursor cursor, int column) {
if( column == 1 ){
TextView tv = (TextView) view;
String mPltc = cursor.getString(cursor.getColumnIndex("FPLTC"));
if (BuildConfig.DEBUG) {
Log.i(Constants.TAG_ACTALLIANCES, "loadAllianceData(): Political Relation: "+mPltc);
}
// Set color of item based on Political Relation
if(mPltc == "Ally"){tv.setTextColor(Color.parseColor("#6699ff"));}
if(mPltc == "Vassal"){tv.setTextColor(Color.parseColor("#00ff00"));}
if(mPltc == "Enemy"){tv.setTextColor(Color.parseColor("#ff0000"));}
return true;
}
return false;
}
});
// Assign adapter to ListView
mListView.setAdapter(dataAdapter);
mListView.setOnItemClickListener( new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
// selected item
mAllianceForDetail = ((TextView) arg1.findViewById(R.id.allc_lstRow_textView2)).getText().toString();
startAct("AllianceDetail");
}
});
mTAlliances.close();
}
Everything in the SimpleCursorAdapter.ViewBinder seems to be in order, but the color won't change...i suspect that it may be WHERE i placed the ViewBinder more than the ViewBinder itself.
Any help would be appreciated!

You can't equalize object with a string. You need to use equals or equalsIgnoreCase functions
if (mPltc.equalsIgnoreCase("Ally")){tv.setTextColor(Color.parseColor("#6699ff"));}
if (mPltc.equalsIgnoreCase("Vassal")){tv.setTextColor(Color.parseColor("#00ff00"));}
if (mPltc.equalsIgnoreCase("Enemy")){tv.setTextColor(Color.parseColor("#ff0000"));}
return true;

Try using
if(mPltc.equals("Ally"))...
instead of
if(mPltc == "Ally")
(Same with "Vassal", "Enemy", etc)
You shouldn't use == on String objects, as it doesn't work the way you'd expect.