Access handler placed in onBindViewHolder

[Nat Thomas]

Hello, I have a handler in my onBindViewHolder method which looks like this:

        Handler handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                if (position <= 4) {
                    holder.mTextView.setTextColor(Color.BLACK);
                }
            }
        };

I am trying to call it from another method using: handler.sendEmptyMessage(0);
But symbol "handler" cannot be resolved.

I tried creating a field for "handler" but this is not useful.

How can I connect my handler to my method?

[Norm Radder]

tried creating a field for "handler" but this is not useful.  

Please explain.

symbol "handler" cannot be resolved.

The variable: handler needs to be in scope where you are trying to access it.

[Nat Thomas]

If I declare the variable "handler" with other variables at the top, below the class name, the app compiles but nothing happens when "handler" is called.

One other possibility would be if I could refer to MyViewHolder (holder) outside of OnBindViewHolder. Then I would not need to put my Handler in OnBindViewHolder. Is this possible?

[Norm Radder]

nothing happens when "handler" is called.

handler is a reference to an object, not a method that can be called.  Please explain what method you are trying to call and why you think that method is not being called.

[Nat Thomas]

Norm Radder wrote:

nothing happens when "handler" is called.

handler is a reference to an object, not a method that can be called.  Please explain what method you are trying to call and why you think that method is not being called.

Hi again, and thanks for your help.

I use "handler.sendEmptyMessage(0);" in another method. Technically, my TextView should turn to black as soon as Handler is called, but this does not happen.

Do you need me to provide more code or am I making sense?

[Nat Thomas]

Nat MadHatter wrote:

Norm Radder wrote:

nothing happens when "handler" is called.

handler is a reference to an object, not a method that can be called.  Please explain what method you are trying to call and why you think that method is not being called.

Hi again, and thanks for your help.

I use "handler.sendEmptyMessage(0);" in another method. Technically, my TextView should turn to black as soon as Handler is called, but this does not happen.

Do you need me to provide more code or am I making sense?

Oh, sorry, I've just realized I already gave that info earlier on. Let me try and explain better what I mean.

[Nat Thomas]

I have a method that checks in realtime whether words exists:

@Override
    public void onMoveItem(int fromPosition, int toPosition) {

        if (fromPosition == toPosition) {
            return;
        }
        mProvider.swapItem(fromPosition, toPosition);
        notifyDataSetChanged();
        checkIfExists();
    }

This method, checkIfExists(), looks like this:

    public void checkIfExists() {

        Runnable r = new Runnable() {
            @Override
            public void run() {
                DatabaseHelper myDbHelper = DatabaseHelper.getInstance(MainActivity.appContext);
                try {
                    myDbHelper.createDataBase();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                db = myDbHelper.getReadableDatabase();

                List<ExampleDataProvider.ConcreteData> firstWord = mData.subList(0, 5);
                String firstWord1 = Collections.singletonList(firstWord).toString().substring(1).replaceAll("\\[", "").replaceAll("\\]", "").replace(", ", "");
                String query = "SELECT 1 FROM sowpods WHERE field1 LIKE '" + firstWord1 + "'";
                Cursor cursor = db.rawQuery(query, null);
                if (cursor.moveToFirst()) {
                    handler.sendEmptyMessage(0);
                    oneCorrect = true;
                    cursor.close();
                }

The problem is that my TextView is inside onBindViewHolder, and the only way I can access it to change it is by putting my handler inside onBindViewHolder too.

I hope this makes more sense now.

[Norm Radder]

Where is the variable: handler defined?
Where is the reference made to that variable?  The variable needs to be in scope to be accessed.

[Nat Thomas]

So basicallly I found out that my handler works if I simply want to send out a Toast message. So the problem is actually not with the handler itself.
The problem is this:

public void onBindViewHolder(final MyViewHolder holder, final int position) {
                if (position <= 4){
                    holder.mTextView.setTextColor(Color.BLACK);
                }}

This works (first five letters turn to black) but :

public void onBindViewHolder(final MyViewHolder holder, final int position) {
        handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                if (position <= 4){
                    holder.mTextView.setTextColor(Color.BLACK);
                }
            }
        };}

This doesn't work (first five letters remain white).

Do you have any ideas what might be the problem?
Thanks!

[Norm Radder]

Where is the code that will cause the  handleMessage method to be called?

[Nat Thomas]

Norm Radder wrote:Where is the code that will cause the  handleMessage method to be called?

It's "handler.sendEmptyMessage(0);" in this method:

    public void checkIfExists() {
 
        Runnable r = new Runnable() {
            @Override
            public void run() {
                DatabaseHelper myDbHelper = DatabaseHelper.getInstance(MainActivity.appContext);
                try {
                    myDbHelper.createDataBase();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                db = myDbHelper.getReadableDatabase();
 
                List<ExampleDataProvider.ConcreteData> firstWord = mData.subList(0, 5);
                String firstWord1 = Collections.singletonList(firstWord).toString().substring(1).replaceAll("\\[", "").replaceAll("\\]", "").replace(", ", "");
                String query = "SELECT 1 FROM sowpods WHERE field1 LIKE '" + firstWord1 + "'";
                Cursor cursor = db.rawQuery(query, null);
                if (cursor.moveToFirst()) {
                    handler.sendEmptyMessage(0);
                    oneCorrect = true;
                    cursor.close();
                }}

[Nat Thomas]

This method is called here:

@Override
    public void onMoveItem(int fromPosition, int toPosition) {
 
        if (fromPosition == toPosition) {
            return;
        }
        mProvider.swapItem(fromPosition, toPosition);
        notifyDataSetChanged();
        checkIfExists();
    }

[Norm Radder]

Is there just one handler variable that is being used?  Hard to tell with the code snippets.

Where is the code that causes the run method to be called?

[Nat Thomas]

Norm Radder wrote:Is there just one handler variable that is being used?  Hard to tell with the code snippets.

Where is the code that causes the run method to be called?

Yes, just the one.

[Nat Thomas]

Nat Thomas wrote:

Norm Radder wrote:Is there just one handler variable that is being used?  Hard to tell with the code snippets.

Where is the code that causes the run method to be called?

Yes, just the one.

The code that causes the run method to be called is just above your post.

[Norm Radder]

The code that causes the run method to be called is just above your post.

Where?  What post (copy post's time stamp) and what line in the code in that post?