Unable to change TextView size on button click, why?

Question

Hello guys right now I'm working on an app in which there are many quotes, in a TextView and I want to change the size of TextView on button click, like if Small button is clicked then the TextView should become small, if Large is clicked it should be large, etc. But each time I press the Button app force closes! What's the problem? Here's OnClickListener for the Button:

small = (Button) findViewById(R.id.small);
small.setOnClickListener(new View.OnClickListener() {
 public void onClick(View v) {
 TextView tv = (TextView)findViewById(R.id.quotes);
 tv.setTextSize(20);
 }
 });

P.S: The TextView and the Button are in different Activities.

• inmyth: TextView and Button are in different Activities ? Then it's not going to work because findViewById is hooked to layout of one Activity.
• Ajinkya More: Any solution for this problem?
• PPartisan: Please include more information. For example, it is possible to change what happens in one activity from another through using Intent.putExtra, LocalBroadcastManager and an EventBus library. It is also possible to set something like preferred font size in SharedPreferences. It all depends on your situation.

Answer 1

There is no way to change the TextView size by Button from one Activity in other Activity. You will get NullPointerException because the findViewById method will not find view and will return null. You should use SharedPreferences. You should save text size value when you click Button and read it in the second Activity.

In your setting Activity:

 small.setOnClickListener(new View.OnClickListener() {
 public void onClick(View v) {
 SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(YourActivity.this.getBaseContext());
 sharedPreferences.edit()
 .putFloat("FONT_SIZE", 22)
 .apply();
 }
 });

In your activity where you have TextView

 TextView tv = (TextView)findViewById(R.id.quotes);
 SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(YourActivity.this.getBaseContext());
 tv.setTextSize(sharedPreferences.getFloat("FONT_SIZE", 13/*DEFAULT VALUE*/));

• Ajinkya More: Is there any solution for that? Please tell me because from 2 months I'm developing this app...Thank You very much!
• Konrad Krakowiak: You can also set your value in some singleton but your issue sounds like some setting. If you want to create something like setting it is a right solution
• Konrad Krakowiak: so this solution is right for you. Do you know how do this? I can give you some example if you want
• Ajinkya More: Oh Thank you very much!!! I really appreciate if you give an example :-) Give me an example and I'll definitely accept it!