Optimising Android/Java Code - Creating multiple instances of the same object type

Question

I have a working application but want to optimise the code. Below is one example where I create 10 separate imagebuttons (note the incrementing objectname and XML reference for each) and set their listeners. Can anyone suggest a more optimal way of doing this, perhaps in a dynamic method/loop please? Thanks....

private void initialiseButtons() {  
    ImageButton imageButton1 = (ImageButton)this.findViewById(R.id.imageButton1);
    imageButton1.setOnClickListener(this);
    ImageButton imageButton2 = (ImageButton)this.findViewById(R.id.imageButton2);
    imageButton2.setOnClickListener(this);
    ImageButton imageButton3 = (ImageButton)this.findViewById(R.id.imageButton3);
    imageButton3.setOnClickListener(this);
    ImageButton imageButton4 = (ImageButton)this.findViewById(R.id.imageButton4);
    imageButton4.setOnClickListener(this);
    ImageButton imageButton5 = (ImageButton)this.findViewById(R.id.imageButton5);
    imageButton5.setOnClickListener(this);
    ImageButton imageButton6 = (ImageButton)this.findViewById(R.id.imageButton6);
    imageButton6.setOnClickListener(this);
    ImageButton imageButton7 = (ImageButton)this.findViewById(R.id.imageButton7);
    imageButton7.setOnClickListener(this);
    ImageButton imageButton8 = (ImageButton)this.findViewById(R.id.imageButton8);
    imageButton8.setOnClickListener(this);
    ImageButton imageButton9 = (ImageButton)this.findViewById(R.id.imageButton9);
    imageButton9.setOnClickListener(this);
    ImageButton imageButton0 = (ImageButton)this.findViewById(R.id.imageButton0);
    imageButton0.setOnClickListener(this);
}

pepea · Accepted Answer · 2013-04-25 12:08:08Z

1

You could use a loop and use getIdentifier() method.

int idToInitialize;
ImageButton ib;
for (int i = 0; i < 9; i++) {
    idToInitialize = getResources().getIdentifier("imageButton" + i, "id", getPackageName());
    ib = (ImageButton) this.findViewById(idToInitialize);
    ib.setOnClickListener(this);
}

Hovewer, it is very slow if we compare to the normal method.

answered Apr 25, 2013 at 12:08

pepea

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Comments

Fredszaq · Accepted Answer · 2013-04-25 12:15:35Z

1

You can reduce the boilerplate code by using http://androidannotations.org/ which will allow you to do someting like that

 @ViewById
 ImageButton imageButton1;

but it would be perhaps better to use an array or a list of buttons rather than multiple references, something like that for example :

private void init() {
    int[] ids=new int[]{R.id.imageButton1, R.id.imageButton2 ...};
    List<ImageButton> buttons=new ArrayList<ImageButton>;
    for(int id : ids) {
        buttons.add((ImageButton)this.findViewById(id));
    }
}

you can then easily iterate on the List, for example to set the listener

for(ImageButton button : buttons) {
   button.setOnClickListener(this);
}

edited Apr 25, 2013 at 12:15

answered Apr 25, 2013 at 11:55

Fredszaq

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Comments

njzk2 · Accepted Answer · 2013-04-26 07:43:04Z

0

You can use arrays, lists ...

For example:

private static final int[] BUTTONS_IDS = new int[] {R.id.imageButton0, R.id.imageButton1, R.id.imageButton2, R.id.imageButton3, R.id.imageButton4, R.id.imageButton5, R.id.imageButton6, R.id.imageButton7, R.id.imageButton8, R.id.imageButton9};

ImageButton[] buttons = new ImageButton[BUTTON_IDS.length];

private void initialiseButtons() {
    for (int i = 0; i < BUTTONS_IDS.length; i++) {
        buttons[i] = (ImageButton) findViewById(BUTTONS_IDS[i]);
        buttons[i].setOnClickListener(this);
    }
}

You can also put the list of ids in the arrays.xml file.

edited Apr 26, 2013 at 7:43

answered Apr 25, 2013 at 12:02

njzk2

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1 Comment

mr_merlin990 Over a year ago

Thank you, I've implemented this and it works perfectly. Just one correction in case anyone else copy/pastes - change BUTTON_IDS to BUTTONS_IDS in the first two lines for a consistent variable name throughout. That said, it's still a top response njzk2.

Hendrik Ebbers · Accepted Answer · 2013-04-25 12:00:16Z

0

I can't try it cause I have no Android Environmetn here. But I think this should work:

private void initialiseButtons() {
   for(int i = 0; i < 10; i++) {
      ImageButton imageButton = (ImageButton)this.findViewById(R.id.getClass().
         getField("imageButton" + i).get(R.id));
      imageButton.setOnClickListener(this);
   }
}

answered Apr 25, 2013 at 12:00

Hendrik Ebbers

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1 Comment

njzk2 Over a year ago

rather than R.id.getClass(), there is getResources().getIdentifier(String, String, String) which is cleaner

Ridcully · Accepted Answer · 2013-04-25 12:38:23Z

0

If it's only for setting the onClickListener, you can get rid off your whole initialiseButtons() methods and simply add android:onClick="handleButtonClick" in your layout xml and define that method in your activity like so:

public void handleButtonClick(View view) {
    switch(view.getId()) {
    case R.id.imageButton1: // handle button 1 pressed ....
    case R.id.imageButton2: // handle button 2 pressed ....
    // ... handle further buttons
    }
}

answered Apr 25, 2013 at 12:38

Ridcully

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