如何缩短代码

Question

I am making a calculator and below is my code. I was wondering is there any way to shorten the code, I have 18 buttons and I have to write 50 lines of code just to take reference from XML and add click listener to it

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

String SelectedOpertator;
int num1, num2, result;

EditText input;
Button b1, b2, b3, b4, b5, b6 ,b7, b8, b9, b0, bdot;
Button bc, bs, bd, bp, bmi, bm, be;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    input = (EditText) findViewById(R.id.input);

    b1 = (Button) findViewById(R.id.b1);
    b2 = (Button) findViewById(R.id.b2);
    b3 = (Button) findViewById(R.id.b3);
    b4 = (Button) findViewById(R.id.b4);
    b5 = (Button) findViewById(R.id.b5);
    b6 = (Button) findViewById(R.id.b6);
    b7 = (Button) findViewById(R.id.b7);
    b8 = (Button) findViewById(R.id.b8);
    b9 = (Button) findViewById(R.id.b9);
    b0 = (Button) findViewById(R.id.b0);
    bdot = (Button) findViewById(R.id.bdot);

    bc = (Button) findViewById(R.id.bc);
    bs = (Button) findViewById(R.id.bs);
    bd = (Button) findViewById(R.id.bd);
    bp = (Button) findViewById(R.id.bp);
    bmi = (Button) findViewById(R.id.bmi);
    bm = (Button) findViewById(R.id.bm);
    be = (Button) findViewById(R.id.be);

    b1.setOnClickListener(this);
    b2.setOnClickListener(this);
    b3.setOnClickListener(this);
    b4.setOnClickListener(this);
    b5.setOnClickListener(this);
    b6.setOnClickListener(this);
    b7.setOnClickListener(this);
    b8.setOnClickListener(this);
    b9.setOnClickListener(this);
    b0.setOnClickListener(this);
    bdot.setOnClickListener(this);
    bc.setOnClickListener(this);
    bs.setOnClickListener(this);
    bd.setOnClickListener(this);
    bp.setOnClickListener(this);
    bmi.setOnClickListener(this);
    bm.setOnClickListener(this);
    be.setOnClickListener(this);

}

Is there any other way to write this code in shorter way?

Answer 1

int ids[] = new int[] {R.id.b1, R.id.b2, R.id.b3, R.id.b4, R.id.b5, R.id.b6, R.id.b7, R.id.b8, R.id.b9, R.id.b0}

for(int i = 0; i < ids.length, i += 1){
    findViewById(ids[i]).setOnClickListener(this); 
}

---

There's no need for storing reference to each button as class members. In the onClick listener we can determine which button was clicked.

public onClick(View v){
    int number = Arrays.asList(ids).indexOf(v.getId()) + 1;
    // Button 'number' was clicked
}

Answer 2

If you add a method to do the findViewById and setOnClickListener , you can reduce the lines for each button from two to one:

private Button findAndSetClickListener(int id) {
  Button button = (Button) findViewById(id);
  button.setOnClickListener(this);
  return button;
}

Then:

b1 = findAndSetClickListener(R.id.b1);
// etc.

Answer 3

try this type code.

public class MainActivity extends AppCompatActivity implements     View.OnClickListener {

String SelectedOpertator;
int num1, num2, result;

EditText input;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    input = (EditText) findViewById(R.id.input);    


     ((Button) findViewById(R.id.b1)).setOnClickListener(this);
     ((Button) findViewById(R.id.b2)).setOnClickListener(this);
     ((Button) findViewById(R.id.b3)).setOnClickListener(this);
     ((Button) findViewById(R.id.b4)).setOnClickListener(this);
     ((Button) findViewById(R.id.b5)).setOnClickListener(this);
     ((Button) findViewById(R.id.b6)).setOnClickListener(this);
     ((Button) findViewById(R.id.b7)).setOnClickListener(this);
     ((Button) findViewById(R.id.b8)).setOnClickListener(this); 
     ((Button) findViewById(R.id.b9)).setOnClickListener(this);
     ((Button) findViewById(R.id.b0)).setOnClickListener(this);

     ((Button) findViewById(R.id.bdot)).setOnClickListener(this);

    ((Button) findViewById(R.id.bc)).setOnClickListener(this);
    ((Button) findViewById(R.id.bs)).setOnClickListener(this);
    ((Button) findViewById(R.id.bp)).setOnClickListener(this);
    ((Button) findViewById(R.id.bmi)).setOnClickListener(this);
    ((Button) findViewById(R.id.bm)).setOnClickListener(this);
    ((Button) findViewById(R.id.be)).setOnClickListener(this);




}

Answer 4

You could write an array where you store the views.

So that you can do something like

for (View v : array.getView()) {
    v.setOnClickListener(this)
}

I think the actual findViewById would be a little more complicated to simplify

Answer 5

You could shorten it at about 50% (and make it a lot more readable) with a private method:

private Button getButtonWithListener(int id) {
    Button btn = (Button) findViewById(id);
    btn.setOnClickListener(this);
    return btn;
}

and call this at every button: (saves you the setOnClickListener)

b1 = getButtonWithListener(R.id.b1);
b2 = getButtonWithListener(R.id.b2);
b3 = getButtonWithListener(R.id.b3);
b4 = getButtonWithListener(R.id.b4);
b5 = getButtonWithListener(R.id.b5);
b6 = getButtonWithListener(R.id.b6);
b7 = getButtonWithListener(R.id.b7);
b8 = getButtonWithListener(R.id.b8);
b9 = getButtonWithListener(R.id.b9);
b0 = getButtonWithListener(R.id.b0);
bdot = getButtonWithListener(R.id.bdot);

bc = getButtonWithListener(R.id.bc);
bs = getButtonWithListener(R.id.bs);
bd = getButtonWithListener(R.id.bd);
bp = getButtonWithListener(R.id.bp);
bmi = getButtonWithListener(R.id.bmi);
bm = getButtonWithListener(R.id.bm);
be = getButtonWithListener(R.id.be);

This way you're not losing the reference to the button. If you need those references to the buttons it won't become much shorter. If you don't need them, then there are some excellent possibilities in the other answers here!

Answer 6

If you need to shorten the button code, Use View's in OnClick() with help of switch statement.

In your XML Layout:

Create the number of buttons that you want with different button id. But use same method name for all button's onClick attribute. Eg: android:onClick="submitBTN" used for all buttons.

In your MainActivity:

Implement that method name to perform different operations using switch statement

    public void submitBTN(View view) {
    switch (view.getId()) {
        case R.id.btnClick1:    // Code of button 1 Click
            break;
        case R.id.btnClick2:    // Code of button 2 Click
            break;
        case R.id.btnClick3:     // Code of button 3 Click
            break;
        case R.id.btnClickn:    // Code of Button n Click
    }
}

Answer 7

Try using butter knife library. You can use syntax like:

@Onclick({R.id.b1, R.id.b2...｝）
public void handleClick(Button  btn){
         // handle click event here
}