更改EditText字段的值相互依赖

Question

I'm trying to build temperature converter (F -> C and C -> F).

I have 2 ET fields. when user types in one, the other displays converted value and vice verse.

I understand that similar programs has been build already, but I couldn't find solution.

It works fine for one field, but app closes when I try to edit the other one.

Here is my piece of code:

public class Temp extends Activity implements OnClickListener, OnFocusChangeListener {

private EditText temp_f, temp_c;

    protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.temp);

    temp_f = (EditText) findViewById(R.id.temp_f_inp);
    temp_c = (EditText) findViewById(R.id.temp_c_inp);

    temp_c.setOnFocusChangeListener((OnFocusChangeListener) this);
    temp_f.setOnFocusChangeListener((OnFocusChangeListener) this);

}

private TextWatcher tempc = new TextWatcher() {
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {

        if (temp_c.getText().length() == 0) 
        {
            temp_f.setText("");
        } else {
            float convValue = Float.parseFloat(temp_c.getText()
                    .toString());

            conv_f = ((convValue - 32) * 5 / 9);

            temp_f.setText(String.valueOf(new DecimalFormat(
                    "##.###").format(conv_f)));
        }

    }
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
    @Override
    public void afterTextChanged(Editable s) {

    }       
};

private TextWatcher tempf = new TextWatcher() {
    @Override
    public void onTextChanged(CharSequence s, int start,int before, int count) {

        // TODO Auto-generated method stub
                    if (temp_f.getText().length() == 0) 
                    {
                        temp_c.setText("");
                    } else {

                        float convValue = Float.parseFloat(temp_f.getText()
                                .toString());

                        conv_c = ((convValue * 9) / 5 + 32);

                        temp_c.setText(String.valueOf(new DecimalFormat(
                                "##.###").format(conv_c)));

    }
    @Override
    public void beforeTextChanged(CharSequence s, int start,int count, int after) {}
    @Override
    public void afterTextChanged(Editable s) {

    }
};

@Override
public void onFocusChange(View v, boolean hasFocus) {
        if ((v == findViewById(R.id.temp_c_inp)) && (hasFocus==true)) {
            temp_c.addTextChangedListener(tempc);
        }

        else if((v == findViewById(R.id.temp_f_inp)) && (hasFocus==true)){
            temp_f.addTextChangedListener(tempf);
        } 
}

it seems like onTextChanged still holds the values of the first ET that has been modified and when I try to edit the other ET fields, it throws an error.

Any help would be greatly appreciated!

Thank you!

Answer 1

You could try this:

@Override
 public void onFocusChange(View v, boolean hasFocus) {
     if (v.equals(findViewById(R.id.temp_c_inp))) {
        if(hasFocus){
            temp_c.addTextChangedListener(tempc);
        }else{
            temp_c.removeTextChangedListener(tempc);
        }
     }
    else if(v.equals(findViewById(R.id.temp_f_inp))){
        if(hasFocus){
        I      temp_f.addTextChangedListener(tempf);
        }else{
             temp_f.removeTextChangedListener(tempf);
        }
    } 
}

I haven't tried the code by myself, but I hope it could help you

Answer 2

Logic seems to be a problem. What I would do is, 1. On text change, do nothing (or just check for valid input values) 2. On focus change, do conversion and populate other text field. Also, you have some @Override functions which are essentially null functions. Why override?