bfg
Reputation: 13
Android Studio: Adding two numbers wihout a button
I'm using Android Studio to develop a program which adds two numbers. First, I used a button to start the calculation but now I don't want to use that button anymore so I'm searching for a possibility to add two numbers in real time. If I change one number, the result should appear instantly. Do you have any suggestions? This is my code für the button variant:
New code:
public class MainActivity extends AppCompatActivity {
EditText firstNumEditText, secondNumEditText;
TextView resultTextView;
class MyTextWatcher implements TextWatcher {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
}
@Override
public void afterTextChanged(Editable s) {
String second = secondNumEditText.getText().toString().trim();
String first = firstNumEditText.getText().toString().trim();
int num1 = Integer.parseInt(second);
int num2 = Integer.parseInt(first);
int result = num1 + num2;
resultTextView.setText(result + "");
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
firstNumEditText = (EditText) findViewById(R.id.firstNumEditText);
firstNumEditText.addTextChangedListener(new MyTextWatcher());
secondNumEditText = (EditText) findViewById(R.id.secondNumEditText);
secondNumEditText.addTextChangedListener(new MyTextWatcher());
resultTextView = (TextView) findViewById(R.id.resultTextView);
}
}
LogCat's output:
java.lang.NumberFormatException: For input string: ""
at java.lang.Integer.parseInt(Integer.java:533)
at java.lang.Integer.parseInt(Integer.java:556)
at com.example.aufgabe2.MainActivity$MyTextWatcher.afterTextChanged(MainActivity.java:33)
at android.widget.TextView.sendAfterTextChanged(TextView.java:8202)
at android.widget.TextView$ChangeWatcher.afterTextChanged(TextView.java:10381)
at android.text.SpannableStringBuilder.sendAfterTextChanged(SpannableStringBuilder.java:1218)
at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:579)
at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:509)
at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:508)
at android.text.method.NumberKeyListener.onKeyDown(NumberKeyListener.java:121)
at android.widget.TextView.doKeyDown(TextView.java:6284)
at android.widget.TextView.onKeyDown(TextView.java:6074)
at android.view.KeyEvent.dispatch(KeyEvent.java:2676)
at android.view.View.dispatchKeyEvent(View.java:9880)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1667)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1667)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1667)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1667)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1667)
at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1667)
at com.android.internal.policy.DecorView.superDispatchKeyEvent(DecorView.java:403)
at com.android.internal.policy.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1800)
at androidx.core.view.KeyEventDispatcher.activitySuperDispatchKeyEventPre28(KeyEventDispatcher.java:130)
at androidx.core.view.KeyEventDispatcher.dispatchKeyEvent(KeyEventDispatcher.java:87)
at androidx.core.app.ComponentActivity.dispatchKeyEvent(ComponentActivity.java:126)
at androidx.appcompat.app.AppCompatActivity.dispatchKeyEvent(AppCompatActivity.java:535)
at androidx.appcompat.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:59)
at androidx.appcompat.app.AppCompatDelegateImpl$AppCompatWindowCallback.dispatchKeyEvent(AppCompatDelegateImpl.java:2533)
at com.android.internal.policy.DecorView.dispatchKeyEvent(DecorView.java:317)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:4327)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4298)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3849)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3902)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3868)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3995)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3876)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4052)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3849)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3902)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3868)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3876)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3849)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6210)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6184)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6145)
at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:3647)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Upvotes: 1
Views: 834
Answers (3)
Arrowsome
Reputation: 2859
TextWatcher can help you dynamically get value from EditTexts:
- I added an inner class to implement TextWatcher
- Passed an Object from that inner class to
editText.addOnTextChangedListener - I used
afterTextChanged()to get result from both EditText and perform my operation.
public class MainActivity extends AppCompatActivity {
private EditText firstNumEditText, secondNumEditText;
private TextView resultTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
firstNumEditText= findViewById(R.id.firstNumEditText);
firstNumEditText.addTextChangedListener(new MyTextWatcher());
secondNumEditText=(EditText) findViewById(R.id.secondNumEditText);
secondNumEditText.addTextChangedListener(new MyTextWatcher());
resultTextView=(TextView) findViewById(R.id.resultTextView);
...
}
class MyTextWatcher implements TextWatcher {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) { }
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) { }
@Override
public void afterTextChanged(Editable s) {
String second = secondNumEditText.getText().toString().trim();
String first = firstNumEditText.getText().toString().trim();
if (!second.isEmpty() && !first.isEmpty()) {
try {
int firstNumber = Integer.parseInt(first);
int secondNumber = Integer.parseInt(second);
//Do calculation
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
Upvotes: 2
Durga M
Reputation: 544
You can do it by adding addTextChangedListener to the editText.
editText.addTextChangeListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// here you can extract the value from edit text and do the addition
}
@Override
public void afterTextChanged(Editable s) {
}
});
Upvotes: 0
Dinh Lam
Reputation: 765
You could use TextWatcher on your EditText to listen the text change event and perform action like Add or Minus.
Upvotes: 0
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