android 文本更改侦听器

Question

I have a situation, where there are two fields. field1 and field2 . All I want to do is empty field2 when field1 is changed and vice versa. So at the end only one field has content on it.

field1 = (EditText)findViewById(R.id.field1);
field2 = (EditText)findViewById(R.id.field2);

field1.addTextChangedListener(new TextWatcher() {

   public void afterTextChanged(Editable s) {}

   public void beforeTextChanged(CharSequence s, int start,
     int count, int after) {
   }

   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
      field2.setText("");
   }
  });

field2.addTextChangedListener(new TextWatcher() {

   public void afterTextChanged(Editable s) {}

   public void beforeTextChanged(CharSequence s, int start,
     int count, int after) {
   }

   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
     field1.setText("");
   }
  });

It works fine if I attach addTextChangedListener to field1 only, but when I do it for both fields the app crashes. Obviously because they try to change each other indefinitely. Once field1 changes it clears field2 at this moment field2 is changed so it will clear field1 and so on...

Can someone suggest any solution?

Answer 1

You can add a check to only clear when the text in the field is not empty (ie when the length is different than 0).

field1.addTextChangedListener(new TextWatcher() {

   @Override
   public void afterTextChanged(Editable s) {}

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

   @Override    
   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
      if(s.length() != 0)
        field2.setText("");
   }
  });

field2.addTextChangedListener(new TextWatcher() {

   @Override
   public void afterTextChanged(Editable s) {}

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

   @Override
   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
      if(s.length() != 0)
         field1.setText("");
   }
  });

Documentation for TextWatcher here .

Also please respect naming conventions .

Answer 2

I know this is old but someone might come across this again someday.

I had a similar problem where I would call setText on a EditText and onTextChanged would be called when I didn't want it to. My first solution was to write some code after calling setText() to undo the damage done by the listener. But that wasn't very elegant. After doing some research and testing I discovered that using getText().clear() clears the text in much the same way as setText(""), but since it isn't setting the text the listener isn't called, so that solved my problem. I switched all my setText("") calls to getText().clear() and I didn't need the bandages anymore, so maybe that will solve your problem too.

Try this:

Field1 = (EditText)findViewById(R.id.field1);
Field2 = (EditText)findViewById(R.id.field2);

Field1.addTextChangedListener(new TextWatcher() {

   public void afterTextChanged(Editable s) {}

   public void beforeTextChanged(CharSequence s, int start,
     int count, int after) {
   }

   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
      Field2.getText().clear();
   }
  });

Field2.addTextChangedListener(new TextWatcher() {

   public void afterTextChanged(Editable s) {}

   public void beforeTextChanged(CharSequence s, int start,
     int count, int after) {
   }

   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
     Field1.getText().clear();
   }
  });

Answer 3

In Kotlin simply use KTX extension function: (It uses TextWatcher )

yourEditText.doOnTextChanged { text, start, count, after -> 
        // action which will be invoked when the text is changing
    }

import core-KTX :

implementation "androidx.core:core-ktx:1.2.0"

Answer 4

If you are using Kotlin for Android development then you can add TextChangedListener() using this code:

myTextField.addTextChangedListener(object : TextWatcher{
        override fun afterTextChanged(s: Editable?) {}

        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}

        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
    })

Answer 5

I have also faced the same problem and keep on getting stackOverflow exceptions, and I come with the following solution.

edt_amnt_sent.addTextChangedListener(new TextWatcher() {    
    @Override
    public void afterTextChanged(Editable s) {
        if (skipOnChange)
            return;

        skipOnChange = true;
        try {
            //method
        } catch (NumberFormatException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            skipOnChange = false;
        }
    }
});

edt_amnt_receive.addTextChangedListener(new TextWatcher() {

    @Override
    public void afterTextChanged(Editable s) {

        if (skipOnChange)
            return;

        skipOnChange = true;
        try {
            //method
        } catch (NumberFormatException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            skipOnChange = false;
        }
    }
});

declared initially boolean skipOnChange = false;

Answer 6

A bit late of a answer, but here is a reusable solution:

/**
 * An extension of TextWatcher which stops further callbacks being called as 
 * a result of a change happening within the callbacks themselves.
 */
public abstract class EditableTextWatcher implements TextWatcher {

    private boolean editing;

    @Override
    public final void beforeTextChanged(CharSequence s, int start, 
                                                    int count, int after) {
        if (editing)
            return;

        editing = true;
        try {
            beforeTextChange(s, start, count, after);
        } finally {
            editing = false;
        }
    }

    protected abstract void beforeTextChange(CharSequence s, int start, 
                                                     int count, int after);

    @Override
    public final void onTextChanged(CharSequence s, int start, 
                                                int before, int count) {
        if (editing)
            return;

        editing = true;
        try {
            onTextChange(s, start, before, count);
        } finally {
            editing = false;
        }
    }

    protected abstract void onTextChange(CharSequence s, int start, 
                                            int before, int count);

    @Override
    public final void afterTextChanged(Editable s) {
        if (editing)
            return;

        editing = true;
        try {
            afterTextChange(s);
        } finally {
            editing = false;
        }
    }

    public boolean isEditing() {
        return editing;
    }

    protected abstract void afterTextChange(Editable s);
}

So when the above is used, any setText() calls happening within the TextWatcher will not result in the TextWatcher being called again:

/**
 * A setText() call in any of the callbacks below will not result in TextWatcher being 
 * called again.
 */
public class MyTextWatcher extends EditableTextWatcher {

    @Override
    protected void beforeTextChange(CharSequence s, int start, int count, int after) {
    }

    @Override
    protected void onTextChange(CharSequence s, int start, int before, int count) {
    }

    @Override
    protected void afterTextChange(Editable s) {
    }
}

Answer 7

I wrote my own extension for this, very helpful for me. (Kotlin)

You can write only like that :

editText.customAfterTextChanged { editable -> 
    //You have accessed the editable object. 
}

My extension :

fun EditText.customAfterTextChanged(action: (Editable?)-> Unit){
    this.addTextChangedListener(object : TextWatcher {
       override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}
       override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}
       override fun afterTextChanged(editable: Editable?) {
        action(editable)
    }
})}

Answer 8

You can also use the hasFocus() method:

public void onTextChanged(CharSequence s, int start,
     int before, int count) {
     if (Field2.hasfocus()){
         Field1.setText("");
     }
   }

Tested this for a college assignment I was working on to convert temperature scales as the user typed them in. Worked perfectly, and it's way simpler.

Answer 9

var filenameText = findViewById(R.id.filename) as EditText
filenameText.addTextChangedListener(object : TextWatcher {
    override fun afterTextChanged(s: Editable?) {
        filename = filenameText.text.toString()
        Log.i("FileName: ", filename)
    }
    
    override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}
    override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
})

Answer 10

check String before set another EditText to empty. if Field1 is empty then why need to change again to ( "" )? so you can check the size of Your String with s.lenght() or any other solution

another way that you can check lenght of String is:

String sUsername = Field1.getText().toString();
if (!sUsername.matches(""))
{
// do your job
}

Answer 11

editText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }
            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                if (noteid != -1) {
                    MainActivity.notes.set(noteid, String.valueOf(charSequence));
                    MainActivity.arrayAdapter.notifyDataSetChanged();
                }
            }
            @Override
            public void afterTextChanged(Editable editable) {

            }
        });

in this code noteid is basically arguments taken back which is being putted into the indent or passed through the indent.

  Intent intent = getIntent();
         noteid = intent.getIntExtra("noteid", -1);

the code on the downside is basically the extra code ,if you want to understand more clearly.

how to make the menu or insert the menu in our code , 
    create the  menu folder this the folder created by going into the raw
    ->rightclick->
    directory->name the folder as you wish->
    then click on the directory formed->
    then click on new file and then name for file as you wish ie the folder name file
    and now type the 2 lines code in it and see the magic.

new activity code named as NoteEditor.java for editing purpose,my app is basicley the note app.

package com.example.elavi.notes;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.Toast;

import static android.media.CamcorderProfile.get;
public class NoteEditorActivity extends AppCompatActivity {
    EditText editText;
    int noteid;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_note_editor);
        editText = findViewById(R.id.editText);
        Intent intent = getIntent();
         noteid = intent.getIntExtra("noteid", -1);
        if (noteid != -1) {
            String text = MainActivity.notes.get(noteid);
            editText.setText(text);

           Toast.makeText(getApplicationContext(),"The arraylist content is"+MainActivity.notes.get(noteid),Toast.LENGTH_SHORT).show();
        }
        else
        {
            Toast.makeText(getApplicationContext(),"Here we go",Toast.LENGTH_SHORT).show();
            MainActivity.notes.add("");
            noteid=MainActivity.notes.size()-1;
        }
        editText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }
            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                if (noteid != -1) {
                    MainActivity.notes.set(noteid, String.valueOf(charSequence));
                    MainActivity.arrayAdapter.notifyDataSetChanged();
                }
            }
            @Override
            public void afterTextChanged(Editable editable) {

            }
        });
    }
}

Answer 12

We can remove the TextWatcher for a field just before editing its text then add it back after editing the text.

Declare Text Watchers for both field1 and field2 as separate variables to give them a name: eg for field1

private TextWatcher Field_1_Watcher = new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

    @Override
    public void afterTextChanged(Editable s) {
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {

    }

};

then add the watcher using its name: field1.addTextChangedListener(Field_1_Watcher) for field1 , and field2.addTextChangedListener(Field_2_Watcher) for field2

Before changing the field2 text remove the TextWatcher: field2.removeTextChangedListener(Field_2_Watcher) change the text: field2.setText("")

then add the TextWatcher back: field2.addTextChangedListener(Field_2_Watcher)

Do the same for the other field

Answer 13

Another solution that may help someone. There are 2 EditText which change instead of each other after editing. By default, it led to cyclicity.

use variable:

Boolean uahEdited = false;
Boolean usdEdited = false;

add TextWatcher

uahEdit = findViewById(R.id.uahEdit);
usdEdit = findViewById(R.id.usdEdit);

uahEdit.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            if (!usdEdited) {
                uahEdited = true;
            }
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            String tmp = uahEdit.getText().toString();

            if(!tmp.isEmpty() && uahEdited) {
                uah = Double.valueOf(tmp);
                usd = uah / 27;
                usdEdit.setText(String.valueOf(usd));
            } else if (tmp.isEmpty()) {
                usdEdit.getText().clear();
            }
        }

        @Override
        public void afterTextChanged(Editable s) {
            uahEdited = false;
        }
    });

usdEdit.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            if (!uahEdited) {
                usdEdited = true;
            }
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            String tmp = usdEdit.getText().toString();

            if (!tmp.isEmpty() && usdEdited) {
                usd = Double.valueOf(tmp);
                uah = usd * 27;
                uahEdit.setText(String.valueOf(uah));
            } else if (tmp.isEmpty()) {
                uahEdit.getText().clear();
            }
        }

        @Override
        public void afterTextChanged(Editable s) {
            usdEdited = false;
        }
    });

Don't criticize too much. I am a novice developer

Answer 14

etSearch.addTextChangedListener(object : TextWatcher {
     override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
          TODO("Not yet implemented")
     }

     override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
          TODO("Not yet implemented")
     }

     override fun afterTextChanged(p0: Editable?) {
          TODO("Not yet implemented")
     }
})

Answer 15

you use this
I have provided latest method for textchangelistner

edMsg.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                
            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                
                if (i2 == 0){
                    ////Edit text blanked
                } 
                
                String msg = charSequence.toString();/// your text on changed in edit text
                
            }

            @Override
            public void afterTextChanged(Editable editable) {

            }
        });

Answer 16

editText.addTextChangedListener(new TextWatcher() 
{
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) 
            {
            }

            @Override
            public void onTextChanged(CharSequence chr, int i, int i1, int i2) 
            {
                //Check char sequence is empty or not
                if (chr.length() > 0)
                {
                    //Your Code Here
                }
            }

            @Override
            public void afterTextChanged(Editable editable) 
            {
            }
 });

Answer 17

Add background dynamically in onCreate method:

getWindow().setBackgroundDrawableResource(R.drawable.background);

also remove background from XML.