我有一个情况，有两个领域。Field1和field2。我想要的
当field1被改变时，要做的是空field2，反之亦然。所以只有在最后
一个字段上有内容。
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("");
}
});
它工作得很好，如果我附加addTextChangedListener到field1，但当
我对两个字段都这么做，应用程序崩溃了。显然是因为他们想要改变
无限地相互联系。一旦field1改变，此时它就会清除field2
Field2被更改，因此它将清除field1，以此类推……
谁能给点建议吗?
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) {
}
});
在这段代码中，noteid基本上是被收回的参数，它被放入缩进中或通过缩进传递。
Intent intent = getIntent();
noteid = intent.getIntExtra("noteid", -1);
下面的代码基本上是额外的代码，如果你想更清楚地理解的话。
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.
新的活动代码命名为NoteEditor.java用于编辑目的，我的应用程序基本上是笔记应用程序。
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) {
}
});
}
}
如果你正在使用Kotlin进行Android开发，那么你可以使用以下代码添加TextChangedListener():
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) {}
})
这个回答有点晚了，但这里有一个可重复使用的解决方案:
/**
* 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);
}
因此，当使用上述方法时，在TextWatcher中发生的任何setText()调用都不会导致TextWatcher再次被调用:
/**
* 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) {
}
}
