如何删除使用 addTextChangedListener 添加的所有侦听器 [英] How to remove all listeners added with addTextChangedListener

问题描述

我有一个 ListView，其中每一行都有一个 EditText 控件.我想为每一行添加一个 TextChangedListener ；一个包含额外数据，说明 EditText 位于哪一行.问题是当 getView 被调用时，添加了多个 TextWatchers；因为 convertView 已经有一个 TextWatcher(和一个指向不同行的).

I have a ListView where each row has an EditText control. I want to add a TextChangedListener to each row; one that contains extra data which says which row the EditText was in. The problem is that as getView gets called, multiple TextWatchers are added; because the convertView already having a TextWatcher (and one that points to a different row).

MyTextWatcher watcher = new MyTextWatcher(currentQuestion);
EditText text = (EditText)convertView.findViewById(R.id.responseText);
text.addTextChangedListener(watcher);

MyTextWatcher 是我实现 TextWatcher 的类；并处理文本事件.CurrentQuestion 让我知道我正在处理哪一行.当我在框中输入时；TextWatcher 的多个实例被调用.

MyTextWatcher is my class that implements TextWatcher; and handles the text events. CurrentQuestion lets me know which row I'm acting upon. When I type in the box; multiple instances of TextWatcher are called.

在添加新的TextWatchers 之前，有没有办法删除它?我看到了 removeTextChangedListener 方法，但这需要传入一个特定的 TextWatcher，我不知道如何获取指向 TextWatcher 的指针代码>已经存在.

Is there any way to remove the TextWatchers before adding the new one? I see the removeTextChangedListener method, but that requires a specific TextWatcher to be passed in, and I don't know how to get the pointer to the TextWatcher that is already there.

推荐答案

直接使用当前的 EditText 接口无法做到这一点.我看到了两种可能的解决方案:

There is no way to do this using current EditText interface directly. I see two possible solutions:

1. 重新设计您的应用程序，以便您始终知道将什么 TextWatcher 添加到特定的 EditText 实例.
2. 扩展 EditText 并添加清除所有观察者的可能性.

1. Redesign your application so you always know what TextWatcher are added to particular EditText instance.
2. Extend EditText and add possibility to clear all watchers.

这是第二种方法的示例 - ExtendedEditText:

Here is an example of second approach - ExtendedEditText:

public class ExtendedEditText extends EditText
{   
    private ArrayList<TextWatcher> mListeners = null;

    public ExtendedEditText(Context ctx)
    {
        super(ctx);
    }

    public ExtendedEditText(Context ctx, AttributeSet attrs)
    {
        super(ctx, attrs);
    }

    public ExtendedEditText(Context ctx, AttributeSet attrs, int defStyle)
    {       
        super(ctx, attrs, defStyle);
    }

    @Override
    public void addTextChangedListener(TextWatcher watcher)
    {       
        if (mListeners == null) 
        {
            mListeners = new ArrayList<TextWatcher>();
        }
        mListeners.add(watcher);

        super.addTextChangedListener(watcher);
    }

    @Override
    public void removeTextChangedListener(TextWatcher watcher)
    {       
        if (mListeners != null) 
        {
            int i = mListeners.indexOf(watcher);
            if (i >= 0) 
            {
                mListeners.remove(i);
            }
        }

        super.removeTextChangedListener(watcher);
    }

    public void clearTextChangedListeners()
    {
        if(mListeners != null)
        {
            for(TextWatcher watcher : mListeners)
            {
                super.removeTextChangedListener(watcher);
            }

            mListeners.clear();
            mListeners = null;
        }
    }
}

这里是如何在 xml 布局中使用 ExtendedEditText:

And here is how you can use ExtendedEditText in xml layouts:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <ua.inazaruk.HelloWorld.ExtendedEditText 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:text="header"
        android:gravity="center" /> 

</LinearLayout>

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