android - 监听器检查自动完成 TextView 中的第一个字符

Question

我在框架布局中有一个 AutocompleteTextview 和一个删除 Button。我可以输入文本并能够看到我的建议列表和删除按钮以立即清除所有文本。

我想要的: 当我输入第一个字符时，删除按钮应该可见，当我按下删除按钮时，可见性应该消失。我可以控制按钮的可见性，但不确定如何控制检查第一个输入的字符。请帮助我。这就是我的 xml 中的内容:

<FrameLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">

    AutoCompleteTextView
        android:id="@+id/srcsutocomplete"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:maxLines="1"
        android:scrollHorizontally="true"
        android:text="My Location "
        android:dropDownSelector="#a0b4f0">

        <requestFocus />
    </AutoCompleteTextView>

    <Button
      android:id="@+id/clearSourceBtn"      
      android:layout_width="30dp"
      android:layout_height="30dp"
      android:layout_marginRight="10dp"
      android:layout_gravity="right|center_vertical"
      android:background="@drawable/ic_navigation_cancel" />

</FrameLayout>

Answer 1

要在键入字符后立即显示删除按钮:

使用 TextWatcher 及其方法。我假设在您的情况下 onTextChanged 可以解决问题。您可以通过调用 YourView.addTextChangedListener(watch)

添加它

TextWatcher watch = new TextWatcher(){

    public void afterTextChanged(Editable s) {
    /* This method is called to notify you that, 
     somewhere within s, the text has been changed. */
    }

    public void beforeTextChanged(CharSequence s, int count, int start,
      int after) {
    /* This method is called to notify you that, within s, the count 
       characters beginning at start are about to be replaced by new 
       text with length after. */
    }

    public void onTextChanged(CharSequence s, int start, int before, int count) {
    /* This method is called to notify you that, within s, the count characters
       beginning at start have just replaced old text that had length before. */
        if(s.length() > 0) {
            DeleteButton.setVisibility(true);
        }
    }
}};

要使删除按钮在按下时立即不可见:

DeleteButton.setOnClickListener(new View.OnClickListener({
    void onClick (View v) {
        DeleteButton.setVisibility(false);
    }
};