addTextChangedListener(new TextWatcher()
时间: 2023-04-10 12:02:54 浏览: 100
这是一个编程类的问题,可以回答。addTextChangedListener(new TextWatcher())是一个用于监听EditText文本变化的方法,它需要传入一个TextWatcher对象作为参数。TextWatcher是一个接口,它定义了三个方法:beforeTextChanged()、onTextChanged()和afterTextChanged(),分别在文本变化前、变化中和变化后被调用。通过实现TextWatcher接口并重写这三个方法,我们可以在EditText文本变化时执行一些自定义的操作。
相关问题
在Searchbox.addTextChangedListener(new TextWatcher()中的@Override public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) 中,这段代码哪错了Cursor cursor=db2.rawQuery("select*from student_course where scname like '%?%'",new String[]{(String) charSequence});
这段代码的问题在于在 SQL 查询中使用了单引号来括住参数占位符 "?",这会导致参数占位符被视为字符串常量,而不是查询中的参数。因此,应该将单引号从参数占位符中移除,同时在查询参数字符串中包含百分号,如下所示:
```
Cursor cursor = db2.rawQuery("SELECT * FROM student_course WHERE scname LIKE ?", new String[]{"%" + charSequence + "%"});
```
这样,查询参数字符串将被正确地拼接到 SQL 查询中,而不会被视为字符串常量。
addTextChangedListener
The addTextChangedListener method is used to set a listener on an EditText view in Android. This listener is called whenever the user types or deletes text within the EditText view.
Syntax:
```
editText.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
// This method is called before the text is changed
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// This method is called when the text is changed
}
@Override
public void afterTextChanged(Editable s) {
// This method is called after the text is changed
}
});
```
This method takes a TextWatcher object as an argument. The TextWatcher interface has three methods that need to be implemented:
- beforeTextChanged: This method is called before the text is changed.
- onTextChanged: This method is called when the text is changed.
- afterTextChanged: This method is called after the text is changed.
You can use these methods to perform actions based on the user's input, such as validating the input, updating a counter, or enabling/disabling a button.