Android ListView：getTag() 返回 null
大家好，
我有一个 ListView，其中每行都包含一个 Button。以下代码是
public View getView(final int position, View convertView, ViewGroup parent) {
View row = convertView;
TextView tv;
Button saveA_button;
EditText edittext;
FITB_ViewWrapper wrapper;
if (row == null) {
LayoutInflater li = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (ChooseMode_Act.modeInfo.equalsIgnoreCase("Training")) {
row = li.inflate(R.layout.exercise_for_training_fitb,parent, false);
}else {
row = li.inflate(R.layout.exercise_for_exam_fitb,parent, false);
}
wrapper=new FITB_ViewWrapper(row);
row.setTag(wrapper);
if (ChooseMode_Act.modeInfo.equalsIgnoreCase("Exam")) {
saveA_button=wrapper.getSaveAnswer_Button();
OnClickListener l=new OnClickListener() {
@Override
public void onClick(View v) {
Integer mp=(Integer)v.getTag();
Log.i("mp","my Position is: "+mp);
}
};
saveA_button.setOnClickListener(l);
}
}else {
wrapper=(FITB_ViewWrapper) row.getTag();
}
我的应用程序的 getView() 方法的一部分，我需要知道按钮属于哪个项目，所以我尝试检测它。代码
Log.i("mp","my Position is: "+mp);
输出一条消息： mp myPosition is: null
我不明白，为什么我得到一个“null”而不是一个 Integer？如何找出 ListView 中项目的位置？
多谢。
Hallo all,
I have a ListView which contains a Button in each line. The following code is part of the getView() Method
public View getView(final int position, View convertView, ViewGroup parent) {
View row = convertView;
TextView tv;
Button saveA_button;
EditText edittext;
FITB_ViewWrapper wrapper;
if (row == null) {
LayoutInflater li = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (ChooseMode_Act.modeInfo.equalsIgnoreCase("Training")) {
row = li.inflate(R.layout.exercise_for_training_fitb,parent, false);
}else {
row = li.inflate(R.layout.exercise_for_exam_fitb,parent, false);
}
wrapper=new FITB_ViewWrapper(row);
row.setTag(wrapper);
if (ChooseMode_Act.modeInfo.equalsIgnoreCase("Exam")) {
saveA_button=wrapper.getSaveAnswer_Button();
OnClickListener l=new OnClickListener() {
@Override
public void onClick(View v) {
Integer mp=(Integer)v.getTag();
Log.i("mp","my Position is: "+mp);
}
};
saveA_button.setOnClickListener(l);
}
}else {
wrapper=(FITB_ViewWrapper) row.getTag();
}
For my App i need to known to which item the Button belongs to, so i try to detect it. The code
Log.i("mp","my Position is: "+mp);
puts out a message: mp myPosition is: null
I can't understand, why do i get a "null" but not an Integer? How can i find out the Position of an Item in a ListView?
Thanks a lot.
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Log.i("mp","我的位置是："+position);
你已经有这个位置了！
Log.i("mp","my Position is: "+position);
you have the position already !
当您上下滚动时，ListView 中的视图会被重用。因此，在 getView 中设置值通常会产生意想不到的后果，例如您打算为项目编号 5 设置的图像也出现在项目编号 10、15 和 20 中。
为了避免这种情况，如果您想在 getView 中设置属性，您需要确保为每个视图设置或取消设置它们。
我不确定您到底想用代码完成什么，但将 setTag 移到 if 语句之外可能会有所帮助，以确保每次使用视图时都对其进行设置。
The Views in a ListView are reused as you scroll up and down. Thus, setting values in getView often has unintented consequences, like the image that you meant to set for item number 5 appearing in item number 10, 15 and 20 also.
To avoid this, if you want to set properties in getView you need to make sure you set or unset them for each view.
I'm not sure what exactly you are trying to accomplish with your code, but it might help to move the setTag outside of the if statement, to make sure you are setting it each time that a view is used.