在ListView Android Studio中实现收藏夹按钮

Question

我正在 ListView 中实现收藏夹按钮，从过去五天开始尝试。我创建了一个ListView，它获取当前文本视图并将其保存在ArrayList(名称(中，如果数据已经存在，则将其删除，工作正常，但是当我关闭应用程序时，ArrayList变为空，我想将数组列表保存在首选项中。

数组声明：

ArrayList<String> names = new ArrayList<>();

下面是代码

favoritebutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick( View v) {
if (!names.contains(textView_name.getText())){
names.add((String) textView_name.getText());
for (int i=0; i<names.size(); i++) {
System.out.println(names.get(i));
favoritebutton.setBackgroundResource(R.drawable.fav_checked);
}
}
else {
System.out.println(textView_name.getText() + "   is already present in the Array at index " + names.indexOf(textView_name.getText()));
int currentIndex = names.indexOf(textView_name.getText());
names.remove(currentIndex);
for (int i=0; i<names.size(); i++) {
System.out.println(names.get(i));
favoritebutton.setBackgroundResource(R.drawable.star_off);
}
}
}
});

Answer 1

您可以使用SharedPreferences来检索和存储数据，如下所示：

private ArrayList<String> names;
private SharedPreferences sharedPreferences;
sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
String favoriteItems = sharedPreferences.getString("FAVORITE_ITEMS", "");
if(favoriteItems.isEmpty())
names = new ArrayList<>();
else
names = new ArrayList<>(Arrays.asList(favoriteItems.split(","));  //Update like this

favoritebutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick( View v) {
if (!names.contains(textView_name.getText())){
names.add((String) textView_name.getText());
for (int i=0; i<names.size(); i++) {
System.out.println(names.get(i));
favoritebutton.setBackgroundResource(R.drawable.fav_checked);
}
}
else {
System.out.println(textView_name.getText() + "   is already present in the Array at index " + names.indexOf(textView_name.getText()));
int currentIndex = names.indexOf(textView_name.getText());
names.remove(currentIndex);
for (int i=0; i<names.size(); i++) {
System.out.println(names.get(i));
favoritebutton.setBackgroundResource(R.drawable.star_off);
}
}
sharedPreferences.edit().putString("FAVORITE_ITEMS", TextUtils.join(",", names)).apply();
}
});

Answer 2

每次更新后，您必须将该列表保存在首选项中，您可以使用 Gson lib 将数组列表转换为 JsonArray 并将 JsonArray 转换为 Arraylist，这将对您有所帮助......

String str = fetchFromPref();
ArrayList<String> names = covertToArrayListFromJSOnString(str);
favoritebutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick( View v) {
if (!names.contains(textView_name.getText())){
names.add((String) textView_name.getText());
for (int i=0; i<names.size(); i++) {
System.out.println(names.get(i));
favoritebutton.setBackgroundResource(R.drawable.fav_checked);
}
}
else {
System.out.println(textView_name.getText() + "   is already present in the Array at index " + names.indexOf(textView_name.getText()));
int currentIndex = names.indexOf(textView_name.getText());
names.remove(currentIndex);
for (int i=0; i<names.size(); i++) {
System.out.println(names.get(i));
favoritebutton.setBackgroundResource(R.drawable.star_off);
}
}
String str = convertArrayListToJson(names).toString();
saveToPrefrences(str);
}
});