我试图了解listview如何为我正在创建的应用程序工作，我已经让应用程序显示列表视图中的项目，图像和复选框。
我想要实现的是：当他们点击复选框时，该状态会在下次打开应用时保存。我认为我的代码是正确的，但不确定我做错了什么，因为当我重新打开应用程序时，所有复选框都被检回错误。
任何帮助将不胜感激：）
我的代码：适配器：
public class ListAdapter extends BaseAdapter {
Context ctx;
LayoutInflater lInflater;
ArrayList<Product> objects;
ListAdapter(Context context, ArrayList<Product> products) {
ctx = context;
objects = products;
lInflater = (LayoutInflater) ctx
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return objects.size();
}
@Override
public Object getItem(int position) {
return objects.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
View view = convertView;
if (view == null) {
view = lInflater.inflate(R.layout.item, parent, false);
}
final Product p = getProduct(position);
((TextView) view.findViewById(R.id.tvDescr)).setText(p.name);
((TextView) view.findViewById(R.id.tvPrice)).setText(p.price + "");
((ImageView) view.findViewById(R.id.ivImage)).setImageResource(p.image);
final CheckBox cbBuy = (CheckBox) view.findViewById(R.id.cbBox);
SharedPreferences settings = ctx.getSharedPreferences("data",ctx.MODE_PRIVATE);
boolean Checked = settings.getBoolean(p.name, false);
cbBuy.setChecked(Checked);
cbBuy.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if(cbBuy.isChecked()==true){
SharedPreferences settings = ctx.getSharedPreferences("data",Context.MODE_PRIVATE);
settings.edit().putBoolean(p.name, true).commit();
Toast.makeText(ctx, "You Selected" + p.name, Toast.LENGTH_SHORT).show();
}else{
SharedPreferences settings = ctx.getSharedPreferences("data", Context.MODE_PRIVATE);
settings.edit().putBoolean(p.name, false).commit();
Toast.makeText(ctx, "You Deselected" +p.name, Toast.LENGTH_SHORT).show();
}
}
});{
return view;
}
}
Product getProduct(int position) {
return ((Product) getItem(position));
}
ArrayList<Product> getBox() {
ArrayList<Product> box = new ArrayList<Product>();
for (Product p : objects) {
if (p.box)
box.add(p);
}
return box;
}
OnCheckedChangeListener myCheckChangList = new OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView,
boolean isChecked) {
getProduct((Integer) buttonView.getTag()).box = isChecked;
}
};
}
产品类别：
public class Product {
String name;
String price;
int image;
boolean isSelected = false;
public boolean isSelected() {
return isSelected;
}
public void setSelected(boolean selected)
{
isSelected = selected;
}
Product(String _describe, String _price, int _image, boolean _box) {
name = _describe;
price = _price;
image = _image;
isSelected = _box;
}
}
主要活动
public class MainActivity extends AppCompatActivity {
ArrayList<Product> products = new ArrayList<Product>();
ListAdapter boxAdapter;
private SharedPreferences mPrefs;
private String mData;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
fillData();
boxAdapter = new ListAdapter(this, products);
ListView lvMain = (ListView) findViewById(R.id.lvMain);
lvMain.setAdapter(boxAdapter);
}
void fillData() {
products.add(new Product("Al", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Al", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Alf", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Alfa", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Alfae", "5120%", R.drawable.ic_launcher, false));
products.add(new Product("Alfsdfsdfakher", "50435%", R.drawable.ic_launcher, false));
products.add(new Product("Alfasdfsdfkher", "5123120%", R.drawable.ic_launcher, false));
products.add(new Product("Alfasdfsdfkher", "501231%", R.drawable.ic_launcher, false));
products.add(new Product("Alfaksdfsdfher", "11250%", R.drawable.ic_launcher, false));
/*for (int i = 1; i <= 20; i++) {
products.add(new Product("Product " + i, i * 100,
R.drawable.ic_launcher, false));
}*/
}
/*public void showResult(View v) {
String result = "Selected Product are :";
int totalAmount=0;
for (Product p : boxAdapter.getBox()) {
if (p.box){
result += "\n" + p.name;
totalAmount+=p.price;
}
}
Toast.makeText(this, result+"\n"+"Total Amount:="+totalAmount, Toast.LENGTH_LONG).show();
}*/
}
答案 0 :(得分：1)
如果你想使用SharedPreference管理你的产品，你可以像这样做
MainActivity.java
public class MainActivity extends AppCompatActivity {
ArrayList<Product> products = new ArrayList<Product>();
ListAdapter boxAdapter;
private SharedPreferences mPrefs;
private String mData;
public static final String PREFS_NAME = "Product_Prefrence";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
products=getProductArray(this,"Products");
if(products==null)
{
fillData();
}
boxAdapter = new ListAdapter(this, products);
ListView lvMain = (ListView) findViewById(R.id.lvMain);
lvMain.setAdapter(boxAdapter);
}
void fillData() {
products.add(new Product("Al", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Al", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Alf", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Alfa", "5230%", R.drawable.ic_launcher, false));
products.add(new Product("Alfae", "5120%", R.drawable.ic_launcher, false));
products.add(new Product("Alfsdfsdfakher", "50435%", R.drawable.ic_launcher, false));
products.add(new Product("Alfasdfsdfkher", "5123120%", R.drawable.ic_launcher, false));
products.add(new Product("Alfasdfsdfkher", "501231%", R.drawable.ic_launcher, false));
products.add(new Product("Alfaksdfsdfher", "11250%", R.drawable.ic_launcher, false));
}
@Override
public void onBackPressed() {
saveProductArray(MainActivity.this,products,"Products");
finish();
}
public void saveProductArray(Context c, List<Product> arrayList, String key) {
SharedPreferences settings = c.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = settings.edit();
Gson gson = new Gson();
String json = gson.toJson(arrayList);
editor.putString(key, json).apply();
}
@NonNull
public ArrayList<Product> getProductArray(Context c, String key) {
Gson gson = new Gson();
SharedPreferences settings = c.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
String json = settings.getString(key, "");
Type type = new TypeToken<ArrayList<Product>>() {
}.getType();
ArrayList<Product> arrayList = gson.fromJson(json, type);
return arrayList;
}
}
适配器getView（）方法：
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
View view = convertView;
if (view == null) {
view = lInflater.inflate(R.layout.item, parent, false);
}
final Product p = getProduct(position);
((TextView) view.findViewById(R.id.tvDescr)).setText(p.name);
((TextView) view.findViewById(R.id.tvPrice)).setText(p.price + "");
((ImageView) view.findViewById(R.id.ivImage)).setImageResource(p.image);
final CheckBox cbBuy = (CheckBox) view.findViewById(R.id.cbBox);
//use click listener instead of checked change
cbBuy.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
if(objects.get(position).isSelected)
{
cbBuy.setChecked(false);
objects.get(position).setSelected(false);
}
else
{
cbBuy.setChecked(true);
objects.get(position).setSelected(true);
}
}
});
//For scrolling issue use this
if(objects.get(position).isSelected)
{
cbBuy.setChecked(true);
}
else
{
cbBuy.setChecked(false);
}
return view;
}
}
无需保持单一产品价值的共享偏好。
希望这会对你有所帮助。如果你仍然遇到问题，我们会找到其他方式