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[英]How do I remove a single item from an Arraylist with a button (a tag) in Java
[英]How Do I Remove Selected Item From ArrayList and ArrayAdapter On Button Click?
我有一個帶有自定義列表布局的ListView。 我為此使用ArrayList和ArrayAdapter。 我很難從arraylist中刪除選定的項目。 我不確定要我做錯了。 這是我擁有的一個數組列表的示例:
項目A
項目B
項目C
項目D
假設我選擇了按鈕C,然后單擊標簽為“刪除”的項目C,然后從列表中刪除了項目C。 我該如何完成? 目前,我的代碼僅刪除索引0上的項目。我希望刪除選定的項目索引。
這是我的密碼...
Java類:
public class MainActivity extends AppCompatActivity {
ListView lstVw;
Button addBtn, removeBtn, clearListBtn;
ArrayList<String> arrayList;
ArrayAdapter<String> adapter;
int getPosition = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lstVw = findViewById(R.id.lstView);
addBtn = findViewById(R.id.add_item_btn);
removeBtn = findViewById(R.id.remove_item_btn);
clearListBtn = findViewById(R.id.clear_list_btn);
arrayList = new ArrayList<>();
adapter = new ArrayAdapter<>(getApplicationContext(), R.layout.item_list, R.id.item_tv, arrayList);
lstVw.setAdapter(adapter);
lstVw.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String getItem = adapter.getItem(position);
getPosition = Integer.parseInt(getItem);
}
});
addBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final AlertDialog.Builder adb = new AlertDialog.Builder(MainActivity.this);
adb.setTitle("Enter Item Name");
final EditText itemTxt = new EditText(MainActivity.this);
itemTxt.setText(getString(R.string.default_item_name_value));
itemTxt.setInputType(InputType.TYPE_CLASS_TEXT);
adb.setView(itemTxt);
adb.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String getItem = itemTxt.getText().toString();
Set<String> s = new LinkedHashSet<>(arrayList);
if (s.contains(getItem)) {
arrayList.clear();
arrayList.addAll(s);
Toast.makeText(getApplicationContext(), getItem + " already exists in the list!", Toast.LENGTH_LONG).show();
} else {
arrayList.add(getItem);
adapter.notifyDataSetChanged();
}
}
});
adb.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
adb.create();
adb.show();
}
});
clearListBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!arrayList.isEmpty()) {
arrayList.clear();
adapter.notifyDataSetChanged();
}
}
});
removeBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String getItem = arrayList.get(getPosition);
arrayList.remove(getItem);
adapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), getItem + " is removed!", Toast.LENGTH_LONG).show();
}
});
}
}
主要XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/rl"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center">
<ScrollView
android:layout_width="match_parent"
android:layout_height="650dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="650dp">
<ListView
android:id="@+id/lstView"
android:layout_width="match_parent"
android:layout_height="650dp"
tools:ignore="NestedScrolling" />
</RelativeLayout>
</ScrollView>
<include layout="@layout/action_buttons"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"/>
動作按鈕XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="50dp"
android:layout_gravity="center|top">
<Button
android:id="@+id/add_item_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:textAllCaps="false"
android:text="@string/add_item_text"
android:textSize="14sp"
android:textStyle="bold"
android:textColor="@android:color/black"/>
<Button
android:id="@+id/remove_item_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toEndOf="@id/add_item_btn"
android:textAllCaps="false"
android:text="Remove Item"
android:textColor="@android:color/black"
android:textSize="14sp"
android:textStyle="bold"/>
<Button
android:id="@+id/clear_list_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_toEndOf="@id/remove_item_btn"
android:textAllCaps="false"
android:text="@string/clear_list_text"
android:textSize="14sp"
android:textStyle="bold"
android:textColor="@android:color/black"/>
我的自定義列表布局XML:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/item_tv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textStyle="bold"
android:textSize="20sp"
android:textColor="@android:color/black"/>
</ScrollView>
感謝您的幫助! 謝謝!
在我看來,您的int getPosition = 0;
變量沒有更新為您的新職位。 在您的點擊監聽器上,您正在嘗試將所選項目的值解析為Integer,也許您可以嘗試僅使用當前位置進行更新?
lstVw.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
getPosition = position;
}
});
編輯:
你可以這樣:
創建一個接口,您的活動將實現該接口,適配器將使用該接口來通知職位變更:
public interface PositionChangeListener {
void onPositionChanged(int newPosition);
}
創建一個自定義適配器:
public class CustomAdapterView extends BaseAdapter {
private Context context;
private PositionChangeListener listener;
private ArrayList<String> items;
public CustomAdapterView(Context context, ArrayList<String> items, PositionChangeListener listener) {
this.context = context;
this.items = items;
this.listener = listener;
}
@Override
public int getCount() {
return items.size();
}
@Override
public Object getItem(int position) {
return items.get(position);
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder = null;
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate( R.layout.item_list, null);
viewHolder = new ViewHolder();
viewHolder.txt = convertView.findViewById(R.id.item_tv);
viewHolder.txt.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
listener.onPositionChanged(position);
}
});
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
viewHolder.txt.setText(items.get(position));
return convertView;
}
private class ViewHolder {
TextView txt;
}
}
現在在您的活動中:
public class MainActivity extends AppCompatActivity implements PositionChangeListener{
ListView lstVw;
Button addBtn, removeBtn, clearListBtn;
ArrayList<String> arrayList;
BaseAdapter adapter;
int getPosition = 0;
@Override
public void onPositionChanged(int newPosition) {
getPosition = newPosition;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lstVw = findViewById(R.id.lstView);
addBtn = findViewById(R.id.add_item_btn);
removeBtn = findViewById(R.id.remove_item_btn);
clearListBtn = findViewById(R.id.clear_list_btn);
arrayList = new ArrayList<>();
adapter = new CustomAdapterView(this, arrayList, this);
lstVw.setAdapter(adapter);
addBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
final AlertDialog.Builder adb = new AlertDialog.Builder(MainActivity.this);
adb.setTitle("Enter Item Name");
final EditText itemTxt = new EditText(MainActivity.this);
itemTxt.setText("default item name");
itemTxt.setInputType(InputType.TYPE_CLASS_TEXT);
adb.setView(itemTxt);
adb.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String getItem = itemTxt.getText().toString();
Set<String> s = new LinkedHashSet<>(arrayList);
if (s.contains(getItem)) {
arrayList.clear();
arrayList.addAll(s);
Toast.makeText(getApplicationContext(), getItem + " already exists in the list!", Toast.LENGTH_LONG).show();
} else {
arrayList.add(getItem);
adapter.notifyDataSetChanged();
}
}
});
adb.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
});
adb.create();
adb.show();
}
});
clearListBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!arrayList.isEmpty()) {
arrayList.clear();
adapter.notifyDataSetChanged();
}
}
});
removeBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String getItem = arrayList.get(getPosition);
arrayList.remove(getItem);
adapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), getItem + " is removed!", Toast.LENGTH_LONG).show();
}
});
}
}
removeBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String getItem = arrayList.get(getPosition);
arrayList.remove(getItem);
adapter.notifyDataSetChanged();
Toast.makeText(getApplicationContext(), getItem + " is removed!", Toast.LENGTH_LONG).show();
}
});
您從哪里獲得此getPosition?
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