有人能解释或建议一个教程,动态创建一个ListView在android?
以下是我的要求:
我应该能够通过按下按钮动态添加新元素。 应该足够简单易懂(例如,可能没有任何性能改进或convertView)
我知道关于这个话题有很多问题,但我找不到任何一个能回答我的问题。
有人能解释或建议一个教程,动态创建一个ListView在android?
以下是我的要求:
我应该能够通过按下按钮动态添加新元素。 应该足够简单易懂(例如,可能没有任何性能改进或convertView)
我知道关于这个话题有很多问题,但我找不到任何一个能回答我的问题。
当前回答
首先,您必须在activity_main.xml中添加一个ListView、一个EditText和一个按钮。
现在,在ActivityMain中:
private EditText editTxt;
private Button btn;
private ListView list;
private ArrayAdapter<String> adapter;
private ArrayList<String> arrayList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editTxt = (EditText) findViewById(R.id.editText);
btn = (Button) findViewById(R.id.button);
list = (ListView) findViewById(R.id.listView);
arrayList = new ArrayList<String>();
// Adapter: You need three parameters 'the context, id of the layout (it will be where the data is shown),
// and the array that contains the data
adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item, arrayList);
// Here, you set the data in your ListView
list.setAdapter(adapter);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// this line adds the data of your EditText and puts in your array
arrayList.add(editTxt.getText().toString());
// next thing you have to do is check if your adapter has changed
adapter.notifyDataSetChanged();
}
});
}
这对我有用,希望我帮到你了
其他回答
简单的回答是:当你创建一个ListView时,你传递给它一个数据引用。 现在,无论何时该数据将被更改,它都会影响列表视图,因此在调用adapter.notifyDataSetChanged();之后,它将向列表视图中添加该项。
如果你正在使用RecyclerView,只更新最后一个元素(如果你已经在objs列表的末尾添加了它)来节省内存:
首先在项目的res/layout/main.xml文件夹中创建一个XML布局:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<Button
android:id="@+id/addBtn"
android:text="Add New Item"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="addItems"/>
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:drawSelectorOnTop="false"
/>
</LinearLayout>
这是一个简单的布局,顶部有一个按钮,底部有一个列表视图。注意,ListView有id @android:id/list,它定义了ListActivity可以使用的默认ListView。
public class ListViewDemo extends ListActivity {
//LIST OF ARRAY STRINGS WHICH WILL SERVE AS LIST ITEMS
ArrayList<String> listItems=new ArrayList<String>();
//DEFINING A STRING ADAPTER WHICH WILL HANDLE THE DATA OF THE LISTVIEW
ArrayAdapter<String> adapter;
//RECORDING HOW MANY TIMES THE BUTTON HAS BEEN CLICKED
int clickCounter=0;
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
adapter=new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1,
listItems);
setListAdapter(adapter);
}
//METHOD WHICH WILL HANDLE DYNAMIC INSERTION
public void addItems(View v) {
listItems.add("Clicked : "+clickCounter++);
adapter.notifyDataSetChanged();
}
}
android.R.layout。simple_list_item_1是Android提供的默认列表项布局,你可以使用这个库存布局来处理不复杂的事情。
listItems是一个列表,它包含ListView中显示的数据。所有的插入和删除都应该在listItems上完成;listItems中的变化应该反映在视图中。这是由ArrayAdapter<String>适配器处理的,它应该被通知使用:
adapter.notifyDataSetChanged ();
一个Adapter是用3个参数实例化的:context,它可以是activity/listactivity;个人列表项的布局;最后是列表,它是列表中显示的实际数据。
而不是
listItems.add("New Item");
adapter.notifyDataSetChanged();
您可以直接拨打
adapter.add("New Item");
This is the simple answer how to add datas dynamically in listview android kotlin
class MainActivity : AppCompatActivity(){
var listItems = arrayListOf<String>()
val array = arrayOf("a","b","c","d","e")
var listView: ListView? = null
private lateinit var adapter: listViewAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.scrollview_layout)
listItems.add("a")
listItems.add("b")
listItems.add("c")
listItems.add("d")
listItems.add("e")
//if you want to add array items to a list you can try this for each loop
for(items in array)
listItems.add(items)
//check the result in console
Log.e("TAG","listItems array: $listItems")
adapter = ListViewAdapter()
adapter.updateList(listItems)
adapter.notifyDataSetChanged()
}
}
//Here is the adapter class
class ListviewAdapter : BaseAdapter(){
private var itemsList = arrayListOf<String>()
override fun getView(position: Int, container: View?, parent: ViewGroup?): View {
var view = container
val inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
if (view == null)
view = inflater.inflate(R.layout.list_pc_summary, parent, false)
return view
}
override fun getItem(position: Int): Any = itemsList[position]
override fun getItemId(position: Int): Long = position.toLong()
override fun getCount(): Int = itemsList.size
fun updateList(listItems: ArrayList<String>()){
this.itemsList = listItems
notifyDatSetChanged
}
}
//Here I just explained two ways, we can do this many ways.
首先,您必须在activity_main.xml中添加一个ListView、一个EditText和一个按钮。
现在,在ActivityMain中:
private EditText editTxt;
private Button btn;
private ListView list;
private ArrayAdapter<String> adapter;
private ArrayList<String> arrayList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editTxt = (EditText) findViewById(R.id.editText);
btn = (Button) findViewById(R.id.button);
list = (ListView) findViewById(R.id.listView);
arrayList = new ArrayList<String>();
// Adapter: You need three parameters 'the context, id of the layout (it will be where the data is shown),
// and the array that contains the data
adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item, arrayList);
// Here, you set the data in your ListView
list.setAdapter(adapter);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// this line adds the data of your EditText and puts in your array
arrayList.add(editTxt.getText().toString());
// next thing you have to do is check if your adapter has changed
adapter.notifyDataSetChanged();
}
});
}
这对我有用,希望我帮到你了