Android Studio 中 ListView 中的适配器
Adapter in a ListView in Android Studio
我正在尝试通过三个 class 来补充控制自定义 ListView 的代码:AdapterListView
、ItemListView
和 MainActivity
.
到目前为止,代码仅设法通过AdapterListView
输入数据和图像(由代码插入)。在那个 class 中,想知道如何使用应用程序添加或删除项目等其他功能。
下面三个项目classes:
AdapterListView
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
/**
* Created by LuizHMU on 2/7/15.
*/
public class AdapterListView extends BaseAdapter {
private LayoutInflater mInflater;
private ArrayList<ItemListView> itens;
public AdapterListView(Context context, ArrayList<ItemListView> itens) {
//Itens que preencheram o listview
this.itens = itens;
//responsavel por pegar o Layout do item.
mInflater = LayoutInflater.from(context);
}
/**
* Retorna a quantidade de itens
*
* @return
*/
public int getCount() {
return itens.size();
}
/**
* Retorna o item de acordo com a posicao dele na tela.
*
* @param position
* @return
*/
public ItemListView getItem(int position) {
return itens.get(position);
}
/**
* Sem implementação
*
* @param position
* @return
*/
public long getItemId(int position) {
return position;
}
public View getView(int position, View view, ViewGroup parent) {
//Pega o item de acordo com a posção.
ItemListView item = itens.get(position);
//infla o layout para podermos preencher os dados
view = mInflater.inflate(R.layout.item_list, null);
//atravez do layout pego pelo LayoutInflater, pegamos cada id relacionado
//ao item e definimos as informações.
((TextView) view.findViewById(R.id.text)).setText(item.getTexto());
((ImageView) view.findViewById(R.id.imagemview)).setImageResource(item.getIconeRid());
return view;
}
}
ItemListView
/**
* Created by LuizHMU on 2/7/15.
*/
public class ItemListView {
private String texto;
private int iconeRid;
public ItemListView() {
}
public ItemListView(String texto, int iconeRid) {
this.texto = texto;
this.iconeRid = iconeRid;
}
public int getIconeRid() {
return iconeRid;
}
public void setIconeRid(int iconeRid) {
this.iconeRid = iconeRid;
}
public String getTexto() {
return texto;
}
public void setTexto(String texto) {
this.texto = texto;
}
}
MainActivity
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class MainActivity extends Activity implements OnItemClickListener {
private ListView listView;
private AdapterListView adapterListView;
private ArrayList<ItemListView> itens;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//carrega o layout onde contem o ListView
setContentView(R.layout.activity_main);
//Pega a referencia do ListView
listView = (ListView) findViewById(R.id.list);
//Define o Listener quando alguem clicar no item.
listView.setOnItemClickListener(this);
createListView();
}
private void createListView() {
//Criamos nossa lista que preenchera o ListView
itens = new ArrayList<ItemListView>();
ItemListView item1 = new ItemListView("Felpudo", R.drawable.felpudo);
ItemListView item2 = new ItemListView("Felpudão", R.drawable.felpudo1);
ItemListView item3 = new ItemListView("Felpudinho", R.drawable.felpudo2);
itens.add(item1);
itens.add(item2);
itens.add(item3);
//Cria o adapter
adapterListView = new AdapterListView(this, itens);
//Define o Adapter
listView.setAdapter(adapterListView);
//Cor quando a lista é selecionada para ralagem.
listView.setCacheColorHint(Color.TRANSPARENT);
}
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
//Pega o item que foi selecionado.
ItemListView item = adapterListView.getItem(arg2);
//Demostração
Toast.makeText(this, "Você Clicou em: " + item.getTexto(), Toast.LENGTH_LONG).show();
}
}
您可以在 activity 中使用像这样的简单方法:
private void addItemToList(ItemListView item){
if(item != null){
itens.add(item)
}
}
(删除单元格使用 list.remove())
将此添加到您的适配器中:
public void loadNewList(List<ItemListView> list){
if(itens != null){
itens.clear;
}
itens = list;
notifyDataSetChanged();
}
nb :您应该为列表单元格使用 holder 模式 :)
将此添加到您的适配器:
public void addItem(ItemListView item){
items.add(item);
notifyDatasetChanged();
}
public void removeItem(int positionToRemove){
items.remove(positionToRemove);
notifyDatasetChanged();
}
为了进一步解释发生了什么,适配器是控制器,是信息和在视图 (ListView) 中显示信息的方式之间的中间步骤。在这种情况下,信息通过项目列表提供给适配器,因此基本上操作列表并调用 notifyDataSetChanged() 将更改显示给用户的视图。
希望对您有所帮助。
在您的 activity 中,您有 listView
属性。在 onCreate()
方法中,您可以这样做:
listView.setOnItemLongClickListener(new OnItemLongClickListener() {
public boolean onItemLongClick(AdapterView<?> parent, View view,
int position, long id) {
final ItemListView item = (ItemListView) parent.getItemAtPosition(position);
// Do whatever you want here !!
adapterListView.notifyDataSetChanged();
return true;
}
});
我正在尝试通过三个 class 来补充控制自定义 ListView 的代码:AdapterListView
、ItemListView
和 MainActivity
.
到目前为止,代码仅设法通过AdapterListView
输入数据和图像(由代码插入)。在那个 class 中,想知道如何使用应用程序添加或删除项目等其他功能。
下面三个项目classes:
AdapterListView
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
/**
* Created by LuizHMU on 2/7/15.
*/
public class AdapterListView extends BaseAdapter {
private LayoutInflater mInflater;
private ArrayList<ItemListView> itens;
public AdapterListView(Context context, ArrayList<ItemListView> itens) {
//Itens que preencheram o listview
this.itens = itens;
//responsavel por pegar o Layout do item.
mInflater = LayoutInflater.from(context);
}
/**
* Retorna a quantidade de itens
*
* @return
*/
public int getCount() {
return itens.size();
}
/**
* Retorna o item de acordo com a posicao dele na tela.
*
* @param position
* @return
*/
public ItemListView getItem(int position) {
return itens.get(position);
}
/**
* Sem implementação
*
* @param position
* @return
*/
public long getItemId(int position) {
return position;
}
public View getView(int position, View view, ViewGroup parent) {
//Pega o item de acordo com a posção.
ItemListView item = itens.get(position);
//infla o layout para podermos preencher os dados
view = mInflater.inflate(R.layout.item_list, null);
//atravez do layout pego pelo LayoutInflater, pegamos cada id relacionado
//ao item e definimos as informações.
((TextView) view.findViewById(R.id.text)).setText(item.getTexto());
((ImageView) view.findViewById(R.id.imagemview)).setImageResource(item.getIconeRid());
return view;
}
}
ItemListView
/**
* Created by LuizHMU on 2/7/15.
*/
public class ItemListView {
private String texto;
private int iconeRid;
public ItemListView() {
}
public ItemListView(String texto, int iconeRid) {
this.texto = texto;
this.iconeRid = iconeRid;
}
public int getIconeRid() {
return iconeRid;
}
public void setIconeRid(int iconeRid) {
this.iconeRid = iconeRid;
}
public String getTexto() {
return texto;
}
public void setTexto(String texto) {
this.texto = texto;
}
}
MainActivity
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class MainActivity extends Activity implements OnItemClickListener {
private ListView listView;
private AdapterListView adapterListView;
private ArrayList<ItemListView> itens;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//carrega o layout onde contem o ListView
setContentView(R.layout.activity_main);
//Pega a referencia do ListView
listView = (ListView) findViewById(R.id.list);
//Define o Listener quando alguem clicar no item.
listView.setOnItemClickListener(this);
createListView();
}
private void createListView() {
//Criamos nossa lista que preenchera o ListView
itens = new ArrayList<ItemListView>();
ItemListView item1 = new ItemListView("Felpudo", R.drawable.felpudo);
ItemListView item2 = new ItemListView("Felpudão", R.drawable.felpudo1);
ItemListView item3 = new ItemListView("Felpudinho", R.drawable.felpudo2);
itens.add(item1);
itens.add(item2);
itens.add(item3);
//Cria o adapter
adapterListView = new AdapterListView(this, itens);
//Define o Adapter
listView.setAdapter(adapterListView);
//Cor quando a lista é selecionada para ralagem.
listView.setCacheColorHint(Color.TRANSPARENT);
}
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
//Pega o item que foi selecionado.
ItemListView item = adapterListView.getItem(arg2);
//Demostração
Toast.makeText(this, "Você Clicou em: " + item.getTexto(), Toast.LENGTH_LONG).show();
}
}
您可以在 activity 中使用像这样的简单方法:
private void addItemToList(ItemListView item){
if(item != null){
itens.add(item)
}
}
(删除单元格使用 list.remove())
将此添加到您的适配器中:
public void loadNewList(List<ItemListView> list){
if(itens != null){
itens.clear;
}
itens = list;
notifyDataSetChanged();
}
nb :您应该为列表单元格使用 holder 模式 :)
将此添加到您的适配器:
public void addItem(ItemListView item){
items.add(item);
notifyDatasetChanged();
}
public void removeItem(int positionToRemove){
items.remove(positionToRemove);
notifyDatasetChanged();
}
为了进一步解释发生了什么,适配器是控制器,是信息和在视图 (ListView) 中显示信息的方式之间的中间步骤。在这种情况下,信息通过项目列表提供给适配器,因此基本上操作列表并调用 notifyDataSetChanged() 将更改显示给用户的视图。
希望对您有所帮助。
在您的 activity 中,您有 listView
属性。在 onCreate()
方法中,您可以这样做:
listView.setOnItemLongClickListener(new OnItemLongClickListener() {
public boolean onItemLongClick(AdapterView<?> parent, View view,
int position, long id) {
final ItemListView item = (ItemListView) parent.getItemAtPosition(position);
// Do whatever you want here !!
adapterListView.notifyDataSetChanged();
return true;
}
});