android - 更新填充 ListView 的数组列表

Question

我有一个列表 Activity ，其 ListView 由不同的 Activity 填充。

第一个 Activity :

Intent view_order_intent = new Intent(this, thirdpage.class);
view_order_intent.putStringArrayListExtra("selectedData", (ArrayList<String>)selectedData);  

列表 Activity :

Intent intent = getIntent();
Bundle bundle = intent.getExtras
selectedData = (ArrayList<String>) bundle.get("selectedData");  

其他三个 Activity 也是如此。
当前输出:我在每个 Activity 中设置一个 int 并通过 Intent 传递它，它发现 Activity 名称，然后相应地填充相应的数组列表该 Activity 的 ListView 。这对所有四个 Activity 都是一样的。这样我就可以根据单个数组列表的内容生成一个 ListView 。每次加载不同的 Activity 时，arraylist 都会再次加载，因此 ListView 会加载所有新内容。

期望的输出:我想要的是从单个数组列表填充 ListView ，我可以通过组合四个 Activity 的所有数组列表来获得它。此外， ListView 不应包含所有新内容，而应只更新内容(应添加新的数组元素)。为此，我认为我需要保留数组列表，但我不知道如何保留。
有人可以帮我吗？如果有人需要，我会发布代码。

更新:

desserts.java(四个 Activity 之一)

    package a.b.layout;

    import java.util.ArrayList;
    import java.util.List;
    import android.app.ListActivity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.util.SparseBooleanArray;
    import android.view.View;

import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

public class desserts  extends ListActivity  implements  android.view.View.OnClickListener  {

    private List<Item> data;
    private List<String> selectedData;
    private ItemListAdapter adapter;
    ListView lv; 
    int iClass = 1;
    Button view_order,place_order,starters,mains,desserts,drinks;

    @Override
    public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.menuslayout);
    data = new ArrayList<Item>(10);
    selectedData = new ArrayList<String>();

    data.add(new Item(10, "dessert1"));
    data.add(new Item(11, "dessert2"));
    data.add(new Item(12, "dessert3"));
    data.add(new Item(13, "dessert4"));
    data.add(new Item(14, "dessert5"));
    data.add(new Item(15, "dessert6"));
    data.add(new Item(16, "dessert7"));
    data.add(new Item(17, "dessert8"));
    data.add(new Item(18, "dessert9"));
    data.add(new Item(19, "dessert10"));
    data.add(new Item(20, "dessert11"));

    adapter = new ItemListAdapter(this, data);
    setListAdapter(adapter);
    lv = getListView();
    lv.setItemsCanFocus(false);
    lv.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
    view_order=(Button)findViewById(R.id.vieworder);
    view_order.setOnClickListener(this) ;
    starters=(Button)findViewById(R.id.starters);
    starters.setOnClickListener(this) ;
    mains=(Button)findViewById(R.id.mains);
    mains.setOnClickListener(this) ;
    drinks=(Button)findViewById(R.id.drinks);
    drinks.setOnClickListener(this) ;
    }
     //@Override
    public void onBackPressed() {
        Intent i=new Intent(this , layoutact.class);
        startActivity(i); 
        return;
    }

    @Override
    public void onClick(View v) {
        switch(v.getId())
    {
        case R.id.vieworder:
               showSelectedItems();
               Intent view_order_intent = new Intent(this, thirdpage.class);
               view_order_intent.putStringArrayListExtra("selectedData", (ArrayList<String>)selectedData);
               view_order_intent.putExtra("iClass", iClass);
               startActivity(view_order_intent);
               break;

        case R.id.starters:
            Intent starters_intent = new Intent(this, starters.class);
            startActivity(starters_intent);
            break;

        case R.id.mains:
            Intent mains_intent = new Intent(this, mains.class);
            startActivity(mains_intent);
            break;
        case R.id.drinks:
            Intent drinks_intent = new Intent(this, drinks.class);
            startActivity(drinks_intent);
            break;
      }
    }


    private void showSelectedItems() {
        final StringBuffer sb = new StringBuffer("Selection: ");

        // Get an array that tells us for each position whether the item is
        // checked or not
        // --
        final SparseBooleanArray checkedItems = lv
                .getCheckedItemPositions();
        if (checkedItems == null) {
            Toast.makeText(this, "No selection info available",
                    Toast.LENGTH_LONG).show();
            return;
        }

        // For each element in the status array
        // --
        boolean isFirstSelected = true;
        final int checkedItemsCount = checkedItems.size();
        for (int i = 0; i < checkedItemsCount; ++i) {
            // This tells us the item position we are looking at
            // --
            final int position = checkedItems.keyAt(i);

            // This tells us the item status at the above position
            // --
            final boolean isChecked = checkedItems.valueAt(i);

            if (isChecked) {
                if (!isFirstSelected) {
                    sb.append(", ");
                }
                sb.append(data.get(position).getCaption());
                isFirstSelected = false;
                selectedData.add(data.get(position).getCaption());
            }
        }

        // Show a message with the countries that are selected
        // --
        Toast.makeText(this, sb.toString(), Toast.LENGTH_LONG).show();
    }

}

除了列表的内容外，其他三个 Activity 与desserts.java完全相同。
thirdpage.java(列表 Activity )

package a.b.layout;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import android.app.ListActivity;
import android.bluetooth.BluetoothAdapter;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class thirdpage  extends ListActivity  implements  android.view.View.OnClickListener  {

    static final int REQUEST_ENABLE_BT = 0;
    private List<Item> data;
    private List<Item> startersData;
    private List<Item> mainsData;
    private List<Item> drinksData;
    private ViewOrderAdapter adapter;
    private ArrayList<String>selectedData;
    TextView txtRate;
    ImageView img;
    ListView lv; 
    int iClass;
    Button complete_order,place_order,starters,mains,desserts,drinks;
    private List<Item> viewData;

    /* (non-Javadoc)
     * @see android.app.Activity#onCreate(android.os.Bundle)
     */
    @SuppressWarnings("unchecked")
    @Override
    public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.thirdpagelayout);
    selectedData = new ArrayList<String>();

    try
    {
    Intent intent = getIntent();
    Bundle bundle = intent.getExtras();
    selectedData = (ArrayList<String>) bundle.get("selectedData");
    iClass = bundle.getInt("iClass");
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }
    data = new ArrayList<Item>(10);
    startersData = new ArrayList<Item>(10);
    mainsData = new ArrayList<Item>(10);
    drinksData = new ArrayList<Item>(10);
    viewData = new ArrayList<Item>();

    //Desserts
    data.add(new Item(10, "dessert1"));
    data.add(new Item(11, "dessert2"));
    data.add(new Item(12, "dessert3"));
    data.add(new Item(13, "dessert4"));
    data.add(new Item(14, "dessert5"));
    data.add(new Item(15, "dessert6"));
    data.add(new Item(16, "dessert7"));
    data.add(new Item(17, "dessert8"));
    data.add(new Item(18, "dessert9"));
    data.add(new Item(19, "dessert10"));
    data.add(new Item(20, "dessert11"));

    //Starters
    startersData.add(new Item(10, "starter1"));
    startersData.add(new Item(11, "starter2"));
    startersData.add(new Item(12, "starter3"));
    startersData.add(new Item(13, "starter4"));
    startersData.add(new Item(14, "starter5"));
    startersData.add(new Item(15, "starter6"));
    startersData.add(new Item(16, "starter7"));
    startersData.add(new Item(17, "starter8"));
    startersData.add(new Item(18, "starter9"));
    startersData.add(new Item(19, "starter10"));
    startersData.add(new Item(20, "starter11"));

    //Mains
    mainsData.add(new Item(10, "mains1"));
    mainsData.add(new Item(11, "mains2"));
    mainsData.add(new Item(12, "mains3"));
    mainsData.add(new Item(13, "mains4"));
    mainsData.add(new Item(14, "mains5"));
    mainsData.add(new Item(15, "mains6"));
    mainsData.add(new Item(16, "mains7"));
    mainsData.add(new Item(17, "mains8"));
    mainsData.add(new Item(18, "mains9"));
    mainsData.add(new Item(19, "mains10"));
    mainsData.add(new Item(20, "mains11"));

    //Drinks
    drinksData.add(new Item(10, "drinks1"));
    drinksData.add(new Item(11, "drinks2"));
    drinksData.add(new Item(12, "drinks3"));
    drinksData.add(new Item(13, "drinks4"));
    drinksData.add(new Item(14, "drinks5"));
    drinksData.add(new Item(15, "drinks6"));
    drinksData.add(new Item(16, "drinks7"));
    drinksData.add(new Item(17, "drinks8"));
    drinksData.add(new Item(18, "drinks9"));
    drinksData.add(new Item(19, "drinks10"));
    drinksData.add(new Item(20, "drinks11"));

    for(int i=0;i<selectedData.size();i++)
    {
        String str = selectedData.get(i);
        if(iClass == 1)
        {           
for(int idata = 0;idata<data.size();idata++)
{
    if(str.equals(data.get(idata).getCaption()))
    {
         viewData.add(data.get(idata));
    }
    else
    {

    }
}
        }
else if (iClass == 2)
{
    for(int idata = 0;idata<startersData.size();idata++)
    {
        if(str.equals(startersData.get(idata).getCaption()))
        {
            viewData.add(startersData.get(idata));
        }
        else
        {

        }   
}

}
else if (iClass == 3)
{
    for(int idata = 0;idata<mainsData.size();idata++)
    {
        if(str.equals(mainsData.get(idata).getCaption()))
        {
            viewData.add(mainsData.get(idata));
        }
        else
        {

        }   
}
}
else if (iClass == 4)
{
    for(int idata = 0;idata<drinksData.size();idata++)
    {
        if(str.equals(drinksData.get(idata).getCaption()))
        {
            viewData.add(drinksData.get(idata));
        }
        else
        {

        }   
}
}

    }
    long l = 0;
    for(int i=0;i<viewData.size();i++)
    {
        l=l+viewData.get(i).getId();
    }
    TextView txtTotal = (TextView)findViewById(R.id.totalText);
    txtTotal.setText("TOTAL: $"+(String.valueOf(l)));
    adapter = new ViewOrderAdapter(this, viewData);
    setListAdapter(adapter);
    lv = getListView();
    lv.setItemsCanFocus(false);
    lv.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);


    complete_order=(Button)findViewById(R.id.completeorder);
    complete_order.setOnClickListener(this) ;
    }

    @Override
    public void onClick(View v) {
        switch(v.getId())
    {
        case R.id.completeorder:
            BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();    
            if (!mBluetoothAdapter.isEnabled()) {
                    Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                    startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
            }
               break;

      }
    }
}

Answer 1

我还没有喝足够的咖啡来完全理解你需要做的事情，但是如果你想在各种 Activity 类中持久保存你的 ArrayList 数据，那么扩展 Application 类(不要忘记在您的 list 中添加对它的引用)。通过扩展 Application 类，您可以有效地创建一个允许您跨 Activity 维护“全局变量”的类。您可以将 ArrayList 保留在其中。