我正在尝试列出包含从 SQLite 数据库中提取的 Shop 类型的 ArrayList 中的列的行。因此，我有一个自定义适配器。
但是，没有显示任何数据。没有错误消息或异常。
我使用过调试器(我使用的是 Android Studio)。我知道没有调用覆盖的 getView 方法(未触发此方法中的断点)。构造函数中的断点被触发，预期的数据在 ArrayList 中。
ListView 已经为其他方法工作(我已经从一个简单的列表发展到一个简单的列表，其中数据在一个字符串数组中确认，在对现有数据的其他测试中，例如一个对话框显示数据，到一个简单的列表使用Shop类型的ArrayList，列出的是元素而不是数据。
行 View XML 可能存在问题。
如果有人告诉我关于上述问题的代码(如下所示)有什么问题，我将不胜感激。即为什么没有显示任何内容以及如何更正代码(如果时间允许)。
我想确认一下，我查看了很多与此相关的帖子并尝试了各种选项，您可以在代码中看到一些选项。
这是我认为相关的 MainShopActivity 的摘录(完整代码放在最后，因为它很丑陋并且有很多代码被注释掉了)。
ShopListArrayAdapter adapter = new ShopListArrayAdapter(this,shoplist);
//listview.setAdapter(adapter);
setListAdapter(adapter);
这是 ShopListArrayAdapter。
package mjt.shopper;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
import java.util.ArrayList;
/**
* Created by Mike092015 on 1/02/2016.
*/
public class ShopListArrayAdapter extends ArrayAdapter<ArrayList<Shop>> {
private final Context context;
private final ArrayList<Shop> shoplist;
public ShopListArrayAdapter(Context context, ArrayList<Shop> shoplist) {
super(context, R.layout.activity_shop_list_entry);
this.context = context;
this.shoplist = shoplist;
}
@Override
public View getView(int position, View convertview, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(R.layout.activity_shop_list_entry, parent, false);
TextView textViewShopName = (TextView) rowView.findViewById(R.id.shop_name_entry);
TextView textViewShopOrder = (TextView) rowView.findViewById(R.id.shop_order_entry);
TextView textviewShopStreet = (TextView) rowView.findViewById(R.id.shop_street_entry);
textViewShopName.setText(shoplist.get(position).getShopName());
textViewShopOrder.setText(shoplist.get(position).getShopOrderAsString());
textviewShopStreet.setText(shoplist.get(position).getShopstreet());
return rowView;
}
}
这是 ListeView XML activity_shop_list(ps 我尝试删除了四个按钮，结果是一样的。)
<?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:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="mjt.shopper.ShopListActivity">
<Button
android:id="@+id/aslhbtn01"
android:layout_width="@dimen/standard_button_width"
android:layout_height="@dimen/standard_button_height"
android:text="@string/standarddonebutton"
android:textStyle="bold"
android:onClick="doneWithShops"/>
<Button
android:id="@+id/aslhbtn02"
android:layout_width="@dimen/standard_button_width"
android:layout_height="@dimen/standard_button_height"
android:layout_toEndOf="@id/aslhbtn01"
android:layout_toRightOf="@id/aslhbtn01"
android:text="@string/standardaddbuttontext"
android:textStyle="bold"
android:onClick="addShop"
/>
<ListView
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/aslhbtn01"/>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@android:id/list">
<Button
android:id="@+id/aslfbtn01"
android:layout_width="@dimen/standard_button_width"
android:layout_height="@dimen/standard_button_height"
android:text="@string/standarddonebutton"
android:textStyle="bold"
android:onClick="doneWithShops"/>
<Button
android:id="@+id/aslfbtn02"
android:layout_width="@dimen/standard_button_width"
android:layout_height="@dimen/standard_button_height"
android:layout_toEndOf="@id/aslfbtn01"
android:layout_toRightOf="@id/aslfbtn01"
android:text="@string/standardaddbuttontext"
android:textStyle="bold"
android:onClick="addShop"/>
</RelativeLayout>
这是 RowView XML activity_shop_list_entry
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".ShopListEntryActivity">
<TextView
android:id="@+id/shop_name_entry"
android:layout_width="100sp"
android:layout_height="30sp"
android:textStyle="bold" />
<TextView
android:id="@+id/shop_order_entry"
android:layout_width="50sp"
android:layout_height="30sp" />
<TextView
android:id="@+id/shop_street_entry"
android:layout_width="300sp"
android:layout_height="30sp" />
</LinearLayout>
最后是ShopListActivity的完整代码
package mjt.shopper;
import android.app.AlertDialog;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import java.util.ArrayList;
public class ShopListActivity extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shop_list);
int shopcount = 0;
// Need to access the shopper database
ShopperDBHelper shopperdb = new ShopperDBHelper(this, null, null,1);
// Check to see if we should have action buttons at top and bottom of the list
// if so then make the upper buttons invisible. Just in case if not then make
// them visible.
shopcount = shopperdb.numberOfShops();
if(shopcount < 10) {
findViewById(R.id.aslhbtn01).setVisibility(View.INVISIBLE);
findViewById(R.id.aslhbtn02).setVisibility(View.INVISIBLE);
} else {
findViewById(R.id.aslhbtn01).setVisibility(View.VISIBLE);
findViewById(R.id.aslhbtn02).setVisibility(View.VISIBLE);
}
// Call the getShops method setting an ArrayList with the returned ArrayList (list of Shop objects)
final ArrayList<Shop> shoplist = shopperdb.getShops();
//Testing ie display number of shops via both the numberOfShops method and via the ArrayList size method
// according to the ArrayList returned from the getShops method.
// numberOfShops method returns integer count
// getShops method returns an ArrayList of the Shop object per row, this containing all the data
String r; // initialise the string that is to be displayed
// Testing Add the number of shops extracted (both count methods as described above)
r = "Shop List Array contains " + shoplist.size() + " Elements.\nNumber of Shops returns "+shopcount+"\n";
// Alternative/check simplelistview compliant array
final String[] values = new String[shoplist.size()];
int ix = 0;
// Testing report on the contents of the returned list of Shops, also populate the simplelistview array
for(Shop shop : shoplist) {
values[ix++] = shop.getShopName();
r=r+"Shop Name="+shop.getShopName()+
" Order="+shop.getShopOrderAsString()+
" Street="+shop.getShopstreet()+
" City="+shop.getShopCity()+
" State="+shop.getShopstate()+
" Notes="+shop.getShopNotes()+
" DBID="+shop.getShopId()+
"\n\n";
}
// Testing report shop list according to the simplelistview array
r = r+"\n\nExtract Shop names are:";
for(int i=0;i < shoplist.size(); i++ ) {
r=r+"\n "+values[i];
}
// Build the simplelistview (ie just one column, the shop name)
/*WORKS but now trying arraylist adapter
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,values);
final ListView listview = (ListView) findViewById(R.id.aslv01);
// Set up the onclick listener per list item
listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(getApplicationContext(),"You Clicked on List Item #"+position+" Shop="+values[position]+". ALtMthd Shop="+shoplist.get(position).getShopName(),Toast.LENGTH_LONG).show();
}
});
listview.setAdapter(adapter);
*/
ShopListArrayAdapter adapter = new ShopListArrayAdapter(this,shoplist);
//listview.setAdapter(adapter);
setListAdapter(adapter);
// sort of works shows the id of the shoplist element but for all shops
//ArrayAdapter<Shop> adadpter = new ArrayAdapter<Shop>(this,android.R.layout.simple_list_item_1,shoplist);
//listview.setAdapter(adapter);
AlertDialog.Builder okdialog = new AlertDialog.Builder(this);
okdialog.setMessage(r);
okdialog.setCancelable(true);
okdialog.setPositiveButton("OK",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
okdialog.show();
}
public void doneWithShops(View view) { this.finish(); }
public void addShop(View view) {
ShopperDBHelper shopperdb = new ShopperDBHelper(this, null, null, 1);
final ArrayList<Shop> shoplist = shopperdb.getShops();
Intent intent = new Intent(this,ShopAddActivity.class);
startActivity(intent);
final String[] values = new String[shoplist.size()];
int ix = 0;
for(Shop shop : shoplist) {
values[ix++] = shop.getShopName();
}
//ArrayAdapter<String> adapter = new ArrayAdapter<String>(view.getContext(), android.R.layout.simple_list_item_1,values);
//@@@@@@@@ final ListView listview = (ListView) findViewById(R.id.aslv01);
//final ListView listview = (ListView) findViewById(R.id.aslv01);
}
最佳答案
您没有将数据集提交给父类。变化
public ShopListArrayAdapter(Context context, ArrayList<Shop> shoplist) {
super(context, R.layout.activity_shop_list_entry);
与
public ShopListArrayAdapter(Context context, ArrayList<Shop> shoplist) {
super(context, R.layout.activity_shop_list_entry, shoplist);
当然 shoplist 必须包含条目，否则什么也不会显示。在调用setAdapter Android 调用ArrayAdapter.getCount 后，检查是否需要调用getView。由于您既没有向父类显式提供数据集，也没有覆盖 getCount，因此从 Android POV 来看，您没有任何可显示的内容，因此 getView 没有被调用。
编辑
改变
public class ShopListArrayAdapter extends ArrayAdapter<ArrayList<Shop>> {
与
public class ShopListArrayAdapter extends ArrayAdapter<Shop> {
关于Android Studio ListView 自定义适配器无数据显示，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35125531/