当 listView 为空时，setEmptyView 不显示图像
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【中文标题】当 listView 为空时，setEmptyView 不显示图像【英文标题】：setEmptyView is not displaying image when listView is empty 【发布时间】：2019-11-11 18:38:20 【问题描述】：我正在尝试在 listView 为空时显示图像，但不幸的是，当列表视图为空时，只要列表为空，它就不会显示该图像。
我尝试将 setEmptyView 移动到 oncreate 中，在此之前我尝试检查光标是否为空，如果为空则调用 setemptyview 方法
围栏活动 在这个活动中，我尝试使用 setEmptyView 方法。
public class FenceActivity extends AppCompatActivity
List<Fence> fenceList;
SQLiteDatabase sqLiteDatabase;
ListView listViewFences;
FenceAdapter fenceAdapter;
DataBaseHelper dataBaseHelper;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.savedfences);
listViewFences = findViewById(R.id.fencesListView);
fenceList = new ArrayList<>();
showFencesFromDatabase();
public void showFencesFromDatabase()
dataBaseHelper = new DataBaseHelper(this);
Cursor cursor = dataBaseHelper.getAllData();
if (cursor.moveToFirst())
do
fenceList.add(new Fence(cursor.getInt(0), cursor.getDouble(1), cursor.getDouble(2), cursor.getInt(3)));
while (cursor.moveToNext());
cursor.close();
fenceAdapter = new FenceAdapter(FenceActivity.this, R.layout.list_layout_fences, fenceList);
listViewFences.setAdapter(fenceAdapter);
listViewFences.setEmptyView(findViewById(R.id.emptyElement));
public void reloadFencesFromDatabase()
dataBaseHelper = new DataBaseHelper(this);
Cursor cursor = dataBaseHelper.getAllData();
fenceList.clear();
if (cursor.moveToFirst())
do
fenceList.add(new Fence(cursor.getInt(0), cursor.getDouble(1), cursor.getDouble(2), cursor.getInt(3)));
while (cursor.moveToNext());
cursor.close();
fenceAdapter = new FenceAdapter(FenceActivity.this, R.layout.list_layout_fences, fenceList);
listViewFences.setAdapter(fenceAdapter);
listViewFences.setEmptyView(findViewById(R.id.emptyElement));
Savedences.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_ android:layout_>
<ListView
android:id="@+id/fencesListView"
android:layout_
android:layout_ />
<ImageView
android:id="@+id/emptyElement"
android:layout_
android:layout_
android:dividerHeight="1dp"
android:visibility="gone"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"/>
</RelativeLayout>
适配器类
public class FenceAdapter extends ArrayAdapter<Fence>
Context context;
int listLayoutRes;
List<Fence> fenceList;
DataBaseHelper dataBaseHelper;
FenceActivity fenceActivity;
public FenceAdapter(Context context, int listLayoutRes, List<Fence> fenceList)
super(context, listLayoutRes, fenceList);
this.context = context;
this.listLayoutRes = listLayoutRes;
this.fenceList = fenceList;
@Override
public View getView(int position, View convertView, ViewGroup parent)
if (convertView == null)
LayoutInflater mInflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
convertView = mInflater.inflate(R.layout.list_layout_fences, null);
final Fence fence = fenceList.get(position);
TextView textViewSno = convertView.findViewById(R.id.textViewSnoLabel);
TextView textViewLat = convertView.findViewById(R.id.textViewLatitudeValue);
TextView textViewLon = convertView.findViewById(R.id.textViewLongitudeValue);
TextView textViewRadi = convertView.findViewById(R.id.textViewRadiusValue);
textViewSno.setText(Integer.toString(fence.getSno()));
textViewLat.setText(String.valueOf(fence.getLat()));
textViewLon.setText(String.valueOf(fence.getLon()));
textViewRadi.setText(Integer.toString(fence.getRadius()));
Button buttonDel = convertView.findViewById(R.id.buttonDeleteFence);
buttonDel.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("Are you sure");
builder.setPositiveButton("Yes", new DialogInterface.OnClickListener()
@Override
public void onClick(DialogInterface dialogInterface, int i)
dataBaseHelper = new DataBaseHelper(context);
fenceActivity = (FenceActivity)context;
dataBaseHelper.deleteDataById(fence);
fenceActivity.reloadFencesFromDatabase();
);
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener()
@Override
public void onClick(DialogInterface dialogInterface, int i)
);
AlertDialog dialog = builder.create();
dialog.show();
);
return convertView;
当列表为空时，我可以进行哪些更改以显示该图像。
【问题讨论】：
设置适配器后，检查列表的大小，即fenceList。如果 size 小于零，设置 fenceList.setVisibility(View.GONE);和 emptyElement.setVisibility(View.VISIBLE); 【参考方案1】：public class FenceActivity extends AppCompatActivity
List<Fence> fenceList;
SQLiteDatabase sqLiteDatabase;
ListView listViewFences;
FenceAdapter fenceAdapter;
DataBaseHelper dataBaseHelper;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.savedfences);
listViewFences = findViewById(R.id.fencesListView);
fenceList = new ArrayList<>();
showFencesFromDatabase();
public void showFencesFromDatabase()
dataBaseHelper = new DataBaseHelper(this);
Cursor cursor = dataBaseHelper.getAllData();
if (cursor.moveToFirst())
do
fenceList.add(new Fence(cursor.getInt(0), cursor.getDouble(1), cursor.getDouble(2), cursor.getInt(3)));
while (cursor.moveToNext());
cursor.close();
fenceAdapter = new FenceAdapter(FenceActivity.this, R.layout.list_layout_fences, fenceList);
listViewFences.setAdapter(fenceAdapter);
listViewFences.setEmptyView(findViewById(R.id.emptyElement));
public void reloadFencesFromDatabase()
dataBaseHelper = new DataBaseHelper(this);
Cursor cursor = dataBaseHelper.getAllData();
fenceList.clear();
if (cursor.moveToFirst())
do
fenceList.add(new Fence(cursor.getInt(0), cursor.getDouble(1), cursor.getDouble(2), cursor.getInt(3)));
while (cursor.moveToNext());
cursor.close();
fenceAdapter = new FenceAdapter(FenceActivity.this, R.layout.list_layout_fences, fenceList);
listViewFences.setAdapter(fenceAdapter);
listViewFences.setEmptyView(findViewById(R.id.emptyElement));
添加这个而不是listViewFences.setEmptyView(findViewById(R.id.emptyElement));
listViewFences.setVisibility(fenceList.size>0?View.VISIBLE:View.GONE);
emptyElement.setVisibility(fenceList.size>0?View.GONE:View.VISIBLE);
还要在活动中定义emptyElement view。
【讨论】：
在 xml 中的 ImageView 中添加src 并尝试【参考方案2】：
在设置适配器之前尝试设置空视图
fenceAdapter = new FenceAdapter(FenceActivity.this, R.layout.list_layout_fences, fenceList);
listViewFences.setEmptyView(findViewById(R.id.emptyElement));
listViewFences.setAdapter(fenceAdapter);
【讨论】：
【参考方案3】：在您的代码中进行此更改 -
@Override
protected void onCreate(@Nullable Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.savedfences);
listViewFences = findViewById(R.id.fencesListView);
fenceList = new ArrayList<>();
fenceAdapter = new FenceAdapter(FenceActivity.this, R.layout.list_layout_fences, fenceList);
listViewFences.setAdapter(fenceAdapter);
showFencesFromDatabase();
public void showFencesFromDatabase()
dataBaseHelper = new DataBaseHelper(this);
Cursor cursor = dataBaseHelper.getAllData();
if (cursor.moveToFirst())
do
fenceList.add(new Fence(cursor.getInt(0), cursor.getDouble(1), cursor.getDouble(2), cursor.getInt(3)));
while (cursor.moveToNext());
cursor.close();
notifyDataSetChanged();
if(fenceList.size() > 0)
findViewById(R.id.emptyElement.setVisibility(View.GONE);
fenceList.setVisibility(View.VISIBLE);
else
findViewById(R.id.emptyElement.setVisibility(View.VISIBLE);
fenceList.setVisibility(View.GONE);
【讨论】：
can't use functionnotifyDataSetChanged() studio 报错。以上是关于当 listView 为空时，setEmptyView 不显示图像的主要内容，如果未能解决你的问题，请参考以下文章