【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_width="match_parent" android:layout_height="match_parent">
<ListView
android:id="@+id/fencesListView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<ImageView
android:id="@+id/emptyElement"
android:layout_width="200dp"
android:layout_height="200dp"
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);
标签： java android xml android-listview