当 ListView 为空时 Android 显示文本
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Android displaying text when ListView is empty
提问by Daniel
I'm setting a TextViewwith the id @android:id/emptyto display a message when there are no items in the ListView. However, this TextViewgets displayed even if there are items in the ListView, right before the items show up.
我正在设置TextView带有 id 的@android:id/emptya 以在ListView. 但是，TextView即使 , 中存在项目，也会ListView在项目出现之前显示。
How can I make it such that it only gets displayed when there are no elements in the ListView?
我怎样才能让它只在没有元素时显示ListView？
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@android:id/list"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:dividerHeight="1dp" >
</ListView>
<TextView
android:id="@android:id/empty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/empty_list" />
</LinearLayout>
PS: I'm using a Loaderand a SimpleCursorAdapterwith a ListFragment.
PS：我正在使用 aLoader和SimpleCursorAdaptera ListFragment。
回答by dymmeh
I'm guessing you are using a regular Fragmentor Activitywith a ListViewinside of it. If you are, you must add the empty layout to the ListViewmanually.
我猜你是使用常规Fragment或Activity与ListView它的内部。如果是，则必须ListView手动添加空布局。
E.g.
例如
ListView lv = (ListView)findViewById(android.R.id.list);
TextView emptyText = (TextView)findViewById(android.R.id.empty);
lv.setEmptyView(emptyText);
Then your ListViewwill automatically use this view when its adapter is empty
然后ListView当它的适配器为空时你会自动使用这个视图
If you are using a ListActivityyou do not need to call setEmptyView()on the ListViewsince the ListActivityautomatically manages that for you.
如果您使用的是 a ListActivity，则不需要调用setEmptyView()，ListView因为它会ListActivity自动为您管理。
回答by CoderDecoder
Set a TextViewand assign to it whatever you want to display when the ListViewis empty:
设置 aTextView并将其分配给ListView空时要显示的任何内容：
ProjectListAdapter projectListAdapter = new ProjectListAdapter();
TextView empty=(TextView)findViewById(R.id.empty);
projectsListView.setEmptyView(empty);
And in my xml file we write the below code
在我的 xml 文件中，我们编写了以下代码
<TextView
android:id="@+id/empty"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:text="Your text here"
android:textColor="#FFFFFF" />
回答by CircuitBreaker716
I had this problem. You have to set the emptyView explicitly in your code.
我有这个问题。您必须在代码中明确设置 emptyView。
Change your TextView:
改变你的TextView：
<TextView
android:id="@+id/emptyResults"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/empty_list" />
Then in the onCreate():
然后在onCreate()：
listViewResults = (ListView) findViewById(R.id.list);
listViewResults.setEmptyView((LinearLayout) findViewById(R.id.emptyResults));
This code above assumes your ListViewis in a LinearLayout.
上面的代码假设您ListView在LinearLayout.
回答by v1k
I used ListFragmentand had the same issue. I tried all variants from this answers, but the problem wasn't solved.
我使用过ListFragment并遇到了同样的问题。我尝试了这个答案的所有变体，但问题没有解决。
So I found my variant, to override setEmptyText():
所以我找到了我的变体，以覆盖setEmptyText()：
public class NewsFragment extends ListFragment{
private TextView emptyText;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
//...
emptyText = (TextView)view.findViewById(android.R.id.empty);
//...
}
@Override
public void setEmptyText(CharSequence text) {
emptyText.setText(text);
}
}
Hope it will be helpful for somebody.
希望它会对某人有所帮助。
回答by Lena Bru
I know this is kind of late, but for it to work from XML, you need to put a weight on your ListViewand have your TextViewmatch_parent
我知道这有点晚了，但是要使其从 XML 工作，您需要对自己施加压力ListView并让TextViewmatch_parent
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@android:id/list"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_weight="1"
android:dividerHeight="1dp" >
</ListView>
<TextView
android:id="@android:id/empty"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="@string/empty_list" />
</LinearLayout>
回答by Alex Jolig
There's a good exampleof how to do it which works awesome:
有一个很好的例子说明如何做到这一点，效果很棒：
When you want to show a message to the user when the
ListViewis empty, you have to keep in mind the following 3 steps:
- In the xml where the
ListViewis declared, create aTextView(the TextView can be inside aLinearLayoutif you want) right below theListView- Set the
TextView's id as “emptyElement”- And inside the activity, set the
setEmptyView()property to theListView1- Create an xml which will hold the
ListViewand name it “my_activity” and an activity called “MyActivity”.
- Now, in the just created xml “my_activity”, you will have to set the
ListView. And right below theListView, you will have to add aTextView. This will be used to display the empty message.Important: The TextView must have as id the following name: “emptyElement”. This name is mandatory. The message won't be displayed if you use another name.
This is how “my_activity” xml should look like:
<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:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MyActivity"> <ListView android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/listView"/> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/emptyElement" android:text="The list is empty" android:textStyle="bold" android:textSize="15sp" android:visibility="gone" android:layout_centerInParent="true" android:textColor="@android:color/darker_gray"/> </RelativeLayout>
Create an xml for displaying items (when the list is not empty), and name it “list_item”.
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/list_item_text_view" android:textSize="20sp" android:padding="10dp" android:layout_marginLeft="5dp"/>Create a new Java class for the custom adapter which will be used by the ListView and name “MyCustomAdapter”. The code for the adapter is written below:
import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; import java.util.ArrayList; public class MyCustomAdapter extends BaseAdapter { private ArrayList<String> mListItems; private LayoutInflater mLayoutInflater; public MyCustomAdapter(Context context, ArrayList<String> arrayList){ mListItems = arrayList; //get the layout inflater mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } @Override public int getCount() { //getCount() represents how many items are in the list return mListItems.size(); } @Override //get the data of an item from a specific position //i represents the position of the item in the list public Object getItem(int i) { return null; } @Override //get the position id of the item from the list public long getItemId(int i) { return 0; } @Override public View getView(int position, View view, ViewGroup viewGroup) { // create a ViewHolder reference ViewHolder holder; //check to see if the reused view is null or not, if is not null then reuse it if (view == null) { holder = new ViewHolder(); view = mLayoutInflater.inflate(R.layout.list_item, null); holder.itemName = (TextView) view.findViewById(R.id.list_item_text_view); // the setTag is used to store the data within this view view.setTag(holder); } else { // the getTag returns the viewHolder object set as a tag to the view holder = (ViewHolder)view.getTag(); } //get the string item from the position "position" from array list to put it on the TextView String stringItem = mListItems.get(position); if (stringItem != null) { if (holder.itemName != null) { //set the item name on the TextView holder.itemName.setText(stringItem); } } //this method must return the view corresponding to the data at the specified position. return view; } /** * Static class used to avoid the calling of "findViewById" every time the getView() method is called, * because this can impact to your application performance when your list is too big. The class is static so it * cache all the things inside once it's created. */ private static class ViewHolder { protected TextView itemName; } }Now go to
MyActivityclass and add the code below:import android.app.Activity; import android.os.Bundle; import android.widget.ListView; import java.util.ArrayList; import java.util.List; public class MyActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.my_activity); ListView listView = (ListView) findViewById(R.id.listView); // Create an empty array list of strings List<String> items = new ArrayList<String>(); // Set the adapter MyCustomAdapter adapter = new MyCustomAdapter(items); listView.setAdapter(adapter); // Set the emptyView to the ListView listView.setEmptyView(findViewById(R.id.emptyElement)); } }
当你想在
ListView为空时向用户显示消息时，你必须记住以下 3 个步骤：
- 在其中的XML
ListView声明，创建一个TextView（TextView的内心也可以是LinearLayout，如果你想）正下方ListView- 将
TextView的 id设置为“emptyElement”- 在活动中，将
setEmptyView()属性设置为ListView1- 创建一个 xml，将保存
ListView并命名为“my_activity”和一个名为“MyActivity”的活动。
- 现在，在刚刚创建的 xml“my_activity”中，您必须设置
ListView. 在 正下方ListView，您必须添加一个TextView. 这将用于显示空消息。重要提示：TextView 必须具有以下名称作为 id：“emptyElement”。此名称是必需的。如果您使用其他名称，则不会显示该消息。
“my_activity” xml 应该是这样的：
<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:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MyActivity"> <ListView android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/listView"/> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/emptyElement" android:text="The list is empty" android:textStyle="bold" android:textSize="15sp" android:visibility="gone" android:layout_centerInParent="true" android:textColor="@android:color/darker_gray"/> </RelativeLayout>
创建一个用于显示项目的xml（当列表不为空时），并将其命名为“list_item”。
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/list_item_text_view" android:textSize="20sp" android:padding="10dp" android:layout_marginLeft="5dp"/>为 ListView 将使用的自定义适配器创建一个新的 Java 类，并将其命名为“MyCustomAdapter”。适配器的代码如下：
import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; import java.util.ArrayList; public class MyCustomAdapter extends BaseAdapter { private ArrayList<String> mListItems; private LayoutInflater mLayoutInflater; public MyCustomAdapter(Context context, ArrayList<String> arrayList){ mListItems = arrayList; //get the layout inflater mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } @Override public int getCount() { //getCount() represents how many items are in the list return mListItems.size(); } @Override //get the data of an item from a specific position //i represents the position of the item in the list public Object getItem(int i) { return null; } @Override //get the position id of the item from the list public long getItemId(int i) { return 0; } @Override public View getView(int position, View view, ViewGroup viewGroup) { // create a ViewHolder reference ViewHolder holder; //check to see if the reused view is null or not, if is not null then reuse it if (view == null) { holder = new ViewHolder(); view = mLayoutInflater.inflate(R.layout.list_item, null); holder.itemName = (TextView) view.findViewById(R.id.list_item_text_view); // the setTag is used to store the data within this view view.setTag(holder); } else { // the getTag returns the viewHolder object set as a tag to the view holder = (ViewHolder)view.getTag(); } //get the string item from the position "position" from array list to put it on the TextView String stringItem = mListItems.get(position); if (stringItem != null) { if (holder.itemName != null) { //set the item name on the TextView holder.itemName.setText(stringItem); } } //this method must return the view corresponding to the data at the specified position. return view; } /** * Static class used to avoid the calling of "findViewById" every time the getView() method is called, * because this can impact to your application performance when your list is too big. The class is static so it * cache all the things inside once it's created. */ private static class ViewHolder { protected TextView itemName; } }现在转到
MyActivity类并添加以下代码：import android.app.Activity; import android.os.Bundle; import android.widget.ListView; import java.util.ArrayList; import java.util.List; public class MyActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.my_activity); ListView listView = (ListView) findViewById(R.id.listView); // Create an empty array list of strings List<String> items = new ArrayList<String>(); // Set the adapter MyCustomAdapter adapter = new MyCustomAdapter(items); listView.setAdapter(adapter); // Set the emptyView to the ListView listView.setEmptyView(findViewById(R.id.emptyElement)); } }
回答by srinivas
TextView tv=(TextView) view.findViewById(R.id.empty);
tv.setVisibiliy(View.GONE);
