我想为列表视图创建一个自定义适配器。有没有任何文章可以告诉我如何创建一个,并解释它是如何工作的?
当前回答
我知道这个问题已经有人回答了……但我想给出一个更完整的例子。
在我的例子中,ListActivity将显示我们的自定义ListView被称为OptionsActivity,因为在我的项目中,这个活动将显示我的用户可以设置来控制我的应用程序的不同选项。有两种列表项类型,一种列表项类型只是有一个TextView和第二个列表项类型只是有一个按钮。您可以在每个列表项类型中放入任何您喜欢的小部件,但是我保持这个示例的简单性。
getItemView()方法检查哪些列表项应该是类型1或类型2。根据我在上面定义的静态整数,前5个列表项将是列表项类型1,后5个列表项将是列表项类型2。如果你编译并运行这个,你会有一个ListView,它有五个项目,只包含一个按钮,然后五个项目,只包含一个TextView。
下面是活动代码、活动xml文件和每个列表项类型的xml文件。
OptionsActivity.java:
public class OptionsActivity extends ListActivity {
private static final int LIST_ITEM_TYPE_1 = 0;
private static final int LIST_ITEM_TYPE_2 = 1;
private static final int LIST_ITEM_TYPE_COUNT = 2;
private static final int LIST_ITEM_COUNT = 10;
// The first five list items will be list item type 1
// and the last five will be list item type 2
private static final int LIST_ITEM_TYPE_1_COUNT = 5;
private MyCustomAdapter mAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAdapter = new MyCustomAdapter();
for (int i = 0; i < LIST_ITEM_COUNT; i++) {
if (i < LIST_ITEM_TYPE_1_COUNT)
mAdapter.addItem("item type 1");
else
mAdapter.addItem("item type 2");
}
setListAdapter(mAdapter);
}
private class MyCustomAdapter extends BaseAdapter {
private ArrayList<String> mData = new ArrayList<String>();
private LayoutInflater mInflater;
public MyCustomAdapter() {
mInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void addItem(final String item) {
mData.add(item);
notifyDataSetChanged();
}
@Override
public int getItemViewType(int position) {
if(position < LIST_ITEM_TYPE_1_COUNT)
return LIST_ITEM_TYPE_1;
else
return LIST_ITEM_TYPE_2;
}
@Override
public int getViewTypeCount() {
return LIST_ITEM_TYPE_COUNT;
}
@Override
public int getCount() {
return mData.size();
}
@Override
public String getItem(int position) {
return mData.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
int type = getItemViewType(position);
if (convertView == null) {
holder = new ViewHolder();
switch(type) {
case LIST_ITEM_TYPE_1:
convertView = mInflater.inflate(R.layout.list_item_type1, null);
holder.textView = (TextView)convertView.findViewById(R.id.list_item_type1_text_view);
break;
case LIST_ITEM_TYPE_2:
convertView = mInflater.inflate(R.layout.list_item_type2, null);
holder.textView = (TextView)convertView.findViewById(R.id.list_item_type2_button);
break;
}
convertView.setTag(holder);
} else {
holder = (ViewHolder)convertView.getTag();
}
holder.textView.setText(mData.get(position));
return convertView;
}
}
public static class ViewHolder {
public TextView textView;
}
}
activity_options.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<ListView
android:id="@+id/optionsList"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
list_item_type_1.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/list_item_type1_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/list_item_type1_text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Text goes here" />
</LinearLayout>
list_item_type2.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/list_item_type2_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<Button
android:id="@+id/list_item_type2_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button text goes here" />
</LinearLayout>
其他回答
您可以在官方ApiDemos中查看这个示例。它展示了如何扩展BaseAdapter并将其应用到ListView。在此之后,只需查看BaseAdapter的引用,并尝试理解每个方法做什么(包括继承的方法)以及何时/如何使用它。
另外,谷歌是你的朋友:)。
谷歌有一个名为EfficientAdapter的示例,在我看来,它是如何实现自定义适配器的最佳简单示例。http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/List14.html @CommonsWare很好地解释了上面例子中使用的模式 http://commonsware.com/Android/excerpt.pdf
public class CustomAdapter extends BaseAdapter{
ArrayList<BookPojo> data;
Context ctx;
int index=0;
public CustomAdapter(ArrayList<BookPojo> data, Context ctx) {
super();
this.data = data;
this.ctx = ctx;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return data.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return data.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertview, ViewGroup parent) {
// TODO Auto-generated method stub
View v=convertview;
if(v==null){
LayoutInflater vi=LayoutInflater.from(ctx);
v=vi.inflate(R.layout.messgeview,null);
}
RelativeLayout rlmessage=(RelativeLayout)v.findViewById(R.id.rlmessgeview);
TextView tvisdn=(TextView)v.findViewById(R.id.tvisdn);
TextView tvtitle=(TextView)v.findViewById(R.id.tvtitle);
TextView tvauthor=(TextView)v.findViewById(R.id.tvauthor);
TextView tvprice=(TextView)v.findViewById(R.id.tvprice);
BookPojo bpj=data.get(position);
tvisdn.setText(bpj.isdn+"");
tvtitle.setText(bpj.title);
tvauthor.setText(bpj.author);
tvprice.setText(bpj.price+"");
if(index%2==0)
{
rlmessage.setBackgroundColor(Color.BLUE);
}
else
{
rlmessage.setBackgroundColor(Color.YELLOW);
}
index++;
return v;
}
}
这段代码很容易理解。
three_horizontal_text_views_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/leftTextView"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/centreTextView"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/rightTextView"/>
</LinearLayout>
ThreeStrings.java
public class ThreeStrings {
private String left;
private String right;
private String centre;
public ThreeStrings(String left, String right, String centre) {
this.left = left;
this.right = right;
this.centre = centre;
}
}
ThreeHorizontalTextViewsAdapter.java
public class ThreeHorizontalTextViewsAdapter extends ArrayAdapter<ThreeStrings> {
private int layoutResource;
public ThreeHorizontalTextViewsAdapter(Context context, int layoutResource, List<ThreeStrings> threeStringsList) {
super(context, layoutResource, threeStringsList);
this.layoutResource = layoutResource;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = convertView;
if (view == null) {
LayoutInflater layoutInflater = LayoutInflater.from(getContext());
view = layoutInflater.inflate(layoutResource, null);
}
ThreeStrings threeStrings = getItem(position);
if (threeStrings != null) {
TextView leftTextView = (TextView) view.findViewById(R.id.leftTextView);
TextView rightTextView = (TextView) view.findViewById(R.id.rightTextView);
TextView centreTextView = (TextView) view.findViewById(R.id.centreTextView);
if (leftTextView != null) {
leftTextView.setText(threeStrings.getLeft());
}
if (rightTextView != null) {
rightTextView.setText(threeStrings.getRight());
}
if (centreTextView != null) {
centreTextView.setText(threeStrings.getCentre());
}
}
return view;
}
}
main_layout.xml
<LinearLayout 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"
android:orientation="vertical"
tools:context="com.androidapplication.ListActivity">
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/listView"></ListView>
</LinearLayout>
MainActivity.java
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
List<ThreeStrings> threeStringsList = new ArrayList<>();
ThreeStrings threeStrings = new ThreeStrings("a", "b", "c");
threeStringsList.add(threeStrings);
ListView listView = (ListView)findViewById(R.id.listView);
ThreeHorizontalTextViewsAdapter threeHorizontalTextViewsAdapter = new ThreeHorizontalTextViewsAdapter(this, R.layout.three_horizontal_text_views_layout, threeStringsList);
listView.setAdapter(threeHorizontalTextViewsAdapter);
}
//......}
这很简单。
import android.content.Context;
import android.content.DialogInterface;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AlertDialog;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;
/**
* Created by Belal on 9/14/2017.
*/
//we need to extend the ArrayAdapter class as we are building an adapter
public class MyListAdapter extends ArrayAdapter<Hero> {
//the list values in the List of type hero
List<Hero> heroList;
//activity context
Context context;
//the layout resource file for the list items
int resource;
//constructor initializing the values
public MyListAdapter(Context context, int resource, List<Hero> heroList) {
super(context, resource, heroList);
this.context = context;
this.resource = resource;
this.heroList = heroList;
}
//this will return the ListView Item as a View
@NonNull
@Override
public View getView(final int position, @Nullable View convertView, @NonNull ViewGroup parent) {
//we need to get the view of the xml for our list item
//And for this we need a layoutinflater
LayoutInflater layoutInflater = LayoutInflater.from(context);
//getting the view
View view = layoutInflater.inflate(resource, null, false);
//getting the view elements of the list from the view
ImageView imageView = view.findViewById(R.id.imageView);
TextView textViewName = view.findViewById(R.id.textViewName);
TextView textViewTeam = view.findViewById(R.id.textViewTeam);
Button buttonDelete = view.findViewById(R.id.buttonDelete);
//getting the hero of the specified position
Hero hero = heroList.get(position);
//adding values to the list item
imageView.setImageDrawable(context.getResources().getDrawable(hero.getImage()));
textViewName.setText(hero.getName());
textViewTeam.setText(hero.getTeam());
//adding a click listener to the button to remove item from the list
buttonDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//we will call this method to remove the selected value from the list
//we are passing the position which is to be removed in the method
removeHero(position);
}
});
//finally returning the view
return view;
}
//this method will remove the item from the list
private void removeHero(final int position) {
//Creating an alert dialog to confirm the deletion
AlertDialog.Builder builder = new AlertDialog.Builder(context);
builder.setTitle("Are you sure you want to delete this?");
//if the response is positive in the alert
builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
//removing the item
heroList.remove(position);
//reloading the list
notifyDataSetChanged();
}
});
//if response is negative nothing is being done
builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
}
});
//creating and displaying the alert dialog
AlertDialog alertDialog = builder.create();
alertDialog.show();
}
}
来源:自定义ListView Android教程
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