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
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
其他回答
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);
}
//......}
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
检查这个链接，在非常简单的通过convertView，我们可以得到一行的布局，这将显示在listview(这是parentView)。
View v = convertView;
if (v == null) {
LayoutInflater vi;
vi = LayoutInflater.from(getContext());
v = vi.inflate(R.layout.itemlistrow, null);
}
使用position，你可以得到List<Item>的对象。
Item p = items.get(position);
在此之后，我们必须将对象的所需细节设置为标识的表单小部件。
if (p != null) {
TextView tt = (TextView) v.findViewById(R.id.id);
TextView tt1 = (TextView) v.findViewById(R.id.categoryId);
TextView tt3 = (TextView) v.findViewById(R.id.description);
if (tt != null) {
tt.setText(p.getId());
}
if (tt1 != null) {
tt1.setText(p.getCategory().getId());
}
if (tt3 != null) {
tt3.setText(p.getDescription());
}
}
然后它将返回构造的视图，该视图将附加到parentView(这是一个ListView/GridView)。
一个更紧凑的自定义适配器的例子(使用列表数组作为我的数据):
class MyAdapter extends ArrayAdapter<Object> {
public ArrayAdapter(Context context, List<MyObject> objectList) {
super(context, R.layout.my_list_item, R.id.textViewTitle, objectList.toArray());
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = super.getView(position, convertView, parent);
TextView title = (TextView) row.findViewById(R.id.textViewTitle);
ImageView icon = (ImageView) row.findViewById(R.id.imageViewAccessory);
MyObject obj = (MyObject) getItem(position);
icon.setImageBitmap( ... );
title.setText(obj.name);
return row;
}
}
下面是如何使用它:
List<MyObject> objectList = ...
MyAdapter adapter = new MyAdapter(this.getActivity(), objectList);
listView.setAdapter(adapter);
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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