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法律研究如何在 Android RecyclerView 中正确突出显示选中的项目？
此示例演示了如何在 Android RecyclerView 上正确突出显示选中的项目。
步骤 1 - 在 Android Studio 中创建一个新项目，转到文件 ⇒ 新建项目，并填写所有必需的详细信息以创建新项目。
在 build.gradle (Module: app) 中添加以下依赖项
implementation 'com.android.support:recyclerview-v7:28.0.0'
步骤 2 - 将以下代码添加到 res/layout/activity_main.xml 中。
<?xml version="1.0" encoding="utf-8"?> <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:padding="4dp" tools:context=".MainActivity"> <androidx.recyclerview.widget.RecyclerView android:id="@+id/recyclerView" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="8dp" /> </RelativeLayout>
步骤 3 - 创建一个布局资源文件 (list_layout.xml) 并添加以下代码 -
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@drawable/background_selector" android:padding="16dp"> <TextView android:id="@+id/awardTitle" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="10dp" android:text="New Text" android:textSize="18sp" android:textStyle="bold" /> <TextView android:id="@+id/awardYear" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/awardTitle" android:layout_alignStart="@+id/awardTitle" android:layout_marginTop="20dp" android:text="New Text" android:textColor="#000" /> <TextView android:id="@+id/playerName" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentEnd="true" android:text="New Text" /> </RelativeLayout>
步骤 4 - 创建如下所述的可绘制资源文件并添加相应的代码 -
background_selector.xml -
<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:drawable="@color/colorAccent" android:state_pressed="false" android:state_selected="true" /> <item android:drawable="@android:color/white" android:state_selected="false" /> </selector>
line_divider.xml -
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"> <size android:width="2dp" android:height="2dp" /> <solid android:color="@color/colorPrimaryDark" /> </shape>
步骤 5 - 创建如下所述的 Java 类文件并添加相应的代码 -
ItemObject -
class ItemObject {
private String awardTitle;
private String awardYear;
private String player;
ItemObject(String awardTitle, String awardYear, String player) {
this.awardTitle = awardTitle;
this.awardYear = awardYear;
this.player = player;
}
String getAwardTitle() {
return awardTitle;
}
String getAwardYear() {
return awardYear;
}
String getPlayer() {
return player;
}
}RecyclerViewAdapter -
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.util.List;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
public class RecyclerViewAdapter extends
RecyclerView.Adapter<RecyclerViewHolders> {
private List<ItemObject> itemList;
RecyclerViewAdapter(Context context, List<ItemObject> itemList) {
this.itemList = itemList;
}
@NonNull
@Override
public RecyclerViewHolders onCreateViewHolder(ViewGroup parent, int viewType) {
View layoutView = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_layout, null);
return new RecyclerViewHolders(layoutView);
}
@Override
public void onBindViewHolder(RecyclerViewHolders holder, int position) {
holder.awardTitle.setText("Award Title: " + itemList.get(position).getAwardTitle());
holder.awardYear.setText("Award Year: " + itemList.get(position).getAwardYear());
holder.player.setText("Player Name: " + itemList.get(position).getPlayer());
}
@Override
public int getItemCount() {
return this.itemList.size();
}
}RecyclerViewHolders -
import android.util.SparseBooleanArray;
import android.view.View;
import android.widget.TextView;
import androidx.recyclerview.widget.RecyclerView;
class RecyclerViewHolders extends RecyclerView.ViewHolder implements
View.OnClickListener {
TextView awardTitle;
TextView awardYear;
TextView player;
private SparseBooleanArray selectedItems = new SparseBooleanArray();
RecyclerViewHolders(View itemView) {
super(itemView);
itemView.setOnClickListener(this);
awardTitle = itemView.findViewById(R.id.awardTitle);
awardYear = itemView.findViewById(R.id.awardYear);
player = itemView.findViewById(R.id.playerName);
}
@Override
public void onClick(View view) {
if (selectedItems.get(getAdapterPosition(), false)) {
selectedItems.delete(getAdapterPosition());
view.setSelected(false);
}
else {
selectedItems.put(getAdapterPosition(), true);
view.setSelected(true);
}
}
}SimpleItemDecoration -
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.core.content.ContextCompat;
import androidx.recyclerview.widget.RecyclerView;
class SimpleItemDecoration extends RecyclerView.ItemDecoration {
private Drawable drawable;
SimpleItemDecoration(Context context) {
drawable = ContextCompat.getDrawable(context, R.drawable.line_divider);
}
@Override
public void onDrawOver(@NonNull Canvas canvas, RecyclerView parent, @NonNull RecyclerView.State state) {
int left = parent.getPaddingLeft();
int right = parent.getWidth() - parent.getPaddingRight();
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
View child = parent.getChildAt(i);
RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
int top = child.getBottom() + params.bottomMargin;
int bottom = top + drawable.getIntrinsicHeight();
drawable.setBounds(left, top, right, bottom);
drawable.draw(canvas);
}
}
}步骤 6 - 将以下代码添加到 src/MainActivity.java 中
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RecyclerView recyclerView = findViewById(R.id.recyclerView);
recyclerView.addItemDecoration(new SimpleItemDecoration(this));
LinearLayoutManager layoutManager = new LinearLayoutManager(MainActivity.this);
recyclerView.setLayoutManager(layoutManager);
List<ItemObject> posts = returnListItems();
RecyclerViewAdapter adapter = new RecyclerViewAdapter(MainActivity.this, posts);
recyclerView.setAdapter(adapter);
}
private List<ItemObject> returnListItems() {
List<ItemObject> items = new ArrayList<>();
items.add(new ItemObject("Ballon'd'or", "2007", "Ricardo KaKa"));
items.add(new ItemObject("Ballon'd'or", "2008", "Cristiano Ronaldo"));
items.add(new ItemObject("Ballon'd'or", "2009 - 2012, 2015", "Lionel Messi"));
items.add(new ItemObject("Ballon'd'or", "2013, 2014, 2016, 2017", "Cristiano Ronaldo"));
items.add(new ItemObject("Ballon'd'or", "2018", "Luca Modric"));
items.add(new ItemObject("Ballon'd'or", "2019", "Haven't decided yet"));
return items;
}
}步骤 7 - 将以下代码添加到 androidManifest.xml 中
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample"> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
让我们尝试运行您的应用程序。我假设您已将您的实际 Android 移动设备连接到您的计算机。要从 Android Studio 运行应用程序，请打开您的一个项目活动文件，然后单击工具栏中的运行 
图标。选择您的移动设备作为选项，然后检查您的移动设备，它将显示您的默认屏幕 -
点击 这里 下载项目代码。
更新于: 2019年11月22日
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