RecyclerView+Intent传值使用
RecyclerView的基本步骤：
- 创建资源的实体类（Fruit类）
- 创建RecyclerView的子项布局（recycler_item.xml）
- 自定义适配器
- 适配器要继承RecyclerView.Adapter<Fruit.ViewHodler>
- 创建内部类ViewHolder继承RecyclerView.Holder,用来加载控件
- 重写onCreatViewHolder()方法，加载recycler_item的布局，并创建一个ViewHolder实例
- 重写onBindViewHolder()方法，将recyclerView的子项进行赋值
- 重写getItemCount()方法
Fruit.class
package com.example.recyclerviewactivity;
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
既然使用了Intent传值，就需要至少2个Activity，创建一个MainActivity用来显示所有水果数据，一个FruitActivity用来显示具体的水果信息
activity_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
recycler_item.xml
<?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="wrap_content"
>
<ImageView
android:id="@+id/fruit_image"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/ic_apple"
/>
<TextView
android:id="@+id/fruit_name"
android:text="apple"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_marginLeft="10dp"/>
</LinearLayout>
自定义适配器FruitAdapter
package com.example.recyclerviewactivity;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import java.util.List;
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
private List<Fruit> fruits;
public FruitAdapter(List<Fruit> fruits) {
this.fruits = fruits;
}
static public class ViewHolder extends RecyclerView.ViewHolder {
ImageView fruitImage;
TextView fruitName;
View fruitView;
//加载控件
public ViewHolder(@NonNull View itemView) {
super(itemView);
fruitView = itemView;
fruitName = itemView.findViewById(R.id.fruit_name);
fruitImage = itemView.findViewById(R.id.fruit_image);
}
}
//创建ViewHolder实例
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recycler_item, viewGroup, false);
final ViewHolder holder = new ViewHolder(view);
//给recycler_item添加监听器
holder.fruitView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int k = holder.getAdapterPosition();
Fruit fruit1 = fruits.get(k);
FruitActivity.actionStart(holder.fruitView.getContext(),fruit1.getName(),fruit1.getImageId());
//Toast.makeText(v.getContext(), "你选中了" + fruit1.getName(), Toast.LENGTH_LONG).show();
}
});
//给图片添加监听器
holder.fruitImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int k = holder.getAdapterPosition();
Fruit fruit1 = fruits.get(k);
FruitActivity.actionStart(holder.fruitView.getContext(),fruit1.getName(),fruit1.getImageId());
//Toast.makeText(v.getContext(), "你选中了" + fruit1.getName(), Toast.LENGTH_LONG).show();
}
});
return holder;
}
//给recyclerView子项赋值
@Override
public void onBindViewHolder(@NonNull final ViewHolder viewHolder, int i) {
Fruit fruit = fruits.get(i);
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
}
@Override
public int getItemCount() {
return fruits.size();
}
}
MainActivity.class
package com.example.recyclerviewactivity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
public ArrayList<Fruit> fruitList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
RecyclerView recyclerView = findViewById(R.id.recycler_layout);//获取RecyclerView实例
LinearLayoutManager layoutManager=new LinearLayoutManager(this);//指定recyclerView的布局方式为线性布局
recyclerView.setLayoutManager(layoutManager);
FruitAdapter adapter = new FruitAdapter(fruitList);//创建adapter实例
recyclerView.setAdapter(adapter);
}
//初始化水果数据
public void init(){
for (int i = 0; i < 3; i++) {
Fruit apple = new Fruit("apple",R.drawable.ic_apple);
fruitList.add(apple);
Fruit banana= new Fruit("banana",R.drawable.ic_banana);
fruitList.add(banana);
Fruit grape = new Fruit("grape",R.drawable.ic_grape);
fruitList.add(grape);
Fruit mango = new Fruit("mango",R.drawable.ic_mango);
fruitList.add(mango);
Fruit orange = new Fruit("orange",R.drawable.ic_orange);
fruitList.add(orange);
Fruit strawberry = new Fruit("strawberry",R.drawable.ic_strawberry);
fruitList.add(strawberry);
Fruit watermelon = new Fruit("watermelon",R.drawable.ic_watermelon);
fruitList.add(watermelon);
}
}
}
在适配器中，设置了每个recyclerViewItem和水果picture的点击事件，点击之后会跳转到FruitActivity的活动中，并且通过intent将图片和水果名字传到FruitActivit活动中。
activity_fruit.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/fruit_image"
android:layout_width="200dp"
android:layout_height="200dp"
android:layout_gravity="center"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.32" />
<TextView
android:id="@+id/fruit_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20dp"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/fruit_image"
app:layout_constraintVertical_bias="0.22000003" />
</android.support.constraint.ConstraintLayout>
FruitActivity.class
package com.example.recyclerviewactivity;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.TextView;
public class FruitActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fruit);
ImageView imageView = findViewById(R.id.fruit_image);
TextView textView = findViewById(R.id.fruit_name);
Intent intent = getIntent();
textView.setText(intent.getStringExtra("fruitName"));
imageView.setImageResource(intent.getExtras().getInt("fruitId"));
}
public static void actionStart(Context context,String fruitName,int fruitId) {
Intent intent = new Intent(context,FruitActivity.class); //创建intent实例
intent.putExtra("fruitName",fruitName);//放入要传递的参数
intent.putExtra("fruitId",fruitId);
context.startActivity(intent);
}
}
当要传递的参数很多或者2个人分别写不同的activity时，第一个活动不知道要传些什么参数，自己去看代码又太复杂，这时在FruitActivity中创建actionStart（）方法，当MainActivity调用方法时，就知道要传哪些参数了，在FruitActivity中通过getIntent()取出intent，通过intent的getStringExtra()方法得到水果名字，getExtras().getInt()得到水果图片id。
运行结果：
Screenshot_1569763267.png
Screenshot_1569767009.png
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