需要一个关于 RecyclerView.Adapter.notifyItemChanged(int position, Object payload) 的例子 [英] Need an example about RecyclerView.Adapter.notifyItemChanged(int position, Object payload)

问题描述

根据 RecyclerView 文档关于 medthod notifyItemChanged(int position, Object payload)

According to RecyclerView documentation about medthod notifyItemChanged(int position, Object payload)

通知任何已注册的观察者位置的项目已通过可选的有效负载对象更改.

Notify any registered observers that the item at position has changed with an optional payload object.

我不明白如何在这个方法中使用第二个参数payload.我已经搜索了很多关于有效载荷"的文档，但一切都是模棱两可的.

I don't understand how to use second paramenter payload in this method. I have searched many document about "payload" but everything was ambiguous.

所以，如果你知道这个方法，请给我一个清晰的例子.非常感谢.

So, If you know about this method, please show me a clear example about it. Thank you very much.

推荐答案

查看演示该功能的示例代码.它是一个 RecyclerView，当位于 position 位置的项目被点击时调用 notifyItemChanged(position, payload).您可以通过查找 logcat 语句来验证 onBindViewHolder(holder, position, payload) 是否被调用.

Check out this sample code that demonstrates the feature. It's a RecyclerView that calls notifyItemChanged(position, payload) when the item at position position is clicked. You can verify that onBindViewHolder(holder, position, payload) was called by looking for the logcat statement.

确保您至少使用了支持库的 23.1.1 版本，如下所示:

Make sure you are using at least version 23.1.1 of the support libraries, like so:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:recyclerview-v7:23.1.1'
    compile 'com.android.support:cardview-v7:23.1.1'
}

HelloActivity.java

HelloActivity.java

package com.formagrid.hellotest;

import android.app.Activity;
import android.os.Bundle;
import android.support.v7.widget.CardView;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.List;

public class HelloActivity extends Activity {

    private RecyclerView mRecyclerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
        mRecyclerView.setAdapter(new HelloAdapter());
        DefaultItemAnimator animator = new DefaultItemAnimator() {
            @Override
            public boolean canReuseUpdatedViewHolder(RecyclerView.ViewHolder viewHolder) {
                return true;
            }
        };
        mRecyclerView.setItemAnimator(animator);
    }

    private static class HelloAdapter extends RecyclerView.Adapter<HelloAdapter.HelloViewHolder> {

        public class HelloViewHolder extends RecyclerView.ViewHolder {

            public TextView textView;

            public HelloViewHolder(CardView cardView) {
                super(cardView);
                textView = (TextView) cardView.findViewById(R.id.text_view);
            }

        }

        @Override
        public HelloViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            CardView cardView = (CardView) LayoutInflater.from(parent.getContext()).inflate(
                    R.layout.card_item, parent, false);
            return new HelloViewHolder(cardView);
        }

        @Override
        public void onBindViewHolder(HelloViewHolder holder, int position) {
            bind(holder);
        }

        @Override
        public void onBindViewHolder(HelloViewHolder holder, int position, List<Object> payload) {
            Log.d("butt", "payload " + payload.toString());
            bind(holder);
        }

        @Override
        public int getItemCount() {
            return 20;
        }

        private void bind(final HelloViewHolder holder) {
            holder.textView.setText("item " + holder.getAdapterPosition());
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    final int position = holder.getAdapterPosition();
                    Log.d("butt", "click " + position);
                    HelloAdapter.this.notifyItemChanged(position, "payload " + position);
                }
            });
        }

    }

}

activity_main.xml

activity_main.xml

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".HelloActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</RelativeLayout>

card_item.xml

card_item.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="100dip"
    android:layout_margin="5dip"
    card_view:cardElevation="5dip">

    <TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</android.support.v7.widget.CardView>

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