android – 需要一个关于RecyclerView.Adapter.notifyItemChanged(int position,Object payload)的例子

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

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

我不明白如何在此方法中使用第二个参数有效负载.我搜索过很多关于“有效载荷”的文件但是一切都很模糊.

所以,如果你知道这个方法,请给我一个明确的例子.非常感谢你.

解决方法:

查看演示该功能的示例代码.当点击位置位置的项目时,它是一个RecyclerView,它调用notifyItemChanged(位置,有效负载).您可以通过查找logcat语句来验证是否已调用onBindViewHolder(holder,position,payload).

确保您至少使用了支持库的23.1.1版,如下所示：

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

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中

<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

<?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>