Android开发(50) 使用 SwipeRefreshLayout实现下拉刷新

概述

谷歌官方推出了SwipeRefreshLayout 来实现下拉刷新的效果。对比以前我们常用的 pull-to-refesh ，这个方案显得更加的简单方便。

关联项目引用（管理依赖）

在你的 应用级别的 build.gradle 中添加如下：

compile 'com.android.support:appcompat-v7:23.0.0'
compile 'com.android.support:support-v4:23.0.0'

编写布局(Layout)

在代码中 添加监听器处理事件

public void setOnRefreshListener(OnRefreshListener listener)

完整代码

package demo.vir56k.swiperefreshlayoutdemo;

import android.os.Handler;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private static final int REFRESH_COMPLETE = 0X110;
    private SwipeRefreshLayout mSwipeLayout;
    private ListView mListView;
    private ArrayAdapter mAdapter;
    private List mDatas;

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

        mListView = (ListView) findViewById(R.id.listview1);
        mSwipeLayout = (SwipeRefreshLayout) findViewById(R.id.swipeRefreshLayout1);

        mDatas = creatDataSource();
        mSwipeLayout.setOnRefreshListener(mSwipeRefreshLayoutOnRefreshListener);
        mSwipeLayout.setColorSchemeResources(android.R.color.holo_blue_bright, android.R.color.holo_green_light,
                android.R.color.holo_orange_light, android.R.color.holo_red_light);
        mAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, mDatas);
        mListView.setAdapter(mAdapter);
    }

    private List creatDataSource() {
        mDatas = new ArrayList();
        for (int i = 0; i < 5; i++) {
            mDatas.add("item" + i);
        }
        return mDatas;
    }


    SwipeRefreshLayout.OnRefreshListener mSwipeRefreshLayoutOnRefreshListener = new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            mHandler.sendEmptyMessageDelayed(REFRESH_COMPLETE, 2000);
        }
    };

    private Handler mHandler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            switch (msg.what) {
                case REFRESH_COMPLETE:
                    List lst = new ArrayList();
                    for (int i = mDatas.size() + 3; i > mDatas.size(); i--) {
                        lst.add("item -" + i);
                    }
                    mDatas.addAll(0, lst);
                    mAdapter.notifyDataSetChanged();
                    mSwipeLayout.setRefreshing(false);
                    break;

            }
        }

        ;
    };
}

至此完成。

补充：

一种情形，遇到"SwipeRefreshLayout 的子控件不 直接是个listview 等，是个普通 relativewlayout 怎么办？"

解决方法：

继承 SwipeRefreshLayout 重写 canChildScrollUp 方法

代码：

/*
 * Copyright 2016, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.architecture.blueprints.todoapp.tasks;

import android.content.Context;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.AttributeSet;
import android.view.View;

/**
 * Extends {@link SwipeRefreshLayout} to support non-direct descendant scrolling views.
 * 

 * {@link SwipeRefreshLayout} works as expected when a scroll view is a direct child: it triggers
 * the refresh only when the view is on top. This class adds a way (@link #setScrollUpChild} to
 * define which view controls this behavior.
 */
public class ScrollChildSwipeRefreshLayout extends SwipeRefreshLayout {

    private View mScrollUpChild;

    public ScrollChildSwipeRefreshLayout(Context context) {
        super(context);
    }

    public ScrollChildSwipeRefreshLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean canChildScrollUp() {
        if (mScrollUpChild != null) {
            return ViewCompat.canScrollVertically(mScrollUpChild, -1);
        }
        return super.canChildScrollUp();
    }

    public void setScrollUpChild(View view) {
        mScrollUpChild = view;
    }
}