[Android] Simple Paging ListView

前言:

ListView在Android手機是一個常用的UI設計，使用起來也相當方便，但是當大量資料存放到ListView時，為了有良好的使用者體驗，會考慮分批載入資料的處理方式，這裡稱為Paging。
本文提供一個最陽春的範例，說明Paging的效果。

成果:

程式碼:

	<?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: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="com.chengyu.paginglistview.MainActivity">
	<ListView
	android:id="@+id/lv"
	android:layout_width="match_parent"
	android:layout_height="match_parent" />
	</RelativeLayout>

view raw activity_main.xml hosted with ❤ by GitHub

	package com.chengyu.paginglistview;
	import android.app.Activity;
	import android.os.Bundle;
	import android.widget.AbsListView;
	import android.widget.ListView;
	import android.widget.Toast;
	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.Map;
	public class MainActivity extends Activity implements AbsListView.OnScrollListener {
	private ListView list = null;
	private int page = 0;
	private int total = 100; // assume that we have 100 data.
	private boolean isLoading = false;
	private ArrayList<Map<String, String>> data = null;
	private PagingListAdapter mPLAdapter;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);
	list = (ListView) findViewById(R.id.lv);
	data = new ArrayList<Map<String, String>>(); // data
	mPLAdapter = new PagingListAdapter(this, data);
	list.setAdapter(mPLAdapter);
	list.setOnScrollListener(this);
	//load data
	nextPage();
	//
	}
	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
	}
	@Override
	public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
	if (totalItemCount >0 && list != null) {
	int lastPosition = list.getLastVisiblePosition();
	if (lastPosition + 1 == totalItemCount && data.size() < total) {
	// loading
	nextPage();
	}
	}
	}
	private void nextPage() {
	if (!isLoading) {
	Toast.makeText(MainActivity.this, "Loading...", Toast.LENGTH_SHORT).show();
	for (int i=0; i<20; i++) {
	Map<String, String> addData = new HashMap<String, String>();
	addData.put("msg1", String.valueOf(data.size()) + ". msg1");
	addData.put("msg2", String.valueOf(data.size()) + ". msg2");
	data.add(addData);
	}
	isLoading = false;
	mPLAdapter.refreshData(data);
	}
	}
	}

view raw MainActivity.java hosted with ❤ by GitHub

	package com.chengyu.paginglistview;
	import android.content.Context;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.widget.BaseAdapter;
	import android.widget.TextView;
	import java.util.ArrayList;
	import java.util.Map;
	/**
	* Created by chengyu on 2016/02/05.
	*/
	class PagingListAdapter extends BaseAdapter {
	private ArrayList<Map<String, String>> data = null;
	private Context context = null;
	private LayoutInflater inflater;
	private class ViewHolder {
	TextView tv1;
	TextView tv2;
	}
	public PagingListAdapter(Context context, ArrayList<Map<String, String>> data) {
	this.data = data;
	this.context = context;
	}
	@Override
	public int getCount() {
	return (data == null) ? 0 : data.size();
	}
	@Override
	public Object getItem(int position) {
	return (data == null) ? null : data.get(position);
	}
	@Override
	public long getItemId(int position) {
	return position;
	}
	@Override
	public boolean isEnabled(int position) {
	return true;
	}
	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
	View view = convertView;
	final ViewHolder holder;
	if (view == null) {
	inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
	view = inflater.inflate(R.layout.list_item, null);
	holder = new ViewHolder();
	holder.tv1 = (TextView) view.findViewById(R.id.list_item_tv1);
	holder.tv2 = (TextView) view.findViewById(R.id.list_item_tv2);
	view.setTag(holder);
	} else {
	holder = (ViewHolder) view.getTag();
	}
	holder.tv1.setText(data.get(position).get("msg1"));
	holder.tv2.setText(data.get(position).get("msg2"));
	return view;
	}
	/**
	* refresh data
	* @param newData
	*/
	public void refreshData(ArrayList<Map<String, String>> newData) {
	this.data = newData;
	this.notifyDataSetChanged();
	}
	}

view raw PagingListAdapter.java hosted with ❤ by GitHub