Android listview 自动加载数据

实现ListView滑动到底部自动加载更多原理：监听ListView的滑动事件,判断ListView是否滑动到底部,然后去加载数据。
布局文件：activity_test_main.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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="cn.sizebook.activities.measure.userdefine.TestMainActivity">

<ListView
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="match_parent"></ListView>
</android.support.constraint.ConstraintLayout>
布局文件：item.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="match_parent"
android:layout_height="45dp"
android:textSize="16sp"
android:text="测试"
android:gravity="center_vertical"
android:id="@+id/tvContent"/>
</android.support.constraint.ConstraintLayout>Activity文件
package cn.sizebook.activities.measure.userdefine;

import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.TextView;

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

import cn.sizebook.R;

public class TestMainActivity extends AppCompatActivity {

private ListView listview;
private LayoutInflater inflater;
private MyAdapter adapter;
private List<String> contents;

private Handler handler = new Handler();
int lastItem;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test_main);
initData();
inflater = LayoutInflater.from(this);
listview = (ListView) findViewById(R.id.listview);
adapter = new MyAdapter();

listview.setAdapter(adapter);
//添加listview滚动监听
listview.setOnScrollListener(new AbsListView.OnScrollListener() {

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
if (view.getLastVisiblePosition() == view.getCount() - 1) {
loadData();
}
}
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
lastItem = firstVisibleItem + visibleItemCount - 1;
}
});
}

protected void loadData() {
load();
adapter.notifyDataSetChanged();

}

protected void load() {
int count = adapter.getCount() + 1;
for (int i = count; i < count + 20; i++) { //每次加载20条数据
contents.add("加载数据..." + i);
}
}

private void initData() {
contents = new ArrayList<String>();
for (int i = 1; i < 20; i++) {
contents.add("加载数据..." + i);
}
}

class MyAdapter extends BaseAdapter {
@Override
public int getCount() {
return contents.size();
}

@Override
public Object getItem(int position) {
return contents.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = inflater.inflate(R.layout.item, parent, false);
holder = new ViewHolder();
holder.tvContent = (TextView) convertView.findViewById(R.id.tvContent);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.tvContent.setText(contents.get(position));
return convertView;
}

class ViewHolder {
TextView tvContent;
}
}
}