應用場景：
在App開發中，對於信息的獲取與演示。不可能所有將其獲取與演示。為了在用戶使用中，給予用戶以友好、方便的用戶體驗，以滑動、下拉的效果動態載入數據的要求就會出現。為此，該效果功能就須要應用到所須要的展示頁面中。
知識點介紹：
本文主要依據開源項目android-pulltorefresh展開介紹。android-pulltorefresh
【一個強大的拉動刷新開源項目，支持各種控件下拉刷新 ListView、ViewPager、WevView、ExpandableListView、GridView、(Horizontal )ScrollView、Fragment上下左右拉動刷新，比以下johannilsson那個僅僅支持ListView的強大的多。而且他實現的下拉刷新ListView在item不足一屏情況下也不會顯示刷新提示，體驗更好。
】
項目地址：
https://github.com/chrisbanes/Android-PullToRefresh
Demo地址：
https://github.com/Trinea/TrineaDownload/blob/master/pull-to-refreshview-demo.apk?raw=true
使用方式：
第二步：在res/values下新建attrs.xml
<?第三步：將所須要的圖片文件放入對應的目錄以下，所用的圖片文件有：xml version="1.0" encoding="utf-8"?
> <resources> <declare-styleable name="PullToRefresh"> <attr name="mode" format="reference" > <flag name="pullDownFromTop" value="0x1" /> <flag name="pullUpFromBottom" value="0x2" /> <flag name="both" value="0x3" /> </attr> </declare-styleable> </resources> srings.xml <?xml version="1.0" encoding="utf-8"?
> <resources> <string name="app_name">SampleDemo</string> <string name="action_settings">Settings</string> <string name="pull_to_refresh_pull_down_label">滑動刷新</string> <string name="pull_to_refresh_release_label">釋放刷新</string> <string name="pull_to_refresh_refreshing_label">載入中</string> <string name="pull_to_refresh_tap_label">點擊刷新</string> </resources>
1、導入或將開源項目android-pulltorefresh中須要的類文件(.java)，增加到自己的項目中的指定包內。
該演示用例涉及的類文件為：
【library\src\com\handmark\pulltorefresh\library】
PullToRefreshAdapterViewBase.java
PullToRefreshBase.java
PullToRefreshListView.java
【library\src\com\handmark\pulltorefresh\library\internal】
EmptyViewMethodAccessor.java
LoadingLayout.java
2、構建自己所須要的類文件(.java)。
import java.util.LinkedList;
import com.example.sampledemo.view.PullToRefreshListView;
import android.os.AsyncTask;
import android.widget.BaseAdapter;
public class PullTask extends AsyncTask<Void, Void, String>{
private PullToRefreshListView pullToRefreshListView; //實現下拉刷新與上拉載入的ListView
private int pullState; //記錄推斷。上拉與下拉動作
private BaseAdapter baseAdapter; //ListView適配器，用於提醒ListView數據已經更新
private LinkedList<String> linkedList;
public PullTask(PullToRefreshListView pullToRefreshListView, int pullState,
BaseAdapter baseAdapter, LinkedList<String> linkedList) {
this.pullToRefreshListView = pullToRefreshListView;
this.pullState = pullState;
this.baseAdapter = baseAdapter;
this.linkedList = linkedList;
}
@Override
protected String doInBackground(Void... params) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
return "StringTest";
}
@Override
protected void onPostExecute(String result) {
if(pullState == 1) {//name="pullDownFromTop" value="0x1" 下拉
linkedList.addFirst("頂部數據");
}
if(pullState == 2) {//name="pullUpFromBottom" value="0x2" 上拉
linkedList.addLast("底部數據");
}
baseAdapter.notifyDataSetChanged();
pullToRefreshListView.onRefreshComplete();
super.onPostExecute(result);
}
}
【PullAdapter.java】
import java.util.LinkedList;
import com.example.sampledemo.R;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
public class PullAdapter extends BaseAdapter {
private LinkedList<String> linkedList;
private LayoutInflater mInflater;
public PullAdapter(LinkedList<String> linkedList, Context context) {
mInflater = LayoutInflater.from(context);
this.linkedList = linkedList;
}
@Override
public int getCount() {
return linkedList.size();
}
@Override
public Object getItem(int position) {
return linkedList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder=null;
if (convertView == null) {
holder = new ViewHolder();
convertView = mInflater.inflate(R.layout.layout_main_listitem, null);
holder.textView = (TextView) convertView.findViewById(R.id.textView);
convertView.setTag(holder);
}else {
holder = (ViewHolder) convertView.getTag();
}
if(linkedList.size()>0){
final String dataStr = linkedList.get(position);
holder.textView.setText(dataStr);
}
return convertView;
}
private static class ViewHolder {
TextView textView; //數據顯示區域
}
}
3、為PullAdapter.java 設計布局文件layout_main_listitem.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#FFFFFF" android:orientation="vertical" > <TextView android:id="@+id/textView" android:textColor="#99CC66" android:textSize="18dp" android:layout_marginTop="4dp" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="left" /> </LinearLayout>
滑動時出現提醒布局文件pull_to_refresh_header.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingTop="10dp"
android:paddingBottom="10dip">
<TextView
android:id="@+id/pull_to_refresh_text"
android:text="@string/pull_to_refresh_pull_down_label"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textStyle="bold"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true" />
<ProgressBar
android:id="@+id/pull_to_refresh_progress"
android:indeterminate="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="30dip"
android:layout_marginRight="20dip"
android:visibility="gone"
android:layout_centerVertical="true"
style="?android:attr/progressBarStyleSmall" />
<ImageView
android:id="@+id/pull_to_refresh_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="30dip"
android:layout_marginRight="20dip"
android:layout_centerVertical="true" />
</RelativeLayout>
MainActivity.java 主布局文件activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:cp="http://schemas.android.com/apk/res/com.example.sampledemo"
android:layout_width="match_parent"
android:background="#FFFFFF"
android:layout_height="match_parent">
<com.example.sampledemo.view.PullToRefreshListView
android:id="@+id/pullrefresh"
android:background="#FFFFFF"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:divider="@android:color/black"
android:dividerHeight="0.1dip"
android:cacheColorHint="#00000000"
cp:mode="both">
</com.example.sampledemo.view.PullToRefreshListView>
</RelativeLayout>
4、編寫MainActivity.java
import java.util.Arrays;
import java.util.LinkedList;
import com.example.sampledemo.view.PullToRefreshBase.OnRefreshListener;
import com.example.sampledemo.view.PullToRefreshListView;
import com.example.sampledemo.view.adapter.PullAdapter;
import com.example.sampledemo.view.task.PullTask;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.app.Activity;
/**
* @ClassName MainActivity.java
* @Author MaHaochen
* @Date 2014-4-30 15:56:47
*/
public class MainActivity extends Activity {
private LinkedList<String> mListItems;
private PullToRefreshListView mPullRefreshListView;
private ArrayAdapter<String> mAdapter;
private ListView mListView;
private PullAdapter pullAdapter;
private String[] mStrings = { "初始數據01","初始數據02","初始數據03","初始數據04","初始數據05"
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
}
private void initViews() {
mPullRefreshListView = (PullToRefreshListView) findViewById(R.id.pullrefresh);
mPullRefreshListView.setOnRefreshListener(mOnrefreshListener);
mListView = mPullRefreshListView.getRefreshableView();
mListItems = new LinkedList<String>();
mListItems.addAll(Arrays.asList(mStrings));
pullAdapter = new PullAdapter(mListItems, MainActivity.this);
mListView.setAdapter(pullAdapter);
}
OnRefreshListener mOnrefreshListener = new OnRefreshListener() {
public void onRefresh() {
PullTask pullTask = new PullTask(mPullRefreshListView,
mPullRefreshListView.getRefreshType(), pullAdapter, mListItems);
pullTask.execute();
}
};
}