Android開源項目pulltorefresh分析與簡單使用

在Android開發中有時我們需要訪問網路即時重新整理資料，比如QQ好友線上狀態最新資訊，QQ空間需要顯示更多的社交動向更新資訊，EOE論壇用戶端顯示更多的文章文章資訊等。android-pulltorefresh開源項目提供一個向下滑動即重新整理列表的功能，將該項目稍作修改即可應用到自己的項目中。

 

1.

 

2.工程組成

PullToRefreshListView.java

OnRefreshListener 監聽重新整理操作的介面 ，onRefresh()重新整理函數 在列表頭部顯示進行中的重新整理操作進度條

onRefreshComplete() 重新整理操作完成後，恢複列表常態

上述類和介面的具體實現：

 

public class PullToRefreshListView extends ListView implements OnScrollListener{  /**Interface definition for a callback to be invoked when list should be refreshed.     */    public interface OnRefreshListener {        /**         * Called when the list should be refreshed.         * 

* A call to {@link PullToRefreshListView #onRefreshComplete()} is expected to indicate that the refresh has completed. */ public void onRefresh(); } /** * Resets the list to a normal state after a refresh. * @param lastUpdated Last updated at. */ public void onRefreshComplete(CharSequence lastUpdated) { setLastUpdated(lastUpdated); onRefreshComplete(); } /** * Resets the list to a normal state after a refresh. */ public void onRefreshComplete() { Log.d(TAG, onRefreshComplete); resetHeader(); // If refresh view is visible when loading completes, scroll down to // the next item. if (getFirstVisiblePosition() == 0) { invalidateViews(); setSelection(1); } } }

 

pull_to_refresh_header.xml

PullToRefreshListView頭部 顯示重新整理進度條資訊 ，在 PullToRefreshListView.java調用下面的語句將該子布局添加到列表頂部

private LayoutInflater mInflater;

private RelativeLayout mRefreshView;

mInflater = (LayoutInflater) context.getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
//header part of PullToRefreshListView
mRefreshView = (RelativeLayout) mInflater.inflate(R.layout.pull_to_refresh_header, this, false);

//add header part to the ListView
addHeaderView(mRefreshView);

PullToRefreshActivity.java (MainActivity)

pull_to_refresh.xml

 

註：

LiveActivity本身繼承了關於List操作的眾多介面，我們可以方便的重寫這些操作中需要的方法來實現自己需要的功能。如果要用ListActivity，則 Activity的Layout檔案中必須包括一個（只能一個）ListView，且ListView的id= @id/android:list。

 

 

3.PullToRefreshActivity.java

重新整理額外的列表資料String mExtras[]，當額外列表資料顯示完畢時，不再進行重新整理操作。

例如下面這個例子重新整理三次以後，就沒有額外需要顯示的資料，拉松列表進行重新整理操作將提示“No More Messages”

 

package com.markupartist.android.example.pulltorefresh;import java.util.Arrays;import java.util.LinkedList;import android.annotation.SuppressLint;import android.app.ListActivity;import android.os.AsyncTask;import android.os.Bundle;import android.widget.ArrayAdapter;import android.widget.Toast;import com.markupartist.android.widget.PullToRefreshListView;import com.markupartist.android.widget.PullToRefreshListView.OnRefreshListener;@SuppressLint(NewApi)public class PullToRefreshActivity extends ListActivity {        private LinkedList mListItems;    int count = 0;        /** Called when the activity is first created. */    @SuppressLint(NewApi)@Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.pull_to_refresh);                // Set a listener to be invoked when the list should be refreshed.        ((PullToRefreshListView) getListView()).setOnRefreshListener(new OnRefreshListener() {            @Override            public void onRefresh() {                // Do work to refresh the list here.            if(count < mExtras.length)            new GetDataTask().execute(count++);            else{            Toast.makeText(getApplicationContext(), No More Messages,             Toast.LENGTH_LONG).show();                        //Resets the list to a normal state after a refresh            ((PullToRefreshListView) getListView()).onRefreshComplete();            }                        }        });        mListItems = new LinkedList();        mListItems.addAll(Arrays.asList(mStrings));        ArrayAdapter adapter = new ArrayAdapter(this,                android.R.layout.simple_list_item_1, mListItems);        setListAdapter(adapter);    }    private class GetDataTask extends AsyncTask {        private int count;            @Override        protected String[] doInBackground(Integer... params) {        count = params[0];        // Simulates a background job.            try {                Thread.sleep(2000);            } catch (InterruptedException e) {                ;            }            return mStrings;        }        @SuppressLint(NewApi)@Override        protected void onPostExecute(String[] result) {           // mListItems.addFirst(Added after refresh...);        mListItems.addFirst(mExtras[count]);            // Call onRefreshComplete when the list has been refreshed.            ((PullToRefreshListView) getListView()).onRefreshComplete();           // super.onPostExecute(result);        }    }    private String[] mStrings = {            Abbaye de Belloc, Abbaye du Mont des Cats, Abertam,            Abondance, Ackawi, Acorn, Adelost, Affidelice au Chablis,            Afuega'l Pitu, Airag, Airedale, Aisy Cendre,            Allgauer Emmentaler};        private String[] mExtras = {extra1,extra2,extra3};    }