安卓实现下拉刷新

 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:id="@+id/pull_to_refresh_head"
 4     android:layout_width="fill_parent"
 5     android:layout_height="60dip" >
 6     <LinearLayout
 7         android:layout_width="200dip"
 8         android:layout_height="60dip"
 9         android:layout_centerInParent="true"
10         android:orientation="horizontal" >
11         <RelativeLayout
12             android:layout_width="0dip"
13             android:layout_height="60dip"
14             android:layout_weight="3"
15             >
16             <ImageView 
17                 android:id="@+id/arrow"
18                 android:layout_width="wrap_content"
19                 android:layout_height="wrap_content"
20                 android:layout_centerInParent="true"
21                 android:src="@drawable/arrow"
22                 />
23             <ProgressBar 
24                 android:id="@+id/progress_bar"
25                 android:layout_width="30dip"
26                 android:layout_height="30dip"
27                 android:layout_centerInParent="true"
28                 android:visibility="gone"
29                 />
30         </RelativeLayout>
31         <LinearLayout
32             android:layout_width="0dip"
33             android:layout_height="60dip"
34             android:layout_weight="12"
35             android:orientation="vertical" >
36             <TextView
37                 android:id="@+id/description"
38                 android:layout_width="fill_parent"
39                 android:layout_height="0dip"
40                 android:layout_weight="1"
41                 android:gravity="center_horizontal|bottom"
42                 android:text="@string/pull_to_refresh" />
43             <TextView
44                 android:id="@+id/updated_at"
45                 android:layout_width="fill_parent"
46                 android:layout_height="0dip"
47                 android:layout_weight="1"
48                 android:gravity="center_horizontal|top"
49                 android:text="@string/updated_at" />
50         </LinearLayout>
51     </LinearLayout>
52 </RelativeLayout>

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <resources>
 3     <string name="app_name">PullToRefreshTest</string>
 4  <string name="pull_to_refresh">下拉可以刷新</string>
 5  <string name="release_to_refresh">释放立即刷新</string>
 6  <string name="refreshing">正在刷新…</string>
 7  <string name="not_updated_yet">暂未更新过</string>
 8  <string name="updated_at">上次更新于%1$s前</string>
 9  <string name="updated_just_now">刚刚更新</string>
10  <string name="time_error">时间有问题</string>
11 </resources>

  1 public class RefreshableView extends LinearLayout implements OnTouchListener {
  2 //下拉状态
  3  public static final int STATUS_PULL_TO_REFRESH = 0;
  4 //释放立即刷新状态
  5  public static final int STATUS_RELEASE_TO_REFRESH = 1
  6 //正在刷新状态
  7  public static final int STATUS_REFRESHING = 2;
  8 //刷新完成或未刷新状态
  9  public static final int STATUS_REFRESH_FINISHED = 3;
 10 //下拉头部回滚的速度
 11  public static final int SCROLL_SPEED = -20;
 12 //一分钟的毫秒值，用于判断上次的更新时间
 13  public static final long ONE_MINUTE = 60 * 1000;
 14 //一小时的毫秒值，用于判断上次的更新时间
 15  public static final long ONE_HOUR = 60 * ONE_MINUTE;
 16 //一天的毫秒值，用于判断上次的更新时间
 17  public static final long ONE_DAY = 24 * ONE_HOUR;
 18 //一月的毫秒值，用于判断上次的更新时间
 19  public static final long ONE_MONTH = 30 * ONE_DAY;
 20 //一年的毫秒值，用于判断上次的更新时间
 21  public static final long ONE_YEAR = 12 * ONE_MONTH;
 22 //上次更新时间的字符串常量，用于作为SharedPreferences的键值
 23  private static final String UPDATED_AT = "updated_at";
 24 //下拉刷新的回调接口
 25  private PullToRefreshListener mListener;
 26 //用于存储上次更新时间
 27  private SharedPreferences preferences;
 28 //下拉头的View
 29  private View header;
 30 //需要去下拉刷新的ListView
 31  private ListView listView;
 32 //刷新时显示的进度条
 33  private ProgressBar progressBar;
 34 //指示下拉和释放的箭头
 35  private ImageView arrow;
 36 //指示下拉和释放的文字描述
 37  private TextView description;
 38 //上次更新时间的文字描述
 39  private TextView updateAt;
 40 //下拉头的布局参数
 41  private MarginLayoutParams headerLayoutParams;
 42 //上次更新时间的毫秒值
 43  private long lastUpdateTime;
 44 //为了防止不同界面的下拉刷新在上次更新时间上互相有冲突，使用id来做区分
 45  private int mId = -1;
 46 //下拉头的高度
 47  private int hideHeaderHeight;
 48 //当前处理什么状态，可选值有STATUS_PULL_TO_REFRESH,STATUS_RELEASE_TO_REFRESH,STATUS_REFRESHING 和 STATUS_REFRESH_FINISHED
 49  private int currentStatus = STATUS_REFRESH_FINISHED;;
 50 //记录上一次的状态是什么，避免进行重复操作
 51  private int lastStatus = currentStatus;
 52 //手指按下时的屏幕纵坐标
 53  private float yDown;
 54 //在被判定为滚动之前用户手指可以移动的最大值。
 55  private int touchSlop;
 56 //是否已加载过一次layout，这里onLayout中的初始化只需加载一次
 57  private boolean loadOnce;
 58 //当前是否可以下拉，只有ListView滚动到头的时候才允许下拉
 59  private boolean ableToPull;
 60 
 61 //下拉刷新控件的构造函数，会在运行时动态添加一个下拉头的布局。
 62  public RefreshableView(Context context, AttributeSet attrs) {
 63   super(context, attrs);
 64   preferences = PreferenceManager.getDefaultSharedPreferences(context);
 65   header = LayoutInflater.from(context).inflate(R.layout.pull_to_refresh, null, true);
 66   progressBar = (ProgressBar) header.findViewById(R.id.progress_bar);
 67   arrow = (ImageView) header.findViewById(R.id.arrow);
 68    description = (TextView) header.findViewById(R.id.description);
 69    updateAt = (TextView) header.findViewById(R.id.updated_at);
 70    touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
 71    refreshUpdatedAtValue();
 72    setOrientation(VERTICAL);
 73    addView(header, 0);
 74   }
 75  
 76  //进行一些关键性的初始化操作，比如：将下拉头向上偏移进行隐藏，给ListView注册touch事件。
 77   protected void onLayout(boolean changed, int l, int t, int r, int b) {
 78    super.onLayout(changed, l, t, r, b);
 79    if (changed && !loadOnce) {
 80     hideHeaderHeight = -header.getHeight();
 81     headerLayoutParams = (MarginLayoutParams) header.getLayoutParams();
 82     headerLayoutParams.topMargin = hideHeaderHeight;
 83     listView = (ListView) getChildAt(1);
 84     listView.setOnTouchListener(this);
 85     loadOnce = true;
 86    }
 87   }
 88  
 89  //当ListView被触摸时调用，其中处理了各种下拉刷新的具体逻辑。
 90   public boolean onTouch(View v, MotionEvent event) {
 91    setIsAbleToPull(event);
 92    if (ableToPull) {
 93     switch (event.getAction()) {
 94     case MotionEvent.ACTION_DOWN:
 95      yDown = event.getRawY();
 96      break;
 97     case MotionEvent.ACTION_MOVE:
 98      float yMove = event.getRawY();
 99      int distance = (int) (yMove - yDown);
100  
101      // 如果手指是下滑状态，并且下拉头是完全隐藏的，就屏蔽下拉事件
102      if (distance <= 0 && headerLayoutParams.topMargin <= hideHeaderHeight) {
103       return false;
104      }
105      if (distance < touchSlop) {
106       return false;
107      }
108      if (currentStatus != STATUS_REFRESHING) {
109       if (headerLayoutParams.topMargin > 0) {
110        currentStatus = STATUS_RELEASE_TO_REFRESH;
111       } else {
112        currentStatus = STATUS_PULL_TO_REFRESH;
113       }
114  
115       // 通过偏移下拉头的topMargin值，来实现下拉效果
116       headerLayoutParams.topMargin = (distance / 2) + hideHeaderHeight;
117       header.setLayoutParams(headerLayoutParams);
118      }
119      break;
120     case MotionEvent.ACTION_UP:
121     default:
122      if (currentStatus == STATUS_RELEASE_TO_REFRESH) {
123  
124       // 松手时如果是释放立即刷新状态，就去调用正在刷新的任务
125       new RefreshingTask().execute();
126      } else if (currentStatus == STATUS_PULL_TO_REFRESH) {
127  
128       // 松手时如果是下拉状态，就去调用隐藏下拉头的任务
129       new HideHeaderTask().execute();
130      }
131      break;
132     }
133  
134     // 时刻记得更新下拉头中的信息
135     if (currentStatus == STATUS_PULL_TO_REFRESH
136       || currentStatus == STATUS_RELEASE_TO_REFRESH) {
137      updateHeaderView();
138  
139      // 当前正处于下拉或释放状态，要让ListView失去焦点，否则被点击的那一项会一直处于选中状态
140      listView.setPressed(false);
141      listView.setFocusable(false);
142      listView.setFocusableInTouchMode(false);
143      lastStatus = currentStatus;
144  
145      // 当前正处于下拉或释放状态，通过返回true屏蔽掉ListView的滚动事件
146      return true;
147     }
148    }
149    return false;
150   }
151  
152  //给下拉刷新控件注册一个监听器。
153  
154  //为了防止不同界面的下拉刷新在上次更新时间上互相有冲突， 请不同界面在注册下拉刷新监听器时一定要传入不同的id。
155   public void setOnRefreshListener(PullToRefreshListener listener, int id) {
156    mListener = listener;
157    mId = id;
158   }
159  
160  // 当所有的刷新逻辑完成后，记录调用一下，否则你的ListView将一直处于正在刷新状态。
161   public void finishRefreshing() {
162    currentStatus = STATUS_REFRESH_FINISHED;
163    preferences.edit().putLong(UPDATED_AT + mId, System.currentTimeMillis()).commit();
164    new HideHeaderTask().execute();
165   }
166  
167  //根据当前ListView的滚动状态来设定 {@link #ableToPull}的值，每次都需要在onTouch中第一个执行，这样可以判断出当前应该是滚动ListView，还是应该进行下拉。
168   private void setIsAbleToPull(MotionEvent event) {
169    View firstChild = listView.getChildAt(0);
170    if (firstChild != null) {
171     int firstVisiblePos = listView.getFirstVisiblePosition();
172     if (firstVisiblePos == 0 && firstChild.getTop() == 0) {
173      if (!ableToPull) {
174       yDown = event.getRawY();
175      }
176  
177      // 如果首个元素的上边缘，距离父布局值为0，就说明ListView滚动到了最顶部，此时应该允许下拉刷新
178      ableToPull = true;
179     } else {
180      if (headerLayoutParams.topMargin != hideHeaderHeight) {
181       headerLayoutParams.topMargin = hideHeaderHeight;
182       header.setLayoutParams(headerLayoutParams);
183      }
184      ableToPull = false;
185     }
186    } else {
187  
188     // 如果ListView中没有元素，也应该允许下拉刷新
189     ableToPull = true;
190    }
191   }
192  
193  //更新下拉头中的信息。
194   private void updateHeaderView() {
195    if (lastStatus != currentStatus) {
196     if (currentStatus == STATUS_PULL_TO_REFRESH) {
197      description.setText(getResources().getString(R.string.pull_to_refresh));
198      arrow.setVisibility(View.VISIBLE);
199      progressBar.setVisibility(View.GONE);
200      rotateArrow();
201     } else if (currentStatus == STATUS_RELEASE_TO_REFRESH) {
202      description.setText(getResources().getString(R.string.release_to_refresh));
203      arrow.setVisibility(View.VISIBLE);
204      progressBar.setVisibility(View.GONE);
205      rotateArrow();
206     } else if (currentStatus == STATUS_REFRESHING) {
207      description.setText(getResources().getString(R.string.refreshing));
208      progressBar.setVisibility(View.VISIBLE);
209      arrow.clearAnimation();
210      arrow.setVisibility(View.GONE);
211     }
212     refreshUpdatedAtValue();
213    }
214   }
215  
216  //根据当前的状态来旋转箭头。
217   private void rotateArrow() {
218    float pivotX = arrow.getWidth() / 2f;
219    float pivotY = arrow.getHeight() / 2f;
220    float fromDegrees = 0f;
221    float toDegrees = 0f;
222    if (currentStatus == STATUS_PULL_TO_REFRESH) {
223     fromDegrees = 180f;
224     toDegrees = 360f;
225    } else if (currentStatus == STATUS_RELEASE_TO_REFRESH) {
226     fromDegrees = 0f;
227     toDegrees = 180f;
228    }
229  
230    RotateAnimation animation = new RotateAnimation(fromDegrees, toDegrees, pivotX, pivotY);
231    animation.setDuration(100);
232    animation.setFillAfter(true);
233    arrow.startAnimation(animation);
234   }
235  
236  //刷新下拉头中上次更新时间的文字描述。
237   private void refreshUpdatedAtValue() {
238    lastUpdateTime = preferences.getLong(UPDATED_AT + mId, -1);
239    long currentTime = System.currentTimeMillis();
240    long timePassed = currentTime - lastUpdateTime;
241    long timeIntoFormat;
242    String updateAtValue;
243    if (lastUpdateTime == -1) {
244     updateAtValue = getResources().getString(R.string.not_updated_yet);
245    } else if (timePassed < 0) {
246     updateAtValue = getResources().getString(R.string.time_error);
247    } else if (timePassed < ONE_MINUTE) {
248     updateAtValue = getResources().getString(R.string.updated_just_now);
249    } else if (timePassed < ONE_HOUR) {
250     timeIntoFormat = timePassed / ONE_MINUTE;
251     String value = timeIntoFormat + "分钟";
252     updateAtValue = String.format(getResources().getString(R.string.updated_at), value);
253    } else if (timePassed < ONE_DAY) {
254     timeIntoFormat = timePassed / ONE_HOUR;
255     String value = timeIntoFormat + "小时";
256     updateAtValue = String.format(getResources().getString(R.string.updated_at), value);
257    } else if (timePassed < ONE_MONTH) {
258     timeIntoFormat = timePassed / ONE_DAY;
259     String value = timeIntoFormat + "天";
260     updateAtValue = String.format(getResources().getString(R.string.updated_at), value);
261    } else if (timePassed < ONE_YEAR) {
262     timeIntoFormat = timePassed / ONE_MONTH;
263     String value = timeIntoFormat + "个月";
264     updateAtValue = String.format(getResources().getString(R.string.updated_at), value);
265    } else {
266     timeIntoFormat = timePassed / ONE_YEAR;
267     String value = timeIntoFormat + "年";
268     updateAtValue = String.format(getResources().getString(R.string.updated_at), value);
269    }
270    updateAt.setText(updateAtValue);
271   }
272  
273  //正在刷新的任务，在此任务中会去回调注册进来的下拉刷新监听器。
274   class RefreshingTask extends AsyncTask<Void, Integer, Void> {
275    protected Void doInBackground(Void... params) {
276     int topMargin = headerLayoutParams.topMargin;
277     while (true) {
278      topMargin = topMargin + SCROLL_SPEED;
279      if (topMargin <= 0) {
280       topMargin = 0;
281       break;
282      }
283      publishProgress(topMargin);
284      sleep(10);
285     }
286     currentStatus = STATUS_REFRESHING;
287     publishProgress(0);
288     if (mListener != null) {
289      mListener.onRefresh();
290     }
291     return null;
292    }
293  
294    protected void onProgressUpdate(Integer... topMargin) {
295     updateHeaderView();
296     headerLayoutParams.topMargin = topMargin[0];
297     header.setLayoutParams(headerLayoutParams);
298    }
299   }
300  
301  //隐藏下拉头的任务，当未进行下拉刷新或下拉刷新完成后，此任务将会使下拉头重新隐藏。
302  
303   class HideHeaderTask extends AsyncTask<Void, Integer, Integer> {
304    protected Integer doInBackground(Void... params) {
305     int topMargin = headerLayoutParams.topMargin;
306     while (true) {
307      topMargin = topMargin + SCROLL_SPEED;
308      if (topMargin <= hideHeaderHeight) {
309       topMargin = hideHeaderHeight;
310       break;
311      }
312      publishProgress(topMargin);
313      sleep(10);
314     }
315     return topMargin;
316    }
317  
318    protected void onProgressUpdate(Integer... topMargin) {
319     headerLayoutParams.topMargin = topMargin[0];
320     header.setLayoutParams(headerLayoutParams);
321    }
322  
323    protected void onPostExecute(Integer topMargin) {
324     headerLayoutParams.topMargin = topMargin;
325     header.setLayoutParams(headerLayoutParams);
326     currentStatus = STATUS_REFRESH_FINISHED;
327    }
328   }
329  
330  //使当前线程睡眠指定的毫秒数。指定当前线程睡眠多久，以毫秒为单位
331   private void sleep(int time) {
332    try {
333     Thread.sleep(time);
334    } catch (InterruptedException e) {
335     e.printStackTrace();
336    }
337   }
338  
339  //下拉刷新的监听器，使用下拉刷新的地方应该注册此监听器来获取刷新回调。
340   public interface PullToRefreshListener {
341  
342  //刷新时会去回调此方法，在方法内编写具体的刷新逻辑。注意此方法是在子线程中调用的， 你可以不必另开线程来进行耗时操作。
343   void onRefresh();
344  }
345 }

 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     tools:context=".MainActivity" >
 6 
 7     <com.example.pulltorefreshtest.RefreshableView
 8         android:id="@+id/refreshable_view"
 9         android:layout_width="fill_parent"
10         android:layout_height="fill_parent" >
11 
12         <ListView
13             android:id="@+id/list_view"
14             android:layout_width="fill_parent"
15             android:layout_height="fill_parent" >
16         </ListView>
17 
18     </com.example.pulltorefreshtest.RefreshableView>
19 </RelativeLayout>

 1 public class MainActivity extends Activity {
 2  RefreshableView refreshableView;
 3  ListView listView;
 4  ArrayAdapter<String> adapter;
 5  String[] items = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L" };
 6 
 7  protected void onCreate(Bundle savedInstanceState) {
 8   super.onCreate(savedInstanceState);
 9   requestWindowFeature(Window.FEATURE_NO_TITLE);
10   setContentView(R.layout.activity_main);
11   refreshableView = (RefreshableView) findViewById(R.id.refreshable_view);
12   listView = (ListView) findViewById(R.id.list_view);
13   adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);
14   listView.setAdapter(adapter);
15   refreshableView.setOnRefreshListener(new PullToRefreshListener() {
16 
17    public void onRefresh() {
18     try {
19      Thread.sleep(3000);
20     } catch (InterruptedException e) {
21      e.printStackTrace();
22     }
23     refreshableView.finishRefreshing();
24    }
25   }, 0);
26  }
27 }