Android 仿新浪微博的ListView下拉更新功能
openkk
13年前
由于最近做的项目中也用到了这个功能，今天刚好实现了下，就趁现在有时间写篇博客分享下。在做的时候也参考了下别人的代码，毕竟站在巨人的肩膀上才会是自己更加强大。哈哈！先看看新浪的下拉更新是什么样的吧！
OK，今天我们要实现的就是上面的下拉刷新功能。
首先实现下拉刷新的布局文件 layout/head.xml
<?xml version="1.0" encoding="utf-8"?> <!-- ListView的头部 --> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="#ffffff" > <!-- 内容 --> <RelativeLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:id="@+id/head_contentLayout" android:paddingLeft="30dp" > <!-- 箭头图像、进度条 --> <FrameLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_centerVertical="true" > <!-- 箭头 --> <ImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:src="@drawable/arrow_down" android:id="@+id/head_arrowImageView" /> <!-- 进度条 --> <ProgressBar android:layout_width="wrap_content" android:layout_height="wrap_content" style="?android:attr/progressBarStyleSmall" android:layout_gravity="center" android:id="@+id/head_progressBar" android:visibility="gone" /> </FrameLayout> <!-- 提示、最近更新 --> <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerHorizontal="true" android:orientation="vertical" android:gravity="center_horizontal" > <!-- 提示 --> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="下拉刷新" android:textSize="15dp" android:id="@+id/head_tipsTextView" /> <!-- 最近更新 --> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/head_lastUpdatedTextView" android:text="上次更新" android:textSize="12dp" /> </LinearLayout> </RelativeLayout> </LinearLayout>然后设置item的布局模板item.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="wrap_content" android:gravity="center_vertical" android:background="#ffffff" android:orientation="horizontal" > <ImageView android:id="@+id/imageView_item" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="10dp" android:src="@drawable/ic_launcher" /> <TextView android:id="@+id/textView_item" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="10dp" android:text="TextView" /> </LinearLayout>接下来是main.xml布局：
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <cn.com.karl.list.MyListView android:layout_width="fill_parent" android:layout_height="fill_parent" android:id="@+id/listView" /> </LinearLayout>这里的MyListView是我们自定义的ListView，因为顶部的下拉刷新系统的ListView不能够实现，所以我们需要自定义ListView。
布局文件搞定，下面看下自定义的MyListView：
package cn.com.karl.list; import java.text.SimpleDateFormat; import java.util.Date; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.LayoutInflater; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.view.animation.LinearInterpolator; import android.view.animation.RotateAnimation; import android.widget.AbsListView; import android.widget.BaseAdapter; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.AbsListView.OnScrollListener; import android.widget.ProgressBar; import android.widget.TextView; public class MyListView extends ListView implements OnScrollListener { private static final String TAG = "listview"; private final static int RELEASE_To_REFRESH = 0; private final static int PULL_To_REFRESH = 1; private final static int REFRESHING = 2; private final static int DONE = 3; private final static int LOADING = 4; // 实际的padding的距离与界面上偏移距离的比例 private final static int RATIO = 3; private LayoutInflater inflater; private LinearLayout headView; private TextView tipsTextview; private TextView lastUpdatedTextView; private ImageView arrowImageView; private ProgressBar progressBar; private RotateAnimation animation; private RotateAnimation reverseAnimation; // 用于保证startY的值在一个完整的touch事件中只被记录一次 private boolean isRecored; private int headContentWidth; private int headContentHeight; private int startY; private int firstItemIndex; private int state; private boolean isBack; private OnRefreshListener refreshListener; private boolean isRefreshable; public MyListView(Context context) { super(context); init(context); } public MyListView(Context context, AttributeSet attrs) { super(context, attrs); init(context); } private void init(Context context) { //setCacheColorHint(context.getResources().getColor(R.color.transparent)); inflater = LayoutInflater.from(context); headView = (LinearLayout) inflater.inflate(R.layout.head, null); arrowImageView = (ImageView) headView .findViewById(R.id.head_arrowImageView); arrowImageView.setMinimumWidth(70); arrowImageView.setMinimumHeight(50); progressBar = (ProgressBar) headView .findViewById(R.id.head_progressBar); tipsTextview = (TextView) headView.findViewById(R.id.head_tipsTextView); lastUpdatedTextView = (TextView) headView .findViewById(R.id.head_lastUpdatedTextView); measureView(headView); headContentHeight = headView.getMeasuredHeight(); headContentWidth = headView.getMeasuredWidth(); headView.setPadding(0, -1 * headContentHeight, 0, 0); headView.invalidate(); Log.v("size", "width:" + headContentWidth + " height:" + headContentHeight); addHeaderView(headView, null, false); setOnScrollListener(this); animation = new RotateAnimation(0, -180, RotateAnimation.RELATIVE_TO_SELF, 0.5f, RotateAnimation.RELATIVE_TO_SELF, 0.5f); animation.setInterpolator(new LinearInterpolator()); animation.setDuration(250); animation.setFillAfter(true); reverseAnimation = new RotateAnimation(-180, 0, RotateAnimation.RELATIVE_TO_SELF, 0.5f, RotateAnimation.RELATIVE_TO_SELF, 0.5f); reverseAnimation.setInterpolator(new LinearInterpolator()); reverseAnimation.setDuration(200); reverseAnimation.setFillAfter(true); state = DONE; isRefreshable = false; } public void onScroll(AbsListView arg0, int firstVisiableItem, int arg2, int arg3) { firstItemIndex = firstVisiableItem; } public void onScrollStateChanged(AbsListView arg0, int arg1) { } public boolean onTouchEvent(MotionEvent event) { if (isRefreshable) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: if (firstItemIndex == 0 && !isRecored) { isRecored = true; startY = (int) event.getY(); Log.v(TAG, "在down时候记录当前位置‘"); } break; case MotionEvent.ACTION_UP: if (state != REFRESHING && state != LOADING) { if (state == DONE) { // 什么都不做 } if (state == PULL_To_REFRESH) { state = DONE; changeHeaderViewByState(); Log.v(TAG, "由下拉刷新状态，到done状态"); } if (state == RELEASE_To_REFRESH) { state = REFRESHING; changeHeaderViewByState(); onRefresh(); Log.v(TAG, "由松开刷新状态，到done状态"); } } isRecored = false; isBack = false; break; case MotionEvent.ACTION_MOVE: int tempY = (int) event.getY(); if (!isRecored && firstItemIndex == 0) { Log.v(TAG, "在move时候记录下位置"); isRecored = true; startY = tempY; } if (state != REFRESHING && isRecored && state != LOADING) { // 保证在设置padding的过程中，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动 // 可以松手去刷新了 if (state == RELEASE_To_REFRESH) { setSelection(0); // 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步 if (((tempY - startY) / RATIO < headContentHeight) && (tempY - startY) > 0) { state = PULL_To_REFRESH; changeHeaderViewByState(); Log.v(TAG, "由松开刷新状态转变到下拉刷新状态"); } // 一下子推到顶了 else if (tempY - startY <= 0) { state = DONE; changeHeaderViewByState(); Log.v(TAG, "由松开刷新状态转变到done状态"); } // 往下拉了，或者还没有上推到屏幕顶部掩盖head的地步 else { // 不用进行特别的操作，只用更新paddingTop的值就行了 } } // 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态 if (state == PULL_To_REFRESH) { setSelection(0); // 下拉到可以进入RELEASE_TO_REFRESH的状态 if ((tempY - startY) / RATIO >= headContentHeight) { state = RELEASE_To_REFRESH; isBack = true; changeHeaderViewByState(); Log.v(TAG, "由done或者下拉刷新状态转变到松开刷新"); } // 上推到顶了 else if (tempY - startY <= 0) { state = DONE; changeHeaderViewByState(); Log.v(TAG, "由DOne或者下拉刷新状态转变到done状态"); } } // done状态下 if (state == DONE) { if (tempY - startY > 0) { state = PULL_To_REFRESH; changeHeaderViewByState(); } } // 更新headView的size if (state == PULL_To_REFRESH) { headView.setPadding(0, -1 * headContentHeight + (tempY - startY) / RATIO, 0, 0); } // 更新headView的paddingTop if (state == RELEASE_To_REFRESH) { headView.setPadding(0, (tempY - startY) / RATIO - headContentHeight, 0, 0); } } break; } } return super.onTouchEvent(event); } // 当状态改变时候，调用该方法，以更新界面 private void changeHeaderViewByState() { switch (state) { case RELEASE_To_REFRESH: arrowImageView.setVisibility(View.VISIBLE); progressBar.setVisibility(View.GONE); tipsTextview.setVisibility(View.VISIBLE); lastUpdatedTextView.setVisibility(View.VISIBLE); arrowImageView.clearAnimation(); arrowImageView.startAnimation(animation); tipsTextview.setText("松开刷新"); Log.v(TAG, "当前状态，松开刷新"); break; case PULL_To_REFRESH: progressBar.setVisibility(View.GONE); tipsTextview.setVisibility(View.VISIBLE); lastUpdatedTextView.setVisibility(View.VISIBLE); arrowImageView.clearAnimation(); arrowImageView.setVisibility(View.VISIBLE); // 是由RELEASE_To_REFRESH状态转变来的 if (isBack) { isBack = false; arrowImageView.clearAnimation(); arrowImageView.startAnimation(reverseAnimation); tipsTextview.setText("下拉刷新"); } else { tipsTextview.setText("下拉刷新"); } Log.v(TAG, "当前状态，下拉刷新"); break; case REFRESHING: headView.setPadding(0, 0, 0, 0); progressBar.setVisibility(View.VISIBLE); arrowImageView.clearAnimation(); arrowImageView.setVisibility(View.GONE); tipsTextview.setText("正在刷新..."); lastUpdatedTextView.setVisibility(View.VISIBLE); Log.v(TAG, "当前状态,正在刷新..."); break; case DONE: headView.setPadding(0, -1 * headContentHeight, 0, 0); progressBar.setVisibility(View.GONE); arrowImageView.clearAnimation(); arrowImageView.setImageResource(R.drawable.arrow_down); tipsTextview.setText("下拉刷新"); lastUpdatedTextView.setVisibility(View.VISIBLE); Log.v(TAG, "当前状态，done"); break; } } public void setonRefreshListener(OnRefreshListener refreshListener) { this.refreshListener = refreshListener; isRefreshable = true; } public interface OnRefreshListener { public void onRefresh(); } public void onRefreshComplete() { state = DONE; SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月dd日 HH:mm"); String date=format.format(new Date()); lastUpdatedTextView.setText("最近更新:" + date); changeHeaderViewByState(); } private void onRefresh() { if (refreshListener != null) { refreshListener.onRefresh(); } } // 此方法直接照搬自网络上的一个下拉刷新的demo，此处是“估计”headView的width以及height private void measureView(View child) { ViewGroup.LayoutParams p = child.getLayoutParams(); if (p == null) { p = new ViewGroup.LayoutParams( ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT); } int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width); int lpHeight = p.height; int childHeightSpec; if (lpHeight > 0) { childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY); } else { childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); } child.measure(childWidthSpec, childHeightSpec); } public void setAdapter(BaseAdapter adapter) { SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月dd日 HH:mm"); String date=format.format(new Date()); lastUpdatedTextView.setText("最近更新:" + date); super.setAdapter(adapter); } }最后在MainActivity中添加内容： public class MainActivity extends Activity { private LinkedList<String> data; private BaseAdapter adapter; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); data = new LinkedList<String>(); for(int i=0;i<10;i++){ data.add(String.valueOf(i)); } final MyListView listView = (MyListView) findViewById(R.id.listView); adapter = new BaseAdapter() { public View getView(int position, View convertView, ViewGroup parent) { convertView=LayoutInflater.from(getApplicationContext()).inflate(R.layout.item, null); TextView textView = (TextView) convertView.findViewById(R.id.textView_item); textView.setText(data.get(position)); return convertView; } public long getItemId(int position) { return position; } public Object getItem(int position) { return data.get(position); } public int getCount() { return data.size(); } }; listView.setAdapter(adapter); listView.setonRefreshListener(new OnRefreshListener() { public void onRefresh() { new AsyncTask<Void, Void, Void>() { protected Void doInBackground(Void... params) { try { Thread.sleep(1000); } catch (Exception e) { e.printStackTrace(); } data.addFirst("刷新后的内容"); return null; } @Override protected void onPostExecute(Void result) { adapter.notifyDataSetChanged(); listView.onRefreshComplete(); } }.execute(null); } }); } } 运行效果： 
