Android 仿新浪微博的ListView下拉更新功能
由于最近做的項目中也用到了這個功能，今天剛好實現了下，就趁現在有時間寫篇博客分享下。在做的時候也參考了下別人的代碼，畢竟站在巨人的肩膀上才會是自己更加強大。哈哈！先看看新浪的下拉更新是什么樣的吧！
OK，今天我們要實現的就是上面的下拉刷新功能。
首先實現下拉刷新的布局文件 layout/head.xml
<?xml version="1.0" encoding="utf-8"?> <!-- ListView的頭部 --> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="#ffffff" > <!-- 內容 --> <RelativeLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:id="@+id/head_contentLayout" android:paddingLeft="30dp" > <!-- 箭頭圖像、進度條 --> <FrameLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_centerVertical="true" > <!-- 箭頭 --> <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" /> <!-- 進度條 --> <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>然后設置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> 接下來是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> 這里的MyListView是我們自定義的ListView，因為頂部的下拉刷新系統的ListView不能夠實現，所以我們需要自定義ListView。
布局文件搞定，下面看下自定義的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;
// 實際的padding的距離與界面上偏移距離的比例
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;
// 用于保證startY的值在一個完整的touch事件中只被記錄一次
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時候記錄當前位置‘");
}
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, "由下拉刷新狀態，到done狀態");
}
if (state == RELEASE_To_REFRESH) {
state = REFRESHING;
changeHeaderViewByState();
onRefresh();
Log.v(TAG, "由松開刷新狀態，到done狀態");
}
}
isRecored = false;
isBack = false;
break;
case MotionEvent.ACTION_MOVE:
int tempY = (int) event.getY();
if (!isRecored && firstItemIndex == 0) {
Log.v(TAG, "在move時候記錄下位置");
isRecored = true;
startY = tempY;
}
if (state != REFRESHING && isRecored && state != LOADING) {
// 保證在設置padding的過程中，當前的位置一直是在head，否則如果當列表超出屏幕的話，當在上推的時候，列表會同時進行滾動
// 可以松手去刷新了
if (state == RELEASE_To_REFRESH) {
setSelection(0);
// 往上推了，推到了屏幕足夠掩蓋head的程度，但是還沒有推到全部掩蓋的地步
if (((tempY - startY) / RATIO < headContentHeight)
&& (tempY - startY) > 0) {
state = PULL_To_REFRESH;
changeHeaderViewByState();
Log.v(TAG, "由松開刷新狀態轉變到下拉刷新狀態");
}
// 一下子推到頂了
else if (tempY - startY <= 0) {
state = DONE;
changeHeaderViewByState();
Log.v(TAG, "由松開刷新狀態轉變到done狀態");
}
// 往下拉了，或者還沒有上推到屏幕頂部掩蓋head的地步
else {
// 不用進行特別的操作，只用更新paddingTop的值就行了
}
}
// 還沒有到達顯示松開刷新的時候,DONE或者是PULL_To_REFRESH狀態
if (state == PULL_To_REFRESH) {
setSelection(0);
// 下拉到可以進入RELEASE_TO_REFRESH的狀態
if ((tempY - startY) / RATIO >= headContentHeight) {
state = RELEASE_To_REFRESH;
isBack = true;
changeHeaderViewByState();
Log.v(TAG, "由done或者下拉刷新狀態轉變到松開刷新");
}
// 上推到頂了
else if (tempY - startY <= 0) {
state = DONE;
changeHeaderViewByState();
Log.v(TAG, "由DOne或者下拉刷新狀態轉變到done狀態");
}
}
// done狀態下
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);
}
// 當狀態改變時候，調用該方法，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("松開刷新");
Log.v(TAG, "當前狀態，松開刷新");
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狀態轉變來的
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, "當前狀態，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, "當前狀態,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, "當前狀態，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();
}
}
// 此方法直接照搬自網絡上的一個下拉刷新的demo，此處是“估計”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中添加內容： 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("刷新后的內容");
return null;
}
@Override
protected void onPostExecute(Void result) {
adapter.notifyDataSetChanged();
listView.onRefreshComplete();
}
}.execute(null);
}
});
}
} 運行效果：
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