Android实现ListView阻尼式（下拉回弹）效果
最近想模仿小米MIUI V5短信里面的一个功能——私密短信，它的入口在短信列表，列表往下拉到1/3左右，我用Eclipse上的工具截了图，包括该结构的布局，如下图：
从它的UI结构可以看出，用的是层叠结构，即将ListView和一个普通View（取名叫privateEntry）层叠在一起，ListView里面有四个数据项，第0项和第3项都是FrameLayout，应该分别是添加的HeaderView（搜索框）和FooterView，FooterView的用途应该是为了填充屏幕，挡住平时隐藏的那个普通View（取名叫privateEntry）。
下面是我自己写的代码，借鉴了网上的BounceScrollView写的BounceListView，实现后的效果没有小米的那么好，有待改进。
首先看BounceListView.java，这是主要实现代码：
package com.lee.listviewdemo;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.GestureDetector.OnGestureListener;
import android.view.animation.TranslateAnimation;
import android.widget.ListView;
public class BounceListView extends ListView {
private boolean outBound = false;
private int distance;
private int firstOut;
private Context mContext;
private BounceCallBack mBounceCallback;
public static final String TAG = "BounceListView";
private boolean isCalled = false;
public BounceListView(Context context, AttributeSet attrs) {
super(context, attrs);
mContext = context;
}
public BounceListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mContext = context;
}
public BounceListView(Context context) {
super(context);
mContext = context;
}
GestureDetector gestureDetector = new GestureDetector(mContext,
new OnGestureListener() {
@Override
public boolean onSingleTapUp(MotionEvent e) {
// TODO Auto-generated method stub
Log.d(TAG, "I'am onSingleTapUp().");
return false;
}
@Override
public void onShowPress(MotionEvent e) {
// TODO Auto-generated method stub
Log.d(TAG, "I'am onShowPress().");
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
Log.e(TAG, "Entry onscroll distanceX = " + distanceX
+ ", distanceY = " + distanceX);
int firstPos = getFirstVisiblePosition();
// outbound Top
if (outBound && firstPos != 0) {
scrollTo(0, 0);
return false;
}
View firstView = getChildAt(firstPos);
// View lastView = getChildAt(lastPos - 1);
if (!outBound) {
firstOut = (int) e2.getRawY();
}
if (firstView != null
&& (outBound || (firstPos == 0
&& firstView.getTop() == 0 && distanceY < 0))) {
// Record the length of each slide
distance = firstOut - (int) e2.getRawY();
Log.e(TAG, "Lee--------distance = " + distance);
Log.e(TAG, "firstOut = " + firstOut + ", firstPos = "
+ firstPos + ", firstView.getTop() = "
+ firstView.getTop());
int tempdistance = 60 * (-distance) / 100; //为了增加下拉的难度
if (tempdistance > getHeight() / 2)
scrollTo(0, -getHeight() / 2);
else
scrollTo(0, -tempdistance);
if (mBounceCallback != null && shouldCallBack(tempdistance)) {
isCalled = true;
mBounceCallback.onBounceCallBack();
}
return true;
}
return false;
}
@Override
public void onLongPress(MotionEvent e) {
// TODO Auto-generated method stub
Log.d(TAG, "I'am onLongPress().");
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2,
float velocityX, float velocityY) {
// TODO Auto-generated method stub
Log.d(TAG, "I'am onFling().");
return false;
}
@Override
public boolean onDown(MotionEvent e) {
// TODO Auto-generated method stub
Log.d(TAG, "I'am onDown().");
return false;
}
});
private boolean shouldCallBack(int tempdistance) {
if ((tempdistance > getHeight() / 2) && !isCalled) { //下拉到ListView高度的一半就会触发事件
Log.e(TAG, "shouldCallBack()");
return true;
}
return false;
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
int act = event.getAction();
if ((act == MotionEvent.ACTION_UP || act == MotionEvent.ACTION_CANCEL)
&& outBound) {
outBound = false;
isCalled = false;
// scroll back
}
if (!gestureDetector.onTouchEvent(event)) {
outBound = false;
} else {
outBound = true;
}
Rect rect = new Rect();
getLocalVisibleRect(rect);
Log.i(TAG, "rect.top = " + rect.top);
TranslateAnimation am = new TranslateAnimation(0, 0, -rect.top, 0);
am.setDuration(300);
startAnimation(am);
scrollTo(0, 0);
return super.dispatchTouchEvent(event);
}
public void setOnBounceCallBack(BounceCallBack callback) {
mBounceCallback = callback;
}
//回调触发接口
public interface BounceCallBack {
public void onBounceCallBack();
}
}
然后是Main.java，
package com.lee.listviewdemo;
import java.util.ArrayList;
import java.util.HashMap;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.SimpleAdapter;
import android.util.Log;
import android.view.View;
import com.lee.listviewdemo.R;
import com.lee.listviewdemo.BounceListView.BounceCallBack;
public class Main extends Activity {
/** Called when the activity is first created. */
private View footerView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
BounceListView list = (BounceListView) findViewById(R.id.MyListView);
footerView = getLayoutInflater().inflate(R.layout.footer_container, null);
ArrayList> mylist = new ArrayList>();
for (int i = 0; i < 5; i++) {
HashMap map = new HashMap();
map.put("ItemTitle", "BounceListView.....");
map.put("ItemText", "This is text.....");
mylist.add(map);
}
//设置listview弹性下拉事件触发
list.setOnBounceCallBack(new BounceCallBack() {
@Override
public void onBounceCallBack() {
// TODO Auto-generated method stub
Intent intent = new Intent(Main.this,
TestActivity.class);
startActivity(intent);
overridePendingTransition(R.anim.fade_in, R.anim.fade_out);
}
});
SimpleAdapter mSchedule = new SimpleAdapter(this,
mylist,
R.layout.my_listitem,
new String[] { "ItemTitle", "ItemText" },
new int[] { R.id.ItemTitle, R.id.ItemText });
//添加FooterView，当listview数据少时，可以填充屏幕
list.addFooterView(footerView, null, false);
list.setAdapter(mSchedule);
Log.e(BounceListView.TAG, "footerview == " + footerView + "list.count == " + list.getCount());
}
} FooterView的布局，就是加一个layout，让其宽高自适应：
上面就是主要的实现代码了，接下来看一下效果图：
弱弱的问一下我上传的gif图片不动，这是为啥呢。。以前没上传过
公司代码加了密，源代码就不上传了。。。
Android学习中。。。