我正在使用功能下拉来刷新使用这个library的chrisbanes 但是当我尝试在我的xml文件中导入这个小部件时 它向我显示以下错误。请帮我解决这个问题。 错误：
com.handmark.pulltorefresh.library.PullToRefreshListView failed to instantiate.
答案 0 :(得分：1)
我肯定会看一下Chris Banes' implementation of pull-to-refresh。他的代码不仅包括ListView的这种交互方式，还包括GridView和WebView。
特别是后者在您的情况下会很有用，因为它是一个不对其内容使用适配器的视图的pull-to-refresh的示例实现。如果你看一下源代码，你会发现Banes项目中每个具体的pull-to-refreh视图都是从一个普通的PullToRefreshBase扩展而来的，它包含了动画和刷新的大部分逻辑。拥有该基类的好处是为任何其他类型的视图做同样的事情，例如一个TextView，应该非常简单。
这种方法的唯一缺点是实现是其他视图的包装器，这意味着您将编写一些额外的行来获取实际视图。所以这不是一个完全的替代品。但是，它的功能和特性远远超过了这么小的不便。
已编辑：
查看我已实施的以下代码
主JAVA文件中的：
PullToRefreshListView listview;
listview = (PullToRefreshListView) findViewById(R.id.airpost_listView);
listview.setOnRefreshListener(new OnRefreshListener() {
public void onRefresh() {
// TODO Auto-generated method stub
new GetPost().execute(); // AsyncTask where you can put your logic when to call the listview for getting new data or let it be same as before
}
});
在xml文件中定义的Listview：
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/bhavesh"
android:padding="5dp" >
<com.FlightMate.AirpostTab.PullToRefreshListView
android:id="@+id/airpost_listView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ffffff"
android:cacheColorHint="@android:color/transparent"
android:divider="#00000000" />
</LinearLayout>
这是PullToRefreshListView：
package com.FlightMate.AirpostTab;
import android.content.Context;
import android.util.AttributeSet;
import android.widget.ListView;
public class PullToRefreshListView extends PullToRefreshBase<ListView> {
public PullToRefreshListView(Context context) {
super(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected final ListView createAdapterView(Context context,
AttributeSet attrs) {
ListView lv = new ListView(context, attrs);
// Set it to this so it can be used in ListActivity/ListFragment
lv.setId(android.R.id.list);
return lv;
}
}
这里是PullToRefreshBase：
package com.FlightMate.AirpostTab;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Color;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Interpolator;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.LinearLayout;
import com.FlightMate.R;
public abstract class PullToRefreshBase<T extends AbsListView> extends
LinearLayout implements OnTouchListener, OnScrollListener {
private final class SmoothScrollRunnable implements Runnable {
static final int ANIMATION_DURATION_MS = 190;
static final int ANIMATION_FPS = 1000 / 60;
private final Interpolator interpolator;
private final int scrollToY;
private final int scrollFromY;
private final Handler handler;
private boolean continueRunning = true;
private long startTime = -1;
private int currentY = -1;
public SmoothScrollRunnable(Handler handler, int fromY, int toY) {
this.handler = handler;
this.scrollFromY = fromY;
this.scrollToY = toY;
this.interpolator = new AccelerateDecelerateInterpolator();
}
// @Override
public void run() {
/**
* Only set startTime if this is the first time we're starting, else
* actually calculate the Y delta
*/
if (startTime == -1) {
startTime = System.currentTimeMillis();
} else {
/**
* We do do all calculations in long to reduce software float
* calculations. We use 1000 as it gives us good accuracy and
* small rounding errors
*/
long normalizedTime = (1000 * (System.currentTimeMillis() - startTime))
/ ANIMATION_DURATION_MS;
normalizedTime = Math.max(Math.min(normalizedTime, 1000), 0);
final int deltaY = Math
.round((scrollFromY - scrollToY)
* interpolator
.getInterpolation(normalizedTime / 1000f));
this.currentY = scrollFromY - deltaY;
setHeaderScroll(currentY);
}
// If we're not at the target Y, keep going...
if (continueRunning && scrollToY != currentY) {
handler.postDelayed(this, ANIMATION_FPS);
}
}
public void stop() {
this.continueRunning = false;
this.handler.removeCallbacks(this);
}
};
// ===========================================================
// Constants
// ===========================================================
static final int PULL_TO_REFRESH = 0;
static final int RELEASE_TO_REFRESH = PULL_TO_REFRESH + 1;
static final int REFRESHING = RELEASE_TO_REFRESH + 1;
static final int EVENT_COUNT = 3;
public static final int MODE_PULL_DOWN_TO_REFRESH = 0x1;
public static final int MODE_PULL_UP_TO_REFRESH = 0x2;
public static final int MODE_BOTH = 0x3;
// ===========================================================
// Fields
// ===========================================================
private int state = PULL_TO_REFRESH;
private int mode = MODE_PULL_DOWN_TO_REFRESH;
private int currentMode;
private boolean disableScrollingWhileRefreshing = true;
private T adapterView;
private boolean isPullToRefreshEnabled = true;
private LoadingLayout headerLayout;
private LoadingLayout footerLayout;
private int headerHeight;
private final Handler handler = new Handler();
private OnTouchListener onTouchListener;
private OnRefreshListener onRefreshListener;
private OnScrollListener onScrollListener;
private OnLastItemVisibleListener onLastItemVisibleListener;
private int lastSavedFirstVisibleItem = -1;
private SmoothScrollRunnable currentSmoothScrollRunnable;
private float startY = -1;
private final float[] lastYs = new float[EVENT_COUNT];
// ===========================================================
// Constructors
// ===========================================================
public PullToRefreshBase(Context context) {
this(context, null);
}
public PullToRefreshBase(Context context, int mode) {
this(context);
this.mode = mode;
}
public PullToRefreshBase(Context context, AttributeSet attrs) {
super(context, attrs);
init(context, attrs);
}
// ===========================================================
// Getter & Setter
// ===========================================================
/**
* Get the Wrapped AdapterView. Anything returned here has already been
* added to the content view.
*
* @return The AdapterView which is currently wrapped
*/
public final T getAdapterView() {
return adapterView;
}
/**
* Whether Pull-to-Refresh is enabled
*
* @return enabled
*/
public final boolean isPullToRefreshEnabled() {
return isPullToRefreshEnabled;
}
public void setDisableScrollingWhileRefreshing(
boolean disableScrollingWhileRefreshing) {
this.disableScrollingWhileRefreshing = disableScrollingWhileRefreshing;
}
/**
* Mark the current Refresh as complete. Will Reset the UI and hide the
* Refreshing View
*/
public final void onRefreshComplete() {
resetHeader();
}
public final void setOnLastItemVisibleListener(
OnLastItemVisibleListener listener) {
onLastItemVisibleListener = listener;
}
public final void setOnRefreshListener(OnRefreshListener listener) {
onRefreshListener = listener;
}
/**
* A mutator to enable/disable Pull-to-Refresh for the current AdapterView
*
* @param enable
* Whether Pull-To-Refresh should be used
*/
public final void setPullToRefreshEnabled(boolean enabled) {
this.isPullToRefreshEnabled = enabled;
}
public final void setReleaseLabel(String releaseLabel) {
if (null != headerLayout) {
headerLayout.setReleaseLabel(releaseLabel);
}
if (null != footerLayout) {
footerLayout.setReleaseLabel(releaseLabel);
}
}
public final void setPullLabel(String pullLabel) {
if (null != headerLayout) {
headerLayout.setPullLabel(pullLabel);
}
if (null != footerLayout) {
footerLayout.setPullLabel(pullLabel);
}
}
public final void setRefreshingLabel(String refreshingLabel) {
if (null != headerLayout) {
headerLayout.setRefreshingLabel(refreshingLabel);
}
if (null != footerLayout) {
footerLayout.setRefreshingLabel(refreshingLabel);
}
}
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
public final void setOnScrollListener(OnScrollListener listener) {
onScrollListener = listener;
}
@Override
public final void setOnTouchListener(OnTouchListener listener) {
onTouchListener = listener;
}
public final void onScroll(final AbsListView view,
final int firstVisibleItem, final int visibleItemCount,
final int totalItemCount) {
if (null != onLastItemVisibleListener) {
// detect if last item is visible
if (visibleItemCount > 0 && visibleItemCount < totalItemCount
&& (firstVisibleItem + visibleItemCount == totalItemCount)) {
// only process first event
if (firstVisibleItem != lastSavedFirstVisibleItem) {
lastSavedFirstVisibleItem = firstVisibleItem;
onLastItemVisibleListener.onLastItemVisible();
}
}
}
if (null != onScrollListener) {
onScrollListener.onScroll(view, firstVisibleItem, visibleItemCount,
totalItemCount);
}
}
public final void onScrollStateChanged(final AbsListView view,
final int scrollState) {
if (null != onScrollListener) {
onScrollListener.onScrollStateChanged(view, scrollState);
}
}
// @Override
public final boolean onTouch(View view, MotionEvent ev) {
if (isPullToRefreshEnabled) {
// Returning true here stops the ListView being scrollable while we
// refresh
if (state == REFRESHING && disableScrollingWhileRefreshing) {
return true;
} else if (onAdapterViewTouch(view, ev)) {
return true;
}
}
if (null != onTouchListener) {
return onTouchListener.onTouch(view, ev);
}
return false;
}
/**
* This is implemented by derived classes to return the created AdapterView.
* If you need to use a custom AdapterView (such as a custom ListView),
* override this method and return an instance of your custom class.
*
* Be sure to set the ID of the view in this method, especially if you're
* using a ListActivity or ListFragment.
*
* @param context
* @param attrs
* AttributeSet from wrapped class. Means that anything you
* include in the XML layout declaration will be routed to the
* AdapterView
* @return New instance of the AdapterView
*/
protected abstract T createAdapterView(Context context, AttributeSet attrs);
// ===========================================================
// Methods
// ===========================================================
protected final void resetHeader() {
state = PULL_TO_REFRESH;
initializeYsHistory();
startY = -1;
if (null != headerLayout) {
headerLayout.reset();
}
if (null != footerLayout) {
footerLayout.reset();
}
smoothScrollTo(0);
}
private void init(Context context, AttributeSet attrs) {
setOrientation(LinearLayout.VERTICAL);
// Styleables from XML
final TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.PullToRefresh);
mode = a.getInteger(R.styleable.PullToRefresh_mode,
MODE_PULL_DOWN_TO_REFRESH);
// AdapterView
// By passing the attrs, we can add ListView/GridView params via XML
adapterView = this.createAdapterView(context, attrs);
adapterView.setOnTouchListener(this);
adapterView.setOnScrollListener(this);
addView(adapterView, new LinearLayout.LayoutParams(
LayoutParams.FILL_PARENT, 0, 1.0f));
// Loading View Strings
String pullLabel = context
.getString(R.string.pull_to_refresh_pull_label);
String refreshingLabel = context
.getString(R.string.pull_to_refresh_refreshing_label);
String releaseLabel = context
.getString(R.string.pull_to_refresh_release_label);
// Add Loading Views
if (mode == MODE_PULL_DOWN_TO_REFRESH || mode == MODE_BOTH) {
headerLayout = new LoadingLayout(context,
MODE_PULL_DOWN_TO_REFRESH, releaseLabel, pullLabel,
refreshingLabel);
addView(headerLayout, 0, new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
measureView(headerLayout);
headerHeight = headerLayout.getMeasuredHeight();
}
if (mode == MODE_PULL_UP_TO_REFRESH || mode == MODE_BOTH) {
footerLayout = new LoadingLayout(context, MODE_PULL_UP_TO_REFRESH,
releaseLabel, pullLabel, refreshingLabel);
addView(footerLayout, new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
measureView(footerLayout);
headerHeight = footerLayout.getMeasuredHeight();
}
// Styleables from XML
if (a.hasValue(R.styleable.PullToRefresh_headerTextColor)) {
final int color = a.getColor(
R.styleable.PullToRefresh_headerTextColor, Color.BLACK);
if (null != headerLayout) {
headerLayout.setTextColor(color);
}
if (null != footerLayout) {
footerLayout.setTextColor(color);
}
}
if (a.hasValue(R.styleable.PullToRefresh_headerBackground)) {
this.setBackgroundResource(a.getResourceId(
R.styleable.PullToRefresh_headerBackground, Color.WHITE));
}
if (a.hasValue(R.styleable.PullToRefresh_adapterViewBackground)) {
adapterView.setBackgroundResource(a.getResourceId(
R.styleable.PullToRefresh_adapterViewBackground,
Color.WHITE));
}
a.recycle();
// Hide Loading Views
switch (mode) {
case MODE_BOTH:
setPadding(getPaddingLeft(), -headerHeight, getPaddingRight(),
-headerHeight);
break;
case MODE_PULL_UP_TO_REFRESH:
setPadding(getPaddingLeft(), getPaddingTop(), getPaddingRight(),
-headerHeight);
break;
case MODE_PULL_DOWN_TO_REFRESH:
default:
setPadding(getPaddingLeft(), -headerHeight, getPaddingRight(),
getPaddingBottom());
break;
}
// If we're not using MODE_BOTH, then just set currentMode to current
// mode
if (mode != MODE_BOTH) {
currentMode = mode;
}
}
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);
}
private boolean onAdapterViewTouch(View view, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_MOVE:
updateEventStates(event);
if (isPullingToRefresh() && startY == -1) {
startY = event.getY();
// Need to set current Mode if we're using both
if (mode == MODE_BOTH) {
if (isUserDraggingDownwards()) {
currentMode = MODE_PULL_DOWN_TO_REFRESH;
} else if (isUserDraggingUpwards()) {
currentMode = MODE_PULL_UP_TO_REFRESH;
}
}
return false;
}
if (startY != -1 && !adapterView.isPressed()) {
pullEvent(event, startY);
return true;
}
break;
case MotionEvent.ACTION_UP:
initializeYsHistory();
startY = -1;
if (state == RELEASE_TO_REFRESH) {
setRefreshing();
if (onRefreshListener != null) {
onRefreshListener.onRefresh();
}
} else {
smoothScrollTo(0);
}
break;
}
return false;
}
private void pullEvent(MotionEvent event, float firstY) {
float averageY = average(lastYs);
final int height;
switch (currentMode) {
case MODE_PULL_UP_TO_REFRESH:
height = (int) Math.max(firstY - averageY, 0);
setHeaderScroll(height);
break;
case MODE_PULL_DOWN_TO_REFRESH:
default:
height = (int) Math.max(averageY - firstY, 0);
setHeaderScroll(-height);
break;
}
if (state == PULL_TO_REFRESH && headerHeight < height) {
state = RELEASE_TO_REFRESH;
if (null != headerLayout) {
headerLayout.releaseToRefresh();
}
if (null != footerLayout) {
footerLayout.releaseToRefresh();
}
} else if (state == RELEASE_TO_REFRESH && headerHeight >= height) {
state = PULL_TO_REFRESH;
if (null != headerLayout) {
headerLayout.pullToRefresh();
}
if (null != footerLayout) {
footerLayout.pullToRefresh();
}
}
}
private void setHeaderScroll(int y) {
scrollTo(0, y);
}
private void setRefreshing() {
state = REFRESHING;
if (null != headerLayout) {
headerLayout.refreshing();
}
if (null != footerLayout) {
footerLayout.refreshing();
}
switch (currentMode) {
case MODE_PULL_DOWN_TO_REFRESH:
smoothScrollTo(-headerHeight);
break;
case MODE_PULL_UP_TO_REFRESH:
smoothScrollTo(headerHeight);
break;
}
}
private float average(float[] ysArray) {
float avg = 0;
for (int i = 0; i < EVENT_COUNT; i++) {
avg += ysArray[i];
}
return avg / EVENT_COUNT;
}
private void initializeYsHistory() {
for (int i = 0; i < EVENT_COUNT; i++) {
lastYs[i] = 0;
}
}
private void updateEventStates(MotionEvent event) {
for (int i = 0, z = event.getHistorySize(); i < z; i++) {
this.updateEventStates(event.getHistoricalY(i));
}
this.updateEventStates(event.getY());
}
private void updateEventStates(float y) {
for (int i = 0; i < EVENT_COUNT - 1; i++) {
lastYs[i] = lastYs[i + 1];
}
lastYs[EVENT_COUNT - 1] = y;
}
private boolean isPullingToRefresh() {
if (isPullToRefreshEnabled && state != REFRESHING) {
switch (mode) {
case MODE_PULL_DOWN_TO_REFRESH:
return isFirstItemVisible() && isUserDraggingDownwards();
case MODE_PULL_UP_TO_REFRESH:
return isLastItemVisible() && isUserDraggingUpwards();
case MODE_BOTH:
return (isFirstItemVisible() && isUserDraggingDownwards())
|| (isLastItemVisible() && isUserDraggingUpwards());
}
}
return false;
}
private boolean isFirstItemVisible() {
if (this.adapterView.getCount() == 0) {
return true;
} else if (adapterView.getFirstVisiblePosition() == 0) {
return adapterView.getChildAt(0).getTop() >= adapterView.getTop();
} else {
return false;
}
}
private boolean isLastItemVisible() {
final int count = this.adapterView.getCount();
if (count == 0) {
return true;
} else if (adapterView.getLastVisiblePosition() == count - 1) {
return true;
} else {
return false;
}
}
private boolean isUserDraggingDownwards() {
return this.isUserDraggingDownwards(0, EVENT_COUNT - 1);
}
private boolean isUserDraggingDownwards(int from, int to) {
return lastYs[from] != 0 && lastYs[to] != 0
&& Math.abs(lastYs[from] - lastYs[to]) > 10
&& lastYs[from] < lastYs[to];
}
private boolean isUserDraggingUpwards() {
return this.isUserDraggingUpwards(0, EVENT_COUNT - 1);
}
private boolean isUserDraggingUpwards(int from, int to) {
return lastYs[from] != 0 && lastYs[to] != 0
&& Math.abs(lastYs[to] - lastYs[from]) > 10
&& lastYs[to] < lastYs[from];
}
private void smoothScrollTo(int y) {
if (null != currentSmoothScrollRunnable) {
currentSmoothScrollRunnable.stop();
}
this.currentSmoothScrollRunnable = new SmoothScrollRunnable(handler,
getScrollY(), y);
handler.post(currentSmoothScrollRunnable);
}
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
public static interface OnRefreshListener {
public void onRefresh();
}
public static interface OnLastItemVisibleListener {
public void onLastItemVisible();
}
}
希望它能帮助你解决问题。如果你仍然遇到任何困难，请告诉我。