我正在尝试将 PullToRefresh GridView 与 ViewPager 一起使用，这会导致崩溃并给出 ClassCastException。这是例外。
FATAL EXCEPTION: main java.lang.ClassCastException: android.support.v4.view.ViewPager$LayoutParams
at android.widget.LinearLayout.measureVertical(LinearLayout.java:360)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
at android.view.View.measure(View.java:8313)
at android.widget.RelativeLayout.measureChild(RelativeLayout.java:566)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:381)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:581)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:365)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
at android.view.View.measure(View.java:8313)
at android.view.ViewRoot.performTraversals(ViewRoot.java:845)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1865)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3687)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
at dalvik.system.NativeStart.main(Native Method)
这是实现它的代码片段。
PULL_TO_REFRESH = (PullToRefreshGridView)findViewById(R.id.groupList);
mGroupList = PULL_TO_REFRESH.getAdapterView();
Vector<View> pages = new Vector<View>();
pages.add(mGroupList);
ViewPager vp = (ViewPager)findViewById(R.id.myfivepanelpager);
CustomPagerAdapter adapter = new CustomPagerAdapter(this, pages);
vp.setAdapter(adapter);
// Set a listener to be invoked when the list should be refreshed.
PULL_TO_REFRESH.setOnRefreshListener(new OnRefreshListener() {
@Override
public void onRefresh() {
// TODO Auto-generated method stub
}
});
这是来自 PullToRefresh 库的代码片段，这可能是原因。
package com.syncusup.pulltorefresh.library.my;
import android.content.Context;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.LayoutInflater;
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.Animation;
import android.view.animation.Interpolator;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.ProgressBar;
import android.widget.TextView;
import com.syncusup.R;
public abstract class PullToRefreshBase<T extends AdapterView<ListAdapter>> extends LinearLayout implements
OnTouchListener {
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;
// ===========================================================
// Fields
// ===========================================================
private int state = PULL_TO_REFRESH;
private T adapterView;
private boolean isPullToRefreshEnabled = true;
private ProgressBar headerProgress;
private TextView headerText;
private ImageView headerImage;
private Animation flipAnimation, reverseAnimation;
private int headerHeight;
private final Handler handler = new Handler();
private OnTouchListener onTouchListener;
private OnRefreshListener onRefreshListener;
private SmoothScrollRunnable currentSmoothScrollRunnable;
private float startY = -1;
private final float[] lastYs = new float[EVENT_COUNT];
private String releaseLabel;
private String pullLabel;
private String refreshingLabel;
// ===========================================================
// Constructors
// ===========================================================
public PullToRefreshBase(Context context) {
this(context, null);
}
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 boolean isPullToRefreshEnabled() {
return isPullToRefreshEnabled;
}
/**
* Mark the current Refresh as complete. Will Reset the UI and hide the
* Refreshing View
*/
public void onRefreshComplete() {
resetHeader();
}
public 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 void setPullToRefreshEnabled(boolean enabled) {
this.isPullToRefreshEnabled = enabled;
}
public void setReleaseLabel(String releaseLabel) {
this.releaseLabel = releaseLabel;
}
public void setPullLabel(String pullLabel) {
this.pullLabel = pullLabel;
}
public void setRefreshingLabel(String refreshingLabel) {
this.refreshingLabel = refreshingLabel;
}
public void setHeaderProgress(ProgressBar headerProgress) {
this.headerProgress = headerProgress;
}
// ===========================================================
// Methods for/from SuperClass/Interfaces
// ===========================================================
@Override
public void setOnTouchListener(OnTouchListener listener) {
onTouchListener = listener;
}
@Override
public boolean onTouch(View view, MotionEvent ev) {
if (isPullToRefreshEnabled) {
// Returning true here stops the ListView being scrollable while we
// refresh
if (state == REFRESHING) {
return true;
} else {
return onAdapterViewTouch(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;
headerImage.setVisibility(View.VISIBLE);
headerProgress.setVisibility(View.GONE);
smoothScrollTo(0);
}
private void init(Context context, AttributeSet attrs) {
setOrientation(LinearLayout.VERTICAL);
// Header
ViewGroup header = (ViewGroup) LayoutInflater.from(context).inflate(R.layout.pull_to_refresh_header, this,
false);
headerText = (TextView) header.findViewById(R.id.pull_to_refresh_text);
pullLabel = context.getString(R.string.pull_to_refresh_pull_label);
refreshingLabel = context.getString(R.string.pull_to_refresh_refreshing_label);
releaseLabel = context.getString(R.string.pull_to_refresh_release_label);
headerImage = (ImageView) header.findViewById(R.id.pull_to_refresh_image);
headerProgress = (ProgressBar) header.findViewById(R.id.pull_to_refresh_progress);
addView(header, ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
measureView(header);
headerHeight = header.getMeasuredHeight();
// AdapterView
// By passing the attrs, we can add ListView/GridView params via XML
adapterView = this.createAdapterView(context, attrs);
adapterView.setOnTouchListener(this);
addView(adapterView, ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT);
// Animations
flipAnimation = new RotateAnimation(0, -180, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
flipAnimation.setInterpolator(new LinearInterpolator());
flipAnimation.setDuration(250);
flipAnimation.setFillAfter(true);
reverseAnimation = new RotateAnimation(-180, 0, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
0.5f);
reverseAnimation.setInterpolator(new LinearInterpolator());
reverseAnimation.setDuration(250);
reverseAnimation.setFillAfter(true);
// Hide Header View
setPadding(getPaddingLeft(), -headerHeight, getPaddingRight(), getPaddingBottom());
}
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 (isPullingDownToRefresh() && startY == -1) {
if (startY == -1) {
startY = event.getY();
}
return false;
}
if (startY != -1 && !adapterView.isPressed()) {
pullDown(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;
}
if (null != onTouchListener) {
return onTouchListener.onTouch(view, event);
}
return false;
}
private void pullDown(MotionEvent event, float firstY) {
float averageY = average(lastYs);
int height = (int) (Math.max(averageY - firstY, 0));
setHeaderScroll(height);
if (state == PULL_TO_REFRESH && headerHeight < height) {
state = RELEASE_TO_REFRESH;
headerText.setText(releaseLabel);
headerImage.clearAnimation();
headerImage.startAnimation(flipAnimation);
}
if (state == RELEASE_TO_REFRESH && headerHeight >= height) {
state = PULL_TO_REFRESH;
headerText.setText(pullLabel);
headerImage.clearAnimation();
headerImage.startAnimation(reverseAnimation);
}
}
private void setHeaderScroll(int y) {
scrollTo(0, -y);
}
private int getHeaderScroll() {
return -getScrollY();
}
private void setRefreshing() {
state = REFRESHING;
headerText.setText(refreshingLabel);
headerImage.clearAnimation();
headerImage.setVisibility(View.INVISIBLE);
headerProgress.setVisibility(View.VISIBLE);
smoothScrollTo(headerHeight);
}
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; i < EVENT_COUNT - 1; i++) {
lastYs[i] = lastYs[i + 1];
}
float y = event.getY();
int top = adapterView.getTop();
lastYs[EVENT_COUNT - 1] = y + top;
}
private boolean isPullingDownToRefresh() {
return isPullToRefreshEnabled && state != REFRESHING && isUserDraggingDownwards() && isFirstVisible();
}
private boolean isFirstVisible() {
if (this.adapterView.getCount() == 0) {
return true;
} else if (adapterView.getFirstVisiblePosition() == 0) {
return adapterView.getChildAt(0).getTop() >= adapterView.getTop();
} 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 void smoothScrollTo(int y) {
if (null != currentSmoothScrollRunnable) {
currentSmoothScrollRunnable.stop();
}
this.currentSmoothScrollRunnable = new SmoothScrollRunnable(handler, getHeaderScroll(), y);
handler.post(currentSmoothScrollRunnable);
}
// ===========================================================
// Inner and Anonymous Classes
// ===========================================================
public static interface OnRefreshListener {
public void onRefresh();
}
}