android listview 下拉加载更多demo

package com.markupartist.android.widget;

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.ImageView;

import android.widget.ListAdapter;

import android.widget.ListView;

import android.widget.ProgressBar;

import android.widget.RelativeLayout;

import android.widget.TextView;

import android.widget.AbsListView.OnScrollListener;

import com.markupartist.android.widget.pulltorefresh.R;

public class PullToRefreshListView extends ListView implements OnScrollListener {

private static final int TAP_TO_REFRESH = 1;

private static final int PULL_TO_REFRESH = 2;

private static final int RELEASE_TO_REFRESH = 3;

private static final int REFRESHING = 4;

private static final String TAG = "PullToRefreshListView";

private OnRefreshListener mOnRefreshListener;

/**

* Listener that will receive notifications every time the list scrolls.

*/

private OnScrollListener mOnScrollListener;

private LayoutInflater mInflater;

private RelativeLayout mRefreshView;

private TextView mRefreshViewText;

private ImageView mRefreshViewImage;

private ProgressBar mRefreshViewProgress;

private TextView mRefreshViewLastUpdated;

private int mCurrentScrollState;

private int mRefreshState;

private RotateAnimation mFlipAnimation;

private RotateAnimation mReverseFlipAnimation;

private int mRefreshViewHeight;

private int mRefreshOriginalTopPadding;

private int mLastMotionY;

private boolean mBounceHack;

public PullToRefreshListView(Context context) {

super(context);

init(context);

}

public PullToRefreshListView(Context context, AttributeSet attrs) {

super(context, attrs);

init(context);

}

public PullToRefreshListView(Context context, AttributeSet attrs, int defStyle) {

super(context, attrs, defStyle);

init(context);

}

private void init(Context context) {

// Load all of the animations we need in code rather than through XML

mFlipAnimation = new RotateAnimation(0, -180,

RotateAnimation.RELATIVE_TO_SELF, 0.5f,

RotateAnimation.RELATIVE_TO_SELF, 0.5f);

mFlipAnimation.setInterpolator(new LinearInterpolator());

mFlipAnimation.setDuration(250);

mFlipAnimation.setFillAfter(true);

mReverseFlipAnimation = new RotateAnimation(-180, 0,

RotateAnimation.RELATIVE_TO_SELF, 0.5f,

RotateAnimation.RELATIVE_TO_SELF, 0.5f);

mReverseFlipAnimation.setInterpolator(new LinearInterpolator());

mReverseFlipAnimation.setDuration(250);

mReverseFlipAnimation.setFillAfter(true);

mInflater = (LayoutInflater) context.getSystemService(

Context.LAYOUT_INFLATER_SERVICE);

mRefreshView = (RelativeLayout) mInflater.inflate(

R.layout.pull_to_refresh_header, this, false);

mRefreshViewText =

(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_text);

mRefreshViewImage =

(ImageView) mRefreshView.findViewById(R.id.pull_to_refresh_image);

mRefreshViewProgress =

(ProgressBar) mRefreshView.findViewById(R.id.pull_to_refresh_progress);

mRefreshViewLastUpdated =

(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_updated_at);

mRefreshViewImage.setMinimumHeight(50);

mRefreshView.setOnClickListener(new OnClickRefreshListener());

mRefreshOriginalTopPadding = mRefreshView.getPaddingTop();

mRefreshState = TAP_TO_REFRESH;

addHeaderView(mRefreshView);

super.setOnScrollListener(this);

measureView(mRefreshView);

mRefreshViewHeight = mRefreshView.getMeasuredHeight();

}

@Override

protected void onAttachedToWindow() {

super.onAttachedToWindow();

setSelection(1);

}

@Override

public void setAdapter(ListAdapter adapter) {

super.setAdapter(adapter);

setSelection(1);

}

/**

* Set the listener that will receive notifications every time the list

* scrolls.

*

* @param l The scroll listener.

*/

@Override

public void setOnScrollListener(AbsListView.OnScrollListener l) {

mOnScrollListener = l;

}

/**

* Register a callback to be invoked when this list should be refreshed.

*

* @param onRefreshListener The callback to run.

*/

public void setOnRefreshListener(OnRefreshListener onRefreshListener) {

mOnRefreshListener = onRefreshListener;

}

/**

* Set a text to represent when the list was last updated.

* @param lastUpdated Last updated at.

*/

public void setLastUpdated(CharSequence lastUpdated) {

if (lastUpdated != null) {

mRefreshViewLastUpdated.setVisibility(View.VISIBLE);

mRefreshViewLastUpdated.setText(lastUpdated);

} else {

mRefreshViewLastUpdated.setVisibility(View.GONE);

}

}

@Override

public boolean onTouchEvent(MotionEvent event) {

final int y = (int) event.getY();

mBounceHack = false;

switch (event.getAction()) {

case MotionEvent.ACTION_UP:

if (!isVerticalScrollBarEnabled()) {

setVerticalScrollBarEnabled(true);

}

if (getFirstVisiblePosition() == 0 && mRefreshState != REFRESHING) {

if ((mRefreshView.getBottom() >= mRefreshViewHeight

|| mRefreshView.getTop() >= 0)

&& mRefreshState == RELEASE_TO_REFRESH) {

// Initiate the refresh

mRefreshState = REFRESHING;

prepareForRefresh();

onRefresh();

} else if (mRefreshView.getBottom() < mRefreshViewHeight

|| mRefreshView.getTop() <= 0) {

// Abort refresh and scroll down below the refresh view

resetHeader();

setSelection(1);

}

}

break;

case MotionEvent.ACTION_DOWN:

mLastMotionY = y;

break;

case MotionEvent.ACTION_MOVE:

applyHeaderPadding(event);

break;

}

return super.onTouchEvent(event);

}

private void applyHeaderPadding(MotionEvent ev) {

// getHistorySize has been available since API 1

int pointerCount = ev.getHistorySize();

for (int p = 0; p < pointerCount; p++) {

if (mRefreshState == RELEASE_TO_REFRESH) {

if (isVerticalFadingEdgeEnabled()) {

setVerticalScrollBarEnabled(false);

}

int historicalY = (int) ev.getHistoricalY(p);

// Calculate the padding to apply, we divide by 1.7 to

// simulate a more resistant effect during pull.

int topPadding = (int) (((historicalY - mLastMotionY)

- mRefreshViewHeight) / 1.7);

mRefreshView.setPadding(

mRefreshView.getPaddingLeft(),

topPadding,

mRefreshView.getPaddingRight(),

mRefreshView.getPaddingBottom());

}

}

}

/**

* Sets the header padding back to original size.

*/

private void resetHeaderPadding() {

mRefreshView.setPadding(

mRefreshView.getPaddingLeft(),

mRefreshOriginalTopPadding,

mRefreshView.getPaddingRight(),

mRefreshView.getPaddingBottom());

}

/**

* Resets the header to the original state.

*/

private void resetHeader() {

if (mRefreshState != TAP_TO_REFRESH) {

mRefreshState = TAP_TO_REFRESH;

resetHeaderPadding();

// Set refresh view text to the pull label

mRefreshViewText.setText(R.string.pull_to_refresh_tap_label);

// Replace refresh drawable with arrow drawable

mRefreshViewImage.setImageResource(R.drawable.ic_pulltorefresh_arrow);

// Clear the full rotation animation

mRefreshViewImage.clearAnimation();

// Hide progress bar and arrow.

mRefreshViewImage.setVisibility(View.GONE);

mRefreshViewProgress.setVisibility(View.GONE);

}

}

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);

}

@Override

public void onScroll(AbsListView view, int firstVisibleItem,

int visibleItemCount, int totalItemCount) {

// When the refresh view is completely visible, change the text to say

// "Release to refresh..." and flip the arrow drawable.

if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL

&& mRefreshState != REFRESHING) {

if (firstVisibleItem == 0) {

mRefreshViewImage.setVisibility(View.VISIBLE);

if ((mRefreshView.getBottom() >= mRefreshViewHeight + 20

|| mRefreshView.getTop() >= 0)

&& mRefreshState != RELEASE_TO_REFRESH) {

mRefreshViewText.setText(R.string.pull_to_refresh_release_label);

mRefreshViewImage.clearAnimation();

mRefreshViewImage.startAnimation(mFlipAnimation);

mRefreshState = RELEASE_TO_REFRESH;

} else if (mRefreshView.getBottom() < mRefreshViewHeight + 20

&& mRefreshState != PULL_TO_REFRESH) {

mRefreshViewText.setText(R.string.pull_to_refresh_pull_label);

if (mRefreshState != TAP_TO_REFRESH) {

mRefreshViewImage.clearAnimation();

mRefreshViewImage.startAnimation(mReverseFlipAnimation);

}

mRefreshState = PULL_TO_REFRESH;

}

} else {

mRefreshViewImage.setVisibility(View.GONE);

resetHeader();

}

} else if (mCurrentScrollState == SCROLL_STATE_FLING

&& firstVisibleItem == 0

&& mRefreshState != REFRESHING) {

setSelection(1);

mBounceHack = true;

} else if (mBounceHack && mCurrentScrollState == SCROLL_STATE_FLING) {

setSelection(1);

}

if (mOnScrollListener != null) {

mOnScrollListener.onScroll(view, firstVisibleItem,

visibleItemCount, totalItemCount);

}

}

@Override

public void onScrollStateChanged(AbsListView view, int scrollState) {

mCurrentScrollState = scrollState;

if (mCurrentScrollState == SCROLL_STATE_IDLE) {

mBounceHack = false;

}

if (mOnScrollListener != null) {

mOnScrollListener.onScrollStateChanged(view, scrollState);

}

}

public void prepareForRefresh() {

resetHeaderPadding();

mRefreshViewImage.setVisibility(View.GONE);

// We need this hack, otherwise it will keep the previous drawable.

mRefreshViewImage.setImageDrawable(null);

mRefreshViewProgress.setVisibility(View.VISIBLE);

// Set refresh view text to the refreshing label

mRefreshViewText.setText(R.string.pull_to_refresh_refreshing_label);

mRefreshState = REFRESHING;

}

public void onRefresh() {

Log.d(TAG, "onRefresh");

if (mOnRefreshListener != null) {

mOnRefreshListener.onRefresh();

}

}

/**

* Resets the list to a normal state after a refresh.

* @param lastUpdated Last updated at.

*/

public void onRefreshComplete(CharSequence lastUpdated) {

setLastUpdated(lastUpdated);

onRefreshComplete();

}

/**

* Resets the list to a normal state after a refresh.

*/

public void onRefreshComplete() {

Log.d(TAG, "onRefreshComplete");

resetHeader();

// If refresh view is visible when loading completes, scroll down to

// the next item.

if (mRefreshView.getBottom() > 0) {

invalidateViews();

setSelection(1);

}

}

/**

* Invoked when the refresh view is clicked on. This is mainly used when

* there's only a few items in the list and it's not possible to drag the

* list.

*/

private class OnClickRefreshListener implements OnClickListener {

@Override

public void onClick(View v) {

if (mRefreshState != REFRESHING) {

prepareForRefresh();

onRefresh();

}

}

}

/**

* Interface definition for a callback to be invoked when list should be

* refreshed.

*/

public interface OnRefreshListener {

/**

* Called when the list should be refreshed.

* <p>

* A call to {@link PullToRefreshListView #onRefreshComplete()} is

* expected to indicate that the refresh has completed.

*/

public void onRefresh();

}

}

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