Android下拉刷新可扩展实现

现在几乎所有的主流商业应用都支持某些页面的下拉刷新（如天猫，京东，美团，新浪微博等）,下拉刷新的实现其实可以基于一个重写的framelayout来完成，主要就是重写它的scrollTo方法。进行刷新的页面可以扩展到任何ViewGroup。最近在学习下拉刷新的实现，这个demo的UI效果和一些成熟APP是一致的，并有良好的可扩展性。

        主要包含两个类，一个类是PullRefreshLayout （extends FrameLayout），详细实现见demo源码。另一个是Activtity实现类，demo中仅仅模拟了网络刷新，但预留了刷新页面接口。代码如下：

package com.banking.pullrefresh;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.TextView;
import com.banking.pullrefresh.PullRefreshLayout.OnPullListener;
import com.banking.pullrefresh.PullRefreshLayout.OnPullStateListener;

public class PullRefreshActivity extends Activity implements OnPullListener, OnPullStateListener{

private final String TAG = "PullRefreshActivity";

private Animation mRotateUpAnimation;
private Animation mRotateDownAnimation;
private boolean mInLoading = false;
private PullRefreshLayout mPullLayout;
private TextView mActionText;
private TextView mTimeText;
private View mProgress;
private View mActionImage;
private Handler mHandler;
private TextView contentTv;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);

initPullRefreshView();
dataLoadFinished();
}

/**
* 下拉刷新view初始化
*/
private void initPullRefreshView() {
mHandler = new Handler();
mRotateUpAnimation = AnimationUtils.loadAnimation(this, R.anim.rotate_up);
mRotateDownAnimation = AnimationUtils.loadAnimation(this, R.anim.rotate_down);

mInLoading = true;
contentTv = (TextView)findViewById(R.id.content_tv);
mPullLayout = (PullRefreshLayout) findViewById(R.id.pull_container);
mPullLayout.setOnActionPullListener(this);
mPullLayout.setOnPullStateChangeListener(this);
mPullLayout.setEnableStopInActionView(true);
mProgress = findViewById(android.R.id.progress);
mProgress.setVisibility(View.VISIBLE);
mActionImage = findViewById(android.R.id.icon);
mActionImage.setVisibility(View.GONE);
mActionText = (TextView) findViewById(R.id.pull_note);
mActionText.setText("下拉刷新");
contentTv.setText("初始数据.");
mTimeText = (TextView) findViewById(R.id.refresh_time);
// mTimeText.setText(R.string.note_not_update);
}

@Override
public void onPullOut() {
if (!mInLoading) {
mActionText.setText(R.string.note_pull_refresh);
mActionImage.clearAnimation();
mActionImage.startAnimation(mRotateUpAnimation);
}
}

@Override
public void onPullIn() {
if (!mInLoading) {
mActionText.setText(R.string.note_pull_down);
mActionImage.clearAnimation();
mActionImage.startAnimation(mRotateDownAnimation);
}
}

@Override
public void onSnapToTop() {// 下拉后，弹到顶部时，开始刷新数据
if (!mInLoading) {
mInLoading = true;
mPullLayout.setEnableStopInActionView(true);
mActionImage.clearAnimation();
mActionImage.setVisibility(View.GONE);
mProgress.setVisibility(View.VISIBLE);
mActionText.setText(R.string.note_pull_loading);

pullRefreshData();
}
}

@Override
public void onShow() {
// TODO Auto-generated method stub

}

@Override
public void onHide() {
// TODO Auto-generated method stub

}

/**
* 当当前页面其他元素加载完成后调用该方法
*/
private void dataLoadFinished() {
Log.d(TAG, " dataLoaded -->> mInLoading=" + mInLoading);
if (mInLoading) {
mInLoading = false;
mPullLayout.setEnableStopInActionView(false);
mPullLayout.hideActionView();
mActionImage.setVisibility(View.VISIBLE);
mProgress.setVisibility(View.GONE);

if (mPullLayout.isPullOut()) {
mActionText.setText(R.string.note_pull_refresh);
mActionImage.clearAnimation();
mActionImage.startAnimation(mRotateUpAnimation);
} else {
mActionText.setText(R.string.note_pull_down);
}

mTimeText.setText(getString(R.string.note_update_at, formatDate(new Date(System.currentTimeMillis()))));
}
}

/**
* 这里加入相关网络请求
*/
private void pullRefreshData() {

new Thread() {
public void run() {
Log.d("PullRefreshActivity","pullRefreshData-->data fresh");
//TODO 网络请求
//还原控件，更新页面
mHandler.post(new Runnable() {
@Override
public void run() {
contentTv.setText(""+formatDate(new Date(System.currentTimeMillis()))+"时刻数据");
dataLoadFinished();
}
});

};
}.start();
}

private static DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

public static Date parseDate(String dateStr) throws ParseException {
try {
return dateFormat.parse(dateStr);
} catch (ParseException e) {
throw e;
}
}

public static String formatDate(Date date) {
return dateFormat.format(date);
}
}


demo源码地址：https://github.com/banking/PullRefresh