Android实现简单的下拉刷新pulltorefresh_安卓软件开发教程-查字典教程网

摘要：网上下拉刷新的DEMO很多，但是总有各种不满意的地方，有些会下拉卡住，有些回弹不流畅，有些性能太低会各种卡顿，有些emptyView无法下拉...

网上下拉刷新的DEMO很多，但是总有各种不满意的地方，有些会下拉卡住，有些回弹不流畅，有些性能太低会各种卡顿，有些emptyView无法下拉......

自己写的才是最合适自己的，代码很简单，也很容易修改，稍微阅读下代码就能改出自己需要的各种效果。

首先，重写ListView，自定义Touch事件，为了使emptyView也可下拉，emptyView也加上Touch事件。如果要实现GridView，把这里的ListView改成GridView即可。

PullableListView ：

public class PullableListView extends ListView { private boolean inited; private float density; private int mDownY, mMoveY; private int mPullY; private boolean isPull; private PullListener mPullListener; private VelocityTracker mVelocityTracker; public interface PullListener { public boolean onPullDownStart(); public void onPullDown(int moveY); public void onPullDownDrop(); } public PullableListView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(); } public PullableListView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public PullableListView(Context context) { super(context); init(); } private void init() { if (!inited) { density = getResources().getDisplayMetrics().density; } } public void setPullListener(PullListener mPullListener) { this.mPullListener = mPullListener; } public boolean isPulling() { return isPull; } @Override public void setEmptyView(View emptyView) { super.setEmptyView(emptyView); // 重写emptyView的Touch事件，使显示emptyView时也可以下拉刷新 emptyView.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent ev) { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(ev); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: mDownY = (int) ev.getY(); break; case MotionEvent.ACTION_MOVE: mMoveY = (int) ev.getY(); if (!isPull) { mVelocityTracker.computeCurrentVelocity(1000, 8000f); if (mVelocityTracker.getYVelocity() > 500 // 下拉速度大于500 && Math.abs(mMoveY - mDownY) > 20 * density) { // 下拉距离超过20dp mPullY = mMoveY; if (mPullListener.onPullDownStart()) { isPull = true; } } } else { // 阻尼下拉(随着下拉距离增加，阻力增加) mPullListener.onPullDown(mMoveY - mPullY + v.getScrollY()); // 等阻力下拉(阻力恒定，不随下拉距离增加而增加) // mPullListener.onPullDown(mMoveY - mPullY); if (mMoveY < mPullY) { isPull = false; } return true; } break; case MotionEvent.ACTION_UP: if (mVelocityTracker != null) { mVelocityTracker.clear(); mVelocityTracker.recycle(); mVelocityTracker = null; } if (isPull) { mPullY = 0; isPull = false; mPullListener.onPullDownDrop(); return true; } break; } return true; } }); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (isPull) { // 正在下拉时，阻住Touch事件向下传递，同时会向各个ChildView发送ACTION_CANLE事件， // 使之前捕捉到了ACTION_DOWN事件的ChildView回复到正常状态 return true; } return super.onInterceptTouchEvent(ev); } @Override public boolean onTouchEvent(MotionEvent ev) { if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(ev); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: mDownY = (int) ev.getY(); break; case MotionEvent.ACTION_MOVE: mMoveY = (int) ev.getY(); if (!isPull) { if (getFirstVisiblePosition() == 0) { View view = getChildAt(0); mVelocityTracker.computeCurrentVelocity(1000, 8000f); if (mVelocityTracker.getYVelocity() > 500// 下拉速度大于500 && (view == null || view.getTop() == getPaddingTop()) // 已拉动到顶部 && Math.abs(mMoveY - mDownY) > 15 * density) { // 下拉距离超过20dp mPullY = mMoveY; if (mPullListener.onPullDownStart()) { // 根据返回值确认是否进入下拉状态 isPull = true; } } } } else { // 阻尼下拉(随着下拉距离增加，阻力增加) mPullListener.onPullDown(mMoveY - mPullY); // 等阻力下拉(阻力恒定，不随下拉距离增加而增加) // mPullListener.onPullDown(mMoveY - mPullY - getScrollY()); if (mMoveY < mPullY) { isPull = false; } return true; } break; case MotionEvent.ACTION_UP: if (mVelocityTracker != null) { mVelocityTracker.clear(); mVelocityTracker.recycle(); mVelocityTracker = null; } if (isPull) { mPullY = 0; isPull = false; mPullListener.onPullDownDrop(); return true; } break; case MotionEvent.ACTION_CANCEL: break; } return super.onTouchEvent(ev); } }

然后是外层的LinearyLayer，监听PullableListView的下拉回调，实现下拉效果。同时提供ListView(GridView)的外部接口，如 setEmptyView(View view),setAdapter(ListAdapter adapter)...等等，这里只提供部分我需要使用的，可以根据自身需求去提供外部接口。

代码中R.drawable.pulltorefresh 和 R.drawable.loading 分别是下拉箭头和刷新滚动条的图片，这里不提供了，自己随意找两张图片贴上就行了。

PullToRefreshView：

public class PullToRefreshView extends LinearLayout { protected static final String TAG = "PullToRefreshView"; /** * 下拉阻力系数 */ private static final float SCALL_PULL_DOWW = 2.0f; private View mView; private PullableListView mListView; private TextView mPullTv; private ImageView mProgressBar; private View mPullV; private View mEmptyView; private boolean isInited; private boolean canRefresh; private boolean isRefreshing; private boolean isPullable = true; private int mOrMargin; private ObjectAnimator mArrowRotateAnimator; private Animation mProAnimation; private PullToRefreshListener mPullToRefreshListener; public PullToRefreshView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); initView(context); } public PullToRefreshView(Context context, AttributeSet attrs) { super(context, attrs); initView(context); } public PullToRefreshView(Context context) { super(context); initView(context); } public interface PullToRefreshListener { /** * do data refresh here */ public void onRefreshStart(); /** * do view update here */ public void onRefreshFinished(); } private void initView(Context context) { if (!isInited) { isInited = true; mView = LayoutInflater.from(context).inflate(R.layout.view_pulltorefresh, null); mProgressBar = (ImageView) mView.findViewById(R.id.iv_pulltorefresh_arrow); mProgressBar.setImageResource(R.drawable.pulltorefresh); mPullTv = (TextView) mView.findViewById(R.id.tv_pulltorefresh); mPullV = mView.findViewById(R.id.ly_pulltorefresh_pull); mListView = (PullableListView) mView.findViewById(R.id.gv_smarturc_urcs); mListView.setPullListener(mPullListener); LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT); addView(mView, lp); LayoutParams lParams = (LayoutParams) mPullV.getLayoutParams(); mOrMargin = lParams.topMargin; mProAnimation = AnimationUtils.loadAnimation(getContext(), R.anim.anim_progressbar); } } private PullListener mPullListener = new PullListener() { @Override public boolean onPullDownStart() { if (isRefreshing || !isPullable) { return false; } mPullTv.setText("下拉刷新"); mProgressBar.setRotation(0f); mProgressBar.setImageResource(R.drawable.pulltorefresh); if (mProgressBar.getAnimation() != null) { mProgressBar.clearAnimation(); } return true; } @Override public void onPullDown(int moveY) { if (isRefreshing || !isPullable) { return; } moveY = (int) Math.max(0, moveY / SCALL_PULL_DOWW); mView.scrollTo(0, -moveY); mEmptyView.scrollTo(0, -moveY); if (!canRefresh && Math.abs(mView.getScrollY()) > Math.abs(mOrMargin)) { mPullTv.setText("松开刷新"); canRefresh = true; if (mArrowRotateAnimator != null) { mArrowRotateAnimator.cancel(); } float rotation = mProgressBar.getRotation(); mArrowRotateAnimator = ObjectAnimator.ofFloat(mProgressBar, "rotation", rotation, 180f); mArrowRotateAnimator.setDuration(100).start(); } else if (canRefresh && Math.abs(mView.getScrollY()) <= Math.abs(mOrMargin)) { mPullTv.setText("下拉刷新"); canRefresh = false; if (mArrowRotateAnimator != null) { mArrowRotateAnimator.cancel(); } float rotation = mProgressBar.getRotation(); mArrowRotateAnimator = ObjectAnimator.ofFloat(mProgressBar, "rotation", rotation, 0f); mArrowRotateAnimator.setDuration(100).start(); } } @Override public void onPullDownDrop() { if (canRefresh) { setRefreshing(); } else { isRefreshing = false; backTo(mView.getScrollY(), 0); } } }; private void backTo(final int from, final int to) { ObjectAnimator.ofInt(mView, "scrollY", from, to).setDuration(300) .start(); ObjectAnimator.ofInt(mEmptyView, "scrollY", from, to).setDuration(300) .start(); } /** * 设置为正在刷新状态 */ public void setRefreshing() { isRefreshing = true; mProgressBar.setImageResource(R.drawable.loading); mProgressBar.startAnimation(mProAnimation); mPullTv.setText("正在刷新"); backTo(mView.getScrollY(), mOrMargin); if (mPullToRefreshListener != null) { mPullToRefreshListener.onRefreshStart(); } } /** * 刷新完成 */ public void setRrefreshFinish() { if (isRefreshing) { isRefreshing = false; backTo(mView.getScrollY(), 0); } if (mPullToRefreshListener != null) { mPullToRefreshListener.onRefreshFinished(); } } public void setPullable(boolean pullable) { isPullable = pullable; } public void setPullToRefreshListener( PullToRefreshListener mPullToRefreshListener) { this.mPullToRefreshListener = mPullToRefreshListener; } public void setAdapter(ListAdapter adapter) { mListView.setAdapter(adapter); } public void setEmptyView(View emptyView) { mListView.setEmptyView(emptyView); this.mEmptyView = emptyView; } public void setOnItemClickListener(OnItemClickListener itemClickListener) { mListView.setOnItemClickListener(itemClickListener); } public void setOnItemLongClickListener(OnItemLongClickListener itemLongClickListener) { mListView.setOnItemLongClickListener(itemLongClickListener); } }

layout-view_pulltorefresh:

<"1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#cccccc" android:orientation="vertical" > <LinearLayout android:id="@+id/ly_pulltorefresh_pull" android:layout_width="wrap_content" android:layout_height="48dp" android:layout_gravity="center_horizontal" android:layout_marginTop="-48dp" > <ImageView android:id="@+id/iv_pulltorefresh_arrow" android:layout_width="20dp" android:layout_height="match_parent" android:scaleType="fitCenter" android:src="@drawable/pulltorefresh" /> <TextView android:id="@+id/tv_pulltorefresh" android:layout_width="wrap_content" android:layout_height="match_parent" android:layout_marginBottom="4dp" android:layout_marginLeft="8dp" android:gravity="center" android:textColor="@android:color/white" android:textSize="16sp" /> </LinearLayout> <com.example.pulltorefresh.PullableListView android:id="@+id/gv_smarturc_urcs" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@android:color/transparent" android:overScrollMode="never" android:scrollingCache="false" > </com.example.pulltorefresh.PullableListView> </LinearLayout>

anim-anim_progressbar:

<"1.0" encoding="utf-8"?> <rotate xmlns:android="http://schemas.android.com/apk/res/android" android:fromDegrees="0" android:toDegrees="360" android:pivotX="50%" android:pivotY="50%" android:repeatCount="infinite" android:repeatMode="restart" android:duration="800" android:interpolator="@android:anim/linear_interpolator"/>

最后是DEMO ACTIVITY：

public class PullToRefreshActivity extends Activity { private PullToRefreshView mPullToRefreshView; private List<String> data = new ArrayList<String>(); private MyAdapter mAdapter; private Handler mHandler; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.activity_pulltorefresh); mHandler = new Handler(); mPullToRefreshView = (PullToRefreshView) findViewById(R.id.pullToRefreshView1); mAdapter = new MyAdapter(); mPullToRefreshView.setAdapter(mAdapter); mPullToRefreshView.setEmptyView(findViewById(R.id.empty)); mPullToRefreshView.setOnItemLongClickListener(new OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), "Long click : " + data.get(position), Toast.LENGTH_SHORT).show(); return true; } }); mPullToRefreshView.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Toast.makeText(getApplicationContext(), data.get(position), Toast.LENGTH_SHORT) .show(); } }); mPullToRefreshView.setPullToRefreshListener(new PullToRefreshListener() { @Override public void onRefreshStart() { // 模拟刷新数据 mHandler.postDelayed(new Runnable() { @Override public void run() { data.add(String.valueOf((int) (Math.random() * 1000))); mPullToRefreshView.setRrefreshFinish(); } }, 2000); } @Override public void onRefreshFinished() { // 更新视图 mAdapter.notifyDataSetChanged(); } }); // mHandler.postDelayed(new Runnable() { // @Override // public void run() { // // TODO Auto-generated method stub // mPullToRefreshView.setRefreshing(); // } // }, 500); } public class MyAdapter extends BaseAdapter { @Override public int getCount() { // TODO Auto-generated method stub return data.size(); } @Override public Object getItem(int position) { // TODO Auto-generated method stub return data.get(position); } @Override public long getItemId(int position) { // TODO Auto-generated method stub return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { // TODO Auto-generated method stub if (convertView == null) { convertView = new TextView(PullToRefreshActivity.this); } TextView textView = (TextView) convertView; textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, 40f); textView.setPadding(30, 30, 30, 30); textView.setText(data.get(position)); return convertView; } } }

layout-activity_pulltorefresh:

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持查字典教程网。