1. 引言：
为了提高ListView的效率和应用程序的性能，在Android应用程序中不应该一次性加载ListView所要显示的全部信息，而是采取分批加载策略，随着用户的滑动，动态的从后台加载所需的数据，并渲染到ListView组件中，这样可以极大的改善应用程序的性能和用户体验。2. 交互：
进入ListView组件，首先预加载N条记录，当用户滑动到最后一条记录显示加载提示信息，并从后台加载N条数据，接着渲染UI界面。3. 效果图：
4. 程序实现：
[java] view plain copy package com.focus.loading; import android.app.ListActivity; import android.os.Bundle; import android.os.Handler; import android.view.Gravity; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.BaseAdapter; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.ProgressBar; import android.widget.TextView; import android.widget.AbsListView.OnScrollListener; import android.widget.LinearLayout.LayoutParams; public class ListViewLoadingActivity extends ListActivity implements OnScrollListener { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); /** * "加载项"布局，此布局被添加到ListView的Footer中。 */ mLoadLayout = new LinearLayout(this); mLoadLayout.setMinimumHeight(60); mLoadLayout.setGravity(Gravity.CENTER); mLoadLayout.setOrientation(LinearLayout.HORIZONTAL); /** * 向"加载项"布局中添加一个圆型进度条。 */ ProgressBar mProgressBar = new ProgressBar(this); mProgressBar.setPadding(0, 0, 15, 0); mLoadLayout.addView(mProgressBar, mProgressBarLayoutParams); /** * 向"加载项"布局中添加提示信息。 */ TextView mTipContent = new TextView(this); mTipContent.setText("加载中..."); mLoadLayout.addView(mTipContent, mTipContentLayoutParams); /** * 获取ListView组件，并将"加载项"布局添加到ListView组件的Footer中。 */ mListView = getListView(); mListView.addFooterView(mLoadLayout); /** * 组ListView组件设置Adapter,并设置滑动监听事件。 */ setListAdapter(mListViewAdapter); mListView.setOnScrollListener(this); } public void onScroll(AbsListView view, int mFirstVisibleItem, int mVisibleItemCount, int mTotalItemCount) { mLastItem = mFirstVisibleItem + mVisibleItemCount - 1; if (mListViewAdapter.count > mCount) { mListView.removeFooterView(mLoadLayout); } } public void onScrollStateChanged(AbsListView view, int mScrollState) { /** * 当ListView滑动到最后一条记录时这时，我们会看到已经被添加到ListView的"加载项"布局， 这时应该加载剩余数据。 */ if (mLastItem == mListViewAdapter.count && mScrollState == OnScrollListener.SCROLL_STATE_IDLE) { if (mListViewAdapter.count <= mCount) { mHandler.postDelayed(new Runnable() { @Override public void run() { mListViewAdapter.count += 10; mListViewAdapter.notifyDataSetChanged(); mListView.setSelection(mLastItem); } }, 1000); } } } class ListViewAdapter extends BaseAdapter { int count = 10; public int getCount() { return count; } public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } public View getView(int position, View view, ViewGroup parent) { TextView mTextView; if (view == null) { mTextView = new TextView(ListViewLoadingActivity.this); } else { mTextView = (TextView) view; } mTextView.setText("Item " + position); mTextView.setTextSize(20f); mTextView.setGravity(Gravity.CENTER); mTextView.setHeight(60); return mTextView; } } private LinearLayout mLoadLayout; private ListView mListView; private ListViewAdapter mListViewAdapter = new ListViewAdapter(); private int mLastItem = 0; private int mCount = 41; private final Handler mHandler = new Handler(); private final LayoutParams mProgressBarLayoutParams = new LinearLayout.LayoutParams( LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT); private final LayoutParams mTipContentLayoutParams = new LinearLayout.LayoutParams( LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT); }
转载于:https://www.cnblogs.com/sishahu/p/5366636.html
相关资源：Android开发中Listview动态加载数据的方法示例