1. 引言：
為了提高ListView的效率和應(yīng)用程序的性能，在Android應(yīng)用程序中不應(yīng)該一次性加載ListView所要顯示的全部信息，而是采取分批加載策略，隨著用戶(hù)的滑動(dòng)，動(dòng)態(tài)的從后臺(tái)加載所需的數(shù)據(jù)，并渲染到ListView組件中，這樣可以極大的改善應(yīng)用程序的性能和用戶(hù)體驗(yàn)。
2. 交互：
進(jìn)入ListView組件，首先預(yù)加載N條記錄，當(dāng)用戶(hù)滑動(dòng)到最后一條記錄顯示加載提示信息，并從后臺(tái)加載N條數(shù)據(jù)，接著渲染UI界面。
3. 效果圖：
4. 程序?qū)崿F(xiàn)：
- 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);
-
-
-
- mLoadLayout = new LinearLayout(this);
- mLoadLayout.setMinimumHeight(60);
- mLoadLayout.setGravity(Gravity.CENTER);
- mLoadLayout.setOrientation(LinearLayout.HORIZONTAL);
-
-
-
- ProgressBar mProgressBar = new ProgressBar(this);
- mProgressBar.setPadding(0, 0, 15, 0);
- mLoadLayout.addView(mProgressBar, mProgressBarLayoutParams);
-
-
-
- TextView mTipContent = new TextView(this);
- mTipContent.setText("加載中...");
- mLoadLayout.addView(mTipContent, mTipContentLayoutParams);
-
-
-
- mListView = getListView();
- mListView.addFooterView(mLoadLayout);
-
-
-
- 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) {
-
-
-
-
- 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);
- }
