Android Listview动态加载数据

openkk 12年前

在研究网络数据加载的问题，比如我有几百，甚至上千条数据，这些数据如果一次性全部加载到arraylist，然后再加载到Listview中。我们必然会去单独开线程来做，这样造成的结果就是会出现等待时间很长，用户体验非常不好。我的想法是动态加载数据，第一次加载十条，然后往下面滑动的时候再追加十条，再往下面滑动的时候再去追加，这样大大减少了用户等待的时间，同时给处理数据留下了时间。网上看到了这样一个例子，挺好的，我改动了一下，达到了我想要的结果。

import android.app.Activity;  import android.os.Bundle;  import android.os.Handler;  import android.os.Message;  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.Toast;  import android.widget.AbsListView.OnScrollListener;  import android.widget.LinearLayout.LayoutParams;    public class ListViewForLoading extends Activity implements OnScrollListener {        private listViewAdapter adapter = new listViewAdapter();      ListView listView;      LinearLayout loadingLayout;      private Thread mThread;      /**       * 设置布局显示属性       */      private LayoutParams mLayoutParams = new LinearLayout.LayoutParams(              LinearLayout.LayoutParams.WRAP_CONTENT,              LinearLayout.LayoutParams.WRAP_CONTENT);      /**       * 设置布局显示目标最大化属性       */      private LayoutParams FFlayoutParams = new LinearLayout.LayoutParams(              LinearLayout.LayoutParams.FILL_PARENT,              LinearLayout.LayoutParams.FILL_PARENT);        private ProgressBar progressBar;        /** Called when the activity is first created. */      @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);          init();      }        private void init() {          // TODO Auto-generated method stub          // 线性布局          LinearLayout layout = new LinearLayout(this);          // 设置布局 水平方向          layout.setOrientation(LinearLayout.HORIZONTAL);          // 进度条          progressBar = new ProgressBar(this);          // 进度条显示位置          progressBar.setPadding(0, 0, 15, 0);          // 把进度条加入到layout中          layout.addView(progressBar, mLayoutParams);          // 文本内容          TextView textView = new TextView(this);          textView.setText("加载中...");          textView.setGravity(Gravity.CENTER_VERTICAL);          // 把文本加入到layout中          layout.addView(textView, FFlayoutParams);          // 设置layout的重力方向，即对齐方式是          layout.setGravity(Gravity.CENTER);            // 设置ListView的页脚layout          loadingLayout = new LinearLayout(this);          loadingLayout.addView(layout, mLayoutParams);          loadingLayout.setGravity(Gravity.CENTER);            // 得到一个ListView用来显示条目          listView = (ListView) findViewById(R.id.tv);          // 添加到脚页显示          listView.addFooterView(loadingLayout);          // 给ListView添加适配器          listView.setAdapter(adapter);          // 给ListView注册滚动监听          listView.setOnScrollListener(this);      }        /**       * 要用用于生成显示数据       *        * @author huangbq       *        */      class listViewAdapter extends BaseAdapter {          int count = 10;            public int getCount() {              return count;          }            public Object getItem(int pos) {              return pos;          }            public long getItemId(int pos) {              return pos;          }            public View getView(int pos, View v, ViewGroup p) {              TextView view;              if (v == null) {                  view = new TextView(ListViewForLoading.this);              } else {                  view = (TextView) v;              }              view.setText("ListItem " + pos);              view.setTextSize(20f);              view.setGravity(Gravity.CENTER);              view.setHeight(60);              return view;          }      }        @Override      public void onScroll(AbsListView view, int firstVisibleItem,              int visibleItemCount, int totalItemCount) {          // TODO Auto-generated method stub          if(firstVisibleItem+visibleItemCount==totalItemCount)          {              //开线程去下载网络数据              if (mThread == null || !mThread.isAlive()) {                  mThread = new Thread() {                      @Override                      public void run() {                          try {                              //这里放你网络数据请求的方法，我在这里用线程休眠5秒方法来处理                              Thread.sleep(5000);                          } catch (InterruptedException e) {                              e.printStackTrace();                          }                          Message message = new Message();                          message.what = 1;                          handler.sendMessage(message);                      }                  };                  mThread.start();                              }          }      }        @Override      public void onScrollStateChanged(AbsListView view, int scrollState) {          // TODO Auto-generated method stub              }        private Handler handler = new Handler() {          @Override          public void handleMessage(Message msg) {              // TODO Auto-generated method stub              switch (msg.what) {              case 1:                  if (adapter.count <= 41) {                      adapter.count += 10;                      int currentPage = adapter.count / 10;                      Toast.makeText(getApplicationContext(),"第" + currentPage + "页", Toast.LENGTH_LONG).show();                  } else {                      listView.removeFooterView(loadingLayout);                  }                  //重新刷新Listview的adapter里面数据                  adapter.notifyDataSetChanged();                  break;              default:                  break;              }          }        };  }

运行结果如下图：