Android ListView實現(xiàn)下拉加載功能

更新時間：2017年08月23日 09:49:13 作者：高淳小弟

這篇文章主要為大家詳細介紹了Android ListView實現(xiàn)下拉加載功能，具有一定的參考價值，感興趣的小伙伴們可以參考一下

本文實例為大家分享了ListView下拉加載展示的具體代碼，供大家參考，具體內(nèi)容如下

1、MyListView.Java

public class MyListView extends ListView implements OnScrollListener { 
 
 private final static int RELEASE_To_REFRESH = 0;// 下拉過程的狀態(tài)值 
 private final static int PULL_To_REFRESH = 1; // 從下拉返回到不刷新的狀態(tài)值 
 private final static int REFRESHING = 2;// 正在刷新的狀態(tài)值 
 private final static int DONE = 3; 
 private final static int LOADING = 4; 
 
 // 實際的padding的距離與界面上偏移距離的比例 
 private final static int RATIO = 3; 
 private LayoutInflater inflater; 
 
 // ListView頭部下拉刷新的布局 
 private LinearLayout headerView; 
 private TextView lvHeaderTipsTv; 
 private TextView lvHeaderLastUpdatedTv; 
 private ImageView lvHeaderArrowIv; 
 private ProgressBar lvHeaderProgressBar; 
 
 // 定義頭部下拉刷新的布局的高度 
 private int headerContentHeight; 
 
 private RotateAnimation animation; 
 private RotateAnimation reverseAnimation; 
 
 private int startY; 
 private int state; 
 private boolean isBack; 
 
 // 用于保證startY的值在一個完整的touch事件中只被記錄一次 
 private boolean isRecored; 
 
 private OnRefreshListener refreshListener; 
 
 private boolean isRefreshable; 
 
 public MyListView(Context context) { 
  super(context); 
  init(context); 
 } 
 
 public MyListView(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  init(context); 
 } 
 
 private void init(Context context) { 
  inflater = LayoutInflater.from(context); 
  headerView = (LinearLayout) inflater.inflate(R.layout.lv_header, null); 
  lvHeaderTipsTv = (TextView) headerView 
    .findViewById(R.id.lvHeaderTipsTv); 
  lvHeaderLastUpdatedTv = (TextView) headerView 
    .findViewById(R.id.lvHeaderLastUpdatedTv); 
 
  lvHeaderArrowIv = (ImageView) headerView 
    .findViewById(R.id.lvHeaderArrowIv); 
  // 設置下拉刷新圖標的最小高度和寬度 
  lvHeaderArrowIv.setMinimumWidth(70); 
  lvHeaderArrowIv.setMinimumHeight(50); 
 
  lvHeaderProgressBar = (ProgressBar) headerView 
    .findViewById(R.id.lvHeaderProgressBar); 
  measureView(headerView); 
  headerContentHeight = headerView.getMeasuredHeight(); 
  // 設置內(nèi)邊距，正好距離頂部為一個負的整個布局的高度，正好把頭部隱藏 
  headerView.setPadding(0, -1 * headerContentHeight, 0, 0); 
  // 重繪一下 
  headerView.invalidate(); 
  // 將下拉刷新的布局加入ListView的頂部 
  addHeaderView(headerView, null, false); 
  // 設置滾動監(jiān)聽事件 
  setOnScrollListener(this); 
 
  // 設置旋轉(zhuǎn)動畫事件 
  animation = new RotateAnimation(0, -180, 
    RotateAnimation.RELATIVE_TO_SELF, 0.5f, 
    RotateAnimation.RELATIVE_TO_SELF, 0.5f); 
  animation.setInterpolator(new LinearInterpolator()); 
  animation.setDuration(250); 
  animation.setFillAfter(true); 
 
  reverseAnimation = new RotateAnimation(-180, 0, 
    RotateAnimation.RELATIVE_TO_SELF, 0.5f, 
    RotateAnimation.RELATIVE_TO_SELF, 0.5f); 
  reverseAnimation.setInterpolator(new LinearInterpolator()); 
  reverseAnimation.setDuration(200); 
  reverseAnimation.setFillAfter(true); 
 
  // 一開始的狀態(tài)就是下拉刷新完的狀態(tài)，所以為DONE 
  state = DONE; 
  // 是否正在刷新 
  isRefreshable = false; 
 } 
 
 @Override 
 public void onScrollStateChanged(AbsListView view, int scrollState) { 
 
 } 
 
 @Override 
 public void onScroll(AbsListView view, int firstVisibleItem, 
   int visibleItemCount, int totalItemCount) { 
  if (firstVisibleItem == 0) { 
   isRefreshable = true; 
  } else { 
   isRefreshable = false; 
  } 
 } 
 
 @Override 
 public boolean onTouchEvent(MotionEvent ev) { 
  if (isRefreshable) { 
   switch (ev.getAction()) { 
   case MotionEvent.ACTION_DOWN: 
    if (!isRecored) { 
     isRecored = true; 
     startY = (int) ev.getY();// 手指按下時記錄當前位置 
    } 
    break; 
   case MotionEvent.ACTION_UP: 
    if (state != REFRESHING && state != LOADING) { 
     if (state == PULL_To_REFRESH) { 
      state = DONE; 
      changeHeaderViewByState(); 
     } 
     if (state == RELEASE_To_REFRESH) { 
      state = REFRESHING; 
      changeHeaderViewByState(); 
      onLvRefresh(); 
     } 
    } 
    isRecored = false; 
    isBack = false; 
 
    break; 
 
   case MotionEvent.ACTION_MOVE: 
    int tempY = (int) ev.getY(); 
    if (!isRecored) { 
     isRecored = true; 
     startY = tempY; 
    } 
    if (state != REFRESHING && isRecored && state != LOADING) { 
     // 保證在設置padding的過程中，當前的位置一直是在head，否則如果當列表超出屏幕的話，當在上推的時候，列表會同時進行滾動 
     // 可以松手去刷新了 
     if (state == RELEASE_To_REFRESH) { 
      setSelection(0); 
      // 往上推了，推到了屏幕足夠掩蓋head的程度，但是還沒有推到全部掩蓋的地步 
      if (((tempY - startY) / RATIO < headerContentHeight)// 由松開刷新狀態(tài)轉(zhuǎn)變到下拉刷新狀態(tài) 
        && (tempY - startY) > 0) { 
       state = PULL_To_REFRESH; 
       changeHeaderViewByState(); 
      } 
      // 一下子推到頂了 
      else if (tempY - startY <= 0) {// 由松開刷新狀態(tài)轉(zhuǎn)變到done狀態(tài) 
       state = DONE; 
       changeHeaderViewByState(); 
      } 
     } 
     // 還沒有到達顯示松開刷新的時候,DONE或者是PULL_To_REFRESH狀態(tài) 
     if (state == PULL_To_REFRESH) { 
      setSelection(0); 
      // 下拉到可以進入RELEASE_TO_REFRESH的狀態(tài) 
      if ((tempY - startY) / RATIO >= headerContentHeight) {// 由done或者下拉刷新狀態(tài)轉(zhuǎn)變到松開刷新 
       state = RELEASE_To_REFRESH; 
       isBack = true; 
       changeHeaderViewByState(); 
      } 
      // 上推到頂了 
      else if (tempY - startY <= 0) {// 由DOne或者下拉刷新狀態(tài)轉(zhuǎn)變到done狀態(tài) 
       state = DONE; 
       changeHeaderViewByState(); 
      } 
     } 
     // done狀態(tài)下 
     if (state == DONE) { 
      if (tempY - startY > 0) { 
       state = PULL_To_REFRESH; 
       changeHeaderViewByState(); 
      } 
     } 
     // 更新headView的size 
     if (state == PULL_To_REFRESH) { 
      headerView.setPadding(0, -1 * headerContentHeight 
        + (tempY - startY) / RATIO, 0, 0); 
 
     } 
     // 更新headView的paddingTop 
     if (state == RELEASE_To_REFRESH) { 
      headerView.setPadding(0, (tempY - startY) / RATIO 
        - headerContentHeight, 0, 0); 
     } 
 
    } 
    break; 
 
   default: 
    break; 
   } 
  } 
  return super.onTouchEvent(ev); 
 } 
 
 // 當狀態(tài)改變時候，調(diào)用該方法，以更新界面 
 private void changeHeaderViewByState() { 
  switch (state) { 
  case RELEASE_To_REFRESH: 
   lvHeaderArrowIv.setVisibility(View.VISIBLE); 
   lvHeaderProgressBar.setVisibility(View.GONE); 
   lvHeaderTipsTv.setVisibility(View.VISIBLE); 
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE); 
 
   lvHeaderArrowIv.clearAnimation();// 清除動畫 
   lvHeaderArrowIv.startAnimation(animation);// 開始動畫效果 
 
   lvHeaderTipsTv.setText("松開刷新"); 
   break; 
  case PULL_To_REFRESH: 
   lvHeaderProgressBar.setVisibility(View.GONE); 
   lvHeaderTipsTv.setVisibility(View.VISIBLE); 
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE); 
   lvHeaderArrowIv.clearAnimation(); 
   lvHeaderArrowIv.setVisibility(View.VISIBLE); 
   // 是由RELEASE_To_REFRESH狀態(tài)轉(zhuǎn)變來的 
   if (isBack) { 
    isBack = false; 
    lvHeaderArrowIv.clearAnimation(); 
    lvHeaderArrowIv.startAnimation(reverseAnimation); 
 
    lvHeaderTipsTv.setText("下拉刷新"); 
   } else { 
    lvHeaderTipsTv.setText("下拉刷新"); 
   } 
   break; 
 
  case REFRESHING: 
 
   headerView.setPadding(0, 0, 0, 0); 
 
   lvHeaderProgressBar.setVisibility(View.VISIBLE); 
   lvHeaderArrowIv.clearAnimation(); 
   lvHeaderArrowIv.setVisibility(View.GONE); 
   lvHeaderTipsTv.setText("正在刷新..."); 
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE); 
   break; 
  case DONE: 
   headerView.setPadding(0, -1 * headerContentHeight, 0, 0); 
 
   lvHeaderProgressBar.setVisibility(View.GONE); 
   lvHeaderArrowIv.clearAnimation(); 
   lvHeaderArrowIv.setImageResource(R.drawable.arrow); 
   lvHeaderTipsTv.setText("下拉刷新"); 
   lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE); 
   break; 
  } 
 } 
 
 // 此方法直接照搬自網(wǎng)絡上的一個下拉刷新的demo，此處是“估計”headView的width以及height 
 private void measureView(View child) { 
  ViewGroup.LayoutParams params = child.getLayoutParams(); 
  if (params == null) { 
   params = new ViewGroup.LayoutParams( 
     ViewGroup.LayoutParams.FILL_PARENT, 
     ViewGroup.LayoutParams.WRAP_CONTENT); 
  } 
  int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, 
    params.width); 
  int lpHeight = params.height; 
  int childHeightSpec; 
  if (lpHeight > 0) { 
   childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, 
     MeasureSpec.EXACTLY); 
  } else { 
   childHeightSpec = MeasureSpec.makeMeasureSpec(0, 
     MeasureSpec.UNSPECIFIED); 
  } 
  child.measure(childWidthSpec, childHeightSpec); 
 } 
 
 public void setonRefreshListener(OnRefreshListener refreshListener) { 
  this.refreshListener = refreshListener; 
  isRefreshable = true; 
 } 
 
 public interface OnRefreshListener { 
  public void onRefresh(); 
 } 
 
 public void onRefreshComplete() { 
  state = DONE; 
  lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString()); 
  changeHeaderViewByState(); 
 } 
 
 private void onLvRefresh() { 
  if (refreshListener != null) { 
   refreshListener.onRefresh(); 
  } 
 } 
 
 public void setAdapter(LvAdapter adapter) { 
  lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString()); 
  super.setAdapter(adapter); 
 } 
 
}

2、MainActivity.java

public class MainActivity extends Activity { 
 private List<String> list; 
 private MyListView lv; 
 private LvAdapter adapter; 
 
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.main); 
  lv = (MyListView) findViewById(R.id.lv); 
  list = new ArrayList<String>(); 
  list.add("loonggg"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  list.add("我們都是開發(fā)者"); 
  adapter = new LvAdapter(list, this); 
  lv.setAdapter(adapter); 
 
  lv.setonRefreshListener(new OnRefreshListener() { 
 
   @Override 
   public void onRefresh() { 
    new AsyncTask<Void, Void, Void>() { 
     protected Void doInBackground(Void... params) { 
      try { 
       Thread.sleep(1000); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
      list.add("刷新后添加的內(nèi)容"); 
      return null; 
     } 
 
     @Override 
     protected void onPostExecute(Void result) { 
      adapter.notifyDataSetChanged(); 
      lv.onRefreshComplete(); 
     } 
    }.execute(null, null, null); 
   } 
  }); 
 } 
}

3、LvAdapter
public class LvAdapter extends BaseAdapter {
    private List<String> list;
    private Context context;

    public LvAdapter(List<String> list, Context context) {
        this.list = list;
        this.context = context;
    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        TextView tv = new TextView(context.getApplicationContext());
        tv.setText(list.get(position));
        return tv;
    }

}