listView下拉刷新加载数据

          在2月27号的时候，完成listView滑动刷新代码，昨天的时候，完成listView下拉刷新(sina微博Android客户端效果)效果的解析，其实在三个例子当中，感觉最好的应该是listView下拉刷新(sina微博Android客户端效果)里面的代码，今天进行第三个例子的解析，其中代码中添加了很多注释，所以文中代码和以前上传的代码注释方面会有很多不同，在文章的下面，会提供最新的代码下载。

         看这个代码的时候，刚开始一直是没有弄明白是怎么样运行的，后来通过不断的打log，大概弄了个明白，先给大家看下log:

          在下面，会把log语句的具体含义简单的说明一下。

          然后再把代码贴出来，按照log，一步一步跟踪，看它的实现过程：

public boolean onTouchEvent(MotionEvent event) {if (isRefreshable) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:if (firstItemIndex == 0 && !isRecored) {isRecored = true;startY = (int) event.getY();Log.v("@@@@@@", "ACTION_DOWN 这是第  "+i+++"步" +1 );}break;case MotionEvent.ACTION_UP:if (state != REFRESHING && state != LOADING) {if (state == DONE) {}if (state == PULL_To_REFRESH) {state = DONE;Log.v("@@@@@@", "ACTION_UP PULL_To_REFRESH and changeHeaderViewByState()" +" 这是第  "+i+++"步前"+2 );changeHeaderViewByState();Log.v("@@@@@@", "ACTION_UP PULL_To_REFRESH and changeHeaderViewByState() " +"这是第  "+i+++"步后"+2 );}if (state == RELEASE_To_REFRESH) {state = REFRESHING;Log.v("@@@@@@", "ACTION_UP RELEASE_To_REFRESH changeHeaderViewByState() " +"这是第  "+i+++"步" +3);changeHeaderViewByState();onRefresh();Log.v("@@@@@@", "ACTION_UP RELEASE_To_REFRESH changeHeaderViewByState()" +" 这是第  "+i+++"步" +3);}}isRecored = false;isBack = false;break;case MotionEvent.ACTION_MOVE:int tempY = (int) event.getY();if (!isRecored && firstItemIndex == 0) {isRecored = true;startY = tempY;Log.v("@@@@@@", "ACTION_MOVE 这是第  "+i+++"步" +4);}if (state != REFRESHING && isRecored && state != LOADING) {if (state == RELEASE_To_REFRESH) {setSelection(0);if (((tempY - startY) / RATIO < headContentHeight)&& (tempY - startY) > 0) {state = PULL_To_REFRESH;changeHeaderViewByState();Log.v("@@@@@@", "changeHeaderViewByState() 这是第  "+i+++"步"+5 );}else if (tempY - startY <= 0) {state = DONE;changeHeaderViewByState();Log.v("@@@@@@", "ACTION_MOVE RELEASE_To_REFRESH 2  changeHeaderViewByState " +"这是第  "+i+++"步" +6);}}if (state == PULL_To_REFRESH) {setSelection(0);if ((tempY - startY) / RATIO >= headContentHeight) {state = RELEASE_To_REFRESH;isBack = true;Log.v("@@@@@@", "changeHeaderViewByState " +"这是第  "+i+++"步前"+7 );changeHeaderViewByState();Log.v("@@@@@@", "changeHeaderViewByState " +"这是第  "+i+++"步后"+7 );}else if (tempY - startY <= 0) {state = DONE;changeHeaderViewByState();Log.v("@@@@@@", "ACTION_MOVE changeHeaderViewByState PULL_To_REFRESH 2" +" 这是第  "+i+++"步" +8);}}if (state == DONE) {if (tempY - startY > 0) {state = PULL_To_REFRESH;Log.v("@@@@@@", "ACTION_MOVE DONE changeHeaderViewByState " +"这是第  "+i+++"步前" +9);changeHeaderViewByState();Log.v("@@@@@@", "ACTION_MOVE DONE changeHeaderViewByState " +"这是第  "+i+++"步后" +9);}}if (state == PULL_To_REFRESH) {headView.setPadding(0, -1 * headContentHeight+(tempY - startY) / RATIO, 0, 0);Log.v("@@@@@@", -1 * headContentHeight+(tempY - startY) / RATIO+"ACTION_MOVE PULL_To_REFRESH 3  这是第  "+i+++"步"+10 );}if (state == RELEASE_To_REFRESH) {headView.setPadding(0, (tempY - startY) / RATIO- headContentHeight, 0, 0);Log.v("@@@@@@", "ACTION_MOVE PULL_To_REFRESH 4 这是第  "+i+++"步" +11);}}break;}}return super.onTouchEvent(event);}private void changeHeaderViewByState() {switch (state) {case RELEASE_To_REFRESH:arrowImageView.setVisibility(View.VISIBLE);progressBar.setVisibility(View.GONE);tipsTextview.setVisibility(View.VISIBLE);lastUpdatedTextView.setVisibility(View.VISIBLE);arrowImageView.clearAnimation();arrowImageView.startAnimation(animation);tipsTextview.setText("请释放 刷新");Log.v("@@@@@@", "RELEASE_To_REFRESH 这是第  "+i+++"步"+12 +"请释放 刷新" );break;case PULL_To_REFRESH:progressBar.setVisibility(View.GONE);tipsTextview.setVisibility(View.VISIBLE);lastUpdatedTextView.setVisibility(View.VISIBLE);arrowImageView.clearAnimation();arrowImageView.setVisibility(View.VISIBLE);if (isBack) {isBack = false;arrowImageView.clearAnimation();arrowImageView.startAnimation(reverseAnimation);tipsTextview.setText("isBack  is true ！！！");} else {tipsTextview.setText("isBack  is false ！！！");}Log.v("@@@@@@", "PULL_To_REFRESH 这是第  "+i+++"步" +13+"  changeHeaderViewByState()");break;case REFRESHING:headView.setPadding(0, 0, 0, 0);progressBar.setVisibility(View.VISIBLE);arrowImageView.clearAnimation();arrowImageView.setVisibility(View.GONE);tipsTextview.setText("正在加载中 ...REFRESHING");lastUpdatedTextView.setVisibility(View.VISIBLE);Log.v("@@@@@@", "REFRESHING 这是第  "+i+++"步" +"正在加载中 ...REFRESHING");break;case DONE:headView.setPadding(0, -1 * headContentHeight, 0, 0);progressBar.setVisibility(View.GONE);arrowImageView.clearAnimation();arrowImageView.setImageResource(R.drawable.arrow);tipsTextview.setText("已经加载完毕- DONE ");lastUpdatedTextView.setVisibility(View.VISIBLE);Log.v("@@@@@@", "DONE 这是第  "+i+++"步" +"已经加载完毕- DONE ");break;}}

     以上就是主要的功能代码，这个功能的实现，并没有在重写onScroll和onScrollStateChanged两个方法：

public void onScroll(AbsListView arg0, int firstVisiableItem, int arg2,int arg3) {firstItemIndex = firstVisiableItem;}public void onScrollStateChanged(AbsListView arg0, int arg1) {}

主要就是通过onTouchEvent方法中根据不同的状态，进行不同的变化。

         先看下各个状态的定义：

//释放刷新private final static int RELEASE_To_REFRESH = 0;//下拉刷新private final static int PULL_To_REFRESH = 1;//正在刷新private final static int REFRESHING = 2;//刷新完成private final static int DONE = 3;

        下面就开始通过log，跟踪代码的执行过程，首先执行的肯定是onTouchEvent里面的ACTION_DOWN

if (firstItemIndex == 0 && !isRecored) {isRecored = true;startY = (int) event.getY();Log.v("@@@@@@", "ACTION_DOWN 这是第  "+i+++"步" +1 );}break;

在这里，简单的说明下，log语句的意思，这是第  "+i+++"步"，是说明这是进行的第几步，最后面跟的数字是为了独特的标记该log。

        再往下看：

        

        我们在log中找到9，然后看一下，在ACTION_MOVE中，执行了这一步：

if (state == DONE) {if (tempY - startY > 0) {state = PULL_To_REFRESH;Log.v("@@@@@@", "ACTION_MOVE DONE changeHeaderViewByState " +"这是第  "+i+++"步前" +9);changeHeaderViewByState();Log.v("@@@@@@", "ACTION_MOVE DONE changeHeaderViewByState " +"这是第  "+i+++"步后" +9);}}

        为什么呢？因为在初始化的时候，把state初始化为Done，然后，

state = PULL_To_REFRESH;changeHeaderViewByState();

把state状态转换为PULL_To_REFRESH，然后运行changeHeaderViewByState方法里面

case PULL_To_REFRESH:progressBar.setVisibility(View.GONE);tipsTextview.setVisibility(View.VISIBLE);lastUpdatedTextView.setVisibility(View.VISIBLE);arrowImageView.clearAnimation();arrowImageView.setVisibility(View.VISIBLE);if (isBack) {isBack = false;arrowImageView.clearAnimation();arrowImageView.startAnimation(reverseAnimation);tipsTextview.setText("isBack  is true ！！！");} else {tipsTextview.setText("isBack  is false ！！！");}Log.v("@@@@@@", "PULL_To_REFRESH 这是第  "+i+++"步" +13+"  changeHeaderViewByState()");break;

在这里的各个控件的状态变化。state状态转换为PULL_To_REFRESH，代码继续向下进行

     所以会执行以下代码：

if (state == PULL_To_REFRESH) {headView.setPadding(0, -1 * headContentHeight+(tempY - startY) / RATIO, 0, 0);Log.v("@@@@@@", -1 * headContentHeight+(tempY - startY) / RATIO+"ACTION_MOVE PULL_To_REFRESH 3  这是第  "+i+++"步"+10 );}

设置headView的各个距离，随后break，但是返回以后呢？还是继续进行ACTION_MOVE，由于state状态转换为PULL_To_REFRESH，所以会执行：

if (state == PULL_To_REFRESH) {setSelection(0);if ((tempY - startY) / RATIO >= headContentHeight) {state = RELEASE_To_REFRESH;isBack = true;Log.v("@@@@@@", "changeHeaderViewByState " +"这是第  "+i+++"步前"+7 );changeHeaderViewByState();Log.v("@@@@@@", "changeHeaderViewByState " +"这是第  "+i+++"步后"+7 );}else if (tempY - startY <= 0) {state = DONE;changeHeaderViewByState();Log.v("@@@@@@", "ACTION_MOVE changeHeaderViewByState PULL_To_REFRESH 2" +" 这是第  "+i+++"步" +8);}}

在本log里走的是if的第一分支，把state 的状态转化为RELEASE_To_REFRESH，然后执行changeHeaderViewByState里面：

case RELEASE_To_REFRESH:arrowImageView.setVisibility(View.VISIBLE);progressBar.setVisibility(View.GONE);tipsTextview.setVisibility(View.VISIBLE);lastUpdatedTextView.setVisibility(View.VISIBLE);arrowImageView.clearAnimation();arrowImageView.startAnimation(animation);tipsTextview.setText("请释放 刷新");Log.v("@@@@@@", "RELEASE_To_REFRESH 这是第  "+i+++"步"+12 +"请释放 刷新" );break;

如果继续向下拉，会执行ACTION_MOVE中的：

if (state == RELEASE_To_REFRESH) {headView.setPadding(0, (tempY - startY) / RATIO- headContentHeight, 0, 0);Log.v("@@@@@@", "ACTION_MOVE PULL_To_REFRESH 4 这是第  "+i+++"步" +11);}

继续看log：

进行完两个11以后，又会执行哪些代码呢？我们看到了3，然后我们找下这个log.

case MotionEvent.ACTION_UP:if (state != REFRESHING && state != LOADING) {if (state == DONE) {}if (state == PULL_To_REFRESH) {state = DONE;Log.v("@@@@@@", "ACTION_UP PULL_To_REFRESH and changeHeaderViewByState()" +" 这是第  "+i+++"步前"+2 );changeHeaderViewByState();Log.v("@@@@@@", "ACTION_UP PULL_To_REFRESH and changeHeaderViewByState() " +"这是第  "+i+++"步后"+2 );}if (state == RELEASE_To_REFRESH) {state = REFRESHING;Log.v("@@@@@@", "ACTION_UP RELEASE_To_REFRESH changeHeaderViewByState() " +"这是第  "+i+++"步" +3);changeHeaderViewByState();onRefresh();Log.v("@@@@@@", "ACTION_UP RELEASE_To_REFRESH changeHeaderViewByState()" +" 这是第  "+i+++"步" +3);}}isRecored = false;isBack = false;break;

就是当手指送开的时候，执行到了ACTION_UP，因为state 的状态转化为RELEASE_To_REFRESH，里面调用了

case RELEASE_To_REFRESH:arrowImageView.setVisibility(View.VISIBLE);progressBar.setVisibility(View.GONE);tipsTextview.setVisibility(View.VISIBLE);lastUpdatedTextView.setVisibility(View.VISIBLE);arrowImageView.clearAnimation();arrowImageView.startAnimation(animation);tipsTextview.setText("请释放 刷新");Log.v("@@@@@@", "RELEASE_To_REFRESH 这是第  "+i+++"步"+12 +"请释放 刷新" );break;

    和onRefresh方法，和listView下拉刷新(sina微博Android客户端效果)一样，这是个回调方法。

    最后调用 onRefreshComplete刷新完成方法：

public void onRefreshComplete() {state = DONE;lastUpdatedTextView.setText("已加载完成: " + new Date().toLocaleString());changeHeaderViewByState();Log.v("@@@@@@", "onRefreshComplete() 被调用。。。");}

最后程序运行结果如下：

下拉

 

继续下拉

手指松开

    最后，是源代码下载地址：http://download.csdn.net/detail/aomandeshangxiao/4119893 。