Java Android，从sqlite检索数据并显示在自定义列表中的正确方法

编辑：（（ArrayAdapter）getListAdapter（））.notifyDataSetChanged（）；不起作用-我想这是一个问题，我需要刷新整个列表，而不是仅仅添加新条目，但我不确定-如果是这样，我该怎么做？

从sqlite数据库检索数据并在listactivity中显示数据的正确方法是什么？下面是我的代码，它可以正常工作（有点），但在第一次运行后不能正确刷新列表数据。我需要做的是：

• 要加载并显示数据库内容的ListActivity（在从我也编写的RESTAPI获取之后）
• 用户按下“刷新”按钮，新故事将显示在列表顶部，而用户不会丢失其在列表中的当前位置

任何帮助都将不胜感激

public void populateStoryList() {

    List<StoryItem> stories = datasource.getAllStoryItems();  

    if ( firstrun == true ) {
        adapter = new StoryAdapter(this, stories);
        setListAdapter(adapter);
        firstrun = false;
    } else {
        // DON'T KNOW WHAT TO DO HERE
    }

    setProgressBarIndeterminateVisibility(false);
}

最后一个故事项：

public class StoryItem {
    private String dateApproved;
    private String storyTitle;
    private String storyText;
    private long storyId;
    private long storyOnlineId;

    public StoryItem() {}

    public StoryItem(String storyTitle, String storyText, String dateApproved, long storyId, long storyOnlineId) {
        this.storyTitle = storyTitle;
        this.storyText = storyText;
        this.dateApproved = dateApproved;
        this.storyId = storyId;
        this.storyOnlineId = storyOnlineId;
    }

    public long getId() {
        return storyId;
    }

    public void setId(long id) {
        this.storyId = id;
    }

    public long getOnlineId() {
        return storyOnlineId;
    }

    public void setOnlineId(long online_id) {
        this.storyOnlineId = online_id;
    }

    public void setStoryTitle(String storyTitle) {
        this.storyTitle = storyTitle;
    }
    public String getStoryTitle() {
        return storyTitle;
    }
    public void setStoryText(String storyText) {
        this.storyText = storyText;
    }
    public String getStoryText() {
        return storyText;
    }
    public void setDateApproved(String dateApproved) {
        this.dateApproved = dateApproved;
    }
    public String getDateApproved() {
        return dateApproved;
    }
}

---

firstRun

变量的用途是什么？我确信它应该被移除，然后一切都会好起来

我也会像这样重写你的方法：

public void populateStoryList() {
    setProgressBarIndeterminateVisibility(true);

    if (this.adapter == null) {
        // first time, because adapter = null
        List<StoryItem> stories = datasource.getAllStoryItems();  
        this.adapter = new StoryAdapter(this, stories);
        setListAdapter(this.adapter);
    } else {
        List<StoryItem> newStories = datasource.getOnlyNewStoryItems(); 
        for (StoryItem story : newStories) {
            this.adapter.insert(story, 0);
        }
        // of course you can clear all items and replace them entirely, but it is not good for performance, so I don't recommend to use the commented code
        //List<StoryItem> stories = datasource.getAllStoryItems();  
        //this.adapter.clear();
        //for (StoryItem story : stories) {
        //    this.adapter.add(story);
        //}
    }

    setProgressBarIndeterminateVisibility(false);
}

public void populateStoryList（）{
SetProgressBarInDeterminateVibility（真）；
if（this.adapter==null）{
//第一次，因为adapter=null
List stories=datasource.getAllStoryItems（）；
this.adapter=新故事适配器（this，stories）；
setListAdapter（this.adapter）；
}否则{
List newStories=datasource.getOnlyNewStoryItems（）；
用于（故事项故事：新闻故事）{
this.adapter.insert（故事，0）；
}
//当然，您可以清除所有项并完全替换它们，但这对性能不好，因此我不建议使用注释代码
//List stories=datasource.getAllStoryItems（）；
//this.adapter.clear（）；
//用于（故事项故事：故事）{
//this.adapter.add（故事）；
//}
}
SetProgressBarInDeterminateVibility（假）；
}

您必须编写方法

getOnlyNewStoryItems

---

显然，

notifyDataSetChanged

方法将不起作用，您在这里不需要它。它仅用于在不更改现有项的情况下重绘现有项，而您希望添加新项并更改列表的结构。

我尝试了此操作，但出现了以下错误：类型ListAdapter的notifyDataSetChanged（）方法未定义-我的类定义是：公共类ActivityStoryList扩展ListActivity{我添加了一个演员阵容（ArrayAdapter）它可以工作-谢谢！您还可以将适配器类扩展到BaseAdapter而不是ArrayAdapter。很高兴看到您找到了解决方案。我想我找到了，但在我重新打开活动之前它似乎不会刷新数据-我有点过早…我想这是因为我没有添加到现有列表中（在线阅读文档），我将完全替换它-不知道如何只添加新项目？感谢vorrtex，这似乎可以实现这个技巧-关于notifyDataSetChanged方法的良好信息。

public class StoryItem {
    private String dateApproved;
    private String storyTitle;
    private String storyText;
    private long storyId;
    private long storyOnlineId;

    public StoryItem() {}

    public StoryItem(String storyTitle, String storyText, String dateApproved, long storyId, long storyOnlineId) {
        this.storyTitle = storyTitle;
        this.storyText = storyText;
        this.dateApproved = dateApproved;
        this.storyId = storyId;
        this.storyOnlineId = storyOnlineId;
    }

    public long getId() {
        return storyId;
    }

    public void setId(long id) {
        this.storyId = id;
    }

    public long getOnlineId() {
        return storyOnlineId;
    }

    public void setOnlineId(long online_id) {
        this.storyOnlineId = online_id;
    }

    public void setStoryTitle(String storyTitle) {
        this.storyTitle = storyTitle;
    }
    public String getStoryTitle() {
        return storyTitle;
    }
    public void setStoryText(String storyText) {
        this.storyText = storyText;
    }
    public String getStoryText() {
        return storyText;
    }
    public void setDateApproved(String dateApproved) {
        this.dateApproved = dateApproved;
    }
    public String getDateApproved() {
        return dateApproved;
    }
}

else {
   getListAdapter().notifyDataSetChanged();
}

public void populateStoryList() {
    setProgressBarIndeterminateVisibility(true);

    if (this.adapter == null) {
        // first time, because adapter = null
        List<StoryItem> stories = datasource.getAllStoryItems();  
        this.adapter = new StoryAdapter(this, stories);
        setListAdapter(this.adapter);
    } else {
        List<StoryItem> newStories = datasource.getOnlyNewStoryItems(); 
        for (StoryItem story : newStories) {
            this.adapter.insert(story, 0);
        }
        // of course you can clear all items and replace them entirely, but it is not good for performance, so I don't recommend to use the commented code
        //List<StoryItem> stories = datasource.getAllStoryItems();  
        //this.adapter.clear();
        //for (StoryItem story : stories) {
        //    this.adapter.add(story);
        //}
    }

    setProgressBarIndeterminateVisibility(false);
}