Question

嘿伙计们我使用简单的适配器从我的数据库制作了数据列表视图，但我不知道每次数据库更改时如何更新它。任何帮助？notifyDataSetChanged（）;方法不起作用，我不知道该怎么做。

MainActivity

      @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_general_discussion);
    db = new SQLiteHandler(this);

    ArrayList<HashMap<String, String>> emaillist = db.getMessage();
    if (emaillist.size() != 0) {
         ListAdapter adapter = new SimpleAdapter(MainActivity.this, emaillist,
                R.layout.raw_layout,
                new String[]{"user_posted", "post", "posted_at", "post_id"}, new int[]{
                R.id.text_user_name, R.id.text_user_post, R.id.text_user_date, R.id.text_user_number});
        setListAdapter(adapter);

    }

助手类

    public ArrayList<HashMap<String, String>> getMessage(){
    ArrayList<HashMap<String, String>> message = new ArrayList<HashMap<String, String>>();
    String selectQuery = "SELECT  * FROM " + TABLE_POSTING;

    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    if ( cursor.moveToFirst()) {
        do {
            HashMap<String, String> map = new HashMap<String, String>();
            map.put("post_id", cursor.getString(0));
            map.put("user_posted", cursor.getString(1));
            map.put("post", cursor.getString(2));
            map.put("posted_at", cursor.getString(3));
            message.add(map);
        } while (cursor.moveToNext());
    }

    return message;
}

Answer 1

声明您的适配器＆amp;列出全球水平

class example{
ListAdapter adapter;
ArrayList<HashMap<String, String>> emaillist;

 @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_general_discussion);
    db = new SQLiteHandler(this);

    emaillist = db.getMessage();
    if (emaillist.size() != 0) {
         adapter = new SimpleAdapter(MainActivity.this, emaillist,
                R.layout.raw_layout,
                new String[]{"user_posted", "post", "posted_at", "post_id"}, new int[]{
                R.id.text_user_name, R.id.text_user_post, R.id.text_user_date, R.id.text_user_number});
        setListAdapter(adapter);

    }

如果您只想更新

    adapter.notifyDataSetChanged();

Answer 2

将您的适配器声明为Public，然后调用
的 adapter.notifyDatasetChange();
何时何地你想要。这会更新。

希望这有帮助。

Answer 3

我认为没有直接的方法来检查数据库中是否有变化但你可以像刷新一样做。

使您的适配器成为全局，当触发操作时再次填充适配器并写入adapter.notifyDatasetChange();

另一种方法是使用Thread，将其放入类型AsyncTask的内部类中然后每分钟重新填充阵列然后在每次检查之后写下adapter.notifyDatasetChange();

doInBackground(){
while(true){
    checkDataBase();
refillAdapter();
adapter.notifyDatasetChange();

    Thread.sleep(1000*60);// sec * 60 sec =1min
} 
}

查看此链接如何使用AsyncTask类http://developer.android.com/reference/android/os/AsyncTask.html

简单的适配器不能更新数据库

3 个答案: