android listview 不更新
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【中文标题】android listview 不更新【英文标题】：android listview doesn't update 【发布时间】：2015-12-29 09:39:58 【问题描述】：我在使用从 sqlite 数据库填充的 listView 的日期范围时遇到问题，代码完美运行，但是我遇到的问题是 listView 在我没有更新（刷新）时选择另一个日期范围（当我再次触摸“搜索”按钮时），虽然数据适配器确实从数据库中获取了数据（通过使用logcat 确保了这一点）但不会在listView 中打印它。我无法使用函数notifyDataSetChanged()，它不起作用，并且每当我在add() 之后使用它时，应用程序就会崩溃。
这里是代码：-
public class ProductionCommentsActivity extends Activity implements View.OnClickListener
private DBHandler dbHandler;
private ListView listView;
private Context context;
private ArrayList<String> results = new ArrayList<String>();
private ArrayAdapter adapter;
private static String newline = System.getProperty("line.separator");//a variable for line break
private EditText editTextFrom, editTextTo;
private DatePickerDialog datePickerDialogFrom, datePickerDialogTo;
private SimpleDateFormat simpleDateFormat;
private String fromDate,toDate ; // variables to store the chosen dates
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_production_comments);
dbHandler = new DBHandler(this, dbHandler.DATABASE_NAME_PRODUCTION, null, 1);
try
dbHandler.copyDataBase();
Log.d("copydb", dbHandler.getDatabaseName());
catch (IOException e)
e.printStackTrace();
Log.d("copydb",e.getMessage());
//defining list view
listView = (ListView) findViewById(R.id.listView);
//defining edit texts properties
editTextFrom = (EditText) findViewById(R.id.editTextFrom);
editTextFrom.setInputType(InputType.TYPE_NULL);
editTextFrom.requestFocus();
editTextTo = (EditText) findViewById(R.id.editTextTo);
editTextTo.setInputType(InputType.TYPE_NULL);
//setting up the date format
simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.US);
setDateTimeField();
context = this;
//method to handle the date pickers properties
private void setDateTimeField()
editTextFrom.setOnClickListener((View.OnClickListener) ProductionCommentsActivity.this);
editTextTo.setOnClickListener((View.OnClickListener) ProductionCommentsActivity.this);
//creating a new instance of the calendar
Calendar newCalendar = Calendar.getInstance();
//creating a pop up date picker
datePickerDialogFrom = new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener()
//getting the chosen date and setting its format
//and writing the chosen date in the edit text
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth)
Calendar newDate = Calendar.getInstance();
newDate.set(year, monthOfYear, dayOfMonth);
editTextFrom.setText(simpleDateFormat.format(newDate.getTime()));
fromDate = editTextFrom.getText().toString();
,newCalendar.get(Calendar.YEAR), newCalendar.get(Calendar.MONTH),
newCalendar.get(Calendar.DAY_OF_MONTH));
datePickerDialogTo = new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener()
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth)
Calendar newDate = Calendar.getInstance();
newDate.set(year, monthOfYear, dayOfMonth);
editTextTo.setText(simpleDateFormat.format(newDate.getTime()));
toDate = editTextTo.getText().toString();
,newCalendar.get(Calendar.YEAR), newCalendar.get(Calendar.MONTH),
newCalendar.get(Calendar.DAY_OF_MONTH));
// on click method to handle which edit text was touched
// and show the appropriate pop up calendar
@Override
public void onClick(View view)
if(view == editTextFrom)
datePickerDialogFrom.show();
else if(view == editTextTo)
datePickerDialogTo.show();
//method to set format of date and attach the array adapter to the list view
public void searchDates(View view)
if(!editTextFrom.getText().toString().matches("From:")
&& !editTextTo.getText().toString().matches("To:"))
setDateTimeField();
getProductionComments(fromDate, toDate);
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, results);
listView.setAdapter(adapter);
Log.d("fire",adapter.toString());
else
Toast.makeText(this,"Please enter valid dates", Toast.LENGTH_LONG).show();
//get production comments data
public void getProductionComments(String from, String to)
try
SQLiteDatabase db = dbHandler.getReadableDatabase();
String query = "SELECT Date,Item,Comments FROM ProductionCommentData WHERE Date " +
"BETWEEN ? AND ? ORDER BY Date DESC";
Cursor cursor = db.rawQuery(query,new String[]from,to);
if (cursor != null)
if (cursor.moveToFirst())
do
String date = cursor.getString(cursor.getColumnIndex("Date"));
String item = cursor.getString(cursor.getColumnIndex("Item"));
String comments = cursor.getString(cursor.getColumnIndex("Comments"));
results.add("Date: " + date.substring(0, 10) + newline + newline +
"Item: " + item + newline + newline + comments);
while (cursor.moveToNext());
else
Toast.makeText(this,"No Data was found for the chosen dates",Toast.LENGTH_LONG).show();
catch (SQLiteException se)
Log.e(getClass().getSimpleName(), se.getMessage());
这是布局代码：-
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_
android:layout_ android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.qarun.qpcbeta.ProductionCommentsActivity"
android:id="@+id/relativeLayout">
<TextView
android:layout_
android:layout_
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Production Comments"
android:id="@+id/textView6"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<EditText
android:layout_
android:layout_
android:inputType="date"
android:ems="10"
android:id="@+id/editTextFrom"
android:layout_below="@+id/textView6"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="29dp"
android:editable="false"
android:textSize="13sp"
android:text="From:"
android:focusable="false"/>
<EditText
android:layout_
android:layout_
android:inputType="date"
android:ems="10"
android:id="@+id/editTextTo"
android:layout_alignTop="@+id/editTextFrom"
android:layout_toLeftOf="@+id/btnSearch"
android:layout_toStartOf="@+id/btnSearch"
android:textSize="13sp"
android:textIsSelectable="false"
android:text="To:"
android:focusable="false"/>
<ListView
android:layout_
android:layout_
android:id="@+id/listView"
android:layout_below="@+id/editTextTo"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"/>
<Button
android:layout_
android:layout_
android:text="Search"
android:id="@+id/btnSearch"
android:onClick="searchDates"
android:layout_above="@+id/listView"
android:layout_alignRight="@+id/listView"
android:layout_alignEnd="@+id/listView"/>
提前致谢
【问题讨论】：
【参考方案1】：adapter.notifyDataSetChanged();
在这种情况下有效。
[如果没有尝试重新加载列表]
【讨论】：
具体在哪里使用？ 在您的点击事件中，或您想要更新的任何地方【参考方案2】：不要在每次搜索时重新创建适配器。
类字段：
mAdapter // instantiate once
mListView // instantiate once
mResults // refresh with new data when available
这应该发生在onCreate()
mListView = (ListView)findViewByid(//etc
mResults = new ArrayList<>();
//Init mAdapter here only
mAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, mResults);
mListView.setAdapter(mAdapter);
然后，在searchDates(...)，做
getProductionComments(fromDate, toDate);//Set mResults with new data
//Don't set adapter here
mAdapter.notifyDataSetChanged(); //refresh adapter
【讨论】：
不幸的是它不起作用，当我触摸搜索按钮时，listView 没有任何反应 您确定您的数据在搜索按钮点击之间发生了变化吗？在您的代码中我看不到任何内容来更改数据库的数据。如果每次检索时db中的数据都是相同的，则ListView内容看起来是一样的。 当然会发生变化，我已经使用 logcat 确定了这一点以上是关于android listview 不更新的主要内容，如果未能解决你的问题，请参考以下文章
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