ListActivity在数据到达时不会更新

时间:2014-06-06 17:42:42

标签: android android-listview android-contentprovider

我正在构建一个小型应用程序,我希望在新数据到达时自动更新。

从我读过的android文档中,我认为是因为我使用了更新的技术,我会在后台创建一个ContentObserver,而我只是自动调用装载程序。

如果有更多有用的信息,我很乐意添加它,或者将整个项目上传到某个地方。

此外,我定位KitKat(sdk版本19)。

应用程序概述

  1. 我们有一个使用内置ListView的ListActivity。
  2. ListActivity使用Loader和SimpleCursorAdapter获取数据。
  3. Loader通过查询ContentProvider来检索其数据。
  4. ContentProvider由SQLite数据库支持。
  5. 此外,在操作栏中,我添加了两个操作,一个用于添加项目,另一个用于清除所有项目。

    在添加项目时,ListView不会使用新条目进行更新,我还可以看到ContentProvider上没有运行任何新查询。如果我关闭应用程序并重新启动它,那么这些条目现在可以在ListView中看到。

    源代码关注

    Activity.java

    package us.lynch.listdemo;
    
    import java.text.DateFormat;
    import java.util.Date;
    
    import us.lynch.listdemo.R;
    import android.app.ListActivity;
    import android.app.LoaderManager.LoaderCallbacks;
    import android.content.ContentValues;
    import android.content.CursorLoader;
    import android.content.Loader;
    import android.database.Cursor;
    import android.net.Uri;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuInflater;
    import android.view.MenuItem;
    import android.widget.CursorAdapter;
    import android.widget.SimpleCursorAdapter;
    
    public class Activity extends ListActivity implements LoaderCallbacks<Cursor> {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
    
            setListAdapter(new SimpleCursorAdapter(this, R.layout.listitem, null, new String[] { "string" }, new int[] { R.id.text }, 0));
            getLoaderManager().initLoader(0, null, this);
        }
    
        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            MenuInflater inflater = getMenuInflater();
            inflater.inflate(R.menu.main, menu);
            return true;
        }
    
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            ContentValues values = new ContentValues();
    
            switch (item.getItemId()) {
                case R.id.action_add:
                    values.put("string", DateFormat.getDateTimeInstance().format(new Date()));
                    getContentResolver().insert(Uri.parse("content://us.lynch.listdemo/data"), values);
                    return true;
    
                case R.id.action_clear:
                    getContentResolver().delete(Uri.parse("content://us.lynch.listdemo/data"), null, null);
                    return true;
    
                default:
                    return super.onOptionsItemSelected(item);
            }
        }
    
        @Override
        public Loader<Cursor> onCreateLoader(int id, Bundle args) {
            Uri uri = Uri.parse("content://us.lynch.listdemo/data");
            String[] projection = { "_id", "string" };
            return new CursorLoader(this, uri, projection, null, null, "_id");
        }
    
        @Override
        public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
            ((CursorAdapter) getListAdapter()).swapCursor(cursor);
        }
    
        @Override
        public void onLoaderReset(Loader<Cursor> loader) {
            ((CursorAdapter) getListAdapter()).swapCursor(null);
        }
    }
    

    ContentProvider.java

    package us.lynch.listdemo;
    
    import android.content.ContentUris;
    import android.content.ContentValues;
    import android.content.Context;
    import android.content.UriMatcher;
    import android.database.Cursor;
    import android.database.DatabaseUtils;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.net.Uri;
    import android.text.TextUtils;
    
    public class ContentProvider extends android.content.ContentProvider {
        private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        private Database mDatabase;
    
        private static final int MATCH = 1;
        private static final int MATCH_ID = 2;
    
        static {
            sUriMatcher.addURI("us.lynch.listdemo", "data", MATCH);
            sUriMatcher.addURI("us.lynch.listdemo", "data/#", MATCH_ID);
        }
    
        @Override
        public boolean onCreate() {
            mDatabase = new Database(getContext());
            return true;
        }
    
        @Override
        public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
            switch (sUriMatcher.match(uri)) {
                case MATCH:
                    return database().query("data", projection, selection, selectionArgs, null, null, sortOrder);
                case MATCH_ID:
                    selection = addIdToSelection(uri, selection);
                    return database().query("data", projection, selection, selectionArgs, null, null, sortOrder);
                default:
                    throw new IllegalArgumentException("Unknown URI " + uri);
            }
        }
    
        @Override
        public Uri insert(Uri uri, ContentValues values) {
            switch (sUriMatcher.match(uri)) {
                case MATCH: {
                    return ContentUris.withAppendedId(uri, database().insertOrThrow("data", null, values));
                }
                default:
                    throw new IllegalArgumentException("Unknown URI " + uri);
            }
        }
    
        @Override
        public int delete(Uri uri, String selection, String[] selectionArgs) {
            switch (sUriMatcher.match(uri)) {
                case MATCH:
                    return database().delete("data", selection, selectionArgs);
                case MATCH_ID:
                    selection = addIdToSelection(uri, selection);
                    return database().delete("data", selection, selectionArgs);
                default:
                    throw new IllegalArgumentException("Unknown URI " + uri);
            }
        }
    
        @Override
        public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
            switch (sUriMatcher.match(uri)) {
                case MATCH:
                    return database().update("data", values, selection, selectionArgs);
                case MATCH_ID:
                    selection = addIdToSelection(uri, selection);
                    return database().update("data", values, selection, selectionArgs);
                default:
                    throw new IllegalArgumentException("Unknown URI " + uri);
            }
        }
    
        @Override
        public String getType(Uri uri) {
            throw new IllegalArgumentException("Unknown URI " + uri);
        }
    
        private SQLiteDatabase database() {
            return mDatabase.getWritableDatabase();
        }
    
        private static String addIdToSelection(Uri uri, String selection) {
            return DatabaseUtils.concatenateWhere(selection, "_id = " + Long.toString(ContentUris.parseId(uri)));
        }
    }
    
    class Database extends SQLiteOpenHelper {
        Database(Context context) {
            super(context, "database", null, 1);
        }
    
        @Override
        public void onCreate(SQLiteDatabase database) {
            final String[] columns = new String[] {
                    "_id integer primary key autoincrement",
                    "string text not null",
            };
    
            database.execSQL("create table data (" + TextUtils.join(",", columns) + ");");
        }
    
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            assert (false);
        }
    }
    

    RES /布局/ listitem.xml

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    
        <TextView
            android:id="@+id/text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentRight="true"
            android:layout_alignParentTop="true"
            android:text="Large Text"
            android:textAppearance="?android:attr/textAppearanceLarge" />
    
    </RelativeLayout>
    

    RES /菜单/ main.xml中

    <?xml version="1.0" encoding="utf-8"?>
    <menu xmlns:android="http://schemas.android.com/apk/res/android" >
    
        <item
            android:id="@+id/action_clear"
            android:title="Clear Items"
            android:visible="true">
        </item>
        <item
            android:id="@+id/action_add"
            android:title="Add Item"
            android:visible="true">
        </item>
    
    </menu>
    

1 个答案:

答案 0 :(得分:5)

您没有使用Uri通知机制。

在query()方法中写:

Cursor cursor = database().query("data", projection, selection, selectionArgs, null, null, sortOrder);
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;

在修改内容的方法(插入,更新,删除)中,通知相同的Uri:

ContentResolver cr = getContext().getContentResolver();
cr.notifyChange(uri, null);