我的应用程序中的内容提供程序有几个问题。我在提供程序中存储了一项（文本字符串）。它有一个对应的ID。 id是一个String而不是一个int。最初，项目已保存，但在刷卡时并未删除。此后已解决。我之前的主题：
Deleting a single SQlite row RecyclerView onSwiped
现在，当我按下按钮将项目添加到数据库时，应用程序崩溃。重新启动应用程序后，当我选择数据库时，该项目已存在。此外，logcat和debug均显示该项目已保存。 Stacktrace错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: capstone.my.annin.londontubeschedule, PID: 4325
android.database.SQLException: Failed to insert row into content://capstone.my.annin.londontubeschedule/lines
at capstone.my.annin.londontubeschedule.data.TubeLineContentProvider.insert(TubeLineContentProvider.java:89)
at android.content.ContentProvider$Transport.insert(ContentProvider.java:267)
at android.content.ContentResolver.insert(ContentResolver.java:1545)
at capstone.my.annin.londontubeschedule.ui.StationListActivity$1.onClick(StationListActivity.java:91)
错误可能是因为这是一个长字符串而不是字符串吗？
long id = db.insert(TubeLineContract.TubeLineEntry.TABLE_NAME, null, values);
不允许我将其更改为字符串。
主持人：到目前为止，我在这里还没有找到类似的话题。谢谢。
ContentProvider类：
public class TubeLineContentProvider extends ContentProvider
{
//Tag for the log messages
public static final String LOG_TAG = TubeLineContentProvider.class.getSimpleName();
/**
* URI matcher code for the content URI for the lines table
*/
public static final int LINES = 100;
/**
* URI matcher code for the content URI for one line in the lines table
*/
public static final int LINE_WITH_ID = 101;
/**
* UriMatcher object to match a content URI to a corresponding code.
* The input passed into the constructor represents the code to return for the root URI.
* It's common to use NO_MATCH as the input for this case.
*/
private static final UriMatcher sUriMatcher = buildUriMatcher();
// Static initializer. This is run the first time anything is called from this class.
public static UriMatcher buildUriMatcher()
{
// The calls to addURI() go here, for all of the content URI patterns that the provider
// should recognize. All paths added to the UriMatcher have a corresponding code to return
// when a match is found.
UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
uriMatcher.addURI(TubeLineContract.CONTENT_AUTHORITY, TubeLineContract.PATH_LINES, LINES);
uriMatcher.addURI(TubeLineContract.CONTENT_AUTHORITY, TubeLineContract.PATH_LINES + "/*", LINE_WITH_ID);
return uriMatcher;
}
/**
* Database helper object
*/
private TubeLineDbHelper mTubeLineDbHelper;
@Override
public boolean onCreate()
{
// Complete onCreate() and initialize a TubeLineDbhelper on startup
// [Hint] Declare the DbHelper as a global variable
Context context = getContext();
mTubeLineDbHelper = new TubeLineDbHelper(context);
return true;
}
// Implement insert to handle requests to insert a single new row of data
@Override
public Uri insert(@NonNull Uri uri, ContentValues values)
{
// Get access to the line database (to write new data to)
final SQLiteDatabase db = mTubeLineDbHelper.getWritableDatabase();
// Write URI matching code to identify the match for the lines directory
int match = sUriMatcher.match(uri);
Uri returnUri; // URI to be returned
switch (match)
{
case LINES:
// Insert new values into the database
// Inserting values into lines table
long id = db.insert(TubeLineContract.TubeLineEntry.TABLE_NAME, null, values);
if (id == 0)
{
returnUri = ContentUris.withAppendedId(TubeLineContract.TubeLineEntry.CONTENT_URI, id);
}
else
{
throw new android.database.SQLException("Failed to insert row into " + uri);
}
break;
// Set the value for the returnedUri and write the default case for unknown URI's
// Default case throws an UnsupportedOperationException
default:
throw new UnsupportedOperationException("Unknown uri: " + uri);
}
// Notify the resolver if the uri has been changed, and return the newly inserted URI
getContext().getContentResolver().notifyChange(uri, null);
// Return constructed uri (this points to the newly inserted row of data)
return returnUri;
}
// Implement query to handle requests for data by URI
@Override
public Cursor query(@NonNull Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder)
{
// Get access to underlying database (read-only for query)
final SQLiteDatabase db = mTubeLineDbHelper.getReadableDatabase();
// Write URI match code and set a variable to return a Cursor
int match = sUriMatcher.match(uri);
Cursor retCursor;
// Query for the lines directory and write a default case
switch (match)
{
// Query for the lines directory
case LINES:
retCursor = db.query(TubeLineContract.TubeLineEntry.TABLE_NAME,
projection,
selection,
selectionArgs,
null,
null,
sortOrder);
break;
// Default exception
default:
throw new UnsupportedOperationException("Unknown uri: " + uri);
}
// Set a notification URI on the Cursor and return that Cursor
retCursor.setNotificationUri(getContext().getContentResolver(), uri);
// Return the desired Cursor
return retCursor;
}
/**
* Update inventory in the database with the given content values. Apply the changes to the rows
* specified in the selection and selection arguments (which could be 0 or 1 or more pets).
* Return the number of rows that were successfully updated.
*/
@Override
public int update(@NonNull Uri uri, ContentValues values, String selection,
String[] selectionArgs)
{
//Keep track of if an update occurs
int rowsUpdated;
final int match = sUriMatcher.match(uri);
switch (match) {
case LINE_WITH_ID:
String id = uri.getPathSegments().get(1);
rowsUpdated = mTubeLineDbHelper.getWritableDatabase().update(TubeLineContract.TubeLineEntry.TABLE_NAME, values, "_id=?", new String[]{id});
break;
default:
throw new UnsupportedOperationException("Not yet implemented");
}
if (rowsUpdated != 0)
{
//set notifications if a row was updated
getContext().getContentResolver().notifyChange(uri, null);
}
// return number of rows updated
return rowsUpdated;
}
// Implement delete to delete a single row of data
@Override
public int delete(@NonNull Uri uri, String selection, String[] selectionArgs)
{
// Get access to the database and write URI matching code to recognize a single item
final SQLiteDatabase db = mTubeLineDbHelper.getWritableDatabase();
int match = sUriMatcher.match(uri);
// Keep track of the number of deleted rows
int rowsDeleted; // starts as 0
//if (null == selection) selection = "1";
// Write the code to delete a single row of data
// [Hint] Use selections to delete an item by its row ID
switch (match)
{
// Handle the single item case, recognized by the ID included in the URI path
case LINE_WITH_ID:
// Get the line ID from the URI path
String id = uri.getPathSegments().get(1);
// Use selections/selectionArgs to filter for this ID
rowsDeleted = db.delete(TubeLineContract.TubeLineEntry.TABLE_NAME, "id=?",
new String[]{id});
break;
default:
throw new UnsupportedOperationException("Unknown uri: " + uri);
}
// Notify the resolver of a change and return the number of items deleted
if (rowsDeleted != 0)
{
// A line was deleted, set notification
getContext().getContentResolver().notifyChange(uri, null);
}
// Return the number of rows deleted
return rowsDeleted;
}
@Override
public String getType(@NonNull Uri uri)
{
final int match = sUriMatcher.match(uri);
switch (match) {
case LINES:
return TubeLineContract.TubeLineEntry.CONTENT_LIST_TYPE;
case LINE_WITH_ID:
return "vnd.android.cursor.item" + "/" + TubeLineContract.CONTENT_AUTHORITY + "/" + TubeLineContract.PATH_LINES;
default:
throw new UnsupportedOperationException("Not yet implemented");
}
}
}
活动：
//add to favorites
favoritesButton.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View view)
{
ContentValues values = new ContentValues();
values.put(TubeLineContract.TubeLineEntry.COLUMN_LINES_ID, lines.getLineId());
values.put(TubeLineContract.TubeLineEntry.COLUMN_LINES_NAME, lines.getLineName());
//Line 91 error
Uri uri = getContentResolver().insert(TubeLineContract.TubeLineEntry.CONTENT_URI, values);
if (uri != null)
{
Toast.makeText(getBaseContext(), uri.toString(), Toast.LENGTH_LONG).show();
Toast.makeText(StationListActivity.this, R.string.favorites_added, Toast.LENGTH_SHORT).show();
favoritesButton.setVisibility(View.GONE);
}
}
});
// Kick off the loader
getLoaderManager().initLoader(FAVORITES_LOADER, null, this);
}
答案 0 :(得分：2)
尝试将client1.myproject.com
client2.myproject.com
client3.myproject.com
更改为if (id == 0)。
从insert返回的值将是插入行的ID。 id将为1或更大（如果未插入，则为-1，但不会插入0）。
因此，看起来好像您实际上正在插入，但是插入后只是走错了路径。