Java tutorial
/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package android.widget; import android.annotation.UnsupportedAppUsage; import android.content.Context; import android.database.Cursor; import android.net.Uri; import android.os.Build; import android.view.View; /** * An easy adapter to map columns from a cursor to TextViews or ImageViews * defined in an XML file. You can specify which columns you want, which * views you want to display the columns, and the XML file that defines * the appearance of these views. * * Binding occurs in two phases. First, if a * {@link android.widget.SimpleCursorAdapter.ViewBinder} is available, * {@link ViewBinder#setViewValue(android.view.View, android.database.Cursor, int)} * is invoked. If the returned value is true, binding has occured. If the * returned value is false and the view to bind is a TextView, * {@link #setViewText(TextView, String)} is invoked. If the returned value * is false and the view to bind is an ImageView, * {@link #setViewImage(ImageView, String)} is invoked. If no appropriate * binding can be found, an {@link IllegalStateException} is thrown. * * If this adapter is used with filtering, for instance in an * {@link android.widget.AutoCompleteTextView}, you can use the * {@link android.widget.SimpleCursorAdapter.CursorToStringConverter} and the * {@link android.widget.FilterQueryProvider} interfaces * to get control over the filtering process. You can refer to * {@link #convertToString(android.database.Cursor)} and * {@link #runQueryOnBackgroundThread(CharSequence)} for more information. */ public class SimpleCursorAdapter extends ResourceCursorAdapter { /** * A list of columns containing the data to bind to the UI. * This field should be made private, so it is hidden from the SDK. * {@hide} */ @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) protected int[] mFrom; /** * A list of View ids representing the views to which the data must be bound. * This field should be made private, so it is hidden from the SDK. * {@hide} */ @UnsupportedAppUsage protected int[] mTo; private int mStringConversionColumn = -1; private CursorToStringConverter mCursorToStringConverter; private ViewBinder mViewBinder; String[] mOriginalFrom; /** * Constructor the enables auto-requery. * * @deprecated This option is discouraged, as it results in Cursor queries * being performed on the application's UI thread and thus can cause poor * responsiveness or even Application Not Responding errors. As an alternative, * use {@link android.app.LoaderManager} with a {@link android.content.CursorLoader}. */ @Deprecated public SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to) { super(context, layout, c); mTo = to; mOriginalFrom = from; findColumns(c, from); } /** * Standard constructor. * * @param context The context where the ListView associated with this * SimpleListItemFactory is running * @param layout resource identifier of a layout file that defines the views * for this list item. The layout file should include at least * those named views defined in "to" * @param c The database cursor. Can be null if the cursor is not available yet. * @param from A list of column names representing the data to bind to the UI. Can be null * if the cursor is not available yet. * @param to The views that should display column in the "from" parameter. * These should all be TextViews. The first N views in this list * are given the values of the first N columns in the from * parameter. Can be null if the cursor is not available yet. * @param flags Flags used to determine the behavior of the adapter, * as per {@link CursorAdapter#CursorAdapter(Context, Cursor, int)}. */ public SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags) { super(context, layout, c, flags); mTo = to; mOriginalFrom = from; findColumns(c, from); } /** * Binds all of the field names passed into the "to" parameter of the * constructor with their corresponding cursor columns as specified in the * "from" parameter. * * Binding occurs in two phases. First, if a * {@link android.widget.SimpleCursorAdapter.ViewBinder} is available, * {@link ViewBinder#setViewValue(android.view.View, android.database.Cursor, int)} * is invoked. If the returned value is true, binding has occured. If the * returned value is false and the view to bind is a TextView, * {@link #setViewText(TextView, String)} is invoked. If the returned value is * false and the view to bind is an ImageView, * {@link #setViewImage(ImageView, String)} is invoked. If no appropriate * binding can be found, an {@link IllegalStateException} is thrown. * * @throws IllegalStateException if binding cannot occur * * @see android.widget.CursorAdapter#bindView(android.view.View, * android.content.Context, android.database.Cursor) * @see #getViewBinder() * @see #setViewBinder(android.widget.SimpleCursorAdapter.ViewBinder) * @see #setViewImage(ImageView, String) * @see #setViewText(TextView, String) */ @Override public void bindView(View view, Context context, Cursor cursor) { final ViewBinder binder = mViewBinder; final int count = mTo.length; final int[] from = mFrom; final int[] to = mTo; for (int i = 0; i < count; i++) { final View v = view.findViewById(to[i]); if (v != null) { boolean bound = false; if (binder != null) { bound = binder.setViewValue(v, cursor, from[i]); } if (!bound) { String text = cursor.getString(from[i]); if (text == null) { text = ""; } if (v instanceof TextView) { setViewText((TextView) v, text); } else if (v instanceof ImageView) { setViewImage((ImageView) v, text); } else { throw new IllegalStateException(v.getClass().getName() + " is not a " + " view that can be bounds by this SimpleCursorAdapter"); } } } } } /** * Returns the {@link ViewBinder} used to bind data to views. * * @return a ViewBinder or null if the binder does not exist * * @see #bindView(android.view.View, android.content.Context, android.database.Cursor) * @see #setViewBinder(android.widget.SimpleCursorAdapter.ViewBinder) */ public ViewBinder getViewBinder() { return mViewBinder; } /** * Sets the binder used to bind data to views. * * @param viewBinder the binder used to bind data to views, can be null to * remove the existing binder * * @see #bindView(android.view.View, android.content.Context, android.database.Cursor) * @see #getViewBinder() */ public void setViewBinder(ViewBinder viewBinder) { mViewBinder = viewBinder; } /** * Called by bindView() to set the image for an ImageView but only if * there is no existing ViewBinder or if the existing ViewBinder cannot * handle binding to an ImageView. * * By default, the value will be treated as an image resource. If the * value cannot be used as an image resource, the value is used as an * image Uri. * * Intended to be overridden by Adapters that need to filter strings * retrieved from the database. * * @param v ImageView to receive an image * @param value the value retrieved from the cursor */ public void setViewImage(ImageView v, String value) { try { v.setImageResource(Integer.parseInt(value)); } catch (NumberFormatException nfe) { v.setImageURI(Uri.parse(value)); } } /** * Called by bindView() to set the text for a TextView but only if * there is no existing ViewBinder or if the existing ViewBinder cannot * handle binding to a TextView. * * Intended to be overridden by Adapters that need to filter strings * retrieved from the database. * * @param v TextView to receive text * @param text the text to be set for the TextView */ public void setViewText(TextView v, String text) { v.setText(text); } /** * Return the index of the column used to get a String representation * of the Cursor. * * @return a valid index in the current Cursor or -1 * * @see android.widget.CursorAdapter#convertToString(android.database.Cursor) * @see #setStringConversionColumn(int) * @see #setCursorToStringConverter(android.widget.SimpleCursorAdapter.CursorToStringConverter) * @see #getCursorToStringConverter() */ public int getStringConversionColumn() { return mStringConversionColumn; } /** * Defines the index of the column in the Cursor used to get a String * representation of that Cursor. The column is used to convert the * Cursor to a String only when the current CursorToStringConverter * is null. * * @param stringConversionColumn a valid index in the current Cursor or -1 to use the default * conversion mechanism * * @see android.widget.CursorAdapter#convertToString(android.database.Cursor) * @see #getStringConversionColumn() * @see #setCursorToStringConverter(android.widget.SimpleCursorAdapter.CursorToStringConverter) * @see #getCursorToStringConverter() */ public void setStringConversionColumn(int stringConversionColumn) { mStringConversionColumn = stringConversionColumn; } /** * Returns the converter used to convert the filtering Cursor * into a String. * * @return null if the converter does not exist or an instance of * {@link android.widget.SimpleCursorAdapter.CursorToStringConverter} * * @see #setCursorToStringConverter(android.widget.SimpleCursorAdapter.CursorToStringConverter) * @see #getStringConversionColumn() * @see #setStringConversionColumn(int) * @see android.widget.CursorAdapter#convertToString(android.database.Cursor) */ public CursorToStringConverter getCursorToStringConverter() { return mCursorToStringConverter; } /** * Sets the converter used to convert the filtering Cursor * into a String. * * @param cursorToStringConverter the Cursor to String converter, or * null to remove the converter * * @see #setCursorToStringConverter(android.widget.SimpleCursorAdapter.CursorToStringConverter) * @see #getStringConversionColumn() * @see #setStringConversionColumn(int) * @see android.widget.CursorAdapter#convertToString(android.database.Cursor) */ public void setCursorToStringConverter(CursorToStringConverter cursorToStringConverter) { mCursorToStringConverter = cursorToStringConverter; } /** * Returns a CharSequence representation of the specified Cursor as defined * by the current CursorToStringConverter. If no CursorToStringConverter * has been set, the String conversion column is used instead. If the * conversion column is -1, the returned String is empty if the cursor * is null or Cursor.toString(). * * @param cursor the Cursor to convert to a CharSequence * * @return a non-null CharSequence representing the cursor */ @Override public CharSequence convertToString(Cursor cursor) { if (mCursorToStringConverter != null) { return mCursorToStringConverter.convertToString(cursor); } else if (mStringConversionColumn > -1) { return cursor.getString(mStringConversionColumn); } return super.convertToString(cursor); } /** * Create a map from an array of strings to an array of column-id integers in cursor c. * If c is null, the array will be discarded. * * @param c the cursor to find the columns from * @param from the Strings naming the columns of interest */ private void findColumns(Cursor c, String[] from) { if (c != null) { int i; int count = from.length; if (mFrom == null || mFrom.length != count) { mFrom = new int[count]; } for (i = 0; i < count; i++) { mFrom[i] = c.getColumnIndexOrThrow(from[i]); } } else { mFrom = null; } } @Override public Cursor swapCursor(Cursor c) { // super.swapCursor() will notify observers before we have // a valid mapping, make sure we have a mapping before this // happens findColumns(c, mOriginalFrom); return super.swapCursor(c); } /** * Change the cursor and change the column-to-view mappings at the same time. * * @param c The database cursor. Can be null if the cursor is not available yet. * @param from A list of column names representing the data to bind to the UI. Can be null * if the cursor is not available yet. * @param to The views that should display column in the "from" parameter. * These should all be TextViews. The first N views in this list * are given the values of the first N columns in the from * parameter. Can be null if the cursor is not available yet. */ public void changeCursorAndColumns(Cursor c, String[] from, int[] to) { mOriginalFrom = from; mTo = to; // super.changeCursor() will notify observers before we have // a valid mapping, make sure we have a mapping before this // happens findColumns(c, mOriginalFrom); super.changeCursor(c); } /** * This class can be used by external clients of SimpleCursorAdapter * to bind values fom the Cursor to views. * * You should use this class to bind values from the Cursor to views * that are not directly supported by SimpleCursorAdapter or to * change the way binding occurs for views supported by * SimpleCursorAdapter. * * @see SimpleCursorAdapter#bindView(android.view.View, android.content.Context, android.database.Cursor) * @see SimpleCursorAdapter#setViewImage(ImageView, String) * @see SimpleCursorAdapter#setViewText(TextView, String) */ public static interface ViewBinder { /** * Binds the Cursor column defined by the specified index to the specified view. * * When binding is handled by this ViewBinder, this method must return true. * If this method returns false, SimpleCursorAdapter will attempts to handle * the binding on its own. * * @param view the view to bind the data to * @param cursor the cursor to get the data from * @param columnIndex the column at which the data can be found in the cursor * * @return true if the data was bound to the view, false otherwise */ boolean setViewValue(View view, Cursor cursor, int columnIndex); } /** * This class can be used by external clients of SimpleCursorAdapter * to define how the Cursor should be converted to a String. * * @see android.widget.CursorAdapter#convertToString(android.database.Cursor) */ public static interface CursorToStringConverter { /** * Returns a CharSequence representing the specified Cursor. * * @param cursor the cursor for which a CharSequence representation * is requested * * @return a non-null CharSequence representing the cursor */ CharSequence convertToString(Cursor cursor); } }