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Android example source code file (SimpleCursorAdapter.java)

This example Android source code file (SimpleCursorAdapter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, charsequence, content, context, cursor, cursortostringconverter, imageview, internet, net, network, numberformatexception, override, resourcecursoradapter, simplecursoradapter, string, textview, view, viewbinder

The SimpleCursorAdapter.java Android example source code

/*
 * 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.content.Context;
import android.database.Cursor;
import android.net.Uri;
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}
     */
    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}
     */
    protected int[] mTo;

    private int mStringConversionColumn = -1;
    private CursorToStringConverter mCursorToStringConverter;
    private ViewBinder mViewBinder;
    private String[] mOriginalFrom;

    /**
     * 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.
     */
    public SimpleCursorAdapter(Context context, int layout, Cursor c, String[] from, int[] to) {
        super(context, layout, c);
        mTo = to;
        mOriginalFrom = from;
        findColumns(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 an 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 mCursor.
     * If mCursor is null, the array will be discarded.
     * 
     * @param from the Strings naming the columns of interest
     */
    private void findColumns(String[] from) {
        if (mCursor != 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] = mCursor.getColumnIndexOrThrow(from[i]);
            }
        } else {
            mFrom = null;
        }
    }

    @Override
    public void changeCursor(Cursor c) {
        super.changeCursor(c);
        // rescan columns in case cursor layout is different
        findColumns(mOriginalFrom);
    }
    
    /**
     * 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(c);        
        findColumns(mOriginalFrom);
    }

    /**
     * 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);
    }

}

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