Android example source code file (Spinner.java)

This example Android source code file (Spinner.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

absspinner, android, annotate, annotations, app, attributeset, charsequence, content, context, dropdownadapter, listadapter, object, override, runtimeexception, spinner, spinneradapter, ui, view, viewgroup, widget

The Spinner.java Android example source code

/*
 * Copyright (C) 2007 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.Widget;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;


/**
 * A view that displays one child at a time and lets the user pick among them.
 * The items in the Spinner come from the {@link Adapter} associated with
 * this view.
 * 
 * @attr ref android.R.styleable#Spinner_prompt
 */
@Widget
public class Spinner extends AbsSpinner implements OnClickListener {
    
    private CharSequence mPrompt;
    private AlertDialog mPopup;

    public Spinner(Context context) {
        this(context, null);
    }

    public Spinner(Context context, AttributeSet attrs) {
        this(context, attrs, com.android.internal.R.attr.spinnerStyle);
    }

    public Spinner(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a = context.obtainStyledAttributes(attrs,
                com.android.internal.R.styleable.Spinner, defStyle, 0);
        
        mPrompt = a.getString(com.android.internal.R.styleable.Spinner_prompt);

        a.recycle();
    }

    @Override
    public int getBaseline() {
        View child = null;

        if (getChildCount() > 0) {
            child = getChildAt(0);
        } else if (mAdapter != null && mAdapter.getCount() > 0) {
            child = makeAndAddView(0);
            // TODO: We should probably put the child in the recycler
        }

        if (child != null) {
            return child.getTop() + child.getBaseline();
        } else {
            return -1;
        }
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        
        if (mPopup != null && mPopup.isShowing()) {
            mPopup.dismiss();
            mPopup = null;
        }
    }

    /**
     * <p>A spinner does not support item click events. Calling this method
     * will raise an exception.</p>
     *
     * @param l this listener will be ignored
     */
    @Override
    public void setOnItemClickListener(OnItemClickListener l) {
        throw new RuntimeException("setOnItemClickListener cannot be used with a spinner.");
    }

    /**
     * @see android.view.View#onLayout(boolean,int,int,int,int)
     *
     * Creates and positions all views
     *
     */
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        mInLayout = true;
        layout(0, false);
        mInLayout = false;
    }

    /**
     * Creates and positions all views for this Spinner.
     *
     * @param delta Change in the selected position. +1 moves selection is moving to the right,
     * so views are scrolling to the left. -1 means selection is moving to the left.
     */
    @Override
    void layout(int delta, boolean animate) {
        int childrenLeft = mSpinnerPadding.left;
        int childrenWidth = mRight - mLeft - mSpinnerPadding.left - mSpinnerPadding.right;

        if (mDataChanged) {
            handleDataChanged();
        }

        // Handle the empty set by removing all views
        if (mItemCount == 0) {
            resetList();
            return;
        }

        if (mNextSelectedPosition >= 0) {
            setSelectedPositionInt(mNextSelectedPosition);
        }

        recycleAllViews();

        // Clear out old views
        removeAllViewsInLayout();

        // Make selected view and center it
        mFirstPosition = mSelectedPosition;
        View sel = makeAndAddView(mSelectedPosition);
        int width = sel.getMeasuredWidth();
        int selectedOffset = childrenLeft + (childrenWidth / 2) - (width / 2);
        sel.offsetLeftAndRight(selectedOffset);

        // Flush any cached views that did not get reused above
        mRecycler.clear();

        invalidate();

        checkSelectionChanged();

        mDataChanged = false;
        mNeedSync = false;
        setNextSelectedPositionInt(mSelectedPosition);
    }

    /**
     * Obtain a view, either by pulling an existing view from the recycler or
     * by getting a new one from the adapter. If we are animating, make sure
     * there is enough information in the view's layout parameters to animate
     * from the old to new positions.
     *
     * @param position Position in the spinner for the view to obtain
     * @return A view that has been added to the spinner
     */
    private View makeAndAddView(int position) {

        View child;

        if (!mDataChanged) {
            child = mRecycler.get(position);
            if (child != null) {
                // Position the view
                setUpChild(child);

                return child;
            }
        }

        // Nothing found in the recycler -- ask the adapter for a view
        child = mAdapter.getView(position, null, this);

        // Position the view
        setUpChild(child);

        return child;
    }



    /**
     * Helper for makeAndAddView to set the position of a view
     * and fill out its layout paramters.
     *
     * @param child The view to position
     */
    private void setUpChild(View child) {

        // Respect layout params that are already in the view. Otherwise
        // make some up...
        ViewGroup.LayoutParams lp = child.getLayoutParams();
        if (lp == null) {
            lp = generateDefaultLayoutParams();
        }

        addViewInLayout(child, 0, lp);

        child.setSelected(hasFocus());

        // Get measure specs
        int childHeightSpec = ViewGroup.getChildMeasureSpec(mHeightMeasureSpec,
                mSpinnerPadding.top + mSpinnerPadding.bottom, lp.height);
        int childWidthSpec = ViewGroup.getChildMeasureSpec(mWidthMeasureSpec,
                mSpinnerPadding.left + mSpinnerPadding.right, lp.width);

        // Measure child
        child.measure(childWidthSpec, childHeightSpec);

        int childLeft;
        int childRight;

        // Position vertically based on gravity setting
        int childTop = mSpinnerPadding.top
                + ((mMeasuredHeight - mSpinnerPadding.bottom - 
                        mSpinnerPadding.top - child.getMeasuredHeight()) / 2);
        int childBottom = childTop + child.getMeasuredHeight();

        int width = child.getMeasuredWidth();
        childLeft = 0;
        childRight = childLeft + width;

        child.layout(childLeft, childTop, childRight, childBottom);
    }

    @Override
    public boolean performClick() {
        boolean handled = super.performClick();
        
        if (!handled) {
            handled = true;
            Context context = getContext();
            
            final DropDownAdapter adapter = new DropDownAdapter(getAdapter());

            AlertDialog.Builder builder = new AlertDialog.Builder(context);
            if (mPrompt != null) {
                builder.setTitle(mPrompt);
            }
            mPopup = builder.setSingleChoiceItems(adapter, getSelectedItemPosition(), this).show();
        }

        return handled;
    }
    
    public void onClick(DialogInterface dialog, int which) {
        setSelection(which);
        dialog.dismiss();
        mPopup = null;
    }

    /**
     * Sets the prompt to display when the dialog is shown.
     * @param prompt the prompt to set
     */
    public void setPrompt(CharSequence prompt) {
        mPrompt = prompt;
    }

    /**
     * Sets the prompt to display when the dialog is shown.
     * @param promptId the resource ID of the prompt to display when the dialog is shown
     */
    public void setPromptId(int promptId) {
        mPrompt = getContext().getText(promptId);
    }

    /**
     * @return The prompt to display when the dialog is shown
     */
    public CharSequence getPrompt() {
        return mPrompt;
    }
    
    /**
     * <p>Wrapper class for an Adapter. Transforms the embedded Adapter instance
     * into a ListAdapter.</p>
     */
    private static class DropDownAdapter implements ListAdapter, SpinnerAdapter {
        private SpinnerAdapter mAdapter;
        private ListAdapter mListAdapter;

        /**
         * <p>Creates a new ListAdapter wrapper for the specified adapter.

         *
         * @param adapter the Adapter to transform into a ListAdapter
         */
        public DropDownAdapter(SpinnerAdapter adapter) {
            this.mAdapter = adapter;
            if (adapter instanceof ListAdapter) {
                this.mListAdapter = (ListAdapter) adapter;
            }
        }

        public int getCount() {
            return mAdapter == null ? 0 : mAdapter.getCount();
        }

        public Object getItem(int position) {
            return mAdapter == null ? null : mAdapter.getItem(position);
        }

        public long getItemId(int position) {
            return mAdapter == null ? -1 : mAdapter.getItemId(position);
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            return getDropDownView(position, convertView, parent);
        }

        public View getDropDownView(int position, View convertView, ViewGroup parent) {
            return mAdapter == null ? null :
                    mAdapter.getDropDownView(position, convertView, parent);
        }

        public boolean hasStableIds() {
            return mAdapter != null && mAdapter.hasStableIds();
        }

        public void registerDataSetObserver(DataSetObserver observer) {
            if (mAdapter != null) {
                mAdapter.registerDataSetObserver(observer);
            }
        }

        public void unregisterDataSetObserver(DataSetObserver observer) {
            if (mAdapter != null) {
                mAdapter.unregisterDataSetObserver(observer);
            }
        }

        /**
         * If the wrapped SpinnerAdapter is also a ListAdapter, delegate this call.
         * Otherwise, return true. 
         */
        public boolean areAllItemsEnabled() {
            final ListAdapter adapter = mListAdapter;
            if (adapter != null) {
                return adapter.areAllItemsEnabled();
            } else {
                return true;
            }
        }

        /**
         * If the wrapped SpinnerAdapter is also a ListAdapter, delegate this call.
         * Otherwise, return true.
         */
        public boolean isEnabled(int position) {
            final ListAdapter adapter = mListAdapter;
            if (adapter != null) {
                return adapter.isEnabled(position);
            } else {
                return true;
            }
        }

        public int getItemViewType(int position) {
            return 0;
        }

        public int getViewTypeCount() {
            return 1;
        }
        
        public boolean isEmpty() {
            return getCount() == 0;
        }
    }
}