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Android example source code file (ScrollViewScenario.java)

This example Android source code file (ScrollViewScenario.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

activity, android, button, collections, content, context, google, internalselectionview, javadoc, linearlayout, params, scrollview, string, suppresswarnings, textview, ui, unsupportedoperationexception, view, viewfactorybase, widget

The ScrollViewScenario.java Android example source code

/*
 * Copyright (C) 2008 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.util;

import com.google.android.collect.Lists;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.ScrollView;
import android.widget.TextView;

import java.util.List;

/**
 * Utility base class for creating scroll view scenarios, allowing you to add
 * a series of different kinds of views arranged vertically, taking up a
 * specified amount of the screen height.
 */
public abstract class ScrollViewScenario extends Activity {

    /**
     * Holds content of scroll view
     */
    private LinearLayout mLinearLayout;

    /**
     * The actual scroll view
     */
    private ScrollView mScrollView;


    /**
     * What we need of each view that the user wants: the view, and the ratio
     * to the screen height for its desired height.
     */
    private interface ViewFactory {
        View create(final Context context);

        float getHeightRatio();
    }

    /**
     * Partially implement ViewFactory given a height ratio.
     */
    private static abstract class ViewFactoryBase implements ViewFactory {

        private float mHeightRatio;

        @SuppressWarnings({"UnusedDeclaration"})
        private ViewFactoryBase() {throw new UnsupportedOperationException("don't call this!");}

        protected ViewFactoryBase(float heightRatio) {
            mHeightRatio = heightRatio;
        }

        public float getHeightRatio() {
            return mHeightRatio;
        }
    }

    /**
     * Builder for selecting the views to be vertically arranged in the scroll
     * view.
     */
    @SuppressWarnings({"JavaDoc"})
    public static class Params {

        List<ViewFactory> mViewFactories = Lists.newArrayList();

        /**
         * Add a text view.
         * @param text The text of the text view.
         * @param heightRatio The view's height will be this * the screen height.
         */
        public Params addTextView(final String text, float heightRatio) {
            mViewFactories.add(new ViewFactoryBase(heightRatio) {
                public View create(final Context context) {
                    final TextView tv = new TextView(context);
                    tv.setText(text);
                    return tv;
                }
            });
            return this;
        }

        /**
         * Add multiple text views.
         * @param numViews the number of views to add.
         * @param textPrefix The text to prepend to each text view.
         * @param heightRatio The view's height will be this * the screen height.
         */
        public Params addTextViews(int numViews, String textPrefix, float heightRatio) {
            for (int i = 0; i < numViews; i++) {
                addTextView(textPrefix + i, heightRatio);
            }
            return this;
        }

        /**
         * Add a button.
         * @param text The text of the button.
         * @param heightRatio The view's height will be this * the screen height.
         */
        public Params addButton(final String text, float heightRatio) {
            mViewFactories.add(new ViewFactoryBase(heightRatio) {
                public View create(final Context context) {
                    final Button button = new Button(context);
                    button.setText(text);
                    return button;
                }
            });
            return this;
        }

        /**
         * Add multiple buttons.
         * @param numButtons the number of views to add.
         * @param textPrefix The text to prepend to each button.
         * @param heightRatio The view's height will be this * the screen height.
         */
        public Params addButtons(int numButtons, String textPrefix, float heightRatio) {
            for (int i = 0; i < numButtons; i++) {
                addButton(textPrefix + i, heightRatio);
            }
            return this;
        }

        /**
         * Add an {@link InternalSelectionView}.
         * @param numRows The number of rows in the internal selection view.
         * @param heightRatio The view's height will be this * the screen height.
         */
        public Params addInternalSelectionView(final int numRows, float heightRatio) {
            mViewFactories.add(new ViewFactoryBase(heightRatio) {
                public View create(final Context context) {
                    return new InternalSelectionView(context, numRows, "isv");
                }
            });
            return this;
        }

        /**
         * Add a sublayout of buttons as a single child of the scroll view.
         * @param numButtons The number of buttons in the sub layout
         * @param heightRatio The layout's height will be this * the screen height.
         */
        public Params addVerticalLLOfButtons(final String prefix, final int numButtons, float heightRatio) {
            mViewFactories.add(new ViewFactoryBase(heightRatio) {

                public View create(Context context) {
                    final LinearLayout ll = new LinearLayout(context);
                    ll.setOrientation(LinearLayout.VERTICAL);

                    // fill width, equally weighted on height
                    final LinearLayout.LayoutParams lp =
                            new LinearLayout.LayoutParams(
                                    ViewGroup.LayoutParams.MATCH_PARENT, 0, 1f);
                    for (int i = 0; i < numButtons; i++) {
                        final Button button = new Button(context);
                        button.setText(prefix + i);
                        ll.addView(button, lp);
                    }

                    return ll;
                }
            });
            return this;
        }
    }

    /**
     * Override this and initialized the views in the scroll view.
     * @param params Used to configure the contents of the scroll view.
     */
    protected abstract void init(Params params);

    public LinearLayout getLinearLayout() {
        return mLinearLayout;
    }

    public ScrollView getScrollView() {
        return mScrollView;
    }

    /**
     * Get the child contained within the vertical linear layout of the
     * scroll view.
     * @param index The index within the linear layout.
     * @return the child within the vertical linear layout of the scroll view
     *   at the specified index.
     */
    @SuppressWarnings({"unchecked"})
    public <T extends View> T getContentChildAt(int index) {
        return (T) mLinearLayout.getChildAt(index);
    }

    /**
     * Hook for changing how scroll view's are created.
     */
    @SuppressWarnings({"JavaDoc"})
    protected ScrollView createScrollView() {
        return new ScrollView(this);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // for test stability, turn off title bar
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        int screenHeight = getWindowManager().getDefaultDisplay().getHeight()
                - 25;
        mLinearLayout = new LinearLayout(this);
        mLinearLayout.setOrientation(LinearLayout.VERTICAL);

        // initialize params
        final Params params = new Params();
        init(params);

        // create views specified by params
        for (ViewFactory viewFactory : params.mViewFactories) {
            final LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT,
                    (int) (viewFactory.getHeightRatio() * screenHeight));
            mLinearLayout.addView(viewFactory.create(this), lp);
        }

        mScrollView = createScrollView();
        mScrollView.addView(mLinearLayout, new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT));

        // no animation to speed up tests
        mScrollView.setSmoothScrollingEnabled(false);

        setContentView(mScrollView);
    }
}

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