SlidingPanel.java

package com.noshufou.android.su.widget;

import com.noshufou.android.su.R;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Animation;
import android.view.animation.TranslateAnimation;
import android.view.animation.Animation.AnimationListener;
import android.widget.Button;

public class SlidingPanel extends ViewGroup {
//    private static final String TAG = "Su.SlidingPanel";

    private int mButtonId;
    private View mButton;
    private int mAnchorId;
    private View mAnchor;
    private int mContentId;
    private View mContent;
    
    private int mOpenOverlap;
    private int mClosedLimit;
    
    private boolean mAnimating = false;
    private int mFillOffset = 0;
    
    private boolean mExpanded = true;

    public SlidingPanel(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public SlidingPanel(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.SlidingPanel,
                defStyle, 0);

        int buttonId = a.getResourceId(R.styleable.SlidingPanel_button, 0);
        if (buttonId == 0) {
            throw new IllegalArgumentException("The button attribute is required and must refer" +
                    " to a valid child");
        }
        
        int anchorId = a.getResourceId(R.styleable.SlidingPanel_anchor, 0);
        if (anchorId == buttonId) {
            throw new IllegalArgumentException("The anchor attribute is required and must refer" +
                    " to a different child");
        }
        
        int contentId = a.getResourceId(R.styleable.SlidingPanel_content, 0);
        if (contentId == anchorId || contentId == buttonId) {
            throw new IllegalArgumentException("The content attribute is required and must refer" +
                    " to a different child");
        }
        
        mOpenOverlap = a.getDimensionPixelSize(R.styleable.SlidingPanel_openOverlap, 0);
        mClosedLimit = a.getDimensionPixelSize(R.styleable.SlidingPanel_closedLimit, 0);
        
        a.recycle();
        
        mButtonId = buttonId;
        mAnchorId = anchorId;
        mContentId = contentId;
    }

    @Override
    protected void onFinishInflate() {
        mButton = findViewById(mButtonId);
        ((Button)mButton).setText(">");
        if (mButton == null) {
            throw new IllegalArgumentException("The handle attribute must refer to a child");
        }
        
        mAnchor = findViewById(mAnchorId);
        if (mAnchor == null) {
            throw new IllegalArgumentException("The anchor attribute must refer to a child");
        }
        
        mContent = findViewById(mContentId);
        if (mContent == null) {
            throw new IllegalArgumentException("The content attribute must refer to a child");
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int width = View.resolveSize(0, widthMeasureSpec);
        int height = View.resolveSize(0, heightMeasureSpec);
        
        final View anchor = mAnchor;
        measureChild(anchor, widthMeasureSpec, heightMeasureSpec);
        
        final View button = mButton;
        measureChild(button, MeasureSpec.makeMeasureSpec(anchor.getMeasuredWidth(),
                MeasureSpec.EXACTLY),
                heightMeasureSpec);
        button.setOnClickListener(new Toggler());
        
        final View content = mContent;
        int contentWidth = width - mClosedLimit;
        content.measure(MeasureSpec.makeMeasureSpec(contentWidth, MeasureSpec.EXACTLY),
                MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY));
        
        setMeasuredDimension(width, height);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        final View button = mButton;
        button.layout(0, 0, button.getMeasuredWidth(), button.getMeasuredHeight());
        
        final View anchor = mAnchor;
        anchor.layout(0, button.getMeasuredHeight(), anchor.getMeasuredWidth(),
                button.getMeasuredHeight() + anchor.getMeasuredHeight());
        
        final View content = mContent;
        int contentLeft;
        if (mAnimating) {
            contentLeft = content.getLeft();
        } else if (mExpanded) {
            contentLeft = mClosedLimit;
        } else {
            contentLeft = anchor.getRight() - mOpenOverlap;
        }
        content.layout(contentLeft, 0,
                contentLeft + content.getMeasuredWidth(),
                content.getMeasuredHeight());
    }

    public void toggle() {
        final View content = mContent;
        
        final View anchor = mAnchor;
        final int offset = anchor.getMeasuredWidth() - mOpenOverlap - mClosedLimit;
        TranslateAnimation anim;
        if (mExpanded) {
            anim = new TranslateAnimation(0, offset, 0, 0);
            mFillOffset = offset;
        } else {
            anim = new TranslateAnimation(0, -offset, 0, 0);
            mFillOffset = -offset;
        }
        mExpanded = !mExpanded;
        anim.setFillEnabled(true);
        anim.setFillBefore(true);
        anim.setDuration(300);
        anim.setInterpolator(new AccelerateDecelerateInterpolator());
        anim.setAnimationListener(new AnimationFiller());
        content.startAnimation(anim);
    }
    
    private class Toggler implements OnClickListener {

        @Override
        public void onClick(View v) {
            if (!mAnimating) {
                toggle();
            }
        }
        
    }
    
    private class AnimationFiller implements AnimationListener {

        @Override
        public void onAnimationEnd(Animation animation) {
            mAnimating = false;
            final View content = mContent;
            content.offsetLeftAndRight(mFillOffset);
            final Button button = (Button) mButton;
            if (mExpanded) {
                button.setText(">");
            } else {
                button.setText("<");
            }
        }

        @Override
        public void onAnimationRepeat(Animation animation) {
        }

        @Override
        public void onAnimationStart(Animation animation) {
            mAnimating = true;
        }
        
    }
}