An extension of Android AppBarLayout, that allows to programatically change the CollapsibleToolbarLayout state

Readme.md

DEPRECATED

ControllableAppBarLayout has been made to allow to programatically change the CollapsibleToolbarLayout state.

From v23 of the design support library this function is available in the AppBarLayout itself.

You should probably use that (setExpanded) instead of ControllableAppBarLayout (although setTitle seems to be a bit bugged with setting expanded or collapsed).

ControllableAppBarLayout.java

/**
 * Copyright 2015 Bartosz Lipinski
 *
 * 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.
 */

import android.content.Context;
import android.graphics.Canvas;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.util.AttributeSet;

import java.lang.ref.WeakReference;

public class ControllableAppBarLayout extends AppBarLayout {
    private AppBarLayout.Behavior mBehavior;
    private WeakReference<CoordinatorLayout> mParent;
    private ToolbarChange mQueuedChange = ToolbarChange.NONE;
    private boolean mAfterFirstDraw = false;

    public ControllableAppBarLayout(Context context) {
        super(context);
    }

    public ControllableAppBarLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        if (!(getLayoutParams() instanceof CoordinatorLayout.LayoutParams) || !(getParent() instanceof CoordinatorLayout)) {
            throw new IllegalStateException("ControllableAppBarLayout must be a direct child of CoordinatorLayout.");
        } else {
            mParent = new WeakReference<CoordinatorLayout>((CoordinatorLayout) getParent());
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (mBehavior == null) {
            mBehavior = (Behavior) ((CoordinatorLayout.LayoutParams) getLayoutParams()).getBehavior();
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);
        if (r - l > 0 && b - t > 0 && mAfterFirstDraw && mQueuedChange != ToolbarChange.NONE) {
            analyzeQueuedChange();
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (!mAfterFirstDraw) {
            mAfterFirstDraw = true;
            if (mQueuedChange != ToolbarChange.NONE) {
                analyzeQueuedChange();
            }
        }
    }

    private synchronized void analyzeQueuedChange() {
        switch (mQueuedChange) {
            case COLLAPSE:
                performCollapsingWithoutAnimation();
                break;
            case COLLAPSE_WITH_ANIMATION:
                performCollapsingWithAnimation();
                break;
            case EXPAND:
                performExpandingWithoutAnimation();
                break;
            case EXPAND_WITH_ANIMATION:
                performExpandingWithAnimation();
                break;
        }

        mQueuedChange = ToolbarChange.NONE;
    }

    public void collapseToolbar() {
        collapseToolbar(false);
    }

    public void collapseToolbar(boolean withAnimation) {
        mQueuedChange = withAnimation ? ToolbarChange.COLLAPSE_WITH_ANIMATION : ToolbarChange.COLLAPSE;
        requestLayout();
    }

    public void expandToolbar() {
        expandToolbar(false);
    }

    public void expandToolbar(boolean withAnimation) {
        mQueuedChange = withAnimation ? ToolbarChange.EXPAND_WITH_ANIMATION : ToolbarChange.EXPAND;
        requestLayout();
    }

    private void performCollapsingWithoutAnimation() {
        if (mParent.get() != null) {
            mBehavior.onNestedPreScroll(mParent.get(), this, null, 0, getHeight(), new int[]{0, 0});
        }
    }

    private void performCollapsingWithAnimation() {
        if (mParent.get() != null) {
            mBehavior.onNestedFling(mParent.get(), this, null, 0, getHeight(), true);
        }
    }

    private void performExpandingWithoutAnimation() {
        if (mParent.get() != null) {
            mBehavior.setTopAndBottomOffset(0);
        }
    }

    private void performExpandingWithAnimation() {
        if (mParent.get() != null) {
            mBehavior.onNestedFling(mParent.get(), this, null, 0, -getHeight() * 5, false);
        }
    }

    private enum ToolbarChange {
        COLLAPSE,
        COLLAPSE_WITH_ANIMATION,
        EXPAND,
        EXPAND_WITH_ANIMATION,
        NONE
    }

}