material-components_material-components-android/src/android/support/design/internal/ScrimInsetsFrameLayout.java

/*
 * Copyright (C) 2015 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.support.design.internal;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.design.R;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.WindowInsetsCompat;
import android.util.AttributeSet;
import android.view.View;
import android.widget.FrameLayout;

/**
 * @hide
 */
public class ScrimInsetsFrameLayout extends FrameLayout {

    private Drawable mInsetForeground;

    private Rect mInsets;

    private Rect mTempRect = new Rect();

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

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

    public ScrimInsetsFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        final TypedArray a = context.obtainStyledAttributes(attrs,
                R.styleable.ScrimInsetsFrameLayout, defStyleAttr,
                R.style.Widget_Design_ScrimInsetsFrameLayout);
        mInsetForeground = a.getDrawable(R.styleable.ScrimInsetsFrameLayout_insetForeground);
        a.recycle();
        setWillNotDraw(true); // No need to draw until the insets are adjusted

        ViewCompat.setOnApplyWindowInsetsListener(this,
                new android.support.v4.view.OnApplyWindowInsetsListener() {
                    @Override
                    public WindowInsetsCompat onApplyWindowInsets(View v,
                            WindowInsetsCompat insets) {
                        if (null == mInsets) {
                            mInsets = new Rect();
                        }
                        mInsets.set(insets.getSystemWindowInsetLeft(),
                                insets.getSystemWindowInsetTop(),
                                insets.getSystemWindowInsetRight(),
                                insets.getSystemWindowInsetBottom());
                        setWillNotDraw(mInsets.isEmpty() || mInsetForeground == null);
                        ViewCompat.postInvalidateOnAnimation(ScrimInsetsFrameLayout.this);
                        return insets.consumeSystemWindowInsets();
                    }
                });
    }

    @Override
    public void draw(@NonNull Canvas canvas) {
        super.draw(canvas);

        int width = getWidth();
        int height = getHeight();
        if (mInsets != null && mInsetForeground != null) {
            int sc = canvas.save();
            canvas.translate(getScrollX(), getScrollY());

            // Top
            mTempRect.set(0, 0, width, mInsets.top);
            mInsetForeground.setBounds(mTempRect);
            mInsetForeground.draw(canvas);

            // Bottom
            mTempRect.set(0, height - mInsets.bottom, width, height);
            mInsetForeground.setBounds(mTempRect);
            mInsetForeground.draw(canvas);

            // Left
            mTempRect.set(0, mInsets.top, mInsets.left, height - mInsets.bottom);
            mInsetForeground.setBounds(mTempRect);
            mInsetForeground.draw(canvas);

            // Right
            mTempRect.set(width - mInsets.right, mInsets.top, width, height - mInsets.bottom);
            mInsetForeground.setBounds(mTempRect);
            mInsetForeground.draw(canvas);

            canvas.restoreToCount(sc);
        }
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        if (mInsetForeground != null) {
            mInsetForeground.setCallback(this);
        }
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if (mInsetForeground != null) {
            mInsetForeground.setCallback(null);
        }
    }

}