Add QrDecorateView for QrCode scanner implementation

/*

 * Copyright (C) 2018 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 com.android.settings.wifi.qrcode;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Point;

import android.graphics.Rect;

import android.graphics.RectF;

import android.util.AttributeSet;

import android.util.TypedValue;

import android.view.View;

import com.android.settings.R;

/**

 * Draws the lines at the corner of the inner frame.

 */

public class QrDecorateView extends View {

    private static final float CORNER_STROKE_WIDTH = 3f;    // 3dp

    private static final float CORNER_LINE_LENGTH = 20f;    // 20dp

    final private Paint mPaint;

    private RectF mFrame;

    private boolean mFocused;

    public QrDecorateView(Context context) {

        this(context, null);

    }

    public QrDecorateView(Context context, AttributeSet attrs) {

        this(context, attrs, 0);

    }

    public QrDecorateView(Context context, AttributeSet attrs, int defStyleAttr) {

        this(context, attrs, defStyleAttr, 0);

    }

    public QrDecorateView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {

        super(context, attrs, defStyleAttr, defStyleRes);

        final float strokeWidth = TypedValue.applyDimension(

                TypedValue.COMPLEX_UNIT_DIP,

                CORNER_STROKE_WIDTH,

                getResources().getDisplayMetrics()

        );

        mPaint = new Paint();

        mPaint.setStrokeWidth(strokeWidth);

        mFocused = false;

    }

    @Override

    protected void onDraw(Canvas canvas) {

        calculateFramePos();

        final float cornerLineLength = TypedValue.applyDimension(

                TypedValue.COMPLEX_UNIT_DIP,

                CORNER_LINE_LENGTH,

                getResources().getDisplayMetrics()

        );

        mPaint.setColor(mFocused ? Color.GREEN : Color.WHITE);

        drawCorner(mFrame, cornerLineLength, canvas);

        super.onDraw(canvas);

    }

    private void drawCorner(RectF frame, float lineLength, Canvas canvas) {

        final float strokeWidth = TypedValue.applyDimension(

                TypedValue.COMPLEX_UNIT_DIP,

                CORNER_STROKE_WIDTH,

                getResources().getDisplayMetrics()

        );

        // Draw top-left corner.

        canvas.drawLine(

                frame.left - strokeWidth / 2,

                frame.top,

                frame.left + lineLength,

                frame.top,

                mPaint);

        canvas.drawLine(frame.left, frame.top, frame.left, frame.top + lineLength, mPaint);

        // Draw top-right corner.

        canvas.drawLine(

                frame.right + strokeWidth / 2,

                frame.top,

                frame.right - lineLength,

                frame.top,

                mPaint);

        canvas.drawLine(frame.right, frame.top, frame.right, frame.top + lineLength, mPaint);

        // Draw bottom-left corner.

        canvas.drawLine(

                frame.left - strokeWidth / 2,

                frame.bottom,

                frame.left + lineLength,

                frame.bottom,

                mPaint);

        canvas.drawLine(frame.left, frame.bottom, frame.left, frame.bottom - lineLength, mPaint);

        // Draw bottom-right corner.

        canvas.drawLine(

                frame.right + strokeWidth / 2,

                frame.bottom,

                frame.right - lineLength,

                frame.bottom,

                mPaint);

        canvas.drawLine(frame.right, frame.bottom, frame.right, frame.bottom - lineLength, mPaint);

    }

    private void calculateFramePos() {

        final int centralX = getWidth() / 2;

        final int centralY = getHeight() / 2;

        final float halfFrameWidth = getWidth() / 3;

        mFrame = new RectF(

                centralX - halfFrameWidth,

                centralY - halfFrameWidth,

                centralX + halfFrameWidth,

                centralY + halfFrameWidth);

    }

    // Draws green lines if focued. Otherwise, draws white lines.

    public void setFocused(boolean focused) {

        mFocused = focused;

        invalidate();

    }

}