src/com/android/camera/widget/SettingsCling.java

/*
 * Copyright (C) 2014 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.camera.widget;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.View;
import android.widget.FrameLayout;

import com.android.camera2.R;

/**
 * This is a cling widget for settings button. In addition to drawing a cling button
 * background and overlaying text, it draws a small triangle that points at the
 * settings button that this cling is for.
 */
public class SettingsCling extends FrameLayout {
    private final int mClingTriangleHeight;
    private final int mClingTriangleWidth;
    private final Path mTrianglePath = new Path();
    private final Paint mClingPaint = new Paint();

    public SettingsCling(Context context, AttributeSet attrs) {
        super(context, attrs);
        setWillNotDraw(false);
        mClingTriangleHeight = getResources().getDimensionPixelSize(
                R.dimen.settings_cling_triangle_height);
        mClingTriangleWidth = getResources().getDimensionPixelSize(
                R.dimen.settings_cling_triangle_width);
        mClingPaint.setColor(getResources().getColor(R.color.settings_cling_color));
        mClingPaint.setStyle(Paint.Style.FILL);
    }

    /**
     * Updates the current position of the cling based on a reference view. If there
     * is enough space to lay out the cling on top of the reference view, then have
     * the cling on top. Otherwise, position the cling underneath the reference view.
     *
     * @param referenceView a view that cling uses as a position reference
     */
    public void updatePosition(View referenceView) {
        if (referenceView == null) {
            return;
        }
        // Right align cling:
        float referenceRight = referenceView.getX() + referenceView.getMeasuredWidth();
        setTranslationX(referenceRight - getMeasuredWidth());

        float referenceTop = referenceView.getY();
        if (referenceTop < getMeasuredHeight()) {
            // Layout cling under reference view.
            setTranslationY(referenceTop + referenceView.getMeasuredHeight());
            float triangleStartX = getMeasuredWidth() - referenceView.getMeasuredWidth() / 2;
            float triangleStartY = 0;
            mTrianglePath.reset();
            mTrianglePath.moveTo(triangleStartX, triangleStartY);
            mTrianglePath.lineTo(triangleStartX - mClingTriangleWidth / 2,
                    triangleStartY + mClingTriangleHeight);
            mTrianglePath.lineTo(triangleStartX + mClingTriangleWidth / 2,
                    triangleStartY + mClingTriangleHeight);
            mTrianglePath.lineTo(triangleStartX, triangleStartY);
        } else {
            // Layout cling on top of reference view.
            setTranslationY(referenceTop - getMeasuredHeight());
            float triangleStartX = getMeasuredWidth() - referenceView.getMeasuredWidth() / 2;
            float triangleStartY = getMeasuredHeight();
            mTrianglePath.reset();
            mTrianglePath.moveTo(triangleStartX, triangleStartY);
            mTrianglePath.lineTo(triangleStartX - mClingTriangleWidth / 2,
                    triangleStartY - mClingTriangleHeight);
            mTrianglePath.lineTo(triangleStartX + mClingTriangleWidth / 2,
                    triangleStartY - mClingTriangleHeight);
            mTrianglePath.lineTo(triangleStartX, triangleStartY);
        }
        invalidate();
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // Draw triangle.
        canvas.drawPath(mTrianglePath, mClingPaint);
    }
}