1 /*
2  * Copyright (C) 2012 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.example.android.snake;
18 
19 import android.content.Context;
20 import android.content.res.TypedArray;
21 import android.graphics.Canvas;
22 import android.graphics.Color;
23 import android.graphics.Paint;
24 import android.util.AttributeSet;
25 import android.view.View;
26 
27 import java.util.Arrays;
28 
29 /**
30  * Background View: Draw 4 full-screen RGBY triangles
31  */
32 public class BackgroundView extends View {
33 
34     private int[] mColors = new int[4];
35 
36     private final short[] mIndices =
37             { 0, 1, 2, 0, 3, 4, 0, 1, 4 // Corner points for triangles (with offset = 2)
38     };
39 
40     private float[] mVertexPoints = null;
41 
BackgroundView(Context context, AttributeSet attrs)42     public BackgroundView(Context context, AttributeSet attrs) {
43         super(context, attrs);
44         setFocusable(true);
45 
46         // retrieve colors for 4 segments from styleable properties
47         TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.BackgroundView);
48         mColors[0] = a.getColor(R.styleable.BackgroundView_colorSegmentOne, Color.RED);
49         mColors[1] = a.getColor(R.styleable.BackgroundView_colorSegmentTwo, Color.YELLOW);
50         mColors[2] = a.getColor(R.styleable.BackgroundView_colorSegmentThree, Color.BLUE);
51         mColors[3] = a.getColor(R.styleable.BackgroundView_colorSegmentFour, Color.GREEN);
52 
53         a.recycle();
54     }
55 
56     @Override
onDraw(Canvas canvas)57     protected void onDraw(Canvas canvas) {
58         assert(mVertexPoints != null);
59 
60         // Colors for each vertex
61         int[] mFillColors = new int[mVertexPoints.length];
62 
63         for (int triangle = 0; triangle < mColors.length; triangle++) {
64             // Set color for all vertex points to current triangle color
65             Arrays.fill(mFillColors, mColors[triangle]);
66 
67             // Draw one triangle
68             canvas.drawVertices(Canvas.VertexMode.TRIANGLES, mVertexPoints.length, mVertexPoints,
69                     0, null, 0, // No Textures
70                     mFillColors, 0, mIndices,
71                     triangle * 2, 3, // Use 3 vertices via Index Array with offset 2
72                     new Paint());
73         }
74     }
75 
76     @Override
onSizeChanged(int w, int h, int oldw, int oldh)77     protected void onSizeChanged(int w, int h, int oldw, int oldh) {
78         super.onSizeChanged(w, h, oldw, oldh);
79 
80      // Construct our center and four corners
81         mVertexPoints = new float[] {
82                 w / 2, h / 2,
83                 0, 0,
84                 w, 0,
85                 w, h,
86                 0, h
87         };
88     }
89 
90 }
91