Androidアプリ　テトリス制作について

###前提・実現したいこと
①xmlでボタンや背景を配置してもゲーム画面では表示されないので表示されるようにしたいです。
②ボタンでテトリスのブロックが移動、回転できるようにしたいです。
③ゲームオーバーの追加がしたいです。
ソースコード付きで解説を貰えるとうれしいです。
よろしくお願いします。

###該当のソースコード

Java
1public class sub extends AppCompatActivity {
2    private class FieldView extends SurfaceView {
3
4        Random mRand = new Random(System.currentTimeMillis());
5
6
7        int[][][] blocks = {
8               //省略
9        };
10
11        int[][] block = blocks[mRand.nextInt(blocks.length)];
12        int posx=10, posy=1;
13        int mapWidth  = 40;
14        int mapHeight = 40;
15        int count = 0;
16        int[][] map = new int[mapHeight][];
17        int[][] next = new int[mapHeight][];
18
19        public FieldView(Context context) {
20            super(context);
21
22            setBackgroundColor(0xFFFFFFFF);
23            setFocusable(true);
24            setFocusableInTouchMode(true);
25            requestFocus();
26        }
27
28
29
30        public void initGame() {
31            for (int y = 0; y < mapHeight; y++) {
32                map[y] = new int[mapWidth];
33                for (int x = 0; x < mapWidth; x++) {
34                    map[y][x] = 0;
35                }
36            }
37        }
38
39
40
41        private void paintMatrix(Canvas canvas, int[][] matrix, int offsetx, int offsety, int color) {
42            ShapeDrawable rect = new ShapeDrawable(new RectShape());
43            rect.getPaint().setColor(color);
44            int h = matrix.length;
45            int w = matrix[0].length;
46
47            for (int y = 0; y < h; y ++) {
48                for (int x = 0; x < w; x ++) {
49                    if (matrix[y][x] != 0) {
50                        int px = (x + offsetx) * 20;
51                        int py = (y + offsety) * 20;
52                        rect.setBounds(px, py, px + 20, py + 20);
53                        rect.draw(canvas);
54                    }
55                }
56            }
57        }
58
59
60
61
62        boolean check(int[][] block, int offsetx, int offsety) {
63            if (offsetx < 0 || offsety < 0 ||
64                    mapHeight < offsety + block.length ||
65                    mapWidth < offsetx + block[0].length) {
66                return false;
67            }
68            for (int y = 0; y < block.length; y ++) {
69                for (int x = 0; x < block[y].length; x ++) {
70                    if (block[y][x] != 0 && map[y + offsety][x + offsetx] != 0) {
71                        return false;
72                    }
73                }
74            }
75            return true;
76        }
77
78        void mergeMatrix(int[][] block, int offsetx, int offsety) {
79            for (int y = 0; y < block.length; y ++) {
80                for (int x = 0; x < block[0].length; x ++) {
81                    if (block[y][x] != 0) {
82                        map[offsety + y][offsetx + x] = block[y][x];
83                    }
84                }
85            }
86        }
87
88        void clearRows() {
89            // 埋まった行は消す。nullで一旦マーキング
90            for (int y = 0; y < mapHeight; y ++) {
91
92                boolean full = true;
93                for (int x = 0; x < mapWidth; x ++) {
94                    if (map[y][x] == 0) {
95                        full = false;
96                        break;
97                    }
98                }
99
100                if (full) map[y] = null;
101            }
102
103            // 新しいmapにnull以外の行を詰めてコピーする
104            int[][] newMap = new int[mapHeight][];
105            int y2 = mapHeight - 1;
106            for (int y = mapHeight - 1; y >= 0; y--) {
107                if (map[y] == null) {
108                    continue;
109                } else {
110                    newMap[y2--] = map[y];
111                }
112            }
113
114            // 消えた行数分新しい行を追加する
115            for (int i = 0; i <= y2; i++) {
116                int[] newRow = new int[mapWidth];
117                for (int j = 0; j < mapWidth; j ++) {
118                    newRow[j] = 0;
119                }
120                newMap[i] = newRow;
121            }
122            map = newMap;
123        }
124
125        /**
126         * Draws the 2D layer.
127         */
128        @Override
129        protected void onDraw(Canvas canvas) {
130            ShapeDrawable rect = new ShapeDrawable(new RectShape());
131            rect.setBounds(0, 0, 210, 410);
132            rect.getPaint().setColor(0xff084c9e);
133            rect.draw(canvas);
134            canvas.translate(2, 2);
135            rect.setBounds(0, 0, 200, 400);
136            rect.getPaint().setColor(0xFFFFFFFF);
137            rect.draw(canvas);
138
139            //ブロックカラー
140            paintMatrix(canvas, block, posx, posy, 0xff084c9e);
141            paintMatrix(canvas, map, 0, 0, 0xff084c90);
142
143        }
144
145        int[][] rotate(final int[][] block) {
146            int[][] rotated = new int[block[0].length][];
147            for (int x = 0; x < block[0].length; x ++) {
148                rotated[x] = new int[block.length];
149                for (int y = 0; y < block.length; y ++) {
150                    rotated[x][block.length - y - 1] = block[y][x];
151                }
152            }
153            return rotated;
154        }
155
156        @Override
157        public boolean onKeyDown(int keyCode, KeyEvent event) {
158            switch (keyCode) {
159                case KeyEvent.KEYCODE_DPAD_CENTER:
160                    int[][] newBlock = rotate(block);
161                    if (check(newBlock, posx, posy)) {
162                        block = newBlock;
163                    }
164                    break;
165                case KeyEvent.KEYCODE_DPAD_RIGHT:
166                    if (check(block, posx + 1, posy)) {
167                        posx = posx + 1;
168                    }
169                    break;
170                case KeyEvent.KEYCODE_DPAD_LEFT:
171                    if (check(block, posx - 1, posy)) {
172                        posx = posx - 1;
173                    }
174                    break;
175                case KeyEvent.KEYCODE_DPAD_UP:
176                case KeyEvent.KEYCODE_DPAD_DOWN:
177                    int y = posy;
178                    while (check(block, posx, y)) { y++; }
179                    if (y > 0) posy = y - 1;
180
181                    break;
182            }
183            mHandler.sendEmptyMessage(INVALIDATE);
184            return true;
185        }
186
187        public void startAnime() {
188            mHandler.sendEmptyMessage(INVALIDATE);
189            mHandler.sendEmptyMessage(DROPBLOCK);
190        }
191
192        public void stopAnime() {
193            mHandler.removeMessages(INVALIDATE);
194            mHandler.removeMessages(DROPBLOCK);
195        }
196
197        private static final int INVALIDATE = 1;
198        private static final int DROPBLOCK = 2;
199
200        /**
201         * Controls the animation using the message queue. Every time we receive an
202         * INVALIDATE message, we redraw and place another message in the queue.
203         */
204        private final Handler mHandler = new Handler() {
205            @Override
206            public void handleMessage(Message msg) {
207                switch (msg.what) {
208                    case INVALIDATE:
209                        invalidate();
210                        break;
211                    case DROPBLOCK:
212                        if (check(block, posx, posy + 1)) {
213                            posy++;
214
215                        } else {
216                            mergeMatrix(block, posx, posy);
217                            clearRows();
218                            posx = 10; posy = 1;
219                            block = blocks[mRand.nextInt(blocks.length)];
220                        }
221
222
223
224                        invalidate();
225                        Message massage = new Message();
226                        massage.what = DROPBLOCK;
227                        sendMessageDelayed(massage, 500);
228                        break;
229                }
230            }
231        };
232    }
233
234    FieldView mFieldView;
235
236    private void setFieldView() {
237        if (mFieldView == null) {
238            mFieldView = new FieldView(getApplication());
239            setContentView(mFieldView);
240
241
242        }
243    }
244
245
246
247    @Override
248    protected void onResume() {
249        super.onResume();
250        setFieldView();
251        mFieldView.initGame();
252        mFieldView.startAnime();
253        Looper.myQueue().addIdleHandler(new Idler());
254    }
255
256
257
258
259
260    // Allow the activity to go idle before its animation starts
261    class Idler implements MessageQueue.IdleHandler {
262        public Idler() {
263            super();
264        }
265
266        public final boolean queueIdle() {
267            return false;
268        }
269    }
270
271}