public class MainActivity extends Activity implements OnClickListener,OnSeekBarChangeListener {  private View red_view,green_view,blue_view;   //控制畫筆顏色的三塊區域  private SeekBar seekBar;    //控制畫筆粗細的拖動條  private ImageView iv;    private Bitmap bitmap,backgroud;  //畫紙和背景圖  private Canvas canvas;       //畫布  private Paint paint;        //畫筆  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    red_view = findViewById(R.id.red_view);    green_view = findViewById(R.id.green_view);    blue_view = findViewById(R.id.blue_view);    seekBar = (SeekBar) findViewById(R.id.seekbar);    iv = (ImageView) findViewById(R.id.iv);    iv.setImageResource(R.drawable.bg);    //拿到背景圖    backgroud = BitmapFactory.decodeResource(getResources(), R.drawable.bg);    //拿到和背景圖一樣大小的畫紙    bitmap = Bitmap.createBitmap(backgroud.getWidth(), backgroud.getHeight(), backgroud.getConfig());    //把畫紙固定在畫布上    canvas = new Canvas(bitmap);    //拿到畫筆    paint = new Paint();    paint.setColor(Color.BLACK);//設置畫筆顏色為黑色    paint.setStyle(Style.STROKE);//設置畫筆為空心    //添加處理規則    Matrix matrix = new Matrix();    //照著背景圖畫    canvas.drawBitmap(backgroud, matrix, paint);    red_view.setOnClickListener(this);    green_view.setOnClickListener(this);    blue_view.setOnClickListener(this);    seekBar.setOnSeekBarChangeListener(this);    iv.setOnTouchListener(new OnTouchListener() {      float startX;      float startY;      @Override      public boolean onTouch(View v, MotionEvent event) {        switch (event.getAction()) {        //獲取按下時的坐標        case MotionEvent.ACTION_DOWN:          startX = event.getX();          startY = event.getY();          break;        //獲取移動時的坐標        case MotionEvent.ACTION_MOVE:          float stopX = event.getX();          float stopY = event.getY();//          // 在開始和結束坐標間畫一條線          canvas.drawLine(startX, startY, stopX, stopY, paint);          //實時更新坐標（通過不斷畫線）          startX = event.getX();          startY = event.getY();          iv.setImageBitmap(bitmap);          break;        case MotionEvent.ACTION_UP:          break;        default:          break;        }        return true;      }    });  }  @Override  public void onClick(View v) {    switch (v.getId()) {    case R.id.red_view:      //當點擊紅色區域的時候設置畫筆顏色為紅色      paint.setColor(Color.RED);      break;    case R.id.green_view:      //當點擊綠色區域的時候設置畫筆顏色為綠色      paint.setColor(Color.GREEN);      break;    case R.id.blue_view:      //當點擊藍色區域的時候設置畫筆顏色為藍色      paint.setColor(Color.BLUE);      break;    default:      break;    }  }  //拖動條的值改變的時候調用  @Override  public void onProgressChanged(SeekBar seekBar, int progress,      boolean fromUser) {  }  //開始拖動時調用  @Override  public void onStartTrackingTouch(SeekBar seekBar) {  }  //停止拖動時調用  @Override  public void onStopTrackingTouch(SeekBar seekBar) {    int progress = seekBar.getProgress();//拖動條默認的最大值為100    paint.setStrokeWidth(progress/10f);//控制畫筆的粗細范圍（0-10）  }}