Android自定义控件之开关按钮学习笔记分享

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public SwitchView(Context context, AttributeSet attrs) {
    super(context, attrs);
    //拿到自定义属性
    TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.switchView_attrs);
    //拿到自定义字段的值
    Drawable switchBackground = ta.getDrawable(R.styleable.switchView_attrs_background);
    Drawable switchView_slide = ta.getDrawable(R.styleable.switchView_attrs_slide);
    //把值设置到相应组件上
    backgroundBitmap = convertDrawable2BitmapSimple(switchBackground);
    switchSlide = convertDrawable2BitmapSimple(switchView_slide);
  }

//将Drawable转成Bitmap
  public Bitmap convertDrawable2BitmapSimple(Drawable drawable) {
    BitmapDrawable bd= (BitmapDrawable)drawable;
    return bd.getBitmap();
  }

//控制控件的大小
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    if (backgroundBitmap != null) {
      //控件大小设置为背景的大小
      setMeasuredDimension(backgroundBitmap.getWidth(), backgroundBitmap.getHeight());
    }else {
      super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
  }

/** 
   * switchView开关监听接口
   * 
   * */
  interface OnSwitchChangedListener {
    public void onSwitchChange(boolean isOpen);
  }
  /** 
   * 设置 switchView状态监听 
   * */
  public void setOnChangeListener(OnSwitchChangedListener listener) {
    switchListener = listener;
  }

/**
 * 自定义开关按钮
 * @author Administrator
 *
 */
public class SwitchView extends View {
  //背景图片和滑块图片
  private Bitmap backgroundBitmap,switchSlide;
  //画笔
  private Paint paint;
  //得到的x坐标（点击、移动、抬起）
  private float currentX;
  //判断开关是否打开的标记位
  private boolean isOpen = false;
  //开关打开与关闭的监听器
  private OnSwitchChangedListener switchListener;
  //滑块的四种状态
  public static final int STATE_DOWN = 1; //按下的时候
  public static final int STATE_MOVE = 2; //移动的时候
  public static final int STATE_UP = 3;  //抬起的时候
  public static final int STATE_NOnE= 0; //空的时候（即什么都没干的时候）
  //标记状态（默认为空状态）
  private int state = STATE_NONE;
  public SwitchView(Context context) {
    super(context,null);
  }
  public SwitchView(Context context, AttributeSet attrs) {
    super(context, attrs);
    //拿到自定义属性
    TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.switchView_attrs);
    //拿到自定义字段的值
    Drawable switchBackground = ta.getDrawable(R.styleable.switchView_attrs_background);
    Drawable switchView_slide = ta.getDrawable(R.styleable.switchView_attrs_slide);
    //把值设置到相应组件上
    backgroundBitmap = convertDrawable2BitmapSimple(switchBackground);
    switchSlide = convertDrawable2BitmapSimple(switchView_slide);
  }
  //将Drawable转成Bitmap
  public Bitmap convertDrawable2BitmapSimple(Drawable drawable) {
    BitmapDrawable bd = (BitmapDrawable)drawable;
    return bd.getBitmap();
  }
  //控制控件的大小
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    if (backgroundBitmap != null) {
      //控件大小设置为背景的大小
      setMeasuredDimension(backgroundBitmap.getWidth(), backgroundBitmap.getHeight());
    }else {
      super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
  }
  //绘制控件的样式
  @Override
  protected void onDraw(Canvas canvas) {
    //背景为空的时候才将背景绘制
    if (backgroundBitmap != null) {
      paint = new Paint();
      //第一个参数表示需要画的Bitmap
      //第二个参数表示Bitmap左边离控件的左边距
      //第三个参数表示Bitmap上边离控件的上边距
      //第四个参数表示画笔
      canvas.drawBitmap(backgroundBitmap, 0, 0, paint);
    }
    switch (state) {
    case STATE_DOWN:    //按下和移动的触发事件都一样，都是将滑块移动
    case STATE_MOVE:
      //当按下或移动的坐标大于滑块宽度一半时将滑块右移
      if (currentX > switchSlide.getWidth()/2f) {
        //让滑块向右滑动（重新绘制滑块的位置）
        float left = currentX - switchSlide.getWidth()/2f;
        //防止滑块移至背景外面，最大是滑块右边和背景右边对齐（即最大离左边为背景宽度-滑块宽度）
        float maxLeft = backgroundBitmap.getWidth() - switchSlide.getWidth();
        if (left > maxLeft) {
          left = maxLeft;
        }
        canvas.drawBitmap(switchSlide, left, 0, paint);
      //当按下或移动的坐标小于滑块宽度一半时滑块不动
      }else if (currentX  backgroundBitmap.getWidth()/2f) {
        //滑块在右边,开启
        isOpen = true;
      //抬起的坐标小于背景宽度坐标一 半的时候设为关闭状态
      }else if (currentX 

public class MainActivity extends Activity {

  private SwitchView switchView;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    switchView = (SwitchView) findViewById(R.id.switchView);
    switchView.setOnChangeListener(new OnSwitchChangedListener() {
      @Override
      public void onSwitchChange(boolean isOpen) {
        if (isOpen) {
          //打开开关的时候的逻辑
          Toast.makeText(MainActivity.this, "开关打开了", Toast.LENGTH_LONG).show();
        }else {
          //关闭开关的时候的逻辑
          Toast.makeText(MainActivity.this, "开关关闭了", Toast.LENGTH_LONG).show();
        }
      }
    });
  }
}