[Android]仿新版QQ的tab下面拖拽标记为已读的效果

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来自天天博客：http://www.cnblogs.com/tiantianbyconan/p/4182929.html

可拖拽的红点，（仿新版QQ，tab下面拖拽标记为已读的效果），拖拽一定的距离可以消失回调。

 

GitHub：DraggableFlagView（https://github.com/wangjiegulu/DraggableFlagView）

实现原理：

当根据touch事件的移动，不断调用onDraw()方法进行刷新绘制。

*注意：这里原来的小红点称为红点A；根据手指移动绘制的小红点称为红点B。

touch事件移动的时候需要处理的逻辑：

1. 红点A的半径根据滑动的距离会不断地变小。

2. 红点B会紧随手指的位置移动。

3. 在红点A和红点B之间需要用贝塞尔曲线绘制连接区域。

4. 如果红点A和红点B之间的间距达到了设置的最大的距离，则表示，这次的拖拽会有效，一旦放手红点就会消失。

5. 如果达到了第4中情况，则红点A和中间连接的贝塞尔曲线不会被绘制。

6. 如果红点A和红点B之间的距离没有达到设置的最大的距离，则放手后，红点B消失，红点A从原来变小的半径使用反弹动画变换到原来最初的状态

一些工具类需要依赖 AndroidBucket(https://github.com/wangjiegulu/AndroidBucket)，nineoldandroid

使用方式：

<com.wangjie.draggableflagview.DraggableFlagView
　　　　　　　xmlns:dfv="http://schemas.android.com/apk/res/com.wangjie.draggableflagview"
            android:id="@+id/main_dfv"
            android:layout_width="20dp"
            android:layout_height="20dp"
            android:layout_alignParentBottom="true"
            android:layout_margin="15dp"
            dfv:color="#FF3B30"
            />

 public class MainActivity extends Activity implements DraggableFlagView.OnDraggableFlagViewListener, View.OnClickListener {

     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
         findViewById(R.id.main_btn).setOnClickListener(this);

         DraggableFlagView draggableFlagView = (DraggableFlagView) findViewById(R.id.main_dfv);
         draggableFlagView.setOnDraggableFlagViewListener(this);
         draggableFlagView.setText("7");
     }

     @Override
     public void onFlagDismiss(DraggableFlagView view) {
         Toast.makeText(this, "onFlagDismiss", Toast.LENGTH_SHORT).show();
     }

     @Override
     public void onClick(View v) {
         switch (v.getId()) {
             case R.id.main_btn:
                 Toast.makeText(this, "hello world", Toast.LENGTH_SHORT).show();
                 break;
         }
     }
 }

DraggableFlagView代码：

 /**
  * Author: wangjie
  * Email: tiantian.china.2@gmail.com
  * Date: 12/23/14.
  */
 public class DraggableFlagView extends View {
     private static final String TAG = DraggableFlagView.class.getSimpleName();

     public static interface OnDraggableFlagViewListener {
         /**
          * 拖拽销毁圆点后的回调
          *
          * @param view
          */
         void onFlagDismiss(DraggableFlagView view);
     }

     private OnDraggableFlagViewListener onDraggableFlagViewListener;

     public void setOnDraggableFlagViewListener(OnDraggableFlagViewListener onDraggableFlagViewListener) {
         this.onDraggableFlagViewListener = onDraggableFlagViewListener;
     }

     public DraggableFlagView(Context context) {
         super(context);
         init(context);
     }

     private int patientColor = Color.RED;

     public DraggableFlagView(Context context, AttributeSet attrs) {
         super(context, attrs);
         TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.DraggableFlagView);
         int indexCount = a.getIndexCount();
         for (int i = 0; i < indexCount; i++) {
             int attrIndex = a.getIndex(i);
             if (attrIndex == R.styleable.DraggableFlagView_color) {
                 patientColor = a.getColor(attrIndex, Color.RED);
             }
         }
         a.recycle();
         init(context);
     }

     public DraggableFlagView(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         init(context);
     }

     private Context context;
     private int originRadius; // 初始的圆的半径
     private int originWidth;
     private int originHeight;

     private int maxMoveLength; // 最大的移动拉长距离
     private boolean isArrivedMaxMoved; // 达到了最大的拉长距离（松手可以触发事件）

     private int curRadius; // 当前点的半径
     private int touchedPointRadius; // touch的圆的半径
     private Point startPoint = new Point();
     private Point endPoint = new Point();

     private Paint paint; // 绘制圆形图形
     private Paint textPaint; // 绘制圆形图形
     private Paint.FontMetrics textFontMetrics;

     private int[] location;

     private boolean isTouched; // 是否是触摸状态

     private Triangle triangle = new Triangle();

     private String text = ""; // 正常状态下显示的文字

     private void init(Context context) {
         this.context = context;

         setBackgroundColor(Color.TRANSPARENT);

         // 设置绘制flag的paint
         paint = new Paint();
         paint.setColor(patientColor);
         paint.setAntiAlias(true);

         // 设置绘制文字的paint
         textPaint = new Paint();
         textPaint.setAntiAlias(true);
         textPaint.setColor(Color.WHITE);
         textPaint.setTextSize(ABTextUtil.sp2px(context, 12));
         textPaint.setTextAlign(Paint.Align.CENTER);
         textFontMetrics = paint.getFontMetrics();

     }

     RelativeLayout.LayoutParams originLp; // 实际的layoutparams
     RelativeLayout.LayoutParams newLp; // 触摸时候的LayoutParams

     private boolean isFirst = true;

     @Override
     protected void onSizeChanged(int w, int h, int oldw, int oldh) {
         super.onSizeChanged(w, h, oldw, oldh);
 //        Logger.d(TAG, String.format("onSizeChanged, w: %s, h: %s, oldw: %s, oldh: %s", w, h, oldw, oldh));
         if (isFirst && w > 0 && h > 0) {
             isFirst = false;

             originWidth = w;
             originHeight = h;

             originRadius = Math.min(originWidth, originHeight) / 2;
             curRadius = originRadius;
             touchedPointRadius = originRadius;

             maxMoveLength = ABAppUtil.getDeviceHeight(context) / 6;

             refreshStartPoint();

             ViewGroup.LayoutParams lp = this.getLayoutParams();
             if (RelativeLayout.LayoutParams.class.isAssignableFrom(lp.getClass())) {
                 originLp = (RelativeLayout.LayoutParams) lp;
             }
             newLp = new RelativeLayout.LayoutParams(lp.width, lp.height);
         }

     }

     @Override
     public void setLayoutParams(ViewGroup.LayoutParams params) {
         super.setLayoutParams(params);
         refreshStartPoint();
     }

     /**
      * 修改layoutParams后，需要重新设置startPoint
      */
     private void refreshStartPoint() {
         location = new int[2];
         this.getLocationInWindow(location);
 //        Logger.d(TAG, "location on screen: " + Arrays.toString(location));
 //            startPoint.set(location[0], location[1] + h);
         try {
             location[1] = location[1] - ABAppUtil.getTopBarHeight((Activity) context);
         } catch (Exception ex) {
         }

         startPoint.set(location[0], location[1] + getMeasuredHeight());
 //        Logger.d(TAG, "startPoint: " + startPoint);
     }

     Path path = new Path();

     @Override
     protected void onDraw(Canvas canvas) {
         super.onDraw(canvas);
         canvas.drawColor(Color.TRANSPARENT);

         int startCircleX = 0, startCircleY = 0;
         if (isTouched) { // 触摸状态

             startCircleX = startPoint.x + curRadius;
             startCircleY = startPoint.y - curRadius;
             // 绘制原来的圆形（触摸移动的时候半径会不断变化）
             canvas.drawCircle(startCircleX, startCircleY, curRadius, paint);
             // 绘制手指跟踪的圆形
             int endCircleX = endPoint.x;
             int endCircleY = endPoint.y;
             canvas.drawCircle(endCircleX, endCircleY, originRadius, paint);

             if (!isArrivedMaxMoved) { // 没有达到拉伸最大值
                 path.reset();
                 double sin = triangle.deltaY / triangle.hypotenuse;
                 double cos = triangle.deltaX / triangle.hypotenuse;

                 // A点
                 path.moveTo(
                         (float) (startCircleX - curRadius * sin),
                         (float) (startCircleY - curRadius * cos)
                 );
                 // B点
                 path.lineTo(
                         (float) (startCircleX + curRadius * sin),
                         (float) (startCircleY + curRadius * cos)
                 );
                 // C点
                 path.quadTo(
                         (startCircleX + endCircleX) / 2, (startCircleY + endCircleY) / 2,
                         (float) (endCircleX + originRadius * sin), (float) (endCircleY + originRadius * cos)
                 );
                 // D点
                 path.lineTo(
                         (float) (endCircleX - originRadius * sin),
                         (float) (endCircleY - originRadius * cos)
                 );
                 // A点
                 path.quadTo(
                         (startCircleX + endCircleX) / 2, (startCircleY + endCircleY) / 2,
                         (float) (startCircleX - curRadius * sin), (float) (startCircleY - curRadius * cos)
                 );
                 canvas.drawPath(path, paint);
             }

         } else { // 非触摸状态
             if (curRadius > 0) {
                 startCircleX = curRadius;
                 startCircleY = originHeight - curRadius;
                 canvas.drawCircle(startCircleX, startCircleY, curRadius, paint);
                 if (curRadius == originRadius) { // 只有在恢复正常的情况下才显示文字
                     // 绘制文字
                     float textH = textFontMetrics.bottom - textFontMetrics.top;
                     canvas.drawText(text, startCircleX, startCircleY + textH / 2, textPaint);
 //                    canvas.drawText(text, startCircleX, startCircleY, textPaint);
                 }
             }

         }

 //        Logger.d(TAG, "circleX: " + startCircleX + ", circleY: " + startCircleY + ", curRadius: " + curRadius);

     }

     float downX = Float.MAX_VALUE;
     float downY = Float.MAX_VALUE;

     @Override
     public boolean onTouchEvent(MotionEvent event) {
         super.onTouchEvent(event);
 //        Logger.d(TAG, "onTouchEvent: " + event);
         switch (event.getAction()) {
             case MotionEvent.ACTION_DOWN:
                 isTouched = true;
                 this.setLayoutParams(newLp);
                 endPoint.x = (int) downX;
                 endPoint.y = (int) downY;

                 changeViewHeight(this, ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
                 postInvalidate();

                 downX = event.getX() + location[0];
                 downY = event.getY() + location[1];
 //                Logger.d(TAG, String.format("downX: %f, downY: %f", downX, downY));

                 break;
             case MotionEvent.ACTION_MOVE:
                 // 计算直角边和斜边（用于计算绘制两圆之间的填充去）
                 triangle.deltaX = event.getX() - downX;
                 triangle.deltaY = -1 * (event.getY() - downY); // y轴方向相反，所有需要取反
                 double distance = Math.sqrt(triangle.deltaX * triangle.deltaX + triangle.deltaY * triangle.deltaY);
                 triangle.hypotenuse = distance;
 //                Logger.d(TAG, "triangle: " + triangle);
                 refreshCurRadiusByMoveDistance((int) distance);

                 endPoint.x = (int) event.getX();
                 endPoint.y = (int) event.getY();

                 postInvalidate();

                 break;
             case MotionEvent.ACTION_UP:
                 isTouched = false;
                 this.setLayoutParams(originLp);

                 if (isArrivedMaxMoved) { // 触发事件
                     changeViewHeight(this, originWidth, originHeight);
                     postInvalidate();
                     if (null != onDraggableFlagViewListener) {
                         onDraggableFlagViewListener.onFlagDismiss(this);
                     }
                     Logger.d(TAG, "触发事件...");
                     resetAfterDismiss();
                 } else { // 还原
                     changeViewHeight(this, originWidth, originHeight);
                     startRollBackAnimation(500/*ms*/);
                 }

                 downX = Float.MAX_VALUE;
                 downY = Float.MAX_VALUE;
                 break;
         }

         return true;
     }

     /**
      * 触发事件之后重置
      */
     private void resetAfterDismiss() {
         this.setVisibility(GONE);
         text = "";
         isArrivedMaxMoved = false;
         curRadius = originRadius;
         postInvalidate();
     }

     /**
      * 根据移动的距离来刷新原来的圆半径大小
      *
      * @param distance
      */
     private void refreshCurRadiusByMoveDistance(int distance) {
         if (distance > maxMoveLength) {
             isArrivedMaxMoved = true;
             curRadius = 0;
         } else {
             isArrivedMaxMoved = false;
             float calcRadius = (1 - 1f * distance / maxMoveLength) * originRadius;
             float maxRadius = ABTextUtil.dip2px(context, 2);
             curRadius = (int) Math.max(calcRadius, maxRadius);
 //            Logger.d(TAG, "[refreshCurRadiusByMoveDistance]curRadius: " + curRadius + ", calcRadius: " + calcRadius + ", maxRadius: " + maxRadius);
         }

     }

     /**
      * 改变某控件的高度
      *
      * @param view
      * @param height
      */
     private void changeViewHeight(View view, int width, int height) {
         ViewGroup.LayoutParams lp = view.getLayoutParams();
         if (null == lp) {
             lp = originLp;
         }
         lp.width = width;
         lp.height = height;
         view.setLayoutParams(lp);
     }

     /**
      * 回滚状态动画
      */
     private ValueAnimator rollBackAnim;

     private void startRollBackAnimation(long duration) {
         if (null == rollBackAnim) {
             rollBackAnim = ValueAnimator.ofFloat(curRadius, originRadius);
             rollBackAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                 @Override
                 public void onAnimationUpdate(ValueAnimator animation) {
                     float value = (float) animation.getAnimatedValue();
                     curRadius = (int) value;
                     postInvalidate();
                 }
             });
             rollBackAnim.setInterpolator(new BounceInterpolator()); // 反弹效果
             rollBackAnim.addListener(new AnimatorListenerAdapter() {
                 @Override
                 public void onAnimationEnd(Animator animation) {
                     super.onAnimationEnd(animation);
                     DraggableFlagView.this.clearAnimation();
                 }
             });
         }
         rollBackAnim.setDuration(duration);
         rollBackAnim.start();
     }

     /**
      * 计算四个坐标的三角边关系
      */
     class Triangle {
         double deltaX;
         double deltaY;
         double hypotenuse;

         @Override
         public String toString() {
             return "Triangle{" +
                     "deltaX=" + deltaX +
                     ", deltaY=" + deltaY +
                     ", hypotenuse=" + hypotenuse +
                     '}';
         }
     }

     public String getText() {
         return text;
     }

     public void setText(String text) {
         this.text = text;
         postInvalidate();
     }
 }