Android技术知识Android开发Android自定义View

安卓invalidate()、postInvalidate()、

2018-08-07  本文已影响40人  仕明同学

requestLayout()源码分析

InvalidateTextView------onMeasure
InvalidateTextView------onMeasure
InvalidateTextView-------layout
InvalidateTextView--------onLayout
InvalidateTextView----------draw
InvalidateTextView------------onDraw

  @CallSuper
    public void requestLayout() {
        // 清除绘制的缓存
        if (mMeasureCache != null) mMeasureCache.clear();

        if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == null) {
            //只有在布局逻辑中触发请求，如果这是请求它的视图，而不是其父层次结构中的视图
            ViewRootImpl viewRoot = getViewRootImpl();
            //如果连续请求两次，其中一次自动返回！
            if (viewRoot != null && viewRoot.isInLayout()) {
                if (!viewRoot.requestLayoutDuringLayout(this)) {
                    return;
                }
            }
            mAttachInfo.mViewRequestingLayout = this;
        }
       //todo   为当前view设置标记位 PFLAG_FORCE_LAYOUT
        mPrivateFlags |= PFLAG_FORCE_LAYOUT;
        mPrivateFlags |= PFLAG_INVALIDATED;

        if (mParent != null && !mParent.isLayoutRequested()) {
           //   todo  向父容器请求布局 这里是向父容器请求布局，即调用父容器的requestLayout方法，为父容器添加PFLAG_FORCE_LAYOUT标记位，而父容器又会调用它的父容器的requestLayout方法，即requestLayout事件层层向上传递，直到DecorView，即根View，而根View又会传递给ViewRootImpl，也即是说子View的requestLayout事件，最终会被ViewRootImpl接收并得到处理
            mParent.requestLayout();
        }
        if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == this) {
            mAttachInfo.mViewRequestingLayout = null;
        }
    }

        if (mMeasureCache != null) mMeasureCache.clear();

   if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == null) {
            //只有在布局逻辑中触发请求，如果这是请求它的视图，而不是其父层次结构中的视图
            ViewRootImpl viewRoot = getViewRootImpl();
            //如果连续请求两次，其中一次自动返回！
            if (viewRoot != null && viewRoot.isInLayout()) {
                if (!viewRoot.requestLayoutDuringLayout(this)) {
                    return;
                }
            }
            mAttachInfo.mViewRequestingLayout = this;
        }

   mPrivateFlags |= PFLAG_FORCE_LAYOUT;
   mPrivateFlags |= PFLAG_INVALIDATED;

      if (mParent != null && !mParent.isLayoutRequested()) {
            mParent.requestLayout();
        }

 public final void measure(int widthMeasureSpec, int heightMeasureSpec) {
        ...
        // requestLayout的方法改变的  mPrivateFlags |= PFLAG_FORCE_LAYOUT; 所以 forceLayout = true
        final boolean forceLayout = (mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT;
        ...
        if (forceLayout || needsLayout) {
        ...
            if (cacheIndex < 0 || sIgnoreMeasureCache) {
                //最终会走到这方法来
                onMeasure(widthMeasureSpec, heightMeasureSpec);
                mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
            } 
            // 接着最后为标记位设置为PFLAG_LAYOUT_REQUIRED
            mPrivateFlags |= PFLAG_LAYOUT_REQUIRED;
        }
       ...
    }

 @SuppressWarnings({"unchecked"})
    public void layout(int l, int t, int r, int b) {
        if ((mPrivateFlags3 & PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT) != 0) {
            //第二次调用这个方法，，，
            onMeasure(mOldWidthMeasureSpec, mOldHeightMeasureSpec);
            mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
        }

        int oldL = mLeft;
        int oldT = mTop;
        int oldB = mBottom;
        int oldR = mRight;

        boolean changed = isLayoutModeOptical(mParent) ?
                setOpticalFrame(l, t, r, b) : setFrame(l, t, r, b);
           //判断标记位是否为PFLAG_LAYOUT_REQUIRED，如果有，则对该View进行布局
        if (changed || (mPrivateFlags & PFLAG_LAYOUT_REQUIRED) == PFLAG_LAYOUT_REQUIRED) {
            onLayout(changed, l, t, r, b);

            if (shouldDrawRoundScrollbar()) {
                if(mRoundScrollbarRenderer == null) {
                    mRoundScrollbarRenderer = new RoundScrollbarRenderer(this);
                }
            } else {
                mRoundScrollbarRenderer = null;
            }
            //  onLayout方法完成后，清除PFLAG_LAYOUT_REQUIRED标记位
            mPrivateFlags &= ~PFLAG_LAYOUT_REQUIRED;
        }
    //  //最后清除PFLAG_FORCE_LAYOUT标记位
        mPrivateFlags &= ~PFLAG_FORCE_LAYOUT;
        mPrivateFlags3 |= PFLAG3_IS_LAID_OUT;
       ...
    }

invalidate()源码分析

InvalidateTextView----------draw
InvalidateTextView------------onDraw

  public void invalidate() {
        invalidate(true);
    }

   public void invalidate(boolean invalidateCache) {
        invalidateInternal(0, 0, mRight - mLeft, mBottom - mTop, invalidateCache, true);
    }

  @Override
    public void invalidateChild(View child, Rect dirty) {
        invalidateChildInParent(null, dirty);
    }

    private void invalidateRectOnScreen(Rect dirty) {
        final Rect localDirty = mDirty;
        if (!localDirty.isEmpty() && !localDirty.contains(dirty)) {
            mAttachInfo.mSetIgnoreDirtyState = true;
            mAttachInfo.mIgnoreDirtyState = true;
        }
        // Add the new dirty rect to the current one
        // 添加一个新的 dirty rect 给当前的Rect
        localDirty.union(dirty.left, dirty.top, dirty.right, dirty.bottom);
        // Intersect with the bounds of the window to skip
        // updates that lie outside of the visible region
        final float appScale = mAttachInfo.mApplicationScale;
        final boolean intersected = localDirty.intersect(0, 0,
                (int) (mWidth * appScale + 0.5f), (int) (mHeight * appScale + 0.5f));
        if (!intersected) {
            localDirty.setEmpty();
        }
        if (!mWillDrawSoon && (intersected || mIsAnimating)) {
            scheduleTraversals();
        }
    }

postInvalidate()的源码解析

InvalidateTextView----------draw
InvalidateTextView------------onDraw

   public void postInvalidate() {
        postInvalidateDelayed(0);
    }

   public void postInvalidateDelayed(long delayMilliseconds) {
        final AttachInfo attachInfo = mAttachInfo;
        if (attachInfo != null) {
            attachInfo.mViewRootImpl.dispatchInvalidateDelayed(this, delayMilliseconds);
        }
    }

  /**
     * 用了Handler，发送了一个异步消息到主线程，显然这里发送的是`MSG_INVALIDATE`，即通知主线程刷新视图
      * @param view  只有 postInvalidate() 使用了handler 来发送消息
     * @param delayMilliseconds
     */
    public void dispatchInvalidateDelayed(View view, long delayMilliseconds) {
        Message msg = mHandler.obtainMessage(MSG_INVALIDATE, view);
        mHandler.sendMessageDelayed(msg, delayMilliseconds);
    }

      case MSG_INVALIDATE:
                    //通知对象去 invalidate ，底层也是调用的是 invalidate，只不过使用了handler发送消息
                    ((View) msg.obj).invalidate();
                    break;0
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