Children match_parent 使用 viewdraghelper 在自定义视图中忽略 parent

Question

我最近一直在研究自定义视图，并试图根据位于此处的教程制作一个特定示例：http://flavienlaurent.com/blog/2013/08/28/each-navigation-drawer-hides-a-viewdraghelper/

我会添加相关代码，防止死机丢失信息link。本教程的作者解释了如何创建类似于 YouTube android 应用程序播放器行为的 ViewDragHelper，这些是他提供的代码

activity_main.xml

<FrameLayout

    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

<ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:tag="list"
        />

<com.example.vdh.YoutubeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/youtubeLayout"
        android:orientation="vertical"
        android:visibility="visible">

    <TextView
            android:id="@+id/viewHeader"
            android:layout_width="match_parent"
            android:layout_height="128dp"
            android:fontFamily="sans-serif-thin"
            android:textSize="25sp"
            android:tag="text"
            android:gravity="center"
            android:textColor="@android:color/white"
            android:background="#AD78CC"/>

    <TextView
            android:id="@+id/viewDesc"
            android:tag="desc"
            android:textSize="35sp"
            android:gravity="center"
            android:text="Loreum Loreum"
            android:textColor="@android:color/white"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="#FF00FF"/>

</com.example.vdh.YoutubeLayout>

YoutubeLayout.java

public class YoutubeLayout extends ViewGroup {

    private final ViewDragHelper mDragHelper;

    private View mHeaderView;
    private View mDescView;

    private float mInitialMotionX;
    private float mInitialMotionY;

    private int mDragRange;
    private int mTop;
    private float mDragOffset;


    public YoutubeLayout(Context context) {
      this(context, null);
    }

    public YoutubeLayout(Context context, AttributeSet attrs) {
      this(context, attrs, 0);
    }

    @Override
    protected void onFinishInflate() {
        mHeaderView = findViewById(R.id.viewHeader);
        mDescView = findViewById(R.id.viewDesc);
    }

    public YoutubeLayout(Context context, AttributeSet attrs, int defStyle) {
      super(context, attrs, defStyle);
      mDragHelper = ViewDragHelper.create(this, 1f, new DragHelperCallback());
    }

    public void maximize() {
        smoothSlideTo(0f);
    }

    boolean smoothSlideTo(float slideOffset) {
        final int topBound = getPaddingTop();
        int y = (int) (topBound + slideOffset * mDragRange);

        if (mDragHelper.smoothSlideViewTo(mHeaderView, mHeaderView.getLeft(), y)) {
            ViewCompat.postInvalidateOnAnimation(this);
            return true;
        }
        return false;
    }

    private class DragHelperCallback extends ViewDragHelper.Callback {

      @Override
      public boolean tryCaptureView(View child, int pointerId) {
            return child == mHeaderView;
      }

        @Override
      public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
          mTop = top;

          mDragOffset = (float) top / mDragRange;

            mHeaderView.setPivotX(mHeaderView.getWidth());
            mHeaderView.setPivotY(mHeaderView.getHeight());
            mHeaderView.setScaleX(1 - mDragOffset / 2);
            mHeaderView.setScaleY(1 - mDragOffset / 2);

            mDescView.setAlpha(1 - mDragOffset);

            requestLayout();
      }

      @Override
      public void onViewReleased(View releasedChild, float xvel, float yvel) {
          int top = getPaddingTop();
          if (yvel > 0 || (yvel == 0 && mDragOffset > 0.5f)) {
              top += mDragRange;
          }
          mDragHelper.settleCapturedViewAt(releasedChild.getLeft(), top);
      }

      @Override
      public int getViewVerticalDragRange(View child) {
          return mDragRange;
      }

      @Override
      public int clampViewPositionVertical(View child, int top, int dy) {
          final int topBound = getPaddingTop();
          final int bottomBound = getHeight() - mHeaderView.getHeight() - mHeaderView.getPaddingBottom();

          final int newTop = Math.min(Math.max(top, topBound), bottomBound);
          return newTop;
      }

    }

    @Override
    public void computeScroll() {
      if (mDragHelper.continueSettling(true)) {
          ViewCompat.postInvalidateOnAnimation(this);
      }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
      final int action = MotionEventCompat.getActionMasked(ev);

      if (( action != MotionEvent.ACTION_DOWN)) {
          mDragHelper.cancel();
          return super.onInterceptTouchEvent(ev);
      }

      if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
          mDragHelper.cancel();
          return false;
      }

      final float x = ev.getX();
      final float y = ev.getY();
      boolean interceptTap = false;

      switch (action) {
          case MotionEvent.ACTION_DOWN: {
              mInitialMotionX = x;
              mInitialMotionY = y;
                interceptTap = mDragHelper.isViewUnder(mHeaderView, (int) x, (int) y);
              break;
          }

          case MotionEvent.ACTION_MOVE: {
              final float adx = Math.abs(x - mInitialMotionX);
              final float ady = Math.abs(y - mInitialMotionY);
              final int slop = mDragHelper.getTouchSlop();
              if (ady > slop && adx > ady) {
                  mDragHelper.cancel();
                  return false;
              }
          }
      }

      return mDragHelper.shouldInterceptTouchEvent(ev) || interceptTap;
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
      mDragHelper.processTouchEvent(ev);

      final int action = ev.getAction();
        final float x = ev.getX();
        final float y = ev.getY();

        boolean isHeaderViewUnder = mDragHelper.isViewUnder(mHeaderView, (int) x, (int) y);
        switch (action & MotionEventCompat.ACTION_MASK) {
          case MotionEvent.ACTION_DOWN: {
              mInitialMotionX = x;
              mInitialMotionY = y;
              break;
          }

          case MotionEvent.ACTION_UP: {
              final float dx = x - mInitialMotionX;
              final float dy = y - mInitialMotionY;
              final int slop = mDragHelper.getTouchSlop();
              if (dx * dx + dy * dy < slop * slop && isHeaderViewUnder) {
                  if (mDragOffset == 0) {
                      smoothSlideTo(1f);
                  } else {
                      smoothSlideTo(0f);
                  }
              }
              break;
          }
      }


      return isHeaderViewUnder && isViewHit(mHeaderView, (int) x, (int) y) || isViewHit(mDescView, (int) x, (int) y);
    }


    private boolean isViewHit(View view, int x, int y) {
        int[] viewLocation = new int[2];
        view.getLocationOnScreen(viewLocation);
        int[] parentLocation = new int[2];
        this.getLocationOnScreen(parentLocation);
        int screenX = parentLocation[0] + x;
        int screenY = parentLocation[1] + y;
        return screenX >= viewLocation[0] && screenX < viewLocation[0] + view.getWidth() &&
                screenY >= viewLocation[1] && screenY < viewLocation[1] + view.getHeight();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        measureChildren(widthMeasureSpec, heightMeasureSpec);

        int maxWidth = MeasureSpec.getSize(widthMeasureSpec);
        int maxHeight = MeasureSpec.getSize(heightMeasureSpec);

        setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, 0),
                resolveSizeAndState(maxHeight, heightMeasureSpec, 0));
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
      mDragRange = getHeight() - mHeaderView.getHeight();

        mHeaderView.layout(
                0,
                mTop,
                r,
                mTop + mHeaderView.getMeasuredHeight());

        mDescView.layout(
                0,
                mTop + mHeaderView.getMeasuredHeight(),
                r,
                mTop  + b);
    }
}

作者指出 onLayout 和 onMeasure 写得不好，我认为这些（或其中之一）可能是 children 之一出现问题的原因.

对于我的 objective，我将 mDescView 替换为包含相应 TextView 的 Framelayout 视图。它们的高度都设置为 match_parent 并且 parent (mDescView) 确实正确设置了它的高度，但是它的 children (TextView inside mDescView) 忽略 parent 高度并拉伸以适应它们的高度等于屏幕高度（或自定义视图高度，无法区分）。这是一个问题，因为 mDescView children 永远不会根据 parent 到 match_parent 正确调整他们的高度，我一直在寻找解决方案几天，但是 none 被发现，通过研究我找不到发生这种情况的原因。

这是这个问题的结果，请注意 TextView 的高度如何大于它的 parent mDescView 尽管它们的高度都设置为 match_parent

所以我的问题是，如何让 parent（或任何 parents）的 child（children）匹配他们的 parent他们应该的身高。

作为一个额外的请求，如果可能的话，谁能解释为什么作者认为他的一些方法不是 best/right 的方法，以及应该如何 correctly/better 来代替。

Answer 1

我终于纠正了这个问题，虽然我仍然不知道这是否是正确的方法。我的解决方案是在 onLayout 期间设置两个视图的高度我还在第一次调用此方法时将其设置为仅运行，因此特定语句仅运行一次且仅在第一次（当 firstRun 为 true)

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
    mDragRange = getHeight() - mHeaderView.getHeight();

    if (firstRun) {
        firstRun = false;
        mDescView.getLayoutParams().height = getHeight() - mHeaderView.getMeasuredHeight();
    }

    mHeaderView.layout(
            0,
            mTop,
            r,
            mTop + mHeaderView.getMeasuredHeight());

    mDescView.layout(
            0,
            mTop + mHeaderView.getMeasuredHeight(),
            r,
            mTop  + b);
}

Children match_parent 使用 viewdraghelper 在自定义视图中忽略 parent

Children match_parent ignoring parent in custom view with viewdraghelper

java

android

viewgroup

viewdraghelper