ViewDragHelper Stack Overflow

Question

我一直在关注ViewDragHelper

的演练

http://flavienlaurent.com/blog/2013/08/28/each-navigation-drawer-hides-a-viewdraghelper/

我目前正在尝试实现自定义布局，而我遇到ViewDragHelper问题。我试图得到一个“抽屉”风格的布局，拖动手柄从右到左（即水平）打开。我知道SliderDrawer处理这个任务，但我的目标只是学习ViewDragHelper。这是我得到的错误：

09-24 14:27:21.031: E/AndroidRuntime(24002): FATAL EXCEPTION: main
09-24 14:27:21.031: E/AndroidRuntime(24002): java.lang.StackOverflowError
09-24 14:27:21.031: E/AndroidRuntime(24002):    at android.widget.TextView.setFrame(TextView.java:4365)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at android.view.View.layout(View.java:14293)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at com.example.vdh.DragLayout.onLayout(DragLayout.java:91)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at android.view.View.layout(View.java:14296)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at android.view.ViewGroup.layout(ViewGroup.java:4562)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at com.example.vdh.DragLayout.onLayout(DragLayout.java:97)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at android.view.View.layout(View.java:14296)
09-24 14:27:21.031: E/AndroidRuntime(24002):    at android.view.ViewGroup.layout(ViewGroup.java:4562)

请注意，重复最后3行。我知道这个onLayout函数负责运行时异常。这是源代码：

package com.example.vdh;

import android.content.Context;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.widget.ViewDragHelper;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.LinearLayout;

public class DragLayout extends LinearLayout {

private final ViewDragHelper mDragHelper;
private View mDrawerView;
private View mHandle;

private int mDragRange;
private int mLeft;

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

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

public DragLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mDragHelper = ViewDragHelper.create(this, 1.0f, new DragHelperCallback());
}

@Override
protected void onFinishInflate() {
    mHandle = findViewById(R.id.handle);
    mDrawerView = findViewById(R.id.drawer);
}


@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
  final int action = MotionEventCompat.getActionMasked(ev);
  if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
      mDragHelper.cancel();
      return false;
  }
  return mDragHelper.shouldInterceptTouchEvent(ev);
}

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

private class DragHelperCallback extends ViewDragHelper.Callback {

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

    @Override
    public int clampViewPositionHorizontal(View child, int left, int dx) {
      Log.d("DragLayout", "clampViewPositionHorizontal " + left + "," + dx);

      final int leftBound = getPaddingLeft();
      final int rightBound = getWidth() - mHandle.getWidth();

      final int newLeft = Math.min(Math.max(left, leftBound), rightBound);

      return newLeft;
    }

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

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

    /*Log.d("onLayout", "Handle: " + mHandle.getWidth() + ", " + mHandle.getHeight());
    Log.d("onLayout", "Drawer: " + mDrawerView.getWidth() + ", " + mDrawerView.getHeight());*/


    mHandle.layout(
        mLeft,
        0,
        mLeft + mHandle.getMeasuredWidth(),
        b);

    mDrawerView.layout(
        mLeft + mHandle.getMeasuredWidth(),
        0,
        mLeft + r,
        b);
}

}

    mHandle.layout(
        mLeft,
        0,
        mLeft + mHandle.getMeasuredWidth(),
        b);

    mDrawerView.layout(
        mLeft + mHandle.getMeasuredWidth(),
        0,
        mLeft + r,
        b);
}

Answer 1

根据堆栈跟踪，您对DragLayout的onLayout进行了递归调用。

你的DragLayout只调用两个视图的布局（...）：mHandle＆amp; mDrawerView似乎其中一个（无法通过日志判断哪一个）导致堆栈溢出。

请发布您的观看代码，以便我可以帮您找到问题。