|
View中的属性也是挺多的，搞得初学者都有点懵逼，今天就来捋一捋。
1、mLeft、mTop、mRight、mBottom定义了控件的区域（左上角和右下角的坐标），都有对应的get、set方法，其中mLeft表示控件左边距离父控件左边的距离，mRight表示控件右边距离父控件左边的距离，mTop和mBottom类似；
2、getWidth和getHeight，源码如下：
public final int getWidth() {
return mRight - mLeft;
}
public final int getHeight() {
return mBottom - mTop;
}
由上面的源代码可以发现宽高其实是由mRight-mLeft以及mBottom-mTop计算出来的，看到这里估计大家就知道为什么这两个方法在layout方法之后就可以正常获取到控件的宽高了吧，原因很简单：因为layout之后mRight,mLeft,mTop,mBottom就确定了。
3、getMeasureWidth和getmeasureHeight，获取控件的测量值，在onMeasure方法之后就可以获取正常值，其中onMeasure方法中的核心方法是setOnMeasureDimension。
4、getX、setX、getY和setY方法，源码如下：
/**
* The visual x position of this view, in pixels. This is equivalent to the
* {@link #setTranslationX(float) translationX} property plus the current
* {@link #getLeft() left} property.
*
* @return The visual x position of this view, in pixels.
*/
public float getX() {
return mLeft + (mTransformationInfo != null ? mTransformationInfo.mTranslationX : 0);
}
/**
* Sets the visual x position of this view, in pixels. This is equivalent to setting the
* {@link #setTranslationX(float) translationX} property to be the difference between
* the x value passed in and the current {@link #getLeft() left} property.
*
* @param x The visual x position of this view, in pixels.
*/
public void setX(float x) {
setTranslationX(x - mLeft);
}
从上面的注释可以发现关键字visual,getx和setx方法其实是获取控件可见部分在以父控件左上角为原点、以向下为y正方向、以向右为x正方向的坐标系的坐标值，同理getY和setY一样。
5、getScrollX和getScrollY、setScrollX和setScrollY。
/**
* Return the scrolled left position of this view. This is the left edge of
* the displayed part of your view. You do not need to draw any pixels
* farther left, since those are outside of the frame of your view on
* screen.
*
* @return The left edge of the displayed part of your view, in pixels.
*/
public final int getScrollX() {
return mScrollX;
}
从上面可以看到，这个其实返回的是mScrollX属性，而这个属性表示控件内容的距离左边的滚动距离，特别说明一下，这个属性值的坐标系是以控件左上角为原点、向上为y正轴、向左为x正轴。scrollTo和scrollBy两个方法与之密切相关，并且这两个方法的执行会触发onScrollChanged回调。
6、TransformationInfo静态内部类，封装了与View变化相关的属性。
static class TransformationInfo {
/**
* The transform matrix for the View. This transform is calculated internally
* based on the rotation, scaleX, and scaleY properties. The identity matrix
* is used by default. Do *not* use this variable directly; instead call
* getMatrix(), which will automatically recalculate the matrix if necessary
* to get the correct matrix based on the latest rotation and scale properties.
*/
private final Matrix mMatrix = new Matrix();
/**
* The transform matrix for the View. This transform is calculated internally
* based on the rotation, scaleX, and scaleY properties. The identity matrix
* is used by default. Do *not* use this variable directly; instead call
* getInverseMatrix(), which will automatically recalculate the matrix if necessary
* to get the correct matrix based on the latest rotation and scale properties.
*/
private Matrix mInverseMatrix;
/**
* An internal variable that tracks whether we need to recalculate the
* transform matrix, based on whether the rotation or scaleX/Y properties
* have changed since the matrix was last calculated.
*/
boolean mMatrixDirty = false;
/**
* An internal variable that tracks whether we need to recalculate the
* transform matrix, based on whether the rotation or scaleX/Y properties
* have changed since the matrix was last calculated.
*/
private boolean mInverseMatrixDirty = true;
/**
* A variable that tracks whether we need to recalculate the
* transform matrix, based on whether the rotation or scaleX/Y properties
* have changed since the matrix was last calculated. This variable
* is only valid after a call to updateMatrix() or to a function that
* calls it such as getMatrix(), hasIdentityMatrix() and getInverseMatrix().
*/
private boolean mMatrixIsIdentity = true;
/**
* The Camera object is used to compute a 3D matrix when rotationX or rotationY are set.
*/
private Camera mCamera = null;
/**
* This matrix is used when computing the matrix for 3D rotations.
*/
private Matrix matrix3D = null;
/**
* These prev values are used to recalculate a centered pivot point when necessary. The
* pivot point is only used in matrix operations (when rotation, scale, or translation are
* set), so thes values are only used then as well.
*/
private int mPrevWidth = -1;
private int mPrevHeight = -1;
/**
* The degrees rotation around the vertical axis through the pivot point.
*/
@ViewDebug.ExportedProperty
float mRotationY = 0f;
/**
* The degrees rotation around the horizontal axis through the pivot point.
*/
@ViewDebug.ExportedProperty
float mRotationX = 0f;
/**
* The degrees rotation around the pivot point.
*/
@ViewDebug.ExportedProperty
float mRotation = 0f;
/**
* The amount of translation of the object away from its left property (post-layout).
*/
@ViewDebug.ExportedProperty
float mTranslationX = 0f;
/**
* The amount of translation of the object away from its top property (post-layout).
*/
@ViewDebug.ExportedProperty
float mTranslationY = 0f;
/**
* The amount of scale in the x direction around the pivot point. A
* value of 1 means no scaling is applied.
*/
@ViewDebug.ExportedProperty
float mScaleX = 1f;
/**
* The amount of scale in the y direction around the pivot point. A
* value of 1 means no scaling is applied.
*/
@ViewDebug.ExportedProperty
float mScaleY = 1f;
/**
* The x location of the point around which the view is rotated and scaled.
*/
@ViewDebug.ExportedProperty
float mPivotX = 0f;
/**
* The y location of the point around which the view is rotated and scaled.
*/
@ViewDebug.ExportedProperty
float mPivotY = 0f;
/**
* The opacity of the View. This is a value from 0 to 1, where 0 means
* completely transparent and 1 means completely opaque.
*/
@ViewDebug.ExportedProperty
float mAlpha = 1f;
/**
* The opacity of the view as manipulated by the Fade transition. This is a hidden
* property only used by transitions, which is composited with the other alpha
* values to calculate the final visual alpha value.
*/
float mTransitionAlpha = 1f;
}
7、ListenerInfo封装了多个监听器的静态内部类。
static class ListenerInfo {
/**
* Listener used to dispatch focus change events.
* This field should be made private, so it is hidden from the SDK.
* {@hide}
*/
protected OnFocusChangeListener mOnFocusChangeListener;
/**
* Listeners for layout change events.
*/
private ArrayList<OnLayoutChangeListener> mOnLayoutChangeListeners;
/**
* Listeners for attach events.
*/
private CopyOnWriteArrayList<OnAttachStateChangeListener> mOnAttachStateChangeListeners;
/**
* Listener used to dispatch click events.
* This field should be made private, so it is hidden from the SDK.
* {@hide}
*/
public OnClickListener mOnClickListener;
/**
* Listener used to dispatch long click events.
* This field should be made private, so it is hidden from the SDK.
* {@hide}
*/
protected OnLongClickListener mOnLongClickListener;
/**
* Listener used to build the context menu.
* This field should be made private, so it is hidden from the SDK.
* {@hide}
*/
protected OnCreateContextMenuListener mOnCreateContextMenuListener;
private OnKeyListener mOnKeyListener;
private OnTouchListener mOnTouchListener;
private OnHoverListener mOnHoverListener;
private OnGenericMotionListener mOnGenericMotionListener;
private OnDragListener mOnDragListener;
private OnSystemUiVisibilityChangeListener mOnSystemUiVisibilityChangeListener;
OnApplyWindowInsetsListener mOnApplyWindowInsetsListener;
}
| 
转播
