Android 学习 之 Canvas (一)

1.官方API文档中对save()方法的解释：

 

public class Canvas {
    /**
     * Saves the current matrix and clip onto a private stack. Subsequent
     * calls to translate,scale,rotate,skew,concat or clip Rect,clipPath
     * will all operate as usual, but when the balancing call to restore()
     * is made, those calls will be forgotten, and the settings that existed
     * before the save() will be reinstated.
     */
    /**
     * 保存当前的矩阵和剪裁到一个私有的堆栈，其实矩阵和剪裁就是当前Canvas的状态State

	接着调用位置，缩放，选择，倾斜，concat或者剪辑矩形，剪辑区域等将被正常操作，但是

	当restore()被调用，恢复时，这些操作都将被放弃，并且刚才调用save()之前被保存的状态将被重新恢复。

     */
    public native int save();
}

public class Canvas {
    /**
     * This call balances a previous call to save(), and is used to remove all
     * modifications to the matrix/clip state since the last save call. It is
     * an error to call restore() more times than save() was called.
     */
    /**
     * 移除自上次保存操作后所做的修改，恢复到之前的状态，因为是堆栈实现，所以pull操作不能不等于push操作，
	save()和restore()应该成对使用，否则恢复的状态就很有可能是错误的
     */
    public native void restore();
}