避免ID冲突或重复

问题：

在Fragment或Activity中发生restoreSavedState操作时（比如旋转屏幕），页面中的自定义View，如果有自己复写onSaveInstanceState方法，且该自定义View是以addView()的形式添加的，就有可能造成以下报错：
java.lang.IllegalArgumentException: Wrong state class, expecting View State but received class *.waveswiperefreshlayout.WaterWave$SavedState instead. This usually happens when two views of different type have the same id in the same hierarchy. This view's id is id/swipe_refresh_layout.

解决办法：

在addView()之后，手动设置唯一ID，代码如下：

private void setWaterWaveId() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
        mWaterWave.setId(View.generateViewId());
    } else {
        mWaterWave.setId(AppUtils.generateViewId());
    }
}

private static final AtomicInteger sNextGeneratedId = new AtomicInteger(1);
/**
 * Generate a value suitable for use in View.setId(int).
 * This value will not collide with ID values generated at build time by aapt for R.id.
 *
 * @return a generated ID value
 */
public static int generateViewId() {
    for (;;) {
        final int result = sNextGeneratedId.get();
        // aapt-generated IDs have the high byte nonzero; clamp to the range under that.
        int newValue = result + 1;
        if (newValue > 0x00FFFFFF) newValue = 1; // Roll over to 1, not 0.
        if (sNextGeneratedId.compareAndSet(result, newValue)) {
            return result;
        }
    }
}

参考：

Android: View.setID(int id) programmatically - how to avoid ID conflicts?
Wrong State Class,expecting View State but received class...异常解决思路之一
Wrong state class, expecting View State but