缘由
之前老项目一直有个问题，就是弹窗会顶在屏幕最上面，一直以为是特殊机型适配的问题，一拖再拖没有解决，后来测试实在忍不了，上网上查一查，发现这个bug出现好久了，是安卓7.0之后源码发生改变导致的
兼容性现象
popuwindow设置 showAsDropDown（view）并没有在某个view的下面
popupWindow设置了居中或者底部对齐，但是在7.0机器是跑到顶部。
很明显这个bug是和我们设置了Gravity有关。
展示popupWindow的函数有两个，showAtLocation 和 update。
重点看了那两个函数的API 24 和 API 23 的区别。
源码分析
通过源码分析发现，在update函数里有一个和gravity相关的地方，很明显是个bug。
public void update(int x, int y, int width, int height, boolean force) {
if (width >= 0) {
mLastWidth = width;
setWidth(width);
}
if (height >= 0) {
mLastHeight = height;
setHeight(height);
}
if (!isShowing() || mContentView == null) {
return;
}
final WindowManager.LayoutParams p =
(WindowManager.LayoutParams) mDecorView.getLayoutParams();
boolean update = force;
final int finalWidth = mWidthMode < 0 ? mWidthMode : mLastWidth;
if (width != -1 && p.width != finalWidth) {
p.width = mLastWidth = finalWidth;
update = true;
}
final int finalHeight = mHeightMode < 0 ? mHeightMode : mLastHeight;
if (height != -1 && p.height != finalHeight) {
p.height = mLastHeight = finalHeight;
update = true;
}
if (p.x != x) {
p.x = x;
update = true;
}
if (p.y != y) {
p.y = y;
update = true;
}
final int newAnim = computeAnimationResource();
if (newAnim != p.windowAnimations) {
p.windowAnimations = newAnim;
update = true;
}
final int newFlags = computeFlags(p.flags);
if (newFlags != p.flags) {
p.flags = newFlags;
update = true;
}
final int newGravity = computeGravity();
if (newGravity != p.gravity) {
p.gravity = newGravity;
update = true;
}
int newAccessibilityIdOfAnchor =
(mAnchor != null) ? mAnchor.get().getAccessibilityViewId() : -1;
if (newAccessibilityIdOfAnchor != p.accessibilityIdOfAnchor) {
p.accessibilityIdOfAnchor = newAccessibilityIdOfAnchor;
update = true;
}
if (update) {
setLayoutDirectionFromAnchor();
mWindowManager.updateViewLayout(mDecorView, p);
}
}
有个 computeGravity 函数，我们再看看
private int computeGravity() {
int gravity = Gravity.START | Gravity.TOP;
if (mClipToScreen || mClippingEnabled) {
gravity |= Gravity.DISPLAY_CLIP_VERTICAL;
}
return gravity;
}
噗，我们发现，我们之前设置的gravity被这个函数执行之后覆盖了。。
我忽然觉得估计是Google的大牛自测的时候写死变量好调试，最后发布的时候忘记改了。。
问题定位到了，符合2个条件：
1:popupWindow 在 show 的时候定义了 Gravity，不是 Gravity.START | Gravity.TOP。
2:PopupWindow 调用了update。
下面是比较实用的方法，通过获取要展示的view的坐标，然后计算屏幕减去坐标减去view高度，减去偏移量就得到 popuwindow展示的位置，有效可用
/**
* android 7.0之后的坑
*/
public static void showAsDropDownFor_N(PopupWindow pw, View anchor, int xoff, int yoff) {
if (Build.VERSION.SDK_INT >= 24) {
int[] location = new int[2];
anchor.getLocationOnScreen(location);
// 7.1 版本处理
if (Build.VERSION.SDK_INT == 25) {
//【note!】Gets the screen height without the virtual key
WindowManager wm = (WindowManager) pw.getContentView().getContext().getSystemService(Context.WINDOW_SERVICE);
int screenHeight = wm.getDefaultDisplay().getHeight();
/*
/*
* PopupWindow height for match_parent,
* will occupy the entire screen, it needs to do special treatment in Android 7.1
*/
pw.setHeight(screenHeight - location[1] - anchor.getHeight() - yoff);
}
pw.showAtLocation(anchor, Gravity.NO_GRAVITY, xoff, location[1] + anchor.getHeight() + yoff);
} else {
pw.showAsDropDown(anchor, xoff, yoff);
}
}
还有就是通过反射的方式改变源码
但是我这个方法有缺陷的，反射的办法会遇到Google Api如果把变量名改了，那就直接无效了。
但是要解决这种系统bug也只能做API适配了。
package cc.kinva.widget;
import android.content.Context;
import android.os.Build;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.view.View;
import android.view.WindowManager;
import android.widget.PopupWindow;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
/**
* Created by pang on 17/9/23.
*/
public class FixedPopupWindow extends PopupWindow {
public FixedPopupWindow(Context context) {
super(context);
}
public FixedPopupWindow(Context context, AttributeSet attrs) {
super(context, attrs);
}
public FixedPopupWindow(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public FixedPopupWindow(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
public FixedPopupWindow(View contentView) {
super(contentView);
}
public FixedPopupWindow() {
super();
}
public FixedPopupWindow(int width, int height) {
super(width, height);
}
public FixedPopupWindow(View contentView, int width, int height, boolean focusable) {
super(contentView, width, height, focusable);
}
public FixedPopupWindow(View contentView, int width, int height) {
super(contentView, width, height);
}
@Override
public void update(int x, int y, int width, int height, boolean force) {
if (Build.VERSION.SDK_INT < 24) {
super.update(x, y, width, height, force);
return;
}
if (width >= 0) {
setParam("mLastWidth", width);
setWidth(width);
}
if (height >= 0) {
setParam("mLastHeight", height);
setHeight(height);
}
Object obj = getParam("mContentView");
View mContentView = null;
if (obj instanceof View) {
mContentView = (View) obj;
}
if (!isShowing() || mContentView == null) {
return;
}
obj = getParam("mDecorView");
View mDecorView = null;
if (obj instanceof View) {
mDecorView = (View) obj;
}
final WindowManager.LayoutParams p =
(WindowManager.LayoutParams) mDecorView.getLayoutParams();
boolean update = force;
obj = getParam("mWidthMode");
int mWidthMode = obj != null ? (Integer) obj : 0;
obj = getParam("mLastWidth");
int mLastWidth = obj != null ? (Integer) obj : 0;
final int finalWidth = mWidthMode < 0 ? mWidthMode : mLastWidth;
if (width != -1 && p.width != finalWidth) {
p.width = finalWidth;
setParam("mLastWidth", finalWidth);
update = true;
}
obj = getParam("mHeightMode");
int mHeightMode = obj != null ? (Integer) obj : 0;
obj = getParam("mLastHeight");
int mLastHeight = obj != null ? (Integer) obj : 0;
final int finalHeight = mHeightMode < 0 ? mHeightMode : mLastHeight;
if (height != -1 && p.height != finalHeight) {
p.height = finalHeight;
setParam("mLastHeight", finalHeight);
update = true;
}
if (p.x != x) {
p.x = x;
update = true;
}
if (p.y != y) {
p.y = y;
update = true;
}
obj = execMethod("computeAnimationResource");
final int newAnim = obj == null ? 0 : (Integer) obj;
if (newAnim != p.windowAnimations) {
p.windowAnimations = newAnim;
update = true;
}
obj = execMethod("computeFlags", new Class[]{int.class}, new Object[]{p.flags});
final int newFlags = obj == null ? 0 : (Integer) obj;
if (newFlags != p.flags) {
p.flags = newFlags;
update = true;
}
if (update) {
execMethod("setLayoutDirectionFromAnchor");
obj = getParam("mWindowManager");
WindowManager mWindowManager = obj instanceof WindowManager ? (WindowManager) obj : null;
if (mWindowManager != null) {
mWindowManager.updateViewLayout(mDecorView, p);
}
}
}
/**
* 反射获取对象
* @param paramName
* @return
*/
private Object getParam(String paramName) {
if (TextUtils.isEmpty(paramName)) {
return null;
}
try {
Field field = PopupWindow.class.getDeclaredField(paramName);
field.setAccessible(true);
return field.get(this);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 反射赋值对象
* @param paramName
* @param obj
*/
private void setParam(String paramName, Object obj) {
if (TextUtils.isEmpty(paramName)) {
return;
}
try {
Field field = PopupWindow.class.getDeclaredField(paramName);
field.setAccessible(true);
field.set(this, obj);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 反射执行方法
* @param methodName
* @param args
* @return
*/
private Object execMethod(String methodName, Class[] cls, Object[] args) {
if (TextUtils.isEmpty(methodName)) {
return null;
}
try {
Method method = getMethod(PopupWindow.class, methodName, cls);
method.setAccessible(true);
return method.invoke(this, args);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 利用递归找一个类的指定方法，如果找不到，去父亲里面找直到最上层Object对象为止。
*
* @param clazz
* 目标类
* @param methodName
* 方法名
* @param classes
* 方法参数类型数组
* @return 方法对象
* @throws Exception
*/
private Method getMethod(Class clazz, String methodName,
final Class[] classes) throws Exception {
Method method = null;
try {
method = clazz.getDeclaredMethod(methodName, classes);
} catch (NoSuchMethodException e) {
try {
method = clazz.getMethod(methodName, classes);
} catch (NoSuchMethodException ex) {
if (clazz.getSuperclass() == null) {
return method;
} else {
method = getMethod(clazz.getSuperclass(), methodName,
classes);
}
}
}
return method;
}
}
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