PopWindow 是开发中常用的一种组件,网上对于 PopWindow 的定位方法也众说纷纭,经过看过网上的很多博客,自己也动手尝试了一番,终于对 PopWindow 有了自己的认知,特此记录一下。其实主要是 PopWindow 大小的测量,以及通过相对定位确定 PopWindow 的弹出位置,这样如果遇到了使用场景直接用已有代码即可。
首先是 PopWindow 的大小自适应问题,通过下面这个 Demo 可以非常容易理解,比如下面是 PopWindow 布局文件,在这个布局中间中,PopWindow显示的是 LinearLayout,而不是 RelativeLayout:
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| <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="9999dp" android:layout_height="match_parent">
<LinearLayout android:background="@color/purple_200" android:orientation="vertical" android:padding="10dp" android:layout_width="wrap_content" android:layout_height="wrap_content"> <ImageView android:src="@drawable/ic_launcher_foreground" android:layout_width="match_parent" android:layout_height="wrap_content"/> <TextView android:textColor="@color/white" android:text="Hello PopWindow" android:layout_width="match_parent" android:layout_height="wrap_content"/> </LinearLayout> </RelativeLayout>
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下面是MainActivity的布局文件:
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| <?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">
<Button android:onClick="showPopWindow" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="PopWindow" android:textAllCaps="false" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
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接下来就是如何放置的问题,如果直接用 popWindow.getHeight() 或者 popWindow.getWidth() 获取的值都是 -2
,其实 PopupWindow 在创建时宽度高度设置为 match_parent 或者 wrap_content 时,通过 getWidth、getHeight 或者 getMeasuredWidth、getMeasuredHeight 均不能获取到真实的高度。
研究过 View 的绘制流程的人应该都知道 ViewRootImpl 的内部函数 performTraversals(),进行measure、layout、draw流程。现在我们只需要提前 measure,测量出 ContentView 的宽和高就行了,而剩下的难度就是如何计算了,这里可以参考《自定义View —— Measure-测量过程》。
所以要达到测量PopWindow最终目的其实也很简单,那就是直接对内容布局进行提前 measure。这样的话根据内容宽高很容易就可以对PopWindow进行任意位置摆放。
下面是默认弹窗的位置:
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下面主要是使用 showAsDropDown 来对弹窗位置进行控制:
上部居中弹出
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| public void showTopCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -(pWidth/2 - rWidth/2), -pHeight-rHeight); }
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底部居中弹出
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| public void showBottomCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -(pWidth/2 - rWidth/2), 0); }
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左边居中弹出
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| public void showLeftCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -pWidth, -(rHeight/2 + pHeight/2)); }
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右边居中弹出
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| public void showRightCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, rWidth, -(rHeight/2 + pHeight/2)); }
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左上方弹出
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| public void showLeftTop(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -pWidth, -pHeight-rHeight); }
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先写到这里,主要是根据默认位置进行X、Y偏移量计算即可
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全部代码:
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| import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.PopupWindow;
public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); }
public void showPopWindow(View button) { View contentView = LayoutInflater.from(this).inflate(R.layout.pop_content, null); PopupWindow popupWindow = new PopupWindow(contentView, ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, true); showLeftTop(popupWindow, button); }
public void showTopCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -(pWidth/2 - rWidth/2), -pHeight-rHeight); }
public void showBottomCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -(pWidth/2 - rWidth/2), 0); }
public void showLeftCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -pWidth, -(rHeight/2 + pHeight/2)); }
public void showRightCenter(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, rWidth, -(rHeight/2 + pHeight/2)); }
public void showLeftTop(PopupWindow popupWindow, View refView){ View contentView = popupWindow.getContentView(); contentView.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED); int pWidth = contentView.getMeasuredWidth(); int pHeight = contentView.getMeasuredHeight();
int rWidth = refView.getWidth(); int rHeight = refView.getHeight();
popupWindow.showAsDropDown(refView, -pWidth, -pHeight-rHeight); } }
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