java - 使用 PopupWindow 的 showAtLocation(View, int, int, int) 时遇到问题

Question

我正在尝试创建一个弹出窗口，启动时该弹出窗口将位于该屏幕的中心，并且其宽度不会占据整个屏幕，无论提示它的按钮位于何处。我还想增加透明度，以便用户能够模糊地看到现在在后台的 Activity ，但我也遇到了使用 alpha 的问题。到目前为止我的尝试并不令人满意。

特别是，当尝试在 showAtLocation 方法中使用重力时，系统会提示我以下错误消息:“PopupWindow 类型中的方法 showAtLocation(View, int, int, int) 不适用于该参数”

如有任何帮助，我们将不胜感激；提前致谢。

下面是 Activity 代码

import android.app.Activity; 
import android.graphics.Color;
import android.os.Bundle; 
import android.view.Gravity;
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.ViewGroup.LayoutParams; 
import android.widget.Button; 
import android.widget.LinearLayout; 
import android.widget.PopupWindow; 
import android.widget.TextView; 
import android.view.View.OnClickListener;

public class MainActivity extends Activity implements OnClickListener { 
    LinearLayout popupLayout; 
    PopupWindow popupMessage; 
    Button popupButton, insidePopupButton; 
    TextView popupText;

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.activity_main); init(); popupInit(); } 
        public void init() { popupButton = (Button) findViewById(R.id.popupbutton); 

        popupText = new TextView(this); 
        insidePopupButton = new Button(this); 
        popupLayout = new LinearLayout(this);
        popupLayout.setBackgroundColor(Color.parseColor("#dd000000"));
        popupLayout.setGravity(Gravity.CENTER);

        insidePopupButton.setText("OK"); 
        popupText.setText("This is Popup Window.press OK to dismiss it."); 
        popupText.setPadding(30, 40, 30, 20); 
        popupLayout.setOrientation(1); 
        popupLayout.addView(popupText); 
        popupLayout.addView(insidePopupButton); 
        } 
        public void popupInit() { 
            popupButton.setOnClickListener(this); 
            insidePopupButton.setOnClickListener(this); 
            popupMessage = new PopupWindow(popupLayout, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT); 
            popupMessage.setContentView(popupLayout);
            popupMessage.showAtLocation(this, Gravity.CENTER, 0, 0);


        } 
        @Override public void onClick(View v) { 
            if (v.getId() == R.id.popupbutton) { 
                popupMessage.showAsDropDown(popupButton, 0, 0); 
                } 
            else { 
                popupMessage.dismiss(); 
                } } }

下面是xml布局代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" >
 <TextView android:id="@+id/text" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentTop="true" 
     android:layout_centerHorizontal="true" 
     android:layout_marginTop="56dp" 
     android:text="good day, click button below to see popup" />

     <Button
         android:id="@+id/popupbutton"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentBottom="true"
         android:layout_centerHorizontal="true"
         android:text="Show Popup" />

      </RelativeLayout>

更新了代码

/**
 * Copyright 2010-present Facebook.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.facebook.samples.friendpicker;

import android.app.Activity; 
import android.os.Bundle; 
import android.view.Gravity;
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.ViewGroup.LayoutParams; 
import android.widget.Button; 
import android.widget.LinearLayout; 
import android.widget.PopupWindow; 
import android.widget.TextView; 

public class PopupDemoActivity extends Activity implements OnClickListener { 
    LinearLayout layoutOfPopup; 
    PopupWindow popupMessage; 
    Button popupButton, insidePopupButton; 
    TextView popupText;

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); init(); popupInit(); } 
        public void init() { popupButton = (Button) findViewById(R.id.popupbutton); 
        popupText = new TextView(this); 
        insidePopupButton = new Button(this); 
        layoutOfPopup = new LinearLayout(this); 
        insidePopupButton.setText("OK"); 
        popupText.setText("This is Popup Window.press OK to dismiss it."); 
        popupText.setPadding(0, 0, 0, 20); 
        layoutOfPopup.setOrientation(1); 
        layoutOfPopup.addView(popupText); 
        layoutOfPopup.addView(insidePopupButton); 
        } 
        public void popupInit() { 
            popupButton.setOnClickListener(this); 
            insidePopupButton.setOnClickListener(this); 
            View parent = findViewById(R.layout.main);
            popupMessage = new PopupWindow(layoutOfPopup, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT); 
            popupMessage.setContentView(layoutOfPopup);
            popupMessage.showAtLocation(parent, Gravity.CENTER, 0, 0);
        } 
        @Override public void onClick(View v) { 
            if (v.getId() == R.id.popupbutton) { 
                popupMessage.showAsDropDown(popupButton, 0, 0); 

                } 
            else { 
                popupMessage.dismiss(); 
                } } }

来自 logcat 的消息

07-29 12:36:19.761: E/AndroidRuntime(1720): FATAL EXCEPTION: main
07-29 12:36:19.761: E/AndroidRuntime(1720): Process: com.example.popuptest, PID: 1720
07-29 12:36:19.761: E/AndroidRuntime(1720): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.popuptest/com.example.popuptest.PopupDemoActivity}: java.lang.NullPointerException
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.os.Handler.dispatchMessage(Handler.java:102)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.os.Looper.loop(Looper.java:136)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.ActivityThread.main(ActivityThread.java:5017)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at java.lang.reflect.Method.invokeNative(Native Method)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at java.lang.reflect.Method.invoke(Method.java:515)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at dalvik.system.NativeStart.main(Native Method)
07-29 12:36:19.761: E/AndroidRuntime(1720): Caused by: java.lang.NullPointerException
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.widget.PopupWindow.showAtLocation(PopupWindow.java:814)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at com.example.popuptest.PopupDemoActivity.popupInit(PopupDemoActivity.java:41)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at com.example.popuptest.PopupDemoActivity.onCreate(PopupDemoActivity.java:23)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.Activity.performCreate(Activity.java:5231)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
07-29 12:36:19.761: E/AndroidRuntime(1720):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)

Answer 1

我写的评论的详细答案

<小时/>

这是 showAtLocation() 方法的构造函数:

public void showAtLocation (View parent, int gravity, int x, int y);

如您所见，所需的第一个参数是View。在您的代码中，您传递的是 this，在您的情况下，它指的是 Activity。这就是您收到错误的原因。

您必须传递 PopupWindow 的父 View。它基本上是您在 setContentView 方法中使用的 View。

要修复它，你必须使用这个:

View parent = findViewById(R.layout.activity_main);
popupMessage = new PopupWindow(popupLayout, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT); 
popupMessage.setContentView(popupLayout);
popupMessage.showAtLocation(parent, Gravity.CENTER, 0, 0);