java - 当我单击按钮时，我的 PopUpWindow 未打开

Question

基本上，我单击的按钮是针对商店的，我希望它会出现一个弹出窗口，您可以从中购买升级(很像 Cookie Clicker 菜单)。但是，当我单击该按钮时，应用程序崩溃了。有人类似的帖子说产生的错误是由于未设置 contentView 的结果，所以我设置了这个，但只有当我将 contentView 设置为我用作弹出窗口的布局时它才有效，这意味着我有弹出窗口，但不在原始主布局之上。

我的Java代码:

package com.bipbapapps.leagueclickerapp;


import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.graphics.Typeface;
import android.os.Bundle;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.PopupWindow;
import android.widget.TextView;

public class MainClass extends Activity implements OnClickListener {


public float goldCount;
Button minionClick;
Button storeClick;
TextView textGoldCount;
String textTotal;
private SharedPreferences prefs;

@Override
public void onCreate (Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //Set full-screen
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

    setContentView(R.layout.mainlayout);

    prefs = getSharedPreferences("LeagueClicker", Context.MODE_PRIVATE);


    goldCount = prefs.getFloat("goldCount", 0.0f);

    //Linking the variables
    minionClick = (Button) findViewById(R.id.minioncentreid);
    storeClick = (Button) findViewById(R.id.storeimageid);
    textGoldCount = (TextView) findViewById(R.id.textviewtop);

    //String which will display at the top of the app
    textTotal = goldCount + " Gold";

    //Setting TextView to the String
    textGoldCount.setText(textTotal);
    textGoldCount.setGravity(Gravity.CENTER);
    Typeface tf = Typeface.createFromAsset(getAssets(), "mechanical.ttf");
    textGoldCount.setTypeface(tf);
    textGoldCount.setTextSize(35);

    //Setting onClickListener
    minionClick.setOnClickListener(this);
    storeClick.setOnClickListener(this);

}


@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()){
    case R.id.minioncentreid:
    goldCount += 1.0;
    prefs.edit().putFloat("goldCount", goldCount).commit();
    textTotal = goldCount + " Gold";
    textGoldCount.setText(textTotal);
    textGoldCount.setGravity(Gravity.CENTER);
    break;

    case R.id.storeimageid:
        LayoutInflater inflater = (LayoutInflater)
           this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        PopupWindow pw = new PopupWindow(
           inflater.inflate(R.layout.storemenu, null, false), 
           100, 
           100, 
           true);
        pw.showAtLocation(this.findViewById(R.id.storemenuid), Gravity.CENTER, 0, 0);

    }


}


@Override
public void onPause(){
    super.onPause();
    prefs.edit().putFloat("goldCount", goldCount).commit();
}

@Override
public void onResume(){
    super.onResume();
    goldCount = prefs.getFloat("goldCount", 0.0f);
}

@Override
public void onStop(){
    super.onStop();
    prefs.edit().putFloat("goldCount", goldCount).commit();
    Log.d(prefs.getFloat("goldCount", 0.0f)+"derprolw", "ejwfjbrea");
}




}

LogCat 错误:

04-22 06:24:52.408: D/gralloc_goldfish(2931): Emulator without GPU emulation detected.
04-22 06:24:57.808: D/dalvikvm(2931): GC_FOR_ALLOC freed 2121K, 10% free 20151K/22340K, paused 111ms, total 114ms
04-22 06:24:58.368: D/AndroidRuntime(2931): Shutting down VM
04-22 06:24:58.368: W/dalvikvm(2931): threadid=1: thread exiting with uncaught exception (group=0xb2a1cba8)
04-22 06:24:58.418: E/AndroidRuntime(2931): FATAL EXCEPTION: main
04-22 06:24:58.418: E/AndroidRuntime(2931): Process: com.bipbapapps.leagueclickerapp, PID: 2931
04-22 06:24:58.418: E/AndroidRuntime(2931): java.lang.NullPointerException
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.widget.PopupWindow.showAtLocation(PopupWindow.java:814)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at com.bipbapapps.leagueclickerapp.MainClass.onClick(MainClass.java:86)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.view.View.performClick(View.java:4438)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.view.View$PerformClick.run(View.java:18422)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.os.Handler.handleCallback(Handler.java:733)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.os.Handler.dispatchMessage(Handler.java:95)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.os.Looper.loop(Looper.java:136)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at android.app.ActivityThread.main(ActivityThread.java:5017)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at java.lang.reflect.Method.invokeNative(Native Method)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at java.lang.reflect.Method.invoke(Method.java:515)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-22 06:24:58.418: E/AndroidRuntime(2931):     at dalvik.system.NativeStart.main(Native Method)
04-22 06:25:01.358: I/Process(2931): Sending signal. PID: 2931 SIG: 9

有谁知道我该如何解决这个问题？

Answer 1

在我看来，这一行(第 86 行？)有一个空指针:

pw.showAtLocation(this.findViewById(R.id.storemenuid), Gravity.CENTER, 0, 0);

尝试用 v 替换 this.findViewById(R.id.storemenuid) ，因为从技术上讲，它们是相同的，除非我们知道 v 不为空，否则将无法到达此行。另外，其他值也是恒定的，因此我们知道它们也不为空。

请告诉我这是否有帮助，或者是否为您提供了更多信息。

<小时/>

编辑

其他原因也可能在构造函数中:

 PopupWindow pw = new PopupWindow(
       inflater.inflate(R.layout.storemenu, null, false), 
       100, 
       100, 
       true);

但我发现这种情况不太可能发生，因为它应该通知您引用该行的空指针。