自从我上传了我的应用程序以来，我收到了许多java.lang.NullPointerException崩溃报告。我正在努力理解问题，因为它不会在模拟器或我亲自测试过的物理设备上崩溃。以下是其中一份报告的示例：
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:2072)
at android.view.View.performClick(View.java:2408)
at android.view.View$PerformClick.run(View.java:8817)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:143)
at android.app.ActivityThread.main(ActivityThread.java:4914)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.reflect.InvocationTargetException
at com.bryan.barrett.countdownforandroid.practiceSubscreen.openNumbersSelect(Unknown Source)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at android.view.View$1.onClick(View.java:2067)
... 11 more
Caused by: java.lang.NullPointerException
... 15 more
我假设这在按下'openNumbersSelect'按钮时在'practiceSubscreen'中崩溃。这是该按钮的代码片段：
public void openNumbersSelect(View view){
Intent iNum = new Intent(this, numbersSelect.class);
String gamemode = "practice"; //practice mode
iNum.putExtra("gamemode", gamemode);
startActivity(iNum);
overridePendingTransition(R.anim.fadein, R.anim.fadeout);
if(sound){
soundPool.play(Main.SNDclick, audio.getStreamVolume(AudioManager.STREAM_MUSIC),
audio.getStreamVolume(AudioManager.STREAM_MUSIC), 1, 0, 1f);
}
}
这是下面的numberSelectClass中打算打开的onCreate代码：
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_numbers_select);
Intent i = getIntent();
gamemode = i.getStringExtra("gamemode");
gameround = i.getIntExtra("gameround", 0) + 1;
points = i.getIntExtra("points", 0);
//Shared Preferences
prefs = PreferenceManager.getDefaultSharedPreferences(this);
sound = prefs.getBoolean("sound", true);
//Sounds
setVolumeControlStream(AudioManager.STREAM_MUSIC);
audio = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
soundPool = Main.soundPool;
//Big Numbers
for (int n=25; n<=100; n+=25){ //add 25, 50, 75, 100
bignumbers.add(n);
}
//Small Numbers
for (int m=1; m<=10; m++){ //adds 1-10 twice
smallnumbers.add(m);
smallnumbers.add(m);
}
//Screen metrics
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
int screenw = metrics.widthPixels; int screenh = metrics.heightPixels;
int unitw = (screenw/14); int unith = (screenh/40); //divide screen into 14 columns x 40 rows...
num1 = (Button)findViewById(R.id.num1img); nums.add(num1);
num2 = (Button)findViewById(R.id.num2img); nums.add(num2);
num3 = (Button)findViewById(R.id.num3img); nums.add(num3);
num4 = (Button)findViewById(R.id.num4img); nums.add(num4);
num5 = (Button)findViewById(R.id.num5img); nums.add(num5);
num6 = (Button)findViewById(R.id.num6img); nums.add(num6);
for(int n=0; n<6; n++){
nums.get(n).setHeight(screenh/4); nums.get(n).setTextSize(Main.fontSize);
nums.get(n).setWidth(screenw/6); nums.get(n).setPadding(1, 1, 1, 1);
}
lrg = (Button)findViewById(R.id.largebutton); lrg.setWidth((unitw*200)/35);
sml = (Button)findViewById(R.id.smallbutton); sml.setWidth((unitw*200)/35);
Typeface scribble = Typeface.createFromAsset(getAssets(), "fonts/scribble.ttf");
TextView numbersSeltext = (TextView)findViewById(R.id.numbersSeltext);
numbersSeltext.setTypeface(scribble);
numbersSeltext.setWidth(screenw); numbersSeltext.setHeight(unith*8);
if(gamemode.equals("full")){
numbersSeltext.setText("Round " + gameround + ": Select 6 Numbers");
}
}
如果有人能对此有所了解，将不胜感激！这是一个令人沮丧的问题，因为它在我自己测试过的设备上可以正常工作，并且基于反馈，它在很多设备上都可以正常工作，因此我什至不确定代码是否存在问题，或者某些设备是否存在问题是内置的。如果需要，我可以抛出更多的崩溃报告或代码！
提前感谢！
如果我是你，我将在使用它们之前测试所有按钮num1，num2 ...和许多其他视图是否为空，因为如果尚未为任何视图创建该视图，则仅获取视图可能会引发nullpointerexception原因（例如，可滚动的listview项目仅填充可以放入屏幕的视图）。如果让使用者知道布局xml是什么，则可能会有所帮助。
我也有同样的问题。在小米Redmi Note 5 Pro（白色），3840MB RAM，Android 9中]
java.lang.NullPointerException:
at com.baruchi.simpletime.main.Ud.f (Unknown Source:43)
at b.j.a.h.k (Unknown Source)
at b.j.a.v.m (Unknown Source:13)
at b.j.a.v.w (Unknown Source:77)
at b.j.a.h.k (Unknown Source:7)
at b.j.a.v.m (Unknown Source:13)
at b.j.a.v.w (Unknown Source:77)
at b.j.a.m.m (Unknown Source:4)
at b.j.a.k.onSaveInstanceState (Unknown Source:8)
at androidx.appcompat.app.m.onSaveInstanceState (Unknown Source)
at com.baruchi.simpletime.main.MainActivity.onSaveInstanceState (Unknown Source)
at android.app.Activity.performSaveInstanceState (Activity.java:1599)
at android.app.Instrumentation.callActivityOnSaveInstanceState (Instrumentation.java:1444)
at android.app.ActivityThread.callActivityOnSaveInstanceState (ActivityThread.java:4872)
at android.app.ActivityThread.callActivityOnStop (ActivityThread.java:4214)
at android.app.ActivityThread.handleSleeping (ActivityThread.java:4340)
at android.app.ActivityThread.access$2400 (ActivityThread.java:200)
at android.app.ActivityThread$H.handleMessage (ActivityThread.java:1772)
at android.os.Handler.dispatchMessage (Handler.java:106)
at android.os.Looper.loop (Looper.java:201)
at android.app.ActivityThread.main (ActivityThread.java:6810)
at java.lang.reflect.Method.invoke (Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:873)