Android studio错误（java.lang.NullPointerException [重复]） _Exception

智者不为愚者谋，勇者不为怯者死。这篇文章主要讲述Android studio错误：java.lang.NullPointerException [重复]相关的知识，希望能为你提供帮助。
这个问题在这里已有答案：

What is a NullPointerException, and how do I fix it? 12个答案

我正在尝试从用户那里获取输入并创建给定数字的列表。我收到java.lang.NULLpointerException但我在代码中找不到任何错误。将用户输入从MainActivity传递到选择器Activity。主要活动完美无缺。
主要信息
公共类MainActivity扩展AppCompatActivity {

DatePicker dp; EditText et; Button b; String d; int e; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); dp = (DatePicker)findViewById(R.id.datePicker3); et = (EditText)findViewById(R.id.editText); b = (Button)findViewById(R.id.button); d = dp.toString(); //final int k = Integer.parseInt(e); //Integer. b.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent i = new Intent(MainActivity.this, selector.class); Bundle extras = new Bundle(); e = Integer.parseInt(et.getText().toString()); i.putExtra("date",d); i.putExtra("number", e); i.putExtras(extras); startActivity(i); } }); }

}
【Android studio错误（java.lang.NullPointerException [重复]）】Selector Acitivity公共类选择器扩展AppCompatActivity {

Button b; TextView abs; String []as; boolean[] pora; ArrayList< Integer> mabs = new ArrayList< > (); @Override protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState); setContentView(R.layout.activity_selector); b=(Button)findViewById(R.id.btnOrder); abs=(TextView)findViewById(R.id.tvItemSelected); Bundle extras = getIntent().getExtras(); int result = extras.getInt("number",5); String v2 =Integer.toString(result); abs.setText(v2); as = new String[result+1]; for(int i=1; i< =result; i++) {as[i]=Integer.toString(i); } abs.append(as[2]); pora=new boolean[as.length]; b.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {AlertDialog.Builder mBuilder = new AlertDialog.Builder(selector.this); mBuilder.setTitle("kjsr7c attendace"); mBuilder.setMultiChoiceItems(as, pora, new DialogInterface.OnMultiChoiceClickListener(){ @Overridepublic void onClick(DialogInterface dialogInterface, int position, boolean isChecked) { if(isChecked){mabs.add(position); }else{mabs.remove((Integer.valueOf(position))); }}}); mBuilder.setCancelable(false); mBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialogInterface, int which) {String item = ""; for (int i = 1; i < mabs.size(); i++) {item = item + as[mabs.get(i)]; if (i != mabs.size() - 1) {item = item + ", "; }}abs.setText(item); }}); mBuilder.setNegativeButton("DISMISS", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialogInterface, int i) {dialogInterface.dismiss(); }}); mBuilder.setNeutralButton("CLEAR", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialogInterface, int which) {for (int i = 1; i < pora.length; i++) {pora[i] = false; mabs.clear(); abs.setText(""); }}}); AlertDialog mDialog = mBuilder.create(); mDialog.show(); }}); }

}
logcat的

FATAL EXCEPTION: main Process: com.example.sankar.kjsr7c, PID: 3945 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:409) at android.widget.ArrayAdapter.getView(ArrayAdapter.java:371) at android.support.v7.app.AlertController$AlertParams$1.getView(AlertController.java:974) at android.widget.AbsListView.obtainView(AbsListView.java:2363) at android.widget.ListView.measureHeightOfChildren(ListView.java:1326) at android.widget.ListView.onMeasure(ListView.java:1233) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.view.View.measure(View.java:19857) at android.support.v7.widget.AlertDialogLayout.tryOnMeasure(AlertDialogLayout.java:133) at android.support.v7.widget.AlertDialogLayout.onMeasure(AlertDialogLayout.java:63) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464) at android.widget.LinearLayout.measureVertical(LinearLayout.java:758) at android.widget.LinearLayout.onMeasure(LinearLayout.java:640) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at com.android.internal.policy.DecorView.onMeasure(DecorView.java:689) at android.view.View.measure(View.java:19857) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2275) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1339) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1619) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6337) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874) at android.view.Choreographer.doCallbacks(Choreographer.java:686) at android.view.Choreographer.doFrame(Choreographer.java:621) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

答案在使用Integer.parseInt之前检查EditText是否为空。最有可能的是，Empty EditText将为getText（）操作返回null。