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android：onClick属性をAutoCompleteTextViewに割り当てると、アクティビティをロードするとすぐにアプリケーションがクラッシュします。私はonClickメソッドを割り当てることなくAutoCompleteTextViewをテストしました。それはonClickを他のビュー（EditText、Spinners、TextViews、Buttons、およびImageButtonsを含む）に割り当てるのと同じようにうまくいくようです。私は24行目（setContentView（R.layout.activity_main））にエラーを絞り込むことができました。誰かがこれについていくつかの光を当てることができますか？NullPointerExceptionを与えるAutoCompleteTextViewにOnClickListenerを割り当てるのはなぜですか？
MainActivity.java
package com.example.matt.testapp;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
public class MainActivity extends AppCompatActivity {
public AutoCompleteTextView actv;
public String[] continents = {"North America",
"South America",
"Antarctica",
"Europe",
"Africa",
"Asia",
"Australia"
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
actv = (AutoCompleteTextView) findViewById(R.id.actv);
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, continents);
actv.setAdapter(adapter);
}
public void actvClick (View view) {}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent" >
<AutoCompleteTextView
android:id="@+id/actv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="actvClick" >
</AutoCompleteTextView>
</LinearLayout>
Logcat
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.matt.testapp/com.example.matt.testapp.MainActivity}: android.view.InflateException: Binary XML file line #7: Binary XML file line #7: Error inflating class AutoCompleteTextView
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: android.view.InflateException: Binary XML file line #7: Binary XML file line #7: Error inflating class AutoCompleteTextView
Caused by: android.view.InflateException: Binary XML file line #7: Error inflating class AutoCompleteTextView
Caused by: java.lang.NullPointerException: Attempt to write to field 'android.view.View$OnClickListener android.widget.AutoCompleteTextView$PassThroughClickListener.mWrapped' on a null object reference
at android.widget.AutoCompleteTextView$PassThroughClickListener.-set0(Unknown Source:0)
at android.widget.AutoCompleteTextView.setOnClickListener(AutoCompleteTextView.java:307)
at android.view.View.<init>(View.java:5008)
at android.widget.TextView.<init>(TextView.java:824)
at android.widget.EditText.<init>(EditText.java:88)
at android.widget.AutoCompleteTextView.<init>(AutoCompleteTextView.java:220)
at android.widget.AutoCompleteTextView.<init>(AutoCompleteTextView.java:193)
at android.widget.AutoCompleteTextView.<init>(AutoCompleteTextView.java:172)
at android.support.v7.widget.AppCompatAutoCompleteTextView.<init>(AppCompatAutoCompleteTextView.java:68)
at android.support.v7.widget.AppCompatAutoCompleteTextView.<init>(AppCompatAutoCompleteTextView.java:64)
at android.support.v7.app.AppCompatViewInflater.createView(AppCompatViewInflater.java:130)
at android.support.v7.app.AppCompatDelegateImplV9.createView(AppCompatDelegateImplV9.java:1026)
at android.support.v7.app.AppCompatDelegateImplV9.onCreateView(AppCompatDelegateImplV9.java:1083)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:772)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:289)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139)
at com.example.matt.testapp.MainActivity.onCreate(MainActivity.java:24)
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
[NullPointerExceptionとは何ですか？それを修正するにはどうすればいいですか？]（https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix -it） –
投票者を閉じるための注記：これはOPコードのNPEではなく、プラットフォームコードです。 – laalto