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Button에 대한 코드를 사용할 때 문제가 발생합니다. 그 중 하나는 new Boston tutorials입니다. 정확히 무엇을 말하고 있지만 logcat에 오류가 발생했습니다.불행히도 MyFirstApp이 중지되었습니다
package com.example.myfirstapp;
import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
int counter=0;
TextView display;
Button add;
Button sub;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
add=(Button) findViewById(R.id.bAdd);
sub=(Button) findViewById(R.id.bSub);
display=(TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
counter++;
display.setText("Your Total is " +counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
counter--;
display.setText("Your Total is " +counter);
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}
는
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myfirstapp"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
로그 캣 파일은 이러한 오류를 보여줍니다이 내 매니페스트 파일입니다
: FATAL EXCEPTION: main
Process: com.example.myfirstapp, PID: 1873
E/AndroidRuntime(1873): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.MainActivity}: java.lang.NullPointerException
E/AndroidRuntime(1873): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
E/AndroidRuntime(1873):at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
E/AndroidRuntime(1873):at android.app.ActivityThread.access$800(ActivityThread.java:135)
E/AndroidRuntime(1873): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
E/AndroidRuntime(1873): at android.os.Handler.dispatchMessage(Handler.java:102)
E/AndroidRuntime(1873): at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime(1873): at android.app.ActivityThread.main(ActivityThread.java:5017)
E/AndroidRuntime(1873): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(1873): at java.lang.reflect.Method.invoke(Method.java:515)
E/AndroidRuntime(1873): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
E/AndroidRuntime(1873): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
E/AndroidRuntime(1873): at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(1873): Caused by: java.lang.NullPointerException
E/AndroidRuntime(1873): at android.view.ViewConfiguration.get(ViewConfiguration.java:325)
E/AndroidRuntime(1873): at android.view.View.<init>(View.java:3448)
E/AndroidRuntime(1873): at android.view.View.<init>(View.java:3505)
E/AndroidRuntime(1873): at android.widget.TextView.<init>(TextView.java:623)
E/AndroidRuntime(1873): at android.widget.Button.<init>(Button.java:107)
E/AndroidRuntime(1873): at android.widget.Button.<init>(Button.java:103)
E/AndroidRuntime(1873): at android.widget.Button.<init>(Button.java:99)
E/AndroidRuntime(1873): at com.example.myfirstapp.MainActivity.<init>(MainActivity.java:18)
E/AndroidRuntime(1873): at java.lang.Class.newInstanceImpl(Native Method)
E/AndroidRuntime(1873): at java.lang.Class.newInstance(Class.java:1208)
E/AndroidRuntime(1873): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
E/AndroidRuntime(1873): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
E/AndroidRuntime(1873): ... 11 more
: I/Process(1873): Sending signal. PID: 1873 SIG: 9
이 제발 도와주세요 그리고하지 마십시오 레이아웃 XML 파일을
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.myfirstapp.MainActivity$PlaceholderFragment" >
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/hello_world"
android:textSize="45sp"
android:layout_gravity="center"
android:gravity="center"
android:id="@+id/tvDisplay"
/>
<Button
android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="@string/add_button"
android:gravity="center"
android:layout_gravity="center"
android:id="@+id/bAdd"
/>
<Button
android:id="@+id/bSub"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:text="@string/sub_button" />
</LinearLayout>
입니다 나는 아주 새로운 오전 downvote 학습.
레이아웃 xml 파일을 게시 할 수 있습니까? –