我正在构建一个应用程序，但那里存在问题。当我尝试运行我的应用程序时，出现以下错误：
>09-16 14:07:35.768: E/AndroidRuntime(21484): FATAL EXCEPTION: main
>09-16 14:07:35.768: E/AndroidRuntime(21484): java.lang.RuntimeException: Unable to start activity ComponentInfo{lt.prasom/lt.prasom.MainMenu}: java.lang.NullPointerException
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.os.Handler.dispatchMessage(Handler.java:99)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.os.Looper.loop(Looper.java:130)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.ActivityThread.main(ActivityThread.java:3683)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at java.lang.reflect.Method.invokeNative(Native Method)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at java.lang.reflect.Method.invoke(Method.java:507)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at dalvik.system.NativeStart.main(Native Method)
>09-16 14:07:35.768: E/AndroidRuntime(21484): Caused by: java.lang.NullPointerException
>09-16 14:07:35.768: E/AndroidRuntime(21484): at lt.prasom.MainMenu.onCreate(MainMenu.java:19)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
>09-16 14:07:35.768: E/AndroidRuntime(21484): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
>09-16 14:07:35.768: E/AndroidRuntime(21484): ... 11 more
我的清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="lt.prasom"
android:versionCode="1"
android:versionName="1.0"
android:installLocation="preferExternal" >"
<uses-sdk android:minSdkVersion="8" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name=".MainMenu"
android:label="@string/app_name"
android:theme="@android:style/Theme.Black.NoTitleBar" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".GoodOffers" android:theme="@android:style/Theme.Black.NoTitleBar" />
<activity android:name=".Search" android:theme="@android:style/Theme.Black.NoTitleBar" />
<activity android:name=".Groups" android:theme="@android:style/Theme.Black.NoTitleBar" />
<activity android:name=".Specialmenu" android:theme="@android:style/Theme.Black.NoTitleBar" />
</application>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
</manifest>
我的活动在lt.prasom包中。当我重命名程序包名称时出现错误。
MainMenu.java：
package lt.prasom;
import lt.prasom.R;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainMenu extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button search = (Button) findViewById(R.id.searchbutt);
search.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
Intent i = new Intent(MainMenu.this.getApplicationContext(), Search.class);
startActivity(i);
}
});
Button groups = (Button) findViewById(R.id.groupsbutt);
groups.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
Intent i = new Intent(MainMenu.this.getApplicationContext(), Groups.class);
startActivity(i);
}
});
Button goods = (Button) findViewById(R.id.specialbutt);
goods.setOnClickListener(new OnClickListener(){
public void onClick(View arg0) {
Intent i = new Intent(MainMenu.this.getApplicationContext(), Specialmenu.class);
startActivity(i);
}
});
}
}
Main.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingTop="10dp"
android:orientation="vertical"
xmlns:ui="http://schemas.android.com/apk/res/lt.prasom" xmlns:app="http://schemas.android.com/apk/res/lt.prasom"
android:background="#f8f9fe" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingTop="20dp"
android:layout_gravity="center"
android:src="@drawable/logo" />
<Button android:id="@+id/goodsbutt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="10dp"
android:text="Geri pasiūlymai"
/>
<Button android:id="@+id/akcijabutt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="10dp"
android:text="Akcijinės prekės"
/>
<Button android:id="@+id/newsbutt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="10dp"
android:text="Naujos prekės"
/>
</LinearLayout>
谢谢！
最佳答案
当前活动的main.xml中未声明searchbutt id。您必须通过setContentView（）选择当前显示的元素
因此Button search = (Button) findViewById(R.id.searchbutt);搜索是null，
search.setOnClickListener(new OnClickListener(){
引发异常
关于android - E/AndroidRuntime(21484)无法启动 Activity ComponentInfo {lt.prasom/lt.prasom.MainMenu}:java.lang.NullPointerException，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/12446526/