Question

我真的不知道这个NullPointerException发生在哪里...... 我检查了我的xml文件，它的声明......仍然有一个NULL ...

这是CatLog ..

02-29 00:15:12.988: E/AndroidRuntime(1287): FATAL EXCEPTION: main
02-29 00:15:12.988: E/AndroidRuntime(1287): java.lang.RuntimeException:Unable to start activity ComponentInfo{com.ceit.worldofgravity/com.ceit.worldofgravity.MainMenu}: java.lang.NullPointerException
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.os.Looper.loop(Looper.java:137)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.ActivityThread.main(ActivityThread.java:5041)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at java.lang.reflect.Method.invokeNative(Native Method)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at java.lang.reflect.Method.invoke(Method.java:511)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at dalvik.system.NativeStart.main(Native Method)
02-29 00:15:12.988: E/AndroidRuntime(1287): Caused by: java.lang.NullPointerException
02-29 00:15:12.988: E/AndroidRuntime(1287):     at com.ceit.worldofgravity.MainMenu.onCreate(MainMenu.java:33)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.Activity.performCreate(Activity.java:5104)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-29 00:15:12.988: E/AndroidRuntime(1287):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-29 00:15:12.988: E/AndroidRuntime(1287):     ... 11 more

Main Menu.java

=============================================== ==================

package com.ceit.worldofgravity;


import android.app.Activity;
import android.content.Intent;
import android.graphics.Typeface;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class MainMenu extends Activity{

RelativeLayout Btn;
ImageView ImageButton;
TextView txt;

@Override
public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Btn = (RelativeLayout) findViewById(R.id.btn_start);
    ImageButton = (ImageView) findViewById(R.id.imageView2);


    Typeface Custom = Typeface.createFromAsset(getAssets(),"Sketch 3D.otf");

    txt.setTypeface(Custom);

    Btn.setOnTouchListener(new OnTouchListener() {


        @Override
        public boolean onTouch(View arg0, MotionEvent arg1) {

            return false;
        }
    });

    Btn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            Intent myIntent = new Intent(MainMenu.this, Game.class);
            startActivities(myIntent);
        }
    });
}

protected void startActivities(Intent myIntent) {

}
}

main.xml中

 <RelativeLayout 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:background="@drawable/bb"
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=".MainMenu" >

<ImageView
    android:id="@+id/imageView1"
    android:layout_width="550dp"
    android:layout_height="160dp"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:src="@drawable/title" android:contentDescription="TODO"/>

<RelativeLayout
    android:id="@+id/btn_start"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/imageView1"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="18dp" >

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/play" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/start_game"
        android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>

Answer 1

在MainMenu.java:33抛出NullPointerException，因为txt成员未设置为任何内容（因此它为null）

你忘了初始化它，例如。用：

txt = (TextView) findViewById(R.id.textView1);

无法启动活动ComponentInfo {com.ceit.worldofgravity / com.ceit.worldofgravity.MainMenu} :: java.lang.NullPointerException

1 个答案: