android中的致命错误异常

Question

我正在尝试编写 android 饮食计划器。在我调试它之后，我发现当我的第一页淡出并且活动想要转到第二页然后发生致命错误异常但我找不到问题出在哪里？谁能帮帮我？

错误

10-24 06:35:46.622: E/AndroidRuntime(1102): FATAL EXCEPTION: main
10-24 06:35:46.622: E/AndroidRuntime(1102): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.dietplanneraplication/com.example.dietplanneraplication.FeatureList}: java.lang.NullPointerException
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.os.Looper.loop(Looper.java:137)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.ActivityThread.main(ActivityThread.java:4745)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at java.lang.reflect.Method.invokeNative(Native Method)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at java.lang.reflect.Method.invoke(Method.java:511)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at dalvik.system.NativeStart.main(Native Method)
10-24 06:35:46.622: E/AndroidRuntime(1102): Caused by: java.lang.NullPointerException
10-24 06:35:46.622: E/AndroidRuntime(1102):     at com.example.dietplanneraplication.FeatureList.onCreate(FeatureList.java:26)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.Activity.performCreate(Activity.java:5008)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
10-24 06:35:46.622: E/AndroidRuntime(1102):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
10-24 06:35:46.622: E/AndroidRuntime(1102):     ... 11 more

XML 代码

MAINACTIVITY.XML

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:id="@+id/firstpage"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="#eee"
 android:orientation="vertical" >
 <LinearLayout
    android:id="@+id/logoid"
    android:layout_width="200dip"
    android:layout_height="200dip"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:background="@drawable/logo_shadow4"
    android:orientation="vertical" >

 </LinearLayout>
</RelativeLayout>

FEATURELIST.XML

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/featurelist"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="1" >

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="0dip"
    android:layout_weight="0.25"
    android:background="#ffffff" >
</LinearLayout>
</LinearLayout>

BMICALCULATER>XML

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.dietplanneraplication.BmiCalculaterPage"
tools:ignore="MergeRootFrame" />

JAVA 代码

MAINACTIVITY.JAVA

package com.example.dietplanneraplication;

public class MainActivity extends ActionBarActivity implements AnimationListener{
 RelativeLayout screen;
 int i;
 Intent intent;
 Animation animFadeout;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    screen=(RelativeLayout) findViewById(R.id.firstpage);
    animFadeout=AnimationUtils.loadAnimation(getApplicationContext(),R.anim.fade_out );
    animFadeout.setAnimationListener(MainActivity.this);

    screen.post(new Runnable() {

        @Override
        public void run() {
            screen.startAnimation(animFadeout); 
            animFadeout.setFillAfter(true);
        }
    }); 


}


@Override
public void onAnimationEnd(Animation anim) {
    startActivity(new Intent(getApplicationContext(),FeatureList.class));   
    overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);
    finish();

}

@Override
public void onAnimationRepeat(Animation arg0) {
    // TODO Auto-generated method stub

}

@Override
public void onAnimationStart(Animation arg0) {
    // TODO Auto-generated method stub

}

}

FEATURELIST.JAVA

package com.example.dietplanneraplication;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
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.os.Build;

public class FeatureList extends ActionBarActivity {
Button bmiinformation;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_feature_list);
    bmiinformation = (Button) findViewById(R.id.bmiinformation);
    bmiinformation.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent intent =new Intent(getApplicationContext(),BmiCalculaterPage.class);
            startActivity(intent);
            finish();

        }
    });
  }

BMICALCULATER.JAVA

public class BmiCalculaterPage extends ActionBarActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_bmi_calculater_page);


}

}

Answer 1

您的activity_feature_list layout.xml 中没有名称为bmiinformation 的ID。

 bmiinformation = (Button) findViewById(R.id.bmiinformation); // bmiinformation is null as a result

这就是我认为的问题所在。
尝试添加一个 ID 为 bmiinformation 的按钮。