1

每当我没有“启动”活动作为第一个活动时，我的代码就可以工作。当我的 Main Activity 是第一个并通过具有所有工作功能的整个应用程序时，它可以工作。我必须缺少一些东西才能使此页面成为在应用程序开始时工作的页面。

日志猫

10-30 20:30:22.137: D/AndroidRuntime(783): Shutting down VM
10-30 20:30:22.137: W/dalvikvm(783): threadid=1: thread exiting with uncaught exception (group=0x41465700)
10-30 20:30:22.147: E/AndroidRuntime(783): FATAL EXCEPTION: main
10-30 20:30:22.147: E/AndroidRuntime(783): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.androidassignment2/com.example.androidassignment2.Startup}: java.lang.NullPointerException
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.os.Looper.loop(Looper.java:137)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.ActivityThread.main(ActivityThread.java:5103)
10-30 20:30:22.147: E/AndroidRuntime(783):  at java.lang.reflect.Method.invokeNative(Native Method)
10-30 20:30:22.147: E/AndroidRuntime(783):  at java.lang.reflect.Method.invoke(Method.java:525)
10-30 20:30:22.147: E/AndroidRuntime(783):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-30 20:30:22.147: E/AndroidRuntime(783):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-30 20:30:22.147: E/AndroidRuntime(783):  at dalvik.system.NativeStart.main(Native Method)
10-30 20:30:22.147: E/AndroidRuntime(783): Caused by: java.lang.NullPointerException
10-30 20:30:22.147: E/AndroidRuntime(783):  at com.example.androidassignment2.Startup.onCreate(Startup.java:19)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.Activity.performCreate(Activity.java:5133)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-30 20:30:22.147: E/AndroidRuntime(783):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
10-30 20:30:22.147: E/AndroidRuntime(783):  ... 11 more

布局

<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" >
    <TextView android:id="@+id/Hello"
        android:layout_weight="1"
        android:layout_width="wrap_content"
        android:layout_height="0dip"
        android:text="@string/Hello" />
    <Button android:id="@+id/QuitButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_quit" />
</LinearLayout>

代码

package com.example.androidassignment2;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;

public class Startup extends Activity {

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


        Button next = (Button) findViewById(R.id.QButton);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), MainActivity.class);
                startActivityForResult(myIntent, 0);
            }
        });

    }



    @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;
    }
}

最后是 manifest.xml 文件。怀疑问题可能出在哪里。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.example.androidassignment2"
          android:versionCode="1"
          android:versionName="1.0">

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">
        <activity
            android:name="com.example.androidassignment2.Startup"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

    <activity
        android:name="com.example.androidassignment2.MainActivity"
        android:label="@string/title_activity_android_assignment2_1" >

    </activity>


        <activity
            android:name="com.example.androidassignment2.AndroidAssignment2_1"
            android:label="@string/title_activity_android_assignment2_1">
        </activity>

        <activity
            android:name="com.example.androidassignment2.AndroidAssignment2_2"
            android:label="@string/title_activity_android_assignment2_1">
        </activity>


        <activity
            android:name="com.example.androidassignment2.AndroidAssignment2_3"
            android:label="@string/title_activity_android_assignment2_1">
        </activity>


        <activity
            android:name="com.example.androidassignment2.AndroidAssignment2_4"
            android:label="@string/title_activity_android_assignment2_1">
        </activity>

        <activity
            android:name="com.example.androidassignment2.AndroidAssignment2_5"
            android:label="@string/title_activity_android_assignment2_1">
        </activity>

        <activity
            android:name="com.example.androidassignment2.Goodbye"
            android:label="@string/title_activity_android_assignment2_1">
        </activity>
    </application>
</manifest>
4

1 回答 1

3

您的按钮 ID 错误。QButton未在您的 xml 中定义。

代替

Button next = (Button) findViewById(R.id.QButton);

采用

Button next = (Button) findViewById(R.id.QuitButton);
于 2013-10-31T00:43:13.310 回答