在Android中向“第二个活动”添加了一个“返回至第一个”按钮。 现在，导航到第二个活动时应用程序崩溃

Question

Having a bit of trouble with my app. I'm in the beginning stages of making a game and I have a simple instructions page that was running fine. That is until I added a button at the bottom to return to the homepage. Now when I click the link to the instructions page the app crashes. I looked around and can only find people who haven't added the activity to the manifest which I have done. Please help...

Code for button to return.

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

public class HowTo extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); 
setContentView(R.layout.how_to);

Button btnHomeFromHow = (Button) findViewById(R.id.btnHomeFromHow);
btnHomeFromHow.setOnClickListener(new OnClickListener() {


    public void onClick(View view) {
        startActivity(new Intent(HowTo.this, Home.class));
    }
});

Manifest.

      <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.whackachav"
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.whackachav.Home"
        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.whackachav.HowTo"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.Main" />

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

    <activity 
        android:name="com.example.whackachav.Game"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

    <activity 
        android:name="com.example.whackachav.HighScores"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

</manifest>

Button in layout file.

        <button
        android:id="@+id/btnHomeFromHow"
        style="@style/btnStyleShakespeare"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tvBucky"
        android:text="Back to Main Menu"
        android:layout_marginTop="10dp"
        />

log.

12-13 16:05:25.560: E/Trace(2397): error opening trace file: No such file or directory (2)
12-13 16:05:26.260: D/dalvikvm(2397): GC_FOR_ALLOC freed 53K, 8% free 2456K/2652K, paused 42ms, total 44ms
12-13 16:05:26.431: D/dalvikvm(2397): GC_CONCURRENT freed 2K, 7% free 2909K/3112K, paused 82ms+4ms, total 156ms
12-13 16:05:27.100: D/gralloc_goldfish(2397): Emulator without GPU emulation detected.
12-13 16:05:27.740: I/Choreographer(2397): Skipped 84 frames!  The application may be doing too much work on its main thread.
12-13 16:05:35.921: D/dalvikvm(2397): GC_CONCURRENT freed 30K, 5% free 3349K/3524K, paused 79ms+8ms, total 210ms
12-13 16:05:35.921: D/dalvikvm(2397): WAIT_FOR_CONCURRENT_GC blocked 39ms
12-13 16:05:36.160: D/dalvikvm(2397): GC_FOR_ALLOC freed 50K, 6% free 3546K/3772K, paused 47ms, total 55ms
12-13 16:05:36.170: I/dalvikvm-heap(2397): Grow heap (frag case) to 4.213MB for 643068-byte allocation
12-13 16:05:36.240: D/dalvikvm(2397): GC_FOR_ALLOC freed <1K, 6% free 4174K/4404K, paused 64ms, total 64ms
12-13 16:05:36.360: D/dalvikvm(2397): GC_CONCURRENT freed <1K, 6% free 4174K/4404K, paused 5ms+17ms, total 117ms
12-13 16:05:36.721: D/dalvikvm(2397): GC_FOR_ALLOC freed <1K, 6% free 4178K/4404K, paused 44ms, total 52ms
12-13 16:05:36.740: I/dalvikvm-heap(2397): Grow heap (frag case) to 4.942MB for 760600-byte allocation
12-13 16:05:36.950: D/dalvikvm(2397): GC_CONCURRENT freed <1K, 5% free 4920K/5148K, paused 85ms+4ms, total 210ms
12-13 16:05:37.330: D/AndroidRuntime(2397): Shutting down VM
12-13 16:05:37.340: W/dalvikvm(2397): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
12-13 16:05:37.500: E/AndroidRuntime(2397): FATAL EXCEPTION: main
12-13 16:05:37.500: E/AndroidRuntime(2397): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.whackachav/com.example.whackachav.HowTo}: android.view.InflateException: Binary XML file line #101: Error inflating class button
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.os.Looper.loop(Looper.java:137)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.ActivityThread.main(ActivityThread.java:5041)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at java.lang.reflect.Method.invokeNative(Native Method)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at java.lang.reflect.Method.invoke(Method.java:511)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at dalvik.system.NativeStart.main(Native Method)
12-13 16:05:37.500: E/AndroidRuntime(2397): Caused by: android.view.InflateException: Binary XML file line #101: Error inflating class button
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:698)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:746)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:749)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.inflate(LayoutInflater.java:396)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:270)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.Activity.setContentView(Activity.java:1881)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at com.example.whackachav.HowTo.onCreate(HowTo.java:15)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.Activity.performCreate(Activity.java:5104)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
12-13 16:05:37.500: E/AndroidRuntime(2397):     ... 11 more
12-13 16:05:37.500: E/AndroidRuntime(2397): Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.button" on path: /data/app/com.example.whackachav-1.apk
12-13 16:05:37.500: E/AndroidRuntime(2397):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:65)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.createView(LayoutInflater.java:552)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.onCreateView(LayoutInflater.java:643)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:66)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.onCreateView(LayoutInflater.java:660)
12-13 16:05:37.500: E/AndroidRuntime(2397):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:685)
12-13 16:05:37.500: E/AndroidRuntime(2397):     ... 22 more
12-13 16:05:39.780: I/Process(2397): Sending signal. PID: 2397 SIG: 9

Answer 1

You didn't define the Home.java class in Android Manifest. so try this.

<activity 
    android:name="com.example.whackachav.Home"
    android:label="@string/app_name" >
    </activity>

Answer 2

you should use..

"android.intent.category.DEFAULT"

for HowTo

if you are using LAUNCHER for Home

Answer 3

Change

<button
        android:id="@+id/btnHomeFromHow"
        style="@style/btnStyleShakespeare"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tvBucky"
        android:text="Back to Main Menu"
        android:layout_marginTop="10dp"
        />

To

<Button  // B in caps
    android:id="@+id/btnHomeFromHow"
    style="@style/btnStyleShakespeare"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/tvBucky"
    android:text="Back to Main Menu"
    android:layout_marginTop="10dp"
    />

Answer 4

Your problem might be here:

java.lang.ClassNotFoundException: Didn't find class "android.view.button" on path: /data/app/com.example.whackachav-1.apk

which is likely caused by:

<button
        android:id="@+id/btnHomeFromHow"
        style="@style/btnStyleShakespeare"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/tvBucky"
        android:text="Back to Main Menu"
        android:layout_marginTop="10dp"
        />

Because "button" should actually be "Button" with a capital B.

Also, possibly unrelated, but depending on how you started the "HowTo" activity, it may be better to simply call finish() instead of trying to start the Home activity again.