Exception when I run my application from Eclipse

问题:

I've been having this problem for almost 2 months now and can't figure it out. The problem is that if my application is running and I run (reinstall) my application from Eclipse, I get an error message indicating that my application has crashed 'Unfortunately, has stopped.'. I notice that it also occurs when I run it away from my PC/Eclipse, I think that it happens only after I don't run it for a while.

It only occurs if the app is active in the 3rd activity (BaseDiagramActivity) and then I run the app again from Eclipse. I've stripped out basically all the application except the 3 activities and It's still happening.

I've searched and searched for a solution to this problem but can't find any good answer or one that applies to me.

It doesn't seem like a hardware or android version issue as I'm running this on my tablet (4.0.3) and my phone (4.0.2, was happening on 4.0.1 before update). Unless of course it is an ice cream sandwich bug.

Let me know if any more info is required.

The exception (Tag=AndroidRuntime)

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate application android.app.Application: java.lang.NullPointerException
   at android.app.LoadedApk.makeApplication(LoadedApk.java:482)
   at android.app.ActivityThread.handleBindApplication(ActivityThread.java:3938)
   at android.app.ActivityThread.access$1300(ActivityThread.java:123)
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1185)
   at android.os.Handler.dispatchMessage(Handler.java:99)
   at android.os.Looper.loop(Looper.java:137)
   at android.app.ActivityThread.main(ActivityThread.java:4424)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
   at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
   at android.app.LoadedApk.initializeJavaContextClassLoader(LoadedApk.java:362)
   at android.app.LoadedApk.getClassLoader(LoadedApk.java:305)
   at android.app.LoadedApk.makeApplication(LoadedApk.java:474)
   ... 11 more

The Android Code

LoadedApk.initializeJavaContextClassLoader() - Line 362 seems to be the offender

Below are the relevant files:

AndroidManifest.xml

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

    <uses-sdk android:minSdkVersion="14" />

    <application 
        android:icon="@drawable/ic_launcher" 
        android:label="@string/app_name" >
        <activity 
            android:name="HomeActivity" 
            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="LoadDiagramActivity" android:label="Load Diagram"></activity>
        <activity android:name="BaseDiagramActivity" android:label="Base Diagram"></activity>
    </application>

</manifest>

HomeActivity.java

public class HomeActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.home);

        Button diagramButton = (Button)findViewById(R.id.diagram);
        diagramButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                startActivity(new Intent(HomeActivity.this, LoadDiagramActivity.class));
            }
        });
    }
}

LoadDiagramActivity.java

public class LoadDiagramActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ActionBar actionBar = getActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.menu.load_diagram_menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                finish();
                return true;
            case R.id.add_new_diagram:
                startActivity(new Intent(this, BaseDiagramActivity.class));
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

BaseDiagramActivity.java

it doesn't actually matter what activity this is, the exception occurs as long as a 'third' activity is started (or clicking the add button on LoadDiagramActivity.

public class BaseDiagramActivity extends Activity {
}

home.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:orientation="vertical" >

    <Button
        android:id="@+id/diagram"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Diagram" />

</LinearLayout>

Additional information

When I stripped down my project in order to ask a simpler answer, I moved everything into the package's namespace. In the actual project there are 5 namespaces, they were still present when I was testing with the stripped down version however just not called (as far as I could see).

Here are the packages:

• [package] - general logic
• [package].activities - all activities and base activities
• [package].database - all interaction with the database
• [package].models - models for saving/loading data
• [package].renderables - objects drawn to a canvas

I have tried to add an `android:sharedUserId' attribute to the manifest and and it seemed to do nothing both times I tried. When I was initially investigating this I came to the conclusion that the shared user id only applied to different projects, not different packages.

Also I don't believe there was any interaction with the database when I stripped everything down. The fact that the 3rd activity could be any activity, even HomeActivity, was something against this theory.

Useful links

• stackoverflow: android.app.Application cannot be instantiated due to NullPointerException
• GreoCode android.app.LoadedApk on 4.0.1
• Possible race condition?
• Android issue #25869

Update 1/11/2012

Last couple of days I've jumped back into this project, I created a brand new project in Eclipse Juno (was on Helios before) and transferred everything over manually so that Eclipse and Android tools handled almost all of the Manifest interaction but it's still occurring. I will look at it a bit more over the next few days and update if I find anything.

FYI my new project is targeting the following:

<uses-sdk
    android:minSdkVersion="14"
    android:targetSdkVersion="15" />

The new project structure also has all the activities in the root package now (ie. [package], not [package].activities). I'm also using the (new?) syntax to show the parent activity:

<meta-data
    android:name="android.support.PARENT_ACTIVITY"
    android:value="[my package].LoadDiagramActivity" />

It is also still occurring on my now updated Galaxy Nexus running Jellybean 4.1.2.

回答1:

Try adding one more thing in Manifest file, I am sure you have already tried..

<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="[my package]" 
    android:versionCode="1" 
    android:versionName="1.0"
    android:sharedUserId="com.mj.app" > 

It seems like in your project you have multiple PACKAGES, like com.package.p1 , com.package.p2 ,com.package.p3..

And while starting you are in p1 and then moves on to p2 - p3... and at that time you try to run it again..so the Android gives you error.

回答2:

If you put 13 in your minSdkVersion, it should work.

Either that, or you need to setDisplayHomeAsUpEnabled(false) in the onCreate() of your other activities.

Both those solutions should work.

Starting at API Level 14 according to the documentation, the setHomeButtonEnabled(true) is no longer done for you by default, and it goes on to say that

Setting the DISPLAY_HOME_AS_UP display option will automatically enable the home button.

So we can infer that setDisplayHomeAsUpEnabled(false) works in a similar way as setHomeButtonEnabled(false)

回答3:

If I am not mistaken, this only happens when we reinstall the app from Eclipse Run->As. So this is unlikely to happen when a user upgrades through Play. I can say this with confidence since I did notice my app too with this exception during reinstall through Eclipse, but nothing on Crittercism.

To fix this, I worked on resolving memory consumption of my app.

1. If you only have 1 set of drawables, then change that. Create a drawables-mdpi and copy all the file from that 1 drawables folder (drawables, drawable-ldpi). If you have just 1 set, Android will resize it for its use on bigger screens, thus internally taking up too much memory, and cleanup of this kind of memory (bitmap) is bug prone. Sound crazy, but does wonders. Dont believe me, run it under Heap memory usage watch before and after this change, you will notice that your app is taking 25% less memory for a common scenario.
2. If you are doing any Bitmap operations, you may want to consider downscaling. Atleast when you are setting options you definitely want to downscale it. Check here and here. Search or downscaleing.
3. Finally dont forget to bitmap.recycle(); bitmap = null; in your onDestroy and before all System.exit(0).

Android does a lot of background work, and reinstallation is a abrupt cleanup expectation from the app. Memory not cleaned up can cause issues. This exception is one of those internal ones. So dont think of it to be straightforward.

回答4:

You haven't added the period to the names of your activities in manifest's android:name attributes. Perhaps, this causes the problem.

回答5:

Wait after your application crashes when u run it second time. The app will launch after the crashing again. This happens sometimes with me. If the same is the case with u dont forget to clean your project everytime before u run it.

回答6:

By inspecting your code I feel you are skipping to set "setContentView(rid)" in LoadDiagramActivity. Please try setting the view in onCreate().

Hope this will help you.

回答7:

You need to append "." before the activity name in Menifest.

Like this

<?xml version="1.0" encoding="utf-8"?>

<uses-sdk android:minSdkVersion="14" />

<application 
    android:icon="@drawable/ic_launcher" 
    android:label="@string/app_name" >
    <activity 
        android:name=".HomeActivity" 
        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=".LoadDiagramActivity" android:label="Load Diagram"></activity>
    <activity android:name=".BaseDiagramActivity" android:label="Base Diagram"></activity>
</application>

I update your menifest's activity. Please check it...

回答8:

There is nothing wrong with the code you've given us so far. I just tried it in a new project with the package name com.test and it worked flawlessly. The only thing I added in the files were the package declaration. (And I added the load_diagram_menu.xml, of course.)

If possible, it would be great if you could give us access to the complete project. If the project is working on someone else's computer, it's most likely Eclipse or the Android Eclipse plugin-in that are misbehaving. A clean install of Eclipse would solve that. (Though I understand how being offline could make this difficult. :-) )

回答9:

For this, be sure to have the "Build Automatically" checked when cleaning the project. (Project -> Build Automatically)