Question

I am creating an android app drawer, but it fails when i call the activity. Seems like it’s something wrong on line 39.
It looks something like a NullPointerException.
Could you please help me?

Java code:

package com.mysoftware.mysoftwareos.mobile;

import java.util.ArrayList;

import android.app.ListActivity;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;

public class AllAppsActivity extends ListActivity {
LinearLayout appsLinearLayout;
ListView list;
Intent intent;
private ArrayList<ResolveInfo> mApplicationList;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.allapps_screen);
    //Import views
    appsLinearLayout = (LinearLayout)findViewById(R.id.appsLinearLayout);

    //Set wallpaper
    appsLinearLayout.setBackgroundResource(R.drawable.images);

    //Load all apps
    final PackageManager pm = this.getPackageManager();

    final ArrayList<ResolveInfo> list =
            (ArrayList<ResolveInfo>) pm.queryIntentActivities(intent, 
                    PackageManager.PERMISSION_GRANTED);
    for (ResolveInfo rInfo : list)
    {

        Log.i("TAG", ": Installed Applications " + rInfo.activityInfo.
                applicationInfo.loadLabel(pm).toString());
    }

    final ArrayAdapter<ResolveInfo> adapter = 
        new ArrayAdapter<ResolveInfo>(this, android.R.layout.simple_list_item_1, list)
        {
            @Override
            public View getView(int position, View convertView, ViewGroup parent)
            {
                convertView = super.getView(position, convertView, parent);
                final String text = list.get(position).activityInfo.
                    applicationInfo.loadLabel(pm).toString();
                ((TextView)convertView).setText(text);
                return convertView;
            }
        };
    setListAdapter(adapter);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    final Intent intent = new Intent(Intent.ACTION_MAIN);
    final ActivityInfo info = mApplicationList.get(position).activityInfo;
    intent.setClassName(info.packageName, info.name);
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
    startActivity(intent);
}
}

Xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/appsLinearLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >


<TextView
    android:id="@+id/TextView03"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Apps"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textSize="35dp" />


<ListView
    android:id="@android:id/list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

</ListView>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="35dp"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/ImageView03"
        android:layout_width="match_parent"
        android:layout_height="13dp"
        android:scaleType="fitXY"
        android:src="@drawable/seperator" />
</LinearLayout>

</LinearLayout>

Logcat:

01-27 01:35:24.610: E/AndroidRuntime(2150): FATAL EXCEPTION: main
01-27 01:35:24.610: E/AndroidRuntime(2150): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mysoftware.mysoftwareos.mobile/com.mysoftware.mysoftwareos.mobile.AllAppsActivity}: java.lang.NullPointerException
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1968)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1993)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at  android.app.ActivityThread.access$600(ActivityThread.java:127)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1151)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.os.Looper.loop(Looper.java:137)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.ActivityThread.main(ActivityThread.java:4499)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at java.lang.reflect.Method.invokeNative(Native Method)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at java.lang.reflect.Method.invoke(Method.java:511)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:788)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at dalvik.system.NativeStart.main(Native Method)
01-27 01:35:24.610: E/AndroidRuntime(2150): Caused by: java.lang.NullPointerException
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.ApplicationPackageManager.queryIntentActivities(ApplicationPackageManager.java:440)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at com.mysoftware.mysoftwareos.mobile.AllAppsActivity.onCreate(AllAppsActivity.java:39)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.Activity.performCreate(Activity.java:4637)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1051)
01-27 01:35:24.610: E/AndroidRuntime(2150):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1932)
01-27 01:35:24.610: E/AndroidRuntime(2150):     ... 11 more

Answer 1

From what I can see, from this:

final ArrayList<ResolveInfo> list =
            (ArrayList<ResolveInfo>) pm.queryIntentActivities(intent, 
                    PackageManager.PERMISSION_GRANTED);

intent is still null, you haven’t made an Intent Object.

I’m not sure what Intent you’re trying to match against, but you still need to instantiate it using the new keyword before using it.

Eg

intent = new Intent (Intent.ACTION_MAIN);

Also from that same call, you are shadowing the global variable list. Either consider taking out

final ArrayList<ResolveInfo>

so you are working with the global list or remove that global reference.

Moving on, I don’t thik PackageManager.PERMISSION_GRANTED is a valid flag for this method, since this seems to be a result constant.

Lastly: mApplicationList is also not instantiated, but then you try to read from it. Now this may be set somewhere else, we don’t have the whole code. This only affects the click on a List item.