CODEWITHSUNDEEP
android
sravani
sravani

Reputation: 13

java.lang.NullPointerException:Attempt to invoke virtual method android.content.pm.PackageManager android.content.Context.getPackageManager()

Getting exception "java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.PackageManager android.content.Context.getPackageManager()' on a null object reference"

when i execute below code. Goal: change image dynamically based on some status for one flavor in android studio.

AndroidManifest.xml

 <application
        tools:replace="android:icon,android:roundIcon"
        android:allowBackup="true"
        android:icon="${appIcon}"
        android:label="@string/app_name"
        android:roundIcon="${appIconRound}"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name="devicelist.AddDeviceActivity"/>
        <activity android:name="resourcestatesimulator.NativeActivity" />
        <activity android:name="devicelist.DeviceListActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <activity android:name="CarplayMain" />

        <activity-alias
            android:name=".DeviceListActivityAlias"
            android:enabled="false"
            android:icon="@mipmap/ic_launcher_default"
            android:roundIcon="@mipmap/ic_launcher_default_round"
            android:label="@string/app_name"
            android:targetActivity="devicelist.DeviceListActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity-alias>
    </application>

DeviceListActivity.java

public void defaultIcon()
    {
        Log.i(TAG, "Before default Icon" );
        packageManager = getPackageManager();
        packageManager.setComponentEnabledSetting(new ComponentName(DeviceListActivity.this,"com.bosch.spi.carplay.devicelist.DeviceListActivity"),
                PackageManager.COMPONENT_ENABLED_STATE_ENABLED,
                PackageManager.DONT_KILL_APP);

        packageManager.setComponentEnabledSetting(new ComponentName(DeviceListActivity.this,"com.bosch.spi.carplay.devicelist.DeviceListActivityAlias"),
                PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
        Log.i(TAG, "After default Icon" );
    }
    public void activeIcon()
    {
        Log.i(TAG, "Before active Icon" );
        packageManager = getPackageManager();
        packageManager.setComponentEnabledSetting(new ComponentName(DeviceListActivity.this,"com.bosch.spi.carplay.devicelist.DeviceListActivity"),
                PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);

        packageManager.setComponentEnabledSetting(new ComponentName(DeviceListActivity.this,"com.bosch.spi.carplay.devicelist.DeviceListActivityAlias"),
                PackageManager.COMPONENT_ENABLED_STATE_ENABLED,
                PackageManager.DONT_KILL_APP);
        Log.i(TAG, "After Active Icon" );
    }

Calling methods in DeviceListAdapter.java

DeviceListActivity deviceListActivity= new DeviceListActivity();
deviceListActivity.activeIcon();
deviceListActivity.defaultIcon();

Upvotes: 0

Views: 3566

Answers (1)

Iogui
Iogui

Reputation: 1698

The problem happens because you are trying to manually instantiate the Activity DeviceListActivity. When you call getPackageManager() inside the methods from DeviceListActivity class it throws a NullPointerException because your activity is not managed by Android so it don't know how to provide a package manger for it since Android runtime don't even know about your deviceListActivity since you have instantiated it with new keyword. Don't do this. You have to let Android manage your Activities for you, never instantiate it with new keyword.

Read this to understand the proper way to start an activity.

Upvotes: 1

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