'App not Installed' Error on Android

Question

I have a program working in the Android Emulator. Every now and again I have been creating a signed .apk and exporting it to my HTC Desire to test. It has all been fine.

Answer 1

For me, On Android 9 (API 28), disabling Google Play Protect from play store app worked the trick, and i was able to get rid of the App not Installed error.

To disable Google Play Protect. Open "Play Store" application => tap on Menu button => select "Play Protect" option => Disable the options "Scan device for security threats".

Answer 2

I had the same issue, i.e. App showed up as being installed, but would not launched when the icon was tapped. After some head-banging, I found that I had stupidly placed ' android:exported="false" ' for my main launcher activity within the AndroidManifest file.... Once I removed it, the App launched fine..

Answer 3

If application's not installing, delete the file .android_secure/smdl2tmpl.asec from the SD card.

If the folder .android_secure is empty in the file manager, delete it from the PC.

Answer 4

If you have a previous version for that application try to erase it first, now my problem was solved by that method.

Answer 5

I have also solved this issue,

The problem was that i declared my main activity twice, On as the first activity to load and i specified also an intent-filter for it And once again below it i declared it again .

Just make sure you don't declare your activities twice .

Answer 6

Sideloading debug apps for testing on a physical phone worked reliably until I upgraded the phone from Android Pie to Android 10. After that, the "App not installed" error came up every time I tried to sideload the app.

Based on a warning in my AndroidManifest.xml, I changed from...

<application
    android:name=".App"
    android:allowBackup="true" ... />

to...

<application
    android:name=".App"
    android:allowBackup="false" ... />

After that, I was able to sideload my app -- once. Then, I encountered the same "App not installed" error again. By changing allowBackup back to true, it worked again (at least once).

It is obvious from the number of answers and the variation in the answers that there are many reasons for this problem. I'm sharing this in case it helps others.