无法解析符号，android studio

Question

It's my first time working with android studio and I get error

"Cannot resolve symbol AppCompatActivity", and other symbol errors.

How can I resolve it? I've tried adding things to gradle but nothing workde. Also tried doing "Invalidate caches/restart" but it also didn't work.

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button) findViewById(R.id.buttonCall);

        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View arg0) {
                Intent callIntent = new Intent(Intent.ACTION_CALL);
                callIntent.setData(Uri.parse("tel:1566"));

                if (ActivityCompat.checkSelfPermission(MainActivity.this,
                        Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {
                    return;
                }
                startActivity(callIntent);
            }
        });


    }
}

Here are dependencies in gradle file

dependencies {
    compile 'com.android.support:appcompat-v7'
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

Answer 1

As you are using the AndroidX dependency

androidx.appcompat:appcompat:1.0.2

And in MainActivity you import the

import android.support.v7.app.AppCompatActivity;

remove it and import the androidx AppCompatActivity then the error resolved.

Additional

Also, please add com.google.android.material:material:1.0.0 into the build.gradle

Answer 2

Recently I encountered similar problem - "Cannot resolve symbol AppCompatActivity", although I am using

import androidx.appcompat.app.AppCompatActivity

Of course I migrated to androidx long time ago. This happened when I tried to debug my application on real device running Android 10. Tried many things: delete .gradle and .idea folders, Invalidate caches, etc.

The only thing that helped was shift to Android Studio 4.2 Canary 12 from 4.0.1. Although the topic is old, I wanted to support people encountered this error recently.

Answer 3

Remove this two lines from import part and try

import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;

Answer 4

You cannot user support lib packages and AndroidX packages together. So if you have migrated your project to android x you will need to use that library only.

Answer 5

You are using androidx then you can remove this line in your build.gradle

compile 'com.android.support:appcompat-v7'

Change the import in your class:

//Remove these
//import android.support.v7.app.AppCompatActivity;
//import android.support.v4.app.ActivityCompat;

//Add this
import androidx.appcompat.app.AppCompatActivity