java.lang.RuntimeException: Unable to instantiate activity ComponentInfo in Android Studio

Question

I am beginner in Android Studio. I am trying to run my app on my mobile, but when i try to run my application on my mobile it shows

Unfortunately app has been stopped

Here is the error showed in Logcat android monitor.

10-23 23:19:25.882 18014-18014/com.example.dhara.codesprint E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.dhara.codesprint, PID: 18014
java.lang.RuntimeException: Unable to start activity ComponentInfo

{com.example.dhara.codesprint/com.example.dhara.codesprint.MainActivity}: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2299)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1243)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5372)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:970)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:786)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
at android.support.v7.app.AppCompatDelegateImplV7.setSupportActionBar(AppCompatDelegateImplV7.java:198)
at android.support.v7.app.AppCompatActivity.setSupportActionBar(AppCompatActivity.java:130)
at com.example.dhara.codesprint.MainActivity.onCreate(MainActivity.java:39)
at android.app.Activity.performCreate(Activity.java:5258)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1099)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2239)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349) 
at android.app.ActivityThread.access$800(ActivityThread.java:151) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1243) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:136) 
at android.app.ActivityThread.main(ActivityThread.java:5372) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:515) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:970) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:786) 
at dalvik.system.NativeStart.main(Native Method)

Below is the code for MainActivity.java

package com.example.dhara.codesprint;

import android.content.res.AssetManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    TextView text1;
    TextView text2;
    TextView text3;
    TextView text4;
    TextView text5;
    TextView text6;
    EditText text7;
    Button checkAnswer;
    Button reset;

    //private WordDictionary dictionary;
    private String currentWord;
    private ArrayList<String> words;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        AssetManager assetManager = getAssets();
        try {
            InputStream inputStream = assetManager.open("words.txt");
        } catch (IOException e) {
            Toast toast = Toast.makeText(this, "Could not load dictionary", Toast.LENGTH_LONG);
            toast.show();
        }

        text1 = (TextView) findViewById(R.id.textView1);
        text2 = (TextView) findViewById(R.id.textView2);
        text3 = (TextView) findViewById(R.id.textView3);
        text4 = (TextView) findViewById(R.id.textView4);
        text5 = (TextView) findViewById(R.id.textView5);
        text6 = (TextView) findViewById(R.id.textView6);
        text7 = (EditText) findViewById(R.id.edittext);
        checkAnswer = (Button) findViewById(R.id.button);
        reset = (Button) findViewById(R.id.button2);


        reset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });



        checkAnswer.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });
    }





}

AndroidMainfest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.dhara.codesprint">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="Codesprint"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:background="@color/background"
    tools:context=".MainActivity">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/circle"
        android:layout_marginLeft="13dp"
        android:layout_marginStart="13dp"
        android:layout_marginTop="14dp"
        android:id="@+id/imageView1"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/circle"
        android:id="@+id/imageView2"
        android:layout_alignTop="@+id/imageView3"
        android:layout_alignLeft="@+id/imageView5"
        android:layout_alignStart="@+id/imageView5" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/circle"
        android:id="@+id/imageView3"
        android:layout_alignTop="@+id/imageView1"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_marginRight="24dp"
        android:layout_marginEnd="24dp" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/circle"
        android:layout_marginTop="27dp"
        android:id="@+id/imageView4"
        android:layout_below="@+id/imageView1"
        android:layout_alignLeft="@+id/imageView1"
        android:layout_alignStart="@+id/imageView1" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/circle"
        android:id="@+id/imageView5"
        android:layout_alignTop="@+id/imageView4"
        android:layout_centerHorizontal="true" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:srcCompat="@drawable/circle"
        android:id="@+id/imageView6"
        android:layout_alignTop="@+id/imageView5"
        android:layout_alignLeft="@+id/imageView3"
        android:layout_alignStart="@+id/imageView3" />

    <EditText
        android:text="Your Answer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/imageView5"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="55dp"
        android:id="@+id/edittext"
        android:textSize="20sp"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColorLink="?attr/actionMenuTextColor" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="31dp"
        android:id="@+id/textView2"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:layout_alignTop="@+id/imageView2"
        android:layout_alignLeft="@+id/imageView2"
        android:layout_alignStart="@+id/imageView2"
        android:layout_alignRight="@+id/imageView2"
        android:layout_alignEnd="@+id/imageView2"
        android:textColor="@android:color/background_light" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView2"
        android:layout_alignRight="@+id/imageView3"
        android:layout_alignEnd="@+id/imageView3"
        android:id="@+id/textView3"
        android:layout_alignLeft="@+id/imageView3"
        android:layout_alignStart="@+id/imageView3"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColor="@android:color/background_light" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/imageView4"
        android:layout_alignRight="@+id/imageView4"
        android:layout_alignEnd="@+id/imageView4"
        android:layout_marginTop="30dp"
        android:id="@+id/textView4"
        android:layout_alignLeft="@+id/imageView4"
        android:layout_alignStart="@+id/imageView4"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColor="@android:color/background_light" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/textView4"
        android:layout_alignRight="@+id/imageView5"
        android:layout_alignEnd="@+id/imageView5"
        android:id="@+id/textView5"
        android:layout_alignLeft="@+id/imageView5"
        android:layout_alignStart="@+id/imageView5"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColor="@android:color/background_light" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView5"
        android:layout_alignRight="@+id/imageView6"
        android:layout_alignEnd="@+id/imageView6"
        android:id="@+id/textView6"
        android:layout_alignLeft="@+id/imageView6"
        android:layout_alignStart="@+id/imageView6"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColor="@android:color/background_light" />

    <TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textView2"
        android:layout_alignRight="@+id/imageView1"
        android:layout_alignEnd="@+id/imageView1"
        android:id="@+id/textView1"
        android:layout_alignLeft="@+id/imageView1"
        android:layout_alignStart="@+id/imageView1"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColor="@android:color/background_light" />

    <Button
        android:text="Check Your Answer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="25dp"
        android:id="@+id/button"
        android:textAlignment="center"
        android:textStyle="normal|bold"
        android:textColor="@android:color/background_light"
        android:background="@color/colorPrimary"
        android:layout_below="@+id/edittext"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />

    <Button
        android:text="Reset"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="27dp"
        android:id="@+id/button2"
        android:background="@color/colorPrimary"
        android:textSize="14sp"
        tools:textColor="@android:color/background_light" />

</RelativeLayout>

I have tried some solution from web but it is not working.

Answer 1

You layout does not have a Toolbar , and yet you are calling the following:

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

Either remove these calls or add a Toolbar to your layout.

For the latter to work you also need to use (or derive from) one of the AppCompat themes that do not have an ActionBar , Theme.AppCompat.Light.NoActionBar for example.

So in your styles.xml you would have something like this:

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
</style>

Answer 2

You can't initiate your view elements (TextView, Buttons etc) before setting out the layout xml which for your case is R.layout.activity_main file.

package com.example.dhara.codesprint;

import android.content.res.AssetManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {


    //private WordDictionary dictionary;
    private String currentWord;
    private ArrayList<String> words;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView text1 = (TextView) findViewById(R.id.textView1);
        TextView text2 = (TextView) findViewById(R.id.textView2);
        TextView text3 = (TextView) findViewById(R.id.textView3);
        TextView text4 = (TextView) findViewById(R.id.textView4);
        TextView text5 = (TextView) findViewById(R.id.textView5);
        TextView text6 = (TextView) findViewById(R.id.textView6);
        TextView text7 = (TextView) findViewById(R.id.edittext);
        Button checkAnswer = (Button) findViewById(R.id.button);
        Button reset = (Button) findViewById(R.id.button2);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        AssetManager assetManager = getAssets();
        try {
            InputStream inputStream = assetManager.open("words.txt");
        } catch (IOException e) {
            Toast toast = Toast.makeText(this, "Could not load dictionary", Toast.LENGTH_LONG);
            toast.show();
        }


        reset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });



        checkAnswer.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });
    }
}

Answer 3

请在 onCreate() 中初始化您的布局元素，因为当您的活动开始时它会调用 onCreate() 方法，但在这里您是从您的 onCreate() 方法调用您的布局，但之后您没有初始化您的元素，还要检查您是否是否在您的清单中添加了活动名称，请仔细阅读并实施，希望对您有所帮助。