Android ActionBar问题-应用程序崩溃

Question

I have created a simple app by adding action bar to it. And android studio didn't show any issue in the code, but my app keeps crashing when I run it. I have two activities, in MainActivity I have one button and when you click it it supposed to take you to SecondActivity . And on SecondActivity there should be back arrow in action bar to get back to MainActivity . Btw I'm using API 16. My activity extends Activity.

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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.actionbar3.MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="96dp"
        android:text="Next Activity"
        android:onClick="onClickButton"/>
</RelativeLayout>

MainActivity:

package com.actionbar3;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu){
        getMenuInflater().inflate(R.menu.action, menu);
        return onCreateOptionsMenu(menu);
    }

    public void onClickButton(View view){
        Intent intent = new Intent(this, SecondActivity.class);
        startActivity(intent);
    }
}

res/menu/action.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/main_action"
        android:title="@string/settings"
        android:showAsAction="ifRoom"
        android:icon="@drawable/settings"
        />

    <item
        android:id="@+id/info_action"
        android:title="Info"/>

</menu>

ActivitySecond:

package com.actionbar3;

import android.app.ActionBar;
import android.app.Activity;
import android.os.Bundle;

public class SecondActivity extends Activity {

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

        ActionBar actionBar = getActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setTitle("Second Activity");
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.actionbar3">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        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>
        <activity android:name=".SecondActivity" android:parentActivityName=".MainActivity">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>
    </application>

</manifest>

Answer 1

You are creating a recursion by calling return onCreateOptionsMenu(menu);

so it should be simply return true;

@Override
public boolean onCreateOptionsMenu(Menu menu){
    getMenuInflater().inflate(R.menu.action, menu);
    return true;
    // return onCreateOptionsMenu(menu);
    // call to itself , mean infinite recursion
}

Answer 2

The onCreateOptionMenu method recurses infinitely, so change it as below

@Override
public boolean onCreateOptionsMenu(Menu menu){
    getMenuInflater().inflate(R.menu.action, menu);
    return true;
}

Answer 3

Extend your activity with AppCompatActivity and use get getSupportActionBar() for backward compatibility

import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;

public class SecondActivity extends AppCompatActivity {

and create actionbar using getSupportActionBar

ActionBar actionBar = getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setTitle("Second Activity");