AppCompatPreferenceActivity向上按钮不起作用

我正在尝试创建一个扩展AppCompatPreferenceActivity并在操作栏中实现向上按钮的活动.视觉上一切看起来都很好,但向上按钮不响应触摸事件.以下是我的java和xml代码:

PrefrencesDisplayActivity.java

package com.example.matthew.testsettings;

import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.support.v7.widget.Toolbar;
import android.widget.ListView;
import android.widget.RelativeLayout;

import java.util.List;

public class PreferencesDisplayActivity extends AppCompatPreferenceActivity {
    CoordinatorLayout activityRoot;
    AppBarLayout appBarLayout;
    Toolbar toolbar;
    RelativeLayout contentRoot;
    ListView preferencesList;

    @Override
    public void onBuildHeaders(List
 target) {
        loadHeadersFromResource(R.xml.preferences, target);
        initialiseUI();
    }

    private void initialiseUI() {
        // Inflate activity layout from xml
        setContentView(R.layout.activity_preferences_display);

        // Get handles to UI elements
        activityRoot = (CoordinatorLayout) findViewById(R.id.prefDisplay_activity_root);
        appBarLayout = (AppBarLayout) findViewById(R.id.prefdisplay_activity_appBarLayout);
        toolbar = (Toolbar) findViewById(R.id.prefDisplay_activity_toolbar);
        contentRoot = (RelativeLayout) findViewById(R.id.prefDisplay_content_root);
        preferencesList = (ListView) findViewById(android.R.id.list);

        // Create and configure action bar
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }
}

activity_prefrences_display.xml

content_preferences_display.xml

AndroidManifest.xml中

当我打开应用程序并导航到首选项活动时,屏幕看起来应该如此,但按下向上按钮不会执行任何操作.谁能看到我的错误？

您也可以finish()在按下后退按钮时使用:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == android.R.id.home) {
        finish();
        return true;
    }
    return super.onOptionsItemSelected(item);
}